#define SCPI_PARSER_C
#include "app/scpi/scpi_parser.h"
#include "app/scpi/scpi_core.h"
#include "app/scpi/scpi_numeric.h"
#include "my_assert.h"
#include <ctype.h> // isdigit(), isalpha(), isalnum()
//----------------------------------------------------------------
// Refer to:
// [1] IEEE 488.2 Standard, revision IEEE Std 488.2-1987 (1992)
//     "IEEE Standard Codes, Formats, Protocols, and Common Commands for Use With IEEE Std 488.1-1987, IEEE
//      Standard Digital Interface for Programmable Instrumentation"
// [2] SCPI Specification, revision 1999.0
//     "Standard Commands for Programmable Instruments (SCPI), VERSION 1999.0, May 1999"
//----------------------------------------------------------------
// =================================================================================================================
// Notes:
/* White Space
   7.4.1.2 Encoding Syntax, [1]
   <white-space character> is de?ned as a single ASCII-encoded byte in the range of 00-09, 0B-20 (0-9, 11-32 decimal).
   This range includes the ASCII control characters and the space but excludes the newline.


   New Line
   7.5 <PROGRAM MESSAGE TERMINATOR>, [1]
   NL is defined as a single ASCII-encoded byte 0A (10 decimal).
   NOTE: An END message cannot be sent without an accompanying data byte. See IEEE Std 488.1-1987 [4]. The ^END syntactic
   element implies the IEEE 488.1 END message is sent with the last data byte of the preceding syntactic element.


   Elements Summary
   7.3.3 Functional Element Summary, [1]
*/
// =================================================================================================================
 // @sParserEntryPoint_t
 // Parser context backup/restore point data structure
 // see @parserBackupContext and @parserRestoreContext
 typedef struct
 {
      const char * str;           // temportary buffer iterator, shall not be accessed by user.
      const char * head;          // the head of the buffer, points to the begining of the entity after
                                  // ... the call of any paraser-function.
      const char * tail;          // the tail of the buffer, points to the end of entity after the call 
                                  // ... of any paraser-function.
      int32_t value;              // Generic-Purpose integer value
 }
 sParserEntryPoint_t;

 typedef struct
 {
   struct // common context
   {
       int32_t      error;         // parser error code
       const char * pErrorMsg;     // parser error message
       const char * str;           // temportary buffer iterator, shall not be accessed by user.
       /* --- unused, the (@tail - @head) expression is used instead
       size_t       length;        // input/output field, specifies the length of the buffer before
                                   // ... calling the parser-function, and holds the length of parsed
                                   // ... element after the call.
       */
       
       const char * head;          // the head of the buffer, points to the begining of the entity after
                                   // ... the call of any paraser-function.
       const char * tail;          // the tail of the buffer, points to the end of entity after the call 
                                   // ... of any paraser-function.
       bool         bEndMessage;   // End-of-message indicator. Specifies if the specified buffer holds 
                                   // ... a complete message or not. If the @str points to a portion
                                   // ... of message's data and there no information about the whole 
                                   // ... message length, the @bEndMessage value is 'false'. Otherwise, 
                                   // ... if known that the @str buffer contains the final portion of 
                                   // ... data (inclidung the terminating characters, maybe), the value 
                                   // ... is 'true'.
       bool         bContextKept;  // Clean context indicator. If @prepareParserContext has been called
                                   // ... with keeping context, this variable is 'true'. Otherwise, if
                                   // ... @prepareParserContext has been called with cleaning the context
                                   // ... then this variable is 'false'.
       uint8_t      type;          // the entity type, encoded as described in @eScpiEntityType_t enum.
   };

   sParserEntryPoint_t parseNumber_xSaveObj; // dedicated parser backup/restore structure for @parseNumber routine

   union // private context union
   {
       struct // private context for @parseString function
       {
            bool QuoteOpened;        // Quote-opened indicator: used to help to interpretate each quote 
                                     // ... either as an opening or closing one.
            char QuoteSignature;     // Quote signature: can be either '\"' or '\''
            char LastCharacter;      // The temporary character buffer to store the last processed byte
       } parseString;

       struct // private context for @parseArbitraryBlock function
       {
            size_t LengthDigits;     // the number of demical digits used to encode the actual length
                                     // ... of the block
            uint32_t Length;         // Actual length of the block in bytes, encoded as demical value
                                     // ... in range 0..999999999

            bool KeySign;            // start-character indicator: used to determine if the starting 
                                     // ... character have already processed or not yet.
            bool DataStarted;        // mode indicator: used to determine if all block's header characters
                                     // ... have already processed and the current character is a part of payload.
       } parseArbitraryBlock;

       struct // private context for @parseProgramMnemonic function
       {
            size_t CharsNumber;      // amount of characters in the mnemonic.
            bool FirstAlpha;         // start-character indicator: used to determine if the first alpha-
                                     // ...-character has been processed or not.
       } parseProgramMnemonic;

       struct // private context for @parseCommandProgramHeader function
       {
            // NOTE: @parseCommandProgramHeader function uses the @parseProgramMnemonic
            // ... calls as a part of implementation, thus it is required to keep
            // ... the @parseProgramMnemonic's context valid!
            const size_t CharsNumber;          // reserved, keep unchanged (@parseProgramMnemonic)
            const bool FirstAlpha;             // reserved, keep unchanged (@parseProgramMnemonic)
            
            bool LastCallContinue;             // last call context indicator: shows if it is required to continue
                                               // ... the last call context or it is needed to reset it.
            bool LastCallSuccess;              // last call success indicator: shows if the last call succeded or not.
            bool CommonForm;                   // common form indicator: shows if the command program header have a 
                                               // ... common form (begins from askterisk, 7.6.1.2 Encoding Syntax, [1])
            const char * _head;                // cached @head value
            const char * _tail;                // cached @tail value
            char LastCharacter;                // the last processed character
            
       } parseCommandProgramHeader;

       struct // private context for @parseDemicalNumber function
       {
            bool dotAllowed;                   // dot-character indicator: shows if the character is 
                                               // ... allowed in current state;
            bool signAllowed;                  // sign-character indicator: shows if the character is 
                                               // ... allowed in current state; 
            bool digitAllowed;                 // digit-character indicator: shows if the character is 
                                               // ... allowed in current state; 
            bool whiteAllowed;                 // white-character indicator: shows if the character is 
                                               // ... allowed in current state;
            bool expAllowed;                   // exponent-character indicator: shows if the character is 
                                               // ... allowed in current state;
            bool termAllowed;                  // unit terminator indicator: shows if a group of terminating characters are 
                                               // ... allowed in current state;

            bool manitssaOk;                   // mantissa indicator: shows if mantissa received or not.
            bool exponentOk;                   // exponent indicator: shows if exponent received or not.
            bool dotFound;                     // dot-character indicator: show if the dot character is faced in mantissa
            bool parseStage;                   // the parser state:
                                               //  false - search for mantissa;                                               
                                               //  true - search for exponent;

       } parseDemicalNumber;

       struct // private context for @parseNonDemicalNumber function
       {
            size_t digits;                     // number of digits processed
            bool allow0_1;                     // allow binary characters ( 0..1 )
            bool allow0_7;                     // allow octal characters ( 0..7 )
            bool allow0_f;                     // allow hex characters ( 0..9, a-f )
            bool allowNumChar;                 // allow numeric-system designator character
            bool foundNumericChar;             // numeric character indicator (#)

       } parseNonDemicalNumber;

       struct // private context for @parseProgramDataSeparator function
       {
            bool sepFound;                     // indicator showing if separator-character found or not
       } parseProgramDataSeparator;

       struct // private context for @parseProgramHeaderSeparator function
       {
            bool sepFound;                     // indicator showing if separator-character found or not
       } parseProgramHeaderSeparator;

       struct // private context for @parseProgramMessageSeparator function
       {
            bool sepFound;                     // indicator showing if separator-character found or not
       } parseProgramMessageSeparator;

       struct // private context for @parseEndOfCommand function
       {
            bool sepFound;                     // indicator showing if separator-character found or not
       } parseEndOfCommand;

       struct // private context for @parseWhiteSequence function
       {
            bool whiteFound;                   // indicator showing if separator-character found or not
            bool nlFound;                      // indicator showing if NL-character found or not
       } parseWhiteSequence;
   };
 }
 sParseEntry_t; 
 // =================================================================================================================
 STATIC_ASSERT( sizeof(xParseEntry_t) == sizeof(sParseEntry_t), "Invalid xParseEntry_t/sParseEntry_t size" );
 // =================================================================================================================
 // @parserBackupContext
 // Internal only function.
 // Saves the parser entry point before the parsing to give ability to restore the context iterators after 
 // unsuccessful parsing.
 // Does not guaranee full context backup.
 // @pObj = parser context;
 // @to = parser backup structure 
 static inline void parserBackupContext( const sParseEntry_t * pObj, sParserEntryPoint_t * to )
 {
    my_assert( pObj );
    my_assert( to );
    to->head = pObj->head;
    to->tail = pObj->tail;
    to->str  = pObj->str;    
 }

 // @parserBackupContextValue
 // Internal only function.
 // Saves parser-dependent general puspose value
 // @to = parser backup structure
 // @value = generic purpose value
 static inline void parserBackupContextValue( sParserEntryPoint_t * to, int32_t value )
 {
    my_assert( to );
    to->value = value;
 }

 // @parserRestoreContext
 // Internal only function.
 // Loads the parser entry point after the one has been saved by @parserBackupContext to
 // restore parser entry point after unsuccessful parsing. 
 // Does not guaranee full context restore.
 // @pObj = parser context to restore to;
 // @from = parser restore structure
 // NOTE: resets @bContextKept variable to prevent using invalid data
 static inline void parserRestoreContext( sParseEntry_t * pObj, const sParserEntryPoint_t * from )
 {    
    my_assert( from );
    pObj->head = from->head;
    pObj->tail = from->tail;
    pObj->str  = from->str;

    // reset context keeping indicator to reset the next parser's internal variables
    pObj->bContextKept = false;
 }

 // @parserRestoreContext
 // Internal only function.
 // Loads the parser dependent general purpose value after the one has been saved by @parserBackupContextValue 
 // @pObj = parser context to restore to, optional, can be NULL;
 // @from = parser restore structure
 // @pvalue = pointer to the variable to load generic purpose value saved by @parserBackupContext in 'value' argument,
 // ... optional, can be NULL
 static inline void parserRestoreContextValue( const sParserEntryPoint_t * from, int32_t * pvalue )
 {    
    my_assert( from );
    my_assert( pvalue );
    *pvalue = from->value;
 }
 // =================================================================================================================
 // @scpi_isalnum
 // Detects if the passed character @ch is ASCII alpha-numeric character
 // Refer to:
 //   "7.6.1 <COMMAND PROGPRAM HEADER>", [1]
 //   "7.6.1.2 Encoding Syntax", [1]
 // Note: the implementation is depending on the current locale.
 // This implementation uses the default functions from the standard
 // ...<ctype>-header.
 static inline bool scpi_isalnum( char ch ) 
 {
     // for the default locale only A-Za-z0-9 are allowed
     return isalnum(ch);
 }

 // =================================================================================================================
 // @scpi_isalpha
 // Detects if the passed character @ch is ASCII alpha character
 // Refer to:
 //   "7.6.1 <COMMAND PROGPRAM HEADER>", [1]
 //   "7.6.1.2 Encoding Syntax", [1]
 // Note: the implementation is depending on the current locale.
 // This implementation uses the default functions from the standard
 // ...<ctype>-header.
 static inline bool scpi_isalpha( char ch ) 
 {
     // for the default locale only A-Za-z0-9 are allowed
     return isalpha(ch);
 }

 // =================================================================================================================
 // @scpi_isdigit
 // Detects if the passed character @ch is ASCII digit character
 // Refer to:
 //   "7.6.1 <COMMAND PROGPRAM HEADER>", [1]
 //   "7.6.1.2 Encoding Syntax", [1] 
 static inline bool scpi_isdigit( char ch ) 
 {
     // for the locale does not affect to the implementation, only 0-9 are allowed
     return isdigit(ch);
 }

 // =================================================================================================================
 // @scpi_ishex
 // Detects if the passed character @ch is a HEX character (0..9, A-F, a-f) 
 static inline bool scpi_ishex( char ch ) 
 {
     // for the locale does not affect to the implementation, only 0-9 are allowed
     return isdigit(ch) || ( 'a' <= ch && 'f' >= ch ) || ( 'A' <= ch && 'F' >= ch );
 }
 // =================================================================================================================
 // @prepareParserContext
 // Preapres a parser context @xObj before a parser-function call.
 // The function must be called before each call of any parser-function.
 // If it is required to call the parser function multiple times, user
 // ... shall analyze the last return status and specify the @bKeepContext
 // ... parameter to the corresponding value. See also @eScpiParserStatus_t.
 // Parameters:
 // @xObj - the parse context to prepare;
 // @pBuffer - the memory buffer containing the SCPI element to be parsed;
 // @length - the memory buffer length;
 // @bEndMessage - specifies if the specified buffer holds a complete
 // ... message or not. If the @pBuffer contains a portion of received
 // ... data and there no information about the whole message length,
 // ... the @bEndMessage value must be 'false'. Otherwise, if known that
 // ... the buffer contains the final portion of data (even inclidung the 
 // ... terminating characters), the value must be 'true'.
 // @bKeepContext - specifies if it is required to cleanup the context 
 // ... to restart the parsing ('false'), or it is required to keep the 
 // ... context to continue ('true').
 // Returns: 'true' in success case,
 //          'false' otherwise.
 // Note in case the function returns 'false' user must not use the 
 // ... @xObj context due to it is still not prepared.
 bool prepareParserContext( xParseEntry_t * xObj,
                            const void * pBuffer,
                            size_t length,
                            bool bEndMessage,
                            bool bKeepContext )
 {
    sParseEntry_t * pObj = (sParseEntry_t*)xObj;

    if( NULL != pObj && NULL != pBuffer && 0 != length )
    {
        if( !bKeepContext )
        {
           // Cleanup the private context
           memset( pObj, 0, sizeof(sParseEntry_t) );
           pObj->bContextKept = false;
        }
        else
        {
           pObj->bContextKept = true;
        }
        
      //pObj->length = length;                 // init the buffer length
        pObj->head = (const char*)pBuffer;     // save the buffer start
        pObj->tail = pObj->head + length;      // save the buffer end
        pObj->str = pObj->head;                // init the @str iterator to the beginning of the buffer
        pObj->bEndMessage = bEndMessage;       // save end-of-message flag
        pObj->type = eScpiEntityTypeInvalid;   // forward type set: invalid (default)
        pObj->error = SCPI_ERROR_SUCCESS;      // reset error code
        pObj->pErrorMsg = NULL;                // reset error message
        return true;
    }

    return false;
 }
 // =================================================================================================================
 // @getParsedEntityDetails
 // Retrieves the parsing results from the parser context.
 // The function shall not be called until either the
 // ... @eScpiParserStatus_success status or @eScpiParserStatus_need_data
 // ... are returned by last parser-function call.
 // Note: take in account, that in case @eScpiParserStatus_need_data had 
 // ... been returned during the last parser-function call, the @eEntityType
 // ... will be set to @eScpiEntityTypeInvalid due to the entity is still
 // ... not identified (need more data).
 // Parameters:
 // @xObj - the parser context to get results from;
 // @pxEntityBegin - pointer to the pointer-variable to store the
 // ... parsed entity beginning, can be NULL;
 // @pxEntityEnd - pointer to the pointer-variable to store the
 // ... parsed entity ending, can be NULL;
 // @peEntityType - pointer to the uint8-variable to store the
 // ... parsed entity type, the type is encoded as described
 // ... in @eScpiEntityType_t enum, can be NULL;
 // Note: in case the parameters described above are NULL an appropriate
 // ... information will not be returned and can be retrieved by
 // ... another call of this function with non-NULL argument until
 // ... the @prepareParserContext is called for the specified context.
 // Returns: 'true' in success case,
 //          'false' otherwise.
 bool getParsedEntityDetails(   const xParseEntry_t * xObj,
                                const void * * pxEntityBegin,
                                const void * * pxEntityEnd,
                                uint8_t * peEntityType )
 {
      bool status = false;

      if( NULL != xObj )
      {
          if( NULL != pxEntityBegin ) 
          {
              *pxEntityBegin = ((const sParseEntry_t*)xObj)->head;
              status = status || true;
          }
          if( NULL != pxEntityEnd ) 
          {
              *pxEntityEnd = ((const sParseEntry_t*)xObj)->tail;
              status = status || true;
          }
          if( NULL != peEntityType ) 
          {
              *peEntityType = ((const sParseEntry_t*)xObj)->type; 
              status = status || true;
          }
      }

      my_assert( status );

      return status;
 }
 // =================================================================================================================
 // @getParserError
 // Retrieves the last parser error code and message
 // The function shall not be called until either the @eScpiParserStatus_failed status 
 // is returned by last parser-function call.
 // @xObj - the parser context to get results from;
 // @pErrorCode - optional pointer to the variable to store the error code, can be NULL;
 // Returns:
 //  The parser error message string. Use @getParsedEntityDetails to retrieve more details.
 //  Possible values:
 //  - NULL: no error occurred in specified context or invalid context;
 //  - non-null: valid constant null-terminated string message, no memory free is required;
 const char * getParserError( const xParseEntry_t * xObj,
                              int32_t * pErrorCode )
 {
      if( NULL != xObj )
      {
          if( NULL != pErrorCode ) 
          {
              *pErrorCode = ((const sParseEntry_t*)xObj)->error;
          }
          
          return ((const sParseEntry_t*)xObj)->pErrorMsg;
      }

      return NULL;
 }
 // =================================================================================================================
 // @setParserError
 // Assigne the last parser error code and message
 // The function shall not be called after calling any parser function that return error
 // status code to prevent overwriting actual error code and description. 
 // @xObj - the parser context to get results from;
 // @errorCode - SCPI Error code, [2]
 // @pErrorDesc - Error description, constant null-terminated string;
 // Returns:
 //  true - successful operation,
 //  false - failed
 bool setParserError( const xParseEntry_t * xObj,
                      int32_t errorCode,
                      const char * pErrorDesc  )
 {
      my_assert( xObj );
      
      if( NULL != xObj )
      {
          ((sParseEntry_t*)xObj)->error = errorCode;
          ((sParseEntry_t*)xObj)->pErrorMsg = pErrorDesc;
          
          return true;
      }

      return false;
 }
 // =================================================================================================================
 // @parseArbitraryBlock
 // "Parser-function", parses an arbitrary block (ARBITRARY BLOCK PROGRAM DATA) 
 // References:
 //     "7.7.6 <ARBITRARY BLOCK PROGRAM DATA>", [1]
 //     "7.7.6.2 Encoding Syntax", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseArbitraryBlock( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_failed;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                             // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
             // initialize private context variables
             pObj->parseArbitraryBlock.KeySign = false;
             pObj->parseArbitraryBlock.DataStarted = false;
             pObj->parseArbitraryBlock.LengthDigits = 0;
             pObj->parseArbitraryBlock.Length = 0;
         }

         // walk til the end of the buffer
         while( pObj->str != pObj->tail )
         {   
             char character = *(pObj->str++);

             if( ! pObj->parseArbitraryBlock.KeySign )
             {
                 if( '#' == character ) // !: starting character
                 {
                     pObj->parseArbitraryBlock.KeySign = true; // starting character found
                 }
                 else
                 {
                     pObj->error = SCPI_ERROR_INVALID_BLOCKDATA;
                     pObj->pErrorMsg = SCPI_ERROR_INVALID_BLOCKDATA_MSG;
                     status = eScpiParserStatus_failed; // error: the data does not start from the starting character
                     break;
                 }
             }
             else
             {
                 // check if the data payload is already being processed:
                 if( ! pObj->parseArbitraryBlock.DataStarted )
                 {
                     // nope, need to process the header

                     // check if the number of digits of the length-entity is loaded
                     if( 0 == pObj->parseArbitraryBlock.LengthDigits )
                     {
                         // nope, need to load a number of digits
                         
                         // check if the current character is a digit:
                         if( ! scpi_isdigit( character ) )
                         {
                             pObj->error = SCPI_ERROR_INVALID_BLOCKDATA;
                             pObj->pErrorMsg = SCPI_ERROR_INVALID_BLOCKDATA_MSG;
                             // nope, it is a fiasco
                             status = eScpiParserStatus_failed; // error: invalid data block header
                             break;
                         }
                         else // true == scpi_isdigit(character)
                         {
                             // yep, load the value
                             pObj->parseArbitraryBlock.LengthDigits = (size_t)(character - '0');
                            
                             // check the number loaded:
                             if( 0 == pObj->parseArbitraryBlock.LengthDigits )
                             {
                                 // indefnite format: the data block must be terminated by the
                                 // ... couple of end-of-line and end-of-message terminators (NL + ^END).
                                 // In case there no way to detemine the length of the payload, 
                                 // ... the length field must be set to zero and function shall return 
                                 // ... the warining status "eScpiParserStatus_need_data". Otherwise, in case
                                 // ... it is defenitely known that this portion of data is the last one,
                                 // ... the function shall not to change the length @Length (it is already
                                 // ... set to the passed buffer length) and return success status.
                                 if( pObj->bEndMessage )
                                 {    
                                      pObj->type = eScpiEntityTypeArbitraryBlock; // assign the entity type

                                      // An arbirary block takes the whole buffer, the @tail pointer refers to the 
                                      // ... end of the buffer. The @tail and @head pointers specify the entity length as
                                      // ... whole buffer length.

                                      status = eScpiParserStatus_success; // success: an arbirary block takes the whole buffer
                                 }
                                 else
                                 {    
                                      (void)pObj->type; // do not assign the entity type, it is not identified yet.

                                      // No information about the whole message length on this level: return "eScpiParserStatus_need_data"
                                      pObj->tail = pObj->head; // set to zero length to indicate "indefine format" by
                                                               // ... assigning the @head to the @tail.
                                      status = eScpiParserStatus_need_data; // warning: no closing quote found, need more data
                                 }
                                     
                                 // reset error code/status
                                 pObj->error = SCPI_ERROR_SUCCESS;
                                 pObj->pErrorMsg = NULL;

                                 break;
                             }
                             else // 0 != pObj->parseArbitraryBlock.LengthDigits
                             {
                                 // the next @LengthDigits characters must be interpretated as a
                                 // ... part of the length entity of the header.                                 
                                 // Nothing to do right here, see "if( 0 != pObj->parseArbitraryBlock.LengthDigits )"
                             }
                         }
                     }
                     else // 0 != pObj->parseArbitraryBlock.LengthDigits
                     {
                         // the next @LengthDigits characters must be interpretated as a
                         // ... part of the length entity of the header.                

                         // check if the current character is a digit:
                         if( ! scpi_isdigit( character ) )
                         {
                             pObj->error = SCPI_ERROR_INVALID_BLOCKDATA;
                             pObj->pErrorMsg = SCPI_ERROR_INVALID_BLOCKDATA_MSG;
                             // nope, it is a fiasco
                             status = eScpiParserStatus_failed; // error: invalid data block header
                         }
                         else
                         {
                             pObj->parseArbitraryBlock.LengthDigits--;  // decrease a number of digits

                             // To get the length of the block it is required to process the 
                             // ... length-entity of the header. On each cycle the taken character
                             // ... is a remainder of devision to 10, so it is required to
                             // ... multiply the @Length by 10 and the remainder.
                             pObj->parseArbitraryBlock.Length  = pObj->parseArbitraryBlock.Length * 10 + (size_t)(character - '0');
                             
                             // As soon as all the digits are "swallowed":
                             if( 0 == pObj->parseArbitraryBlock.LengthDigits )
                             {
                                 // check if the length-entity is greater than zero
                                 if( 0 < pObj->parseArbitraryBlock.Length )
                                 {
                                     // Set the "data" indicator: all the @Length next characters
                                     // are the part of the payload.
                                     pObj->parseArbitraryBlock.DataStarted = true;
                                 }
                                 else
                                 {
                                     pObj->type = eScpiEntityTypeArbitraryBlock; // assign the entity type

                                     // Dummy block detected: the @Length is actually zero
                                     // The arbitrary data block has zero-length payload.
                                     // Calculate the whole block size in the buffer:
                                     //  LENGTH = @str - @head 
                                     // Assigning the @tail pointer to indicate the block length:
                                     pObj->tail = pObj->str; // update the tail pointer
                                     status = eScpiParserStatus_success;   // The block was successfully recognized.
                                                                           
                                     // reset error code/status
                                     pObj->error = SCPI_ERROR_SUCCESS;
                                     pObj->pErrorMsg = NULL;

                                     break;
                                 }
                             }
                         }
                     }
                 }
                 else
                 {
                     // Swallow each byte until all the @Length bytes is counted
                     if( 0 < pObj->parseArbitraryBlock.Length )
                     {
                         // It is still a payload...
                         pObj->parseArbitraryBlock.Length--;
                     }

                     // As soon as all the bytes of the block's payload are processed:
                     if( 0 == pObj->parseArbitraryBlock.Length )
                     {
                         pObj->type = eScpiEntityTypeArbitraryBlock; // assign the entity type

                         // the entity size in the buffer
                         // LENGTH = @str - @head
                         // Assign the @tail pointer to indicate the entity length:
                         pObj->tail = pObj->str; // update the tail pointer
                         status = eScpiParserStatus_success;   // The block was successfully recognized.
                                     
                         // reset error code/status
                         pObj->error = SCPI_ERROR_SUCCESS;
                         pObj->pErrorMsg = NULL;

                         break;
                     }
                 }
             }
         }
     }

     return status;
 }

 // =================================================================================================================
 // @parseString
 // "Parser-function", parses a SCPI string (STRING PROGRAM DATA)
 // References:
 //     "<STRING PROGRAM DATA> 7.7.5", [1]
 //     "7.7.5.2 Encoding Syntax", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseString( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_failed;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                             // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
             // initialize private context variables
             pObj->parseString.QuoteOpened = false;
             pObj->parseString.LastCharacter = '\0';  // initialize the @LastCharacter to the any character, but not
                                                      // ... single nor double quote.
         }

         // walk til the end of the buffer
         while( pObj->str != pObj->tail )
         {   
             char character = *(pObj->str++);

             if( ! pObj->parseString.QuoteOpened )
             {
                 if( '\"' == character || '\'' == character ) // !: double/signle quoted string
                 {
                     pObj->parseString.QuoteSignature = character;
                     pObj->parseString.QuoteOpened = true;                   
                     continue;    // avoid of remembering current character in @LastCharacter
                 }                
                 else  // !: non-quote character
                 {
                     pObj->error = SCPI_ERROR_INVALID_STRINGDATA;
                     pObj->pErrorMsg = SCPI_ERROR_INVALID_STRINGDATA_MSG;
                     status = eScpiParserStatus_failed;  // error: the data does not start from a quote
                     break;
                 }
             }
             else
             {
                 // Analyze the character with 1-character delay to detect quote-escaping:
                 if( pObj->parseString.QuoteSignature == pObj->parseString.LastCharacter ) // maybe, it is a nesting quoting (escaping):
                 {   
                     // Need to analyze a couple of characters to ensure, if current character is a 
                     // ... closing quote character, or an ecaping one.

                     if( pObj->parseString.QuoteSignature != character )  // check current character:
                     {   
                         pObj->type = eScpiEntityTypeString; // assign the entity type
          
                         pObj->parseString.QuoteOpened = false;  // last character was a closing quote

                         // calculate the string length:
                         // LENGTH = @str - @head - 1 
                         // Assign the @tail pointer to indicate the entity length:
                         pObj->tail = pObj->str - 1; // update the tail pointer
                         status = eScpiParserStatus_success; // The string was successfully recognized.
                                    
                         // reset error code/status
                         pObj->error = SCPI_ERROR_SUCCESS;
                         pObj->pErrorMsg = NULL;

                         break;
                     }
                     else
                     {
                         pObj->parseString.LastCharacter =  '\0';  // initialize the @LastCharacter to the any character, but not
                                                                   // ... single nor double quote.                       
                         continue;    // avoid of remembering current character in @LastCharacter
                     }
                 }                 
             }

             pObj->parseString.LastCharacter = character;           
         }

         // Check if is there an opend quote: 
         if( pObj->parseString.QuoteOpened )
         {
             if( pObj->bEndMessage )
             {
                 pObj->error = SCPI_ERROR_INVALID_STRINGDATA;
                 pObj->pErrorMsg = SCPI_ERROR_INVALID_STRINGDATA_MSG;
                 status = eScpiParserStatus_failed; // error: last quote had not been closed
             }
             else
             {
                 (void)pObj->type; // do not assign the entity type, it is not identified yet.
                 status = eScpiParserStatus_need_data; // warning: no closing quote found, need more data
             }
         }
     }

     return status;
 }

 // =================================================================================================================
 // @parseProgramMenmonic
 // "Parser-function", parses a SCPI Program Mnemonic (<program mnemonic>)
 // References: 
 //     "<program mnemonic>", "7.6.1.2 Encoding Syntax", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseProgramMenmonic( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_failed;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                         // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
             // initialize private context variables
             pObj->parseProgramMnemonic.FirstAlpha = false;   // reset the start-character indicator          
             pObj->parseProgramMnemonic.CharsNumber = 0;      // reset the number of processed characters
         }

         // walk til the end of the buffer
         while( pObj->str != pObj->tail )
         {   
             char character = *(pObj->str++);

             // If the start-character have not found yet:
             if( ! pObj->parseProgramMnemonic.FirstAlpha )
             {
                 // the first character must be the upper/lower case 
                 // ... ALPHA character, 7.6.1.2 Encoding Syntax, [1]
                 if( scpi_isalpha( character ) )
                 {
                     pObj->parseProgramMnemonic.FirstAlpha = true; // ok, the first character found
                     pObj->parseProgramMnemonic.CharsNumber = 1;   // 1 character has been processed
                 }
                 else
                 {
                     pObj->error = SCPI_ERROR_INVALID_CHARACTER;
                     pObj->pErrorMsg = SCPI_ERROR_INVALID_CHARACTER_MSG;

                     #if 0
                     if( scpi_iscmdsep( character ) || scpi_commonhdrind( character ) )
                     {
                         // conditionally valid character.
                         // must be analyzed by caller
                     }
                     #endif

                     // indicate invalid character
                     pObj->head = (pObj->str - 1); // update head to identify the character
                     pObj->tail = pObj->str;
                     
                     status = eScpiParserStatus_failed; // the first character does not match
                                                    // ... to the rule, error.

                     // avoid of "break" operator here due to it is required to skip all the
                     // ... code section right after the while-cycle.
                     goto L_parseProgramMenmonic_EXIT;
                 }
             }
             else
             {
                 #if 1
                 // check the length of already processed characters:
                 if( pObj->parseProgramMnemonic.CharsNumber >= 12 )      // 7.6.1.4.1 Length, [1]
                 {
                     pObj->error = SCPI_ERROR_MNEMONIC_TOOLONG;
                     pObj->pErrorMsg = SCPI_ERROR_MNEMONIC_TOOLONG_MSG;
                     status = eScpiParserStatus_failed; // error: maximum mnemoic length exceeded

                     // avoid of "break" operator here due to it is required to skip all the
                     // ... code section right after the while-cycle.
                     goto L_parseProgramMenmonic_EXIT; 
                 }
                 #endif
                 
                 // check the character:
                 if( scpi_isalnum( character ) || ( '_' == character ) )
                 {
                     pObj->parseProgramMnemonic.CharsNumber++; // increase number of characters
                 }
                 else
                 {
                     // Since this character does not match to the rule, 
                     // ... it is required to roll back the iterator @str
                     // ... due to it have been incremented illegally for
                     // ... for this condition.
                     pObj->str--; // roll back the iterator
                     break;
                 }
             }
         } // while(...)

         // check if the whole buffer has been processed without errors:
         if( pObj->str >= pObj->tail )
         {
             // yes, no separation element found, maybe, it is not complete entity.             
             // calculate the entity length:
             // LENGTH = WHOLE_BUFFER_LENGTH
             // To indicate the entity length as a whole buffer length,
             // ... do not change the @tail pointer since it refers to
             // ... the end of the buffer.
             (void)pObj->type; // do not assign the entity type, it is not identified yet.

             // check if the end-of-message indicator is set:
             if( pObj->bEndMessage )
             {
                 pObj->error = SCPI_ERROR_COMMAND_ERROR;
                 pObj->pErrorMsg = SCPI_ERROR_COMMAND_ERROR_MSG;
                 // no more data available: error
                 status = eScpiParserStatus_failed;
             }
             else
             {
                 // need more data to analyze:
                 status = eScpiParserStatus_need_data;
             }
         }
         else
         // check if at least one matching character found:
         if( pObj->parseProgramMnemonic.FirstAlpha )
         {
             // assign the entity type
             pObj->type = eScpiEntityTypeProgramMnemonic;

             // calculate the entity length:
             // LENGTH = @str - @head
             // Assign the @tail pointer to indicate the entity length:
             pObj->tail = pObj->str; // assign the @tail pointer to the current iterator

             status = eScpiParserStatus_success; // success: program mnemonic has been found
                                      
             // reset error code/status
             pObj->error = SCPI_ERROR_SUCCESS;
             pObj->pErrorMsg = NULL;
         }
         else
         {
             pObj->error = SCPI_ERROR_COMMAND_ERROR;
             pObj->pErrorMsg = SCPI_ERROR_COMMAND_ERROR_MSG;
             status = eScpiParserStatus_failed;  // error: no matching characters found
         }
     }
L_parseProgramMenmonic_EXIT:
     return status;
 }

 // =================================================================================================================
 // @parseCharacter
 // "Parser-function", parses a SCPI character (CHARACTER PROGRAM DATA)
 // References:
 //     "7.7.1 <CHARACTER PROGRAM DATA>", [1]
 //     "7.7.1.2 Encoding Syntax", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseCharacter( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     // In accordance with "7.7.1 <CHARACTER PROGRAM DATA>", [1], the character
     // ... entity shall be parsed the same way as program mnemonic entity.
     eScpiParserStatus_t status = parseProgramMenmonic( xObj );
   
     if( eScpiParserStatus_success == status )
     {
         // override the entity type:
         pObj->type = eScpiEntityTypeCharacter;
     }

     return status;
 }
 
  // =================================================================================================================
 // @parseArray
 // "Parser-function", parses a SCPI array (ARRAY PROGRAM DATA)
 // References:
 //     "7.7.1 <CHARACTER PROGRAM DATA>", [1]
 //     "7.7.1.2 Encoding Syntax", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseArrayNumber( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     // In accordance with "7.7.1 <CHARACTER PROGRAM DATA>", [1], the character
     // ... entity shall be parsed the same way as program mnemonic entity.
     eScpiParserStatus_t status = parseProgramMenmonic( xObj );
   
     if( eScpiParserStatus_success == status )
     {
         // override the entity type:
         pObj->type = eScpiEntityTypeCharacter;
     }

     return status;
 }

 // =================================================================================================================
 // @parseCommandProgramHeader
 // "Parser-function", parses a SCPI Command/Query Program Header (<COMMAND PROGRAM HEADER>, <QUERY PROGRMA HEADER>)
 // References:
 //     "7.6.1 <COMMAND PROGPRAM HEADER>", [1]
 //     "7.6.1.2 Encoding Syntax", [1]
 //     "7.6.2 <COMMAND PROGPRAM HEADER>", [1]
 //     "7.6.2.2 Encoding Syntax", [1] 
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                         ... there no enough data to process.
 // Notes: All white spaces before the found command program header is skipped,
 // ... the @pxEntityBegin parameter during @getParsedEntityDetails call will refer
 // ... to the command program header beginning.
 eScpiParserStatus_t parseCommandProgramHeader( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_need_data;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                            // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         { 
             // initialize private context variables
             (void)pObj->parseCommandProgramHeader.FirstAlpha;   // do not touch
             (void)pObj->parseCommandProgramHeader.CharsNumber;  // do not touch
             pObj->parseCommandProgramHeader._tail = NULL;       // it will be initialzed later
             pObj->parseCommandProgramHeader.LastCallContinue = false;
             pObj->parseCommandProgramHeader.LastCallSuccess = false;             
             pObj->parseCommandProgramHeader.CommonForm = false;
             pObj->parseCommandProgramHeader.LastCharacter = ' ';  // Rule 1: initialize the @LastCharacter to the 
                                                                   // ... any character, but not a semicolon character.
                                                                   // Rule 2: initialize the @LastCharacter to the 
                                                                   // ... white character to indicate that no non-white
                                                                   // ... character has been faced
         }

         // walk til the end of the buffer
         while( pObj->str != pObj->tail )
         {
            char character = *(pObj->str);  // DO NOT INCREMENT ITERATOR

            // skip white characters:
            if( scpi_iswhite( character ) )
            {
                // In accordance with "7.6.1.2 <COMMAND PROGPRAM HEADER>":
                // Check if the last character is a white character:
                if( scpi_iswhite( pObj->parseCommandProgramHeader.LastCharacter ) )
                {
                    // yes, thus no Non-white character faced yet -> any amount
                    // ... of white-characters can be skipped in the beginning.

                    pObj->parseCommandProgramHeader.LastCharacter = character;
                    pObj->str++; // skip white character
                    pObj->head = pObj->str; // update @head to skip white-spaces
                    continue; 
                }

                if( scpi_ismsgsep( pObj->parseCommandProgramHeader.LastCharacter ) )
                {
                    // this white character can be skipped because the previous was a 
                    // command separator
                    pObj->parseCommandProgramHeader.LastCharacter = character;
                    pObj->str++; // skip separator
                    pObj->head = pObj->str; // update @head to skip separator
                    continue; 
                }
            }

            if( scpi_ismsgsep( character ) )
            {
                if( scpi_ismsgsep( pObj->parseCommandProgramHeader.LastCharacter ) 
                 || scpi_iswhite( pObj->parseCommandProgramHeader.LastCharacter ) )
                {
                    pObj->parseCommandProgramHeader.LastCharacter = character;
                    pObj->str++; // skip separator character
                    pObj->head = pObj->str; // update @head to skip character
                    continue;
                }
            }

            // In accordance with "7.6.1 <COMMAND PROGPRAM HEADER>", [1], the command
            // ... program mnemonic entity shall be parsed the similar way as program 
            // ... mnemonic entity. Thus this implementation uses @parseProgramMenmonic
            // ... as a part.
            //
            // Need to preserve the @tail pointer to recover it after the call:
            pObj->parseCommandProgramHeader._tail = pObj->tail;  // preserve @tail

            // Need to preserve the @head pointer to recover it after the call:
            pObj->parseCommandProgramHeader._head = pObj->head;  // preserve @head

            // Nested @parseProgramMenmonic call uses it's own context needed to be kept
            // between calls. If the last call failed, the context required to be reset.
            // Reset @bContextKept indicator if the last call failed:
            pObj->bContextKept = pObj->parseCommandProgramHeader.LastCallContinue;            

            // It is required to pass the character to the @parseProgramMenmonic() even
            // ... it is a separator character to terminate @parseProgramMenmonic's context.            
            // Check if the @parseProgramMenmonic() have enough data to recognize entity:
            if( eScpiParserStatus_need_data == (status = parseProgramMenmonic( xObj ), status ) )
            {   
                // The processed chunk is a part of program mnemonic.
                // Not enough data for complete recognition.
                // The length of incomleted entity is a whole buffer size,
                // ... it is need to assign the @tail to indicate the entity length.
                // In this case the assigning the @tail is useless due to it is
                // ... already refers to the end of the buffer (@parseProgramMenmonic
                // ... call hasn't change it).                
                (void)pObj->tail;

                // keep the @status code
                (void)status;

                // Remember the last chacracter processed.
                // It is required to retrieve the last character by referring @str iterator.
                // @str has been incremented since the last @parseProgramMenmonic call.
                pObj->parseCommandProgramHeader.LastCharacter = *(pObj->str - 1);

                // set the last-call indicator.
                // It helps to determine if at least one call has been performed without error
                pObj->parseCommandProgramHeader.LastCallContinue = true;  // set last-call indicator

                // reset error code/status
                pObj->error = SCPI_ERROR_SUCCESS;
                pObj->pErrorMsg = NULL;

                break;
            } 
            else if( eScpiParserStatus_success == status )
            {
                // Last call of @parseProgramMenmonic found progrma mnemonic as a part of command program header 
                // The @str iterator refers to the next character after the last mnemonic character

                // reset the last-call indicator.
                // It helps to determine if it is requried to reset the context before call.
                // As soon as a command mnemonic found, it is requried to restart the context
                pObj->parseCommandProgramHeader.LastCallContinue = false;  // reset last-call indicator

                // Remember that at least last call was succeeded,
                // ... this fact will be helpful if the call returns 'eScpiParserStatus_faliled':
                pObj->parseCommandProgramHeader.LastCallSuccess = true; // set last-call success indicator

                // @str iterator already refers to the next character to continue processing.                
                (void)pObj->str;

                // Check if the end of the buffer is reached:
                if( pObj->parseCommandProgramHeader._tail <= pObj->str )
                {
                    // Yes, the end of the buffer is reached
                    // Set 'eScpiParserStatus_success' status
                    (void)status; // @status already is eScpiParserStatus_success
                                    
                    // reset error code/status
                    pObj->error = SCPI_ERROR_SUCCESS;
                    pObj->pErrorMsg = NULL;

                    break;
                }

                // The entity had been recognized successfully, but it is not end of the buffer.
                // Recover @tail before the next call:
                pObj->tail = pObj->parseCommandProgramHeader._tail;

                // Remember the last chacracter processed.
                // It is required to retrieve the last character by referring @str iterator.
                // @str has been incremented since the last @parseProgramMenmonic call.
                pObj->parseCommandProgramHeader.LastCharacter = *(pObj->str - 1);

            } 
            else // eScpiParserStatus_failed (the code 'eScpiParserStatus_invalid' is not considered as possible)
            {   
                // Need to restore the @tail pointer to recover it after the unsuccessful call:
                pObj->tail = pObj->parseCommandProgramHeader._tail;  // restore @tail

                // Need to restore the @head pointer to recover it after the unsuccessful call:
                pObj->head = pObj->parseCommandProgramHeader._head;  // restore @head

                // The @parseProgramMenmonic call failed, maybe it is a separator?
                if( scpi_iscmdsep( character ) ) // character ':'
                {
                    // Check if the command program header is expected in common form:
                    // In common form the program header can not be split up by semicolons.
                    if( ! pObj->parseCommandProgramHeader.CommonForm )
                    {
                        // Compound command program header detected.

                        // Yes, it is a program mnemonic separator
                        // Check if this separator is the only separator by checking last character:
                        if( scpi_iscmdsep( pObj->parseCommandProgramHeader.LastCharacter ) ) // character ':'
                        {
                            // Last character is a colon-character too.
                            // error: double separator detected                        
                            status = eScpiParserStatus_failed;
                            pObj->error = SCPI_ERROR_INVSEP_ERROR;
                            pObj->pErrorMsg = SCPI_ERROR_INVSEP_ERROR_MSG;
                            break;
                        }
                        else
                        {
                            // reset error code/status
                            pObj->error = SCPI_ERROR_SUCCESS;
                            pObj->pErrorMsg = NULL;

                            // Last character is not a colon-character (maybe, there was no last character at all).
                            // Ok, it is a single program mnemonic separator.
                            // Let's remember this character and continue processing.
                            // @str is already incremented.
                            pObj->parseCommandProgramHeader.LastCharacter = character;   // remember the last processed character

                            // warning: need more data to determine if this character is a leading
                            // ... semicolon or not.
                            status = eScpiParserStatus_need_data;
                        }
                    }
                    else
                    {
                        // Error: common command program header can not contain semicolons
                        status = eScpiParserStatus_failed;  // error
                        pObj->error = SCPI_ERROR_COMMAND_HEADER_SEP;
                        pObj->pErrorMsg = SCPI_ERROR_COMMAND_HEADER_SEP_MSG;
                        break;
                    }
                }
                else // ':' !== character
                if( scpi_commonhdrind( character ) )  // check for leading '*' ("common query program header", 7.6.1.2 Encoding Syntax, [1])
                {
                    // Since the command program header can not contain white-character as described in 7.6 [1],
                    // ... if the @LastCharacter is a white-character then this character is the first header character
                    //  processed. The Asterisk character in the beginnning of the command program header means that this
                    // ... is a common command program header. Let's check it:
                    if( scpi_iswhite(pObj->parseCommandProgramHeader.LastCharacter)
                     || scpi_ismsgsep(pObj->parseCommandProgramHeader.LastCharacter) )
                    {
                        // reset error code/status
                        pObj->error = SCPI_ERROR_SUCCESS;
                        pObj->pErrorMsg = NULL;

                        // Let's remember this character and continue processing.                        
                        pObj->parseCommandProgramHeader.LastCharacter = character;   // remember the last processed character

                        // Set the common form indicator
                        pObj->parseCommandProgramHeader.CommonForm = true; // common program header is expected

                        // warning: need more data to determine if this character is a legal Asterisk character 
                        // ... in the beginning of the command program header.
                        status = eScpiParserStatus_need_data;
                    }
                    else
                    {
                        // Asterisk character detected inside the command program header (not in the beginning);
                        // Asterisk character is illeagal inside the command program header.
                        status = eScpiParserStatus_failed;
                        pObj->error = SCPI_ERROR_COMMAND_HEADER_SEP;  // missing separator?
                        pObj->pErrorMsg = SCPI_ERROR_COMMAND_HEADER_SEP_MSG;
                        break;
                    }
                }
                else // '*' !== character
                if( scpi_queryind( character ) )  // check for ending '?' ("common query program header", 7.6.2.2 Encoding Syntax, [1])
                {
                    // Since the command program header can not contain null-character as described in 7.6 [1],
                    // ... if the @LastCharacter is '\0' then this character is the first character processed.
                    // If the question mark character is faced in the end of the entity, it is allowed (7.6.2, [1]).
                    // If the @LastCharacter is not null and the @LastCallSuccess is true, it seems to be ending of
                    // ... the entity, but it's required to analyze next character.
                    if( '\0' != pObj->parseCommandProgramHeader.LastCharacter 
                        &&
                        (!scpi_queryind(pObj->parseCommandProgramHeader.LastCharacter))
                        &&
                        (!scpi_iscmdsep(pObj->parseCommandProgramHeader.LastCharacter))
                        &&
                        pObj->parseCommandProgramHeader.LastCallSuccess )
                    {
                        // reset error code/status
                        pObj->error = SCPI_ERROR_SUCCESS;
                        pObj->pErrorMsg = NULL;

                        // need to continue analyzing to determine if this character is legal.
                        status = eScpiParserStatus_need_data;

                        // Let's remember this character and continue processing.                        
                        pObj->parseCommandProgramHeader.LastCharacter = character;   // remember the last processed character
                    }
                    else
                    {
                        // error: illegal character faced
                        status = eScpiParserStatus_failed;
                        pObj->head = (pObj->str - 1); // update head to identify the character
                        pObj->tail = pObj->str;
                        pObj->error = SCPI_ERROR_INVALID_CHARACTER;
                        pObj->pErrorMsg = SCPI_ERROR_INVALID_CHARACTER_MSG;
                        break;
                    }
                }
                else // '?' !== character
                // 7.4 Separator Functional Elements", [1]
                // -check for terminating character '\n' (7.5 <PROGRAM MESSAGE TERMINATOR>, [1]) 
                // -check for white character
                // -check for program message unit separator (7.4.1 <PROGRAM MESSAGE UNIT SEPARATOR>, [1])
                if( scpi_isnl( character ) || scpi_iswhite( character ) || scpi_ismsgsep( character ) )
                {
                    // it is not a program mnemonic separator => it is a message terminator
                    // Check if the last @parseProgramMenmonic was successeded?
                    // Check if the last processed character is not a colon character?
                    if( pObj->parseCommandProgramHeader.LastCallSuccess && ( !scpi_iscmdsep(pObj->parseCommandProgramHeader.LastCharacter)) )
                    {
                        // yes, the last program mnemonic has been found successfully.
                        // Calculate the entity length:
                        // LENGTH = @str - 1; // minus one due to the last call have incremented it
                        pObj->tail = pObj->str - 1;

                        // It is end of command program header.
                        status = eScpiParserStatus_success;
                                     
                        // reset error code/status
                        pObj->error = SCPI_ERROR_SUCCESS;
                        pObj->pErrorMsg = NULL;
                    }
                    else
                    {
                        pObj->tail = pObj->str - 1; // store the @tail pointer to help the caller to identify the NL-character
                        pObj->error = SCPI_ERROR_COMMAND_HEADER;  // no header?
                        pObj->pErrorMsg = SCPI_ERROR_COMMAND_HEADER_MSG;
                        status = eScpiParserStatus_failed;
                    } 
                    break;
                }
                else // '\n' !== character, undefined character
                {
                    // store the @tail pointer to help the caller to identify the invalid character
                    pObj->tail = pObj->str;

                    if( pObj->parseCommandProgramHeader.LastCallSuccess && (pObj->error != SCPI_ERROR_SUCCESS) )
                    {
                        pObj->head = (pObj->str - 1);
                        pObj->error = SCPI_ERROR_INVALID_CHARACTER;
                        pObj->pErrorMsg = SCPI_ERROR_INVALID_CHARACTER_MSG;
                    }

                    status = eScpiParserStatus_failed;
                    break;
                }
            }
         } // while(...)
     
         if( eScpiParserStatus_success == status )
         {   
             // override the entity type:
             // If the last processed character is question mark character,
             // ... the entity type is the "query program header"
             if( scpi_queryind( pObj->parseCommandProgramHeader.LastCharacter ) )
             {   
                 // Check for "Common form":
                 if( pObj->parseCommandProgramHeader.CommonForm )
                 {
                     pObj->type = eScpiEntityTypeCmnQueryProgHdr;  // Common form
                 }
                 else
                 {
                     pObj->type = eScpiEntityTypeCmpQueryProgHdr;  // Simple or Compound form
                 }
             }
             else // else: the "command program header"
             {
                 // Check for "Common form":
                 if( pObj->parseCommandProgramHeader.CommonForm )
                 {
                     pObj->type = eScpiEntityTypeCmnCommandProgHdr; // Common form
                 }                                                    
                 else                                                 
                 {                                                    
                     pObj->type = eScpiEntityTypeCmpCommandProgHdr; // Simple or Compound form
                 }                 
             }
         }
         else if( eScpiParserStatus_need_data == status ) // if it is requried more data to analyze:
         {
             // check if the end-of-message indicator is set:
             if( pObj->bEndMessage )
             {
                 pObj->error = SCPI_ERROR_COMMAND_HEADER;  // no header, imcomplete string?
                 pObj->pErrorMsg = SCPI_ERROR_COMMAND_HEADER_MSG;
                 // no more data available: error
                 status = eScpiParserStatus_failed;
             }
         }         
     }

// L_parseCommandProgramHeader_EXIT:
     return status;
 }

 // =================================================================================================================
 // @parseDemicalNumber
 // "Parser-function", parses a SCPI Demical Numeric Program Data ()
 // References:
 //     "7.7.2 <DECIMAL NUMERIC PROGRAM DATA>", [1]
 //     "7.7.2.2 Encoding Syntax", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 static eScpiParserStatus_t parseDemicalNumber( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_need_data;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                            // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
             // "7.7.2.2 Encoding Syntax", [1]:
             pObj->parseDemicalNumber.parseStage = false;        // false - search for mantissa
             pObj->parseDemicalNumber.signAllowed = true;        //   sign  - allowed
             pObj->parseDemicalNumber.dotAllowed = true;         //   dot   - allowed
             pObj->parseDemicalNumber.digitAllowed = true;       //   digit - allowed
             pObj->parseDemicalNumber.whiteAllowed = false;      //   white - disallowed
             pObj->parseDemicalNumber.expAllowed = false;        //    exp  - disallowed
             pObj->parseDemicalNumber.termAllowed = false;     //  msgsep - disallowed

             pObj->parseDemicalNumber.dotFound = false;          // reset dot indicator
             pObj->parseDemicalNumber.manitssaOk = false;        // reset mantissa indicator 
             pObj->parseDemicalNumber.exponentOk = false;        // reset exponent indicator  
         }

         // walk til the end of the buffer or message separator is faced
         while( pObj->str != pObj->tail )
         {
            char character = *(pObj->str++);

            // Check if the sign-character is allowed in current state:
            if( pObj->parseDemicalNumber.signAllowed )
            {
                // Check if the character is a sign-character:
                if( '-' == character || '+' == character )
                {
                    if( ! pObj->parseDemicalNumber.parseStage ) // search for mantissa
                    {
                        // Only digits and dot-character are allowed after the sign-character for mantissa

                        // since the sign-character faced, it shall be disallowed.
                        pObj->parseDemicalNumber.signAllowed = false;

                        // since the sign-character faced, white-character shall be disallowed.
                        pObj->parseDemicalNumber.whiteAllowed = false;

                        // since the sign-character faced, dot-character shall be allowed.
                        pObj->parseDemicalNumber.dotAllowed = true;

                        // since the sign-character faced, exp-character shall be disallowed.
                        pObj->parseDemicalNumber.expAllowed = false;

                        // * since the sign-character faced, digits shall be allowed.
                        pObj->parseDemicalNumber.digitAllowed = true;

                        // * since the sign-character faced, message unit separator is disallowed
                        pObj->parseDemicalNumber.termAllowed = false;
                    }
                    else  // search for exponent   
                    {   
                        // Only digits are allowed after the sign-character for exponent
 
                        // since the sign-character faced, it shall be disallowed.
                        pObj->parseDemicalNumber.signAllowed = false;

                        // since the sign-character faced, white-character shall be disallowed.
                        pObj->parseDemicalNumber.whiteAllowed = false;

                        // since the sign-character faced, dot-character shall be disallowed.
                        pObj->parseDemicalNumber.dotAllowed = false;

                        // since the sign-character faced, exp-character shall be disallowed.
                        pObj->parseDemicalNumber.expAllowed = false;

                        // * since the sign-character faced, digits shall be allowed.
                        pObj->parseDemicalNumber.digitAllowed = true;

                        // * since the sign-character faced, message unit separator is disallowed
                        pObj->parseDemicalNumber.termAllowed = false;
                    }

                    // skip character
                    continue;
                }
            }

            // Check if the dot-character is allowed in current state:
            if( pObj->parseDemicalNumber.dotAllowed )
            {
                // Check if the character is a dot-character:
                if( '.' == character )
                {
                    // dot faced
                    pObj->parseDemicalNumber.dotFound = true;

                    if( ! pObj->parseDemicalNumber.parseStage ) // search for mantissa
                    {
                        // Digits, white-character and exp-character are allowed after the dot-character in mantissa.

                        // since the dot-character faced, it shall be disallowed.
                        pObj->parseDemicalNumber.dotAllowed = false;

                        // since the dot-character faced, sign-character shall be disallowed.
                        pObj->parseDemicalNumber.signAllowed = false;

                        // since the dot-character faced, white-character shall be allowed,
                        // ... (switching to exponent mode)
                        pObj->parseDemicalNumber.whiteAllowed = true;

                        // * since the dot-character faced, digits shall be allowed.
                        pObj->parseDemicalNumber.digitAllowed = true;

                        // since the dot-character faced, exp-character shall be allowed,
                        // ... (switching to exponent mode)
                        pObj->parseDemicalNumber.expAllowed = true;                       

                        // * since the dot-character faced, message unit separator is disallowed
                        pObj->parseDemicalNumber.termAllowed = false;
                    }

                    // skip character
                    continue;
                }
            }

            // Check if the digit-character is allowed in current state:
            if( pObj->parseDemicalNumber.digitAllowed )
            {
                // Check if the character is a digit-character:
                if( scpi_isdigit( character ) )
                {
                    if( ! pObj->parseDemicalNumber.parseStage ) // search for mantissa
                    {
                        // Digits, dot-character, exp-character and white-character are allowed after digit in mantissa

                        // since the digit-character faced, sign-character shall be disallowed.
                        pObj->parseDemicalNumber.signAllowed = false;

                        // since the digit-character faced, white-character shall be allowed,
                        // ... (switching to exponent mode)
                        pObj->parseDemicalNumber.whiteAllowed = true;

                        // since the digit-character faced, exp-character shall be allowed,
                        // ... (switching to exponent mode)
                        pObj->parseDemicalNumber.expAllowed = true;

                        // * since the digit-character faced, dot-character shall be allowed.
                        #if 0 // false-positive: "-3.1.e-1", second dot shall not be allowed after digit '1'
                        pObj->parseDemicalNumber.dotAllowed = true;
                        #else
                        (void)pObj->parseDemicalNumber.dotAllowed; // already enabled since start
                        #endif

                        // * since the digit-character faced, message unit separator is allowed
                        pObj->parseDemicalNumber.termAllowed = true;

                        // since at least one digit faced in mantissa, the mantissa is OK
                        pObj->parseDemicalNumber.manitssaOk = true;

                        (void)pObj->parseDemicalNumber.digitAllowed; // already enabled

                    }
                    else  //  2 - search for exponent; 
                    {
                        // Only digits are allowed after digit in exponent or message separator

                        // since the digit-character faced, sign-character shall be disallowed.
                        pObj->parseDemicalNumber.signAllowed = false;

                        // since the digit-character faced, dot-character shall be disallowed.
                        pObj->parseDemicalNumber.dotAllowed = false;

                        // since the digit-character faced, white-character shall be disallowed (note*).
                        pObj->parseDemicalNumber.whiteAllowed = false;

                        // since the digit-character faced, sign-character shall be disallowed.
                        pObj->parseDemicalNumber.signAllowed = false;

                        // since the digit-character faced in exponent, message unit separator is allowed
                        // Note*: @termAllowed covers a white-characters too only if @exponentOk is set.
                        pObj->parseDemicalNumber.termAllowed = true;

                        (void)pObj->parseDemicalNumber.digitAllowed; // already enabled

                        // As soon as first digit faced in exponent, the exponent can be
                        // ... considered as a valid exponent.
                        pObj->parseDemicalNumber.exponentOk = true;
                    }

                    // skip character
                    continue;
                }
            }

            // Check if the message-unit-separator-character is allowed in current state:
            if( pObj->parseDemicalNumber.termAllowed )
            {
                // Check if the character is:
                // - a message-unit separator;
                // - a data-unit separator;
                // - a message-unit terminator;
                // - a white character (a kind of terminating character only if no entities expected more);
                if( scpi_isdatasep( character ) || scpi_ismsgsep( character ) || scpi_isnl( character ) || (scpi_iswhite( character ) && pObj->parseDemicalNumber.exponentOk) )
                {
                    if( ! pObj->parseDemicalNumber.parseStage ) // search for mantissa
                    {  
                        // Facing the separator-character in mantissa means end of number:
                        pObj->str--; // roll back the iterator to previous mantissa character

                        break; // interrupt processing
                    }
                    else // search for exponent 
                    {                        
                        // In general the separator-character in exponent is allowable only if @exponentOk is true.
                        // But if message separator found and no valid exponend anounced, it is required to consider
                        // found entity as a number containing only mantissa. 

                        // only if no exponent is found
                        if( ! pObj->parseDemicalNumber.exponentOk )
                        // switch stage back to mantissa mode 
                        pObj->parseDemicalNumber.parseStage = false; // guarantees the number is valid

                        {  // discard all found white spaces after mantissa:
                        pObj->str--; // roll back iterator to the separator character
                        pObj->str--; // roll back iterator to the character before the separator
                        while( scpi_iswhite( *pObj->str ) ) pObj->str--; // discard white characters found
                        pObj->str++; // skip the last mantissa character
                        }
                        
                        break; // interrupt processing
                    }
                }
            }


            // Check if the white-character is allowed in current state:
            if( pObj->parseDemicalNumber.whiteAllowed )
            {
                // Check if the character is a white-character:
                if( scpi_iswhite( character ) )
                {
                    if( ! pObj->parseDemicalNumber.parseStage ) // search for mantissa
                    {  
                        // Due to facing the white-character in mantissa means switching to
                        // ... searching-for-exponent mode, only exp-character is allowed:

                        // since the white-character faced, the stage shall be changed:
                        pObj->parseDemicalNumber.parseStage = true; // search for exponent

                        // since the white-character faced, exp-character shall be allowed.
                        pObj->parseDemicalNumber.expAllowed = true;

                        // since the white-character faced, dot-character shall be disallowed.
                        pObj->parseDemicalNumber.dotAllowed = false;

                        // since the white-character faced, sign-character shall be disallowed.
                        pObj->parseDemicalNumber.signAllowed = false;

                        // since the white-character faced, digits shall be disallowed.
                        pObj->parseDemicalNumber.digitAllowed = false;

                        // since the mode is being changed, the mantissa has been processed
                        (void)pObj->parseDemicalNumber.manitssaOk; // already set to true in digit-handler

                        (void)pObj->parseDemicalNumber.whiteAllowed; // already enabled
                    }
                    else // search for exponent 
                    {   
                        // Only digits, sign-character and exp-character are allowed in exponent

                        // since the white-character faced, sign-character shall be allowed in exponent,
                        // ... but white-character may be faced either before and after exp-character, thus
                        // ... do not change the allowing of sign-character here:
                        (void)pObj->parseDemicalNumber.signAllowed; // do not touch
                        
                        // * since the white-character faced, dot-character shall be disallowed.
                        pObj->parseDemicalNumber.dotAllowed = false;  // already disabled ealier

                        // Due to white-character may be faced either before and after the exp-character,
                        // ... the digit-character allowing shall not be changed here, but it shall be
                        // ... enabled on either the dot-character and digit-character handler.
                        (void)pObj->parseDemicalNumber.digitAllowed;  // do not touch

                        // Due to white-character may be faced either before and after the exp-character,
                        // ... the exp-character allowing shall not be changed here, but it shall be
                        // ... enabled on either the dot-character and digit-character handler.
                        (void)pObj->parseDemicalNumber.expAllowed;  // do not touch

                        (void)pObj->parseDemicalNumber.whiteAllowed;  // already enabled
                    }

                    // skip character
                    continue;
                }
            }

            // Check if the white-character is allowed in current state:
            if( pObj->parseDemicalNumber.expAllowed )
            {
                // Check if the character is a digit-character:
                if( 'E' == character || 'e' == character )
                {
                    if( ! pObj->parseDemicalNumber.parseStage ) // search for mantissa
                    {
                        // Since the exp-character is faced in mantissa the mode shall be
                        // ... changed to exponent mode. Thus only digits, white-character 
                        // ... and sign-character are allowed.

                        // since the exp-character faced, the stage shall be changed:
                        pObj->parseDemicalNumber.parseStage = true; // search for exponent

                        // since the exp-character faced, it shall be disallowed.
                        pObj->parseDemicalNumber.expAllowed = false;

                        // since the exp-character faced, sign-character shall be allowed.
                        pObj->parseDemicalNumber.signAllowed = true;
                       
                        // since the exp-character faced, dot-character shall be disallowed.
                        pObj->parseDemicalNumber.dotAllowed = false;

                        // * since the exp-character faced, white-character shall be allowed.
                        pObj->parseDemicalNumber.whiteAllowed = true;
                        
                        // * since the exp-character faced, digits shall be allowed.
                        pObj->parseDemicalNumber.digitAllowed = true;
                    }
                    else // possibly if white-character faced after mantissa:
                    { 
                        // since the exp-character faced, the stage shall be changed:
                        (void)pObj->parseDemicalNumber.parseStage; // already set

                        // since the exp-character faced, it shall be disallowed.
                        pObj->parseDemicalNumber.expAllowed = false;

                        // since the exp-character faced, dot-character shall be disallowed.
                        pObj->parseDemicalNumber.dotAllowed = false;

                        // since the exp-character faced, white-character shall be allowed,
                        // ... but this situation is only possible if white-characters has
                        // ... been already faced before exp-character, thus white-character
                        // ... is already allowed.
                        (void)pObj->parseDemicalNumber.whiteAllowed; // already set

                        // * since the exp-character faced, digits shall be allowed.
                        pObj->parseDemicalNumber.digitAllowed = true;

                        // since the exp-character faced, sign-character shall be allowed.
                        pObj->parseDemicalNumber.signAllowed = true;
                    }

                    // * since the exp-character faced, terminating characters are disallowed
                    pObj->parseDemicalNumber.termAllowed = false;

                    // skip character
                    continue;
                }
            }

            // unsupported character faced: break with 'failed' status
            pObj->error = SCPI_ERROR_INVALID_NUMERIC_CHAR;
            pObj->pErrorMsg = SCPI_ERROR_INVALID_NUMERIC_CHAR_MSG;
            pObj->head = pObj->str - 1;
            pObj->tail = pObj->str;
            status = eScpiParserStatus_failed;
            break;
         }

         // If no unsupported character faced (just buffer ran out): eScpiParserStatus_need_data and
         // ... end-of-message indicator is set, or: 
         // ... if unsupported character faced: eScpiParserStatus_failed 
         if( eScpiParserStatus_failed == status || ( eScpiParserStatus_need_data == status && pObj->bEndMessage ) )
         {
             if( eScpiParserStatus_failed == status )
             {
                 pObj->str--; // roll back the iterator to previous supported character
             }

             // easy... Let's check the mantissa:
             if( pObj->parseDemicalNumber.manitssaOk )
             {
                 // the mantissa is ok, then let's check
                 // ... the exponent part only if the parse stage is search-for-exponent:
                 if( pObj->parseDemicalNumber.parseStage )
                 {
                     // exponent expected:
                     // Let's check if valid exponent found:
                     if( pObj->parseDemicalNumber.exponentOk )
                     {
                         // valid exponent found!
                         // Calculate the entity length:                         
                         // LENGTH = @str - @head
                         // Set the length:
                         pObj->tail = pObj->str;
                         pObj->type = eScpiEntityTypeDemicalExpNumber; // set the entity type: mantissa+exponent
                         status = eScpiParserStatus_success;
                                                               
                         // reset error code/status
                         pObj->error = SCPI_ERROR_SUCCESS;
                         pObj->pErrorMsg = NULL;
                     } else { /* no valid mantissa found -> error */ }
                 }
                 else     
                 {
                     // no exponent even announced, just end of mantissa!

                     // Calculate the entity length:                     
                     // LENGTH = @str - @head
                     // Set the length:
                     pObj->tail = pObj->str;
                     if( pObj->parseDemicalNumber.dotFound )
                     pObj->type = eScpiEntityTypeDemicalFloatNumber; // set the entity type: only mantissa
                     else
                     pObj->type = eScpiEntityTypeDemicalIntegerNumber; // set the entity type: integer (mantissa)
                     // reset error code/status
                     pObj->error = SCPI_ERROR_SUCCESS;
                     pObj->pErrorMsg = NULL;

                     status = eScpiParserStatus_success;
                 }
             } else { /* no valid mantissa found -> error */ }
         } else { /* Impossible: eScpiParserStatus_success; Useless: eScpiParserStatus_invalid */  }
     }

     return status;
 }
 // =================================================================================================================
 static eScpiParserStatus_t parseNonDemicalNumber( xParseEntry_t * xObj );
 static eScpiParserStatus_t parseDemicalNumber( xParseEntry_t * xObj );

 // @parseNumber_fParsers[]
 // Array of parser functions to be used in attempts to parse numeric value by @parseNumber routine 
 eScpiParserStatus_t (* const parseNumber_fParsers[2])( xParseEntry_t * xObj ) = 
 {
    parseNonDemicalNumber , parseDemicalNumber // order is important!
 };

 // =================================================================================================================
 // @parseNumber
 // "Parser-function", parses a SCPI Demical Numeric Program Data and SCPI Hexademical/Octal/Binary Numeric Program Data 
 // References:
 //     "7.7.2 <DECIMAL NUMERIC PROGRAM DATA>", [1]
 //     "7.7.2.2 Encoding Syntax", [1]
 //     "7.7.4 <NONDECIMAL NUMERIC PROGRAM DATA>", [1]
 //     "7.7.4.2 Encoding Syntax", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseNumber( xParseEntry_t * xObj )
 {
    eScpiParserStatus_t status = eScpiParserStatus_failed;

    sParseEntry_t * pObj = (sParseEntry_t*)xObj;
    int32_t nParserIdx = 0;

    if( ! pObj->bContextKept )
    {
       // backup parser entry point (save iterators)
       parserBackupContext( pObj, &pObj->parseNumber_xSaveObj );

       // backup parser index (reset index in the storage)
       parserBackupContextValue( &pObj->parseNumber_xSaveObj, nParserIdx );
    }
    else
    {
       // restore parser index
       parserRestoreContextValue( &pObj->parseNumber_xSaveObj, &nParserIdx );
    }

L_parseNumber_DO:

    // try parse
    switch( status = parseNumber_fParsers[nParserIdx]( xObj ), status )
    {
       // parser need more data to decide
       case eScpiParserStatus_need_data:
       {
            // backup parser index (update index in the storage)
            parserBackupContextValue( &pObj->parseNumber_xSaveObj, nParserIdx );

            // return original status to the caller
            (void)status;
       }
       break;

       case eScpiParserStatus_failed:
       {
            // parser failed

            // Check for special condition:
            if( parseNumber_fParsers[nParserIdx] == parseNonDemicalNumber )
            if( pObj->parseNonDemicalNumber.foundNumericChar )
            {
                // @parseNonDemicalNumber failed and the numeric system character was found. 
                // Do not try to parse using @parseDemicalNumber to keep error code and condition.
                // Parsing using @parseDemicalNumber is impossible any way ('#' character)
                break;
            }

            // is there another parser?
            if( (1+nParserIdx) < cellsof(parseNumber_fParsers) )
            {
                // yep, try this
                nParserIdx++;

                // backup parser context again (update index in the storage)
                parserBackupContextValue( &pObj->parseNumber_xSaveObj, nParserIdx );

                // restore parser iterators
                parserRestoreContext( pObj, &pObj->parseNumber_xSaveObj );

                // reset error status code
                pObj->error = SCPI_ERROR_SUCCESS;

                // try another parser
                goto L_parseNumber_DO;
            }

            // return original status to the caller
            (void)status;
       }
       break;

       case eScpiParserStatus_success:
       {
            // succeeded
            // return original status to the caller
            (void)status;
       }
       break;

       case eScpiParserStatus_invalid:
       {
            // wrong param
            // return original status to the caller
            (void)status;
       }
       break;

       default:
            // unexpected code
            status = eScpiParserStatus_invalid;
            my_assert( false );
    }
    
    return status;
 }
 // =================================================================================================================
 // @parseNonDemicalNumber
 // "Parser-function", parses a SCPI Hexademical/Octal/Binary Numeric Program Data ()
 // References:
 //     "7.7.4 <NONDECIMAL NUMERIC PROGRAM DATA>", [1]
 //     "7.7.4.2 Encoding Syntax", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 static eScpiParserStatus_t parseNonDemicalNumber( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_need_data;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                            // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
              pObj->parseNonDemicalNumber.allow0_1 = false;    
              pObj->parseNonDemicalNumber.allow0_7 = false;    
              pObj->parseNonDemicalNumber.allow0_f = false;    
              pObj->parseNonDemicalNumber.allowNumChar = false;
              pObj->parseNonDemicalNumber.foundNumericChar = false;
              pObj->parseNonDemicalNumber.digits = 0;
         }

         // walk til the end of the buffer or message separator is faced
         while( pObj->str != pObj->tail && (!scpi_ismsgsep(*pObj->str)) )
         {
              char character = *(pObj->str++);

              // check if binary character are allowed:
              if( pObj->parseNonDemicalNumber.allow0_1 )
              {
                  // if the character fits to the filter: digits 0..1
                  if( '0' == character || '1' == character )
                  {
                       pObj->parseNonDemicalNumber.digits++; // take the digit in account
                       // skip character
                       continue;
                  }
              }

              // check if octal character are allowed:
              if( pObj->parseNonDemicalNumber.allow0_7 )
              {
                  // if the character fits to the filter: digits 0..7
                  if( '0' <= character && '7' >= character )
                  {
                       pObj->parseNonDemicalNumber.digits++; // take the digit in account
                       // skip character
                       continue;
                  }
              }
                           
              // check if octal character are allowed:
              if( pObj->parseNonDemicalNumber.allow0_f )
              {
                  // if the character fits to the filter: hex-chars
                  if( scpi_ishex( character) )
                  {
                       pObj->parseNonDemicalNumber.digits++; // take the digit in account
                       // skip character
                       continue;
                  }
              }

              // check if numeric system designator is allowed:
              if( ! pObj->parseNonDemicalNumber.allowNumChar )
              {
                  // not yet, thus the '#' is expected to detect the begining of the entity

                  // check if the '#' character is faced:
                  if( '#' == character )
                  {
                       // yes, the entity start is detected
                       pObj->parseNonDemicalNumber.allowNumChar = true;

                       // set indicator: numeric system character found
                       pObj->parseNonDemicalNumber.foundNumericChar = true; // pass to parseNumber

                       // skip character
                       continue;
                  }

                  status = eScpiParserStatus_failed; // invalid character faced
                  pObj->error = SCPI_ERROR_INVALID_NUMERIC_CHAR;
                  pObj->pErrorMsg = SCPI_ERROR_INVALID_NUMERIC_CHAR_MSG;
                  pObj->head = pObj->str - 1;
                  pObj->tail = pObj->str;
                  break;
              }
              else
              {
                  // yes, check for the numeric system designator only if no the numeric
                  // ... system designator has been faced yet:
                  if( !pObj->parseNonDemicalNumber.allow0_1
                      &&
                      !pObj->parseNonDemicalNumber.allow0_7
                      &&
                      !pObj->parseNonDemicalNumber.allow0_f )
                  {
                      switch( character )
                      {
                          case 'B':
                          case 'b':  pObj->parseNonDemicalNumber.allow0_1 = true; continue;
                          case 'Q':
                          case 'q':  pObj->parseNonDemicalNumber.allow0_7 = true; continue;
                          case 'H':
                          case 'h':  pObj->parseNonDemicalNumber.allow0_f = true; continue;
                      }

                      status = eScpiParserStatus_failed; // invalid character faced: unknown designator 
                      pObj->error = SCPI_ERROR_NUMERIC_DATAERROR;
                      pObj->pErrorMsg = SCPI_ERROR_NUMERIC_DATAERROR_MSG;
                      pObj->head = pObj->str - 1;
                      pObj->tail = pObj->str;
                      break;
                  }
                  else
                  {
                      // If @character here is a digit or a letter, it is probably invalid character in the number
                      // Do not consider this character as an end of the number, instead of this it is better to generate an error.
                      if( 0 == pObj->parseNonDemicalNumber.digits || isdigit(character) || isalpha(character) ) 
                      {
                          // No one of @.allow0_* rules match, and no digits faced yet
                          status = eScpiParserStatus_failed; // invalid character faced: 
                          pObj->error = SCPI_ERROR_INVALID_NUMERIC_CHAR;
                          pObj->pErrorMsg = SCPI_ERROR_INVALID_NUMERIC_CHAR_MSG;
                          pObj->head = pObj->str - 1;
                          pObj->tail = pObj->str;
                          break;
                      }
                      else
                      {
                          status = eScpiParserStatus_success; // the entity end found

                          // reset error code/status
                          pObj->error = SCPI_ERROR_SUCCESS;
                          pObj->pErrorMsg = NULL;

                          // roll back the iterator due to current character is invalid
                          pObj->str--;

                          // exit with success status
                          break;
                      }
                  }
              }
         }

         // check the conditions:
         // - if it is required more data and no more data is expected ( @bEndMessage is set)
         // - if the success status set
         if(   (eScpiParserStatus_need_data == status && pObj->bEndMessage) 
            || (eScpiParserStatus_success == status ) )
         {
            // check if at least one numeric character found:
            if( 0 < pObj->parseNonDemicalNumber.digits )
            {
               // set the entity length:
               // LENGTH = @str - @head
               pObj->tail = pObj->str; // set @tail to indicate the length
               
               // set the entity type
               if( pObj->parseNonDemicalNumber.allow0_1 )
               {
                   pObj->type = eScpiEntityTypeBinNumber;  // binary
                   pObj->head += 2; // skip '#B'
               }
               else if( pObj->parseNonDemicalNumber.allow0_7 )
               {
                   pObj->type = eScpiEntityTypeOctNumber;  // octal
                   pObj->head += 2; // skip '#Q'
               }
               else
               {
                   pObj->type = eScpiEntityTypeHexNumber;  // hexademical
                   pObj->head += 2; // skip '#H'
               }

               status = eScpiParserStatus_success;
            }
            else
            {
               status = eScpiParserStatus_failed; // error, no one numeric character found
               pObj->error = SCPI_ERROR_NUMERIC_DATAERROR;
               pObj->pErrorMsg = SCPI_ERROR_NUMERIC_DATAERROR_MSG;
            }
         }
     }

     return status;
 }

 // ================================================================================================================= 
 // @parseProgramDataSeparator
 // "Parser-function", parses a SCPI Program Data Separator
 // References:
 //   "7.4 Separator Functional Elements", [1]
 //   "7.4.2.2 Encoding Syntax", [1]
 //   "7.5 <PROGRAM MESSAGE TERMINATOR>", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseProgramDataSeparator( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_need_data;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                            // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
              pObj->parseProgramDataSeparator.sepFound = false;                  
         }

         // walk til the end of the buffer
         while( pObj->str != pObj->tail )
         {
              char character = *(pObj->str++);

              // check for white-character
              if( scpi_iswhite( character ) )
              {
                  continue; // skip character
              }

              // check for NL-character
              if( scpi_isnl( character ) )
              {
                  pObj->parseProgramDataSeparator.sepFound = true;
                  pObj->type = eScpiEntityType_Service_MsgTerm;
                  status = eScpiParserStatus_success; // NL-character terminates Program Data entity

                  pObj->head = (pObj->str - 1);
                  pObj->tail = pObj->str;

                  // reset error code/status
                  pObj->error = SCPI_ERROR_SUCCESS;
                  pObj->pErrorMsg = NULL;

                  break; 
              }

              // check if the data separator character is found
              if( !pObj->parseProgramDataSeparator.sepFound )
              {
                  // no, search for data separator character
                  if( scpi_isdatasep( character ) )
                  {
                      pObj->parseProgramDataSeparator.sepFound = true; // found
                      pObj->type = eScpiEntityType_Service_DataSep;
                      pObj->head = (pObj->str - 1);
                      pObj->tail = pObj->str;
                      status = eScpiParserStatus_success; // valid character

                      // reset error code/status
                      pObj->error = SCPI_ERROR_SUCCESS;
                      pObj->pErrorMsg = NULL;
                      break; // end of search
                  }
              }

              pObj->head = (pObj->str - 1);
              pObj->tail = pObj->str;
              status = eScpiParserStatus_failed; // unexpected character
              pObj->error = SCPI_ERROR_INVSEP_ERROR;
              pObj->pErrorMsg = SCPI_ERROR_INVSEP_ERROR_MSG;
              break;
         }

         // check if it is required to receive more data to recognize:
         if( eScpiParserStatus_need_data == status )
         {
              // check if this message is the last one?
              if( pObj->bEndMessage )
              {
                  // it is not required to the separator must be found
                  // ... the last message's character is reached.
                  // The end-of-message signal represents another data
                  // ... separator, so thus, the data separator is found.
                  status = eScpiParserStatus_success;

                  pObj->type = eScpiEntityType_Service_MsgTerm;

                  // reset error code/status
                  pObj->error = SCPI_ERROR_SUCCESS;
                  pObj->pErrorMsg = NULL;
              }
              
              // Note: if no unexpected character has been faced yet it means that
              // ... the data separator still continues.
         }
         else
         // check if an unexpected character faced:
         if( eScpiParserStatus_failed == status )
         {
             // check if the separator character has been found?
             if( pObj->parseProgramDataSeparator.sepFound )
             {
                 status = eScpiParserStatus_success;

                 pObj->type = eScpiEntityType_Service_MsgTerm;

                 // reset error code/status
                 pObj->error = SCPI_ERROR_SUCCESS;
                 pObj->pErrorMsg = NULL;
             }

             // Note: if no separator character has been faced yet while an unexpected
              // ... character already faced it means that the data separator not found.
         }
     }

     return status;
 }

 // ================================================================================================================= 
 // @parseProgramDataSeparator
 // "Parser-function", parses a SCPI Program Header Separator
 // References:
 //   "7.4.3 <PROGRAM HEADER SEPARATOR>, [1]
 //   "7.4.3.2 Encoding Syntax", [1] 
 //   "7.5 <PROGRAM MESSAGE TERMINATOR>", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseProgramHeaderSeparator( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_need_data;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                                // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
              pObj->parseProgramHeaderSeparator.sepFound = false;                  
         }

         // walk til the end of the buffer
         while( pObj->str != pObj->tail )
         {
              char character = *(pObj->str);

              // check for white-character
              if( scpi_iswhite( character ) )
              {
                  if( ! pObj->parseProgramHeaderSeparator.sepFound )
                  {
                      pObj->head = pObj->str;
                  }

                  pObj->parseProgramHeaderSeparator.sepFound = true; // at least one white-character found
                  pObj->type = eScpiEntityType_Service_HdrSep;
                  pObj->str++; // skip character
                  continue; // skip character
              }

              // check for NL-character
              if( scpi_isnl( character ) )
              {
                  pObj->parseProgramHeaderSeparator.sepFound = true; // at least one white-character found
                  pObj->type = eScpiEntityType_Service_MsgTerm;
                  pObj->head = pObj->str - 1;
                  pObj->tail = pObj->str;
                  status = eScpiParserStatus_success; // NL character terminates the program header

                  // reset error code/status
                  pObj->error = SCPI_ERROR_SUCCESS;
                  pObj->pErrorMsg = NULL;
                  break;
              }

              // check if an unexpected character found
              // check if at least one white-character found
              if( pObj->parseProgramHeaderSeparator.sepFound )
              {
                  // yes, it is success
                  // At least white character found thus the separator found too
                  status = eScpiParserStatus_success;
             
                  pObj->type = eScpiEntityType_Service_HdrSep;
                  (void)pObj->head;
                  pObj->tail = pObj->str;
             
                  // reset error code/status
                  pObj->error = SCPI_ERROR_SUCCESS;
                  pObj->pErrorMsg = NULL;

                  break;
              }

              pObj->head = (pObj->str - 1);
              pObj->tail = pObj->str;
              status = eScpiParserStatus_failed; // unexpected character found
              pObj->error = SCPI_ERROR_INVSEP_ERROR;
              pObj->pErrorMsg = SCPI_ERROR_INVSEP_ERROR_MSG;
              break;
         }

         // check if there no enough data to detect the end of separator:
         if( eScpiParserStatus_need_data == status )
         {
             // Note: AT LEAST ONE WHITE CHARACTER FOUND due to the @eScpiParserStatus_need_data status set

             // check if this data portion is the last one:
             if( pObj->bEndMessage )
             {
                 // At least white character found thus the separator found too
                 status = eScpiParserStatus_success;

                 pObj->type = eScpiEntityType_Service_MsgTerm;
                 pObj->tail = pObj->str;

                 // reset error code/status
                 pObj->error = SCPI_ERROR_SUCCESS;
                 pObj->pErrorMsg = NULL;
             }             
         }
     }

     return status;
 }

 // ================================================================================================================= 
 // @parseProgramMessageSeparator
 // "Parser-function", parses a SCPI Program Message Separator
 // References:
 //   "7.4.1 <PROGRAM MESSAGE UNIT SEPARATOR>", [1]
 //   "7.4.1.2 Encoding Syntax", [1]
 //   "7.5 <PROGRAM MESSAGE TERMINATOR>", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseProgramMessageSeparator( xParseEntry_t * xObj )
 {     
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_need_data;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                            // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
              pObj->parseProgramMessageSeparator.sepFound = false;                  
         }

         // walk til the end of the buffer
         while( pObj->str != pObj->tail )
         {
              char character = *(pObj->str++);

              if( !pObj->parseProgramMessageSeparator.sepFound )
              {
                  // check for white-character
                  if( scpi_iswhite( character ) )
                  {
                      pObj->tail = pObj->str;
                      continue; // skip character
                  }

                  // check for message-separator-character
                  if( scpi_ismsgsep( character ) )
                  {
                      pObj->parseProgramMessageSeparator.sepFound = true;
                      pObj->type = eScpiEntityType_Service_MsgSep;
                      pObj->head = pObj->str - 1;
                      pObj->tail = pObj->str;
                      break; // separator found
                  }
              }

              pObj->head = (pObj->str - 1);
              pObj->tail = pObj->str;
              status = eScpiParserStatus_failed; // unexpected character
              pObj->error = SCPI_ERROR_INVSEP_ERROR;
              pObj->pErrorMsg = SCPI_ERROR_INVSEP_ERROR_MSG;
              break;
         }

         if( eScpiParserStatus_need_data == status )
         {
             if( pObj->parseProgramMessageSeparator.sepFound )
             {
                 status = eScpiParserStatus_success; // separator found 

                 pObj->type = eScpiEntityType_Service_MsgTerm;

                 // reset error code/status
                 pObj->error = SCPI_ERROR_SUCCESS;
                 pObj->pErrorMsg = NULL;
             }
         }
     }

     return status;
 }
 // ================================================================================================================= 
 // @parseEndOfCommand
 // "Parser-function", searches end of program command unit. 
 // References:
 //   "7.4.1 <PROGRAM MESSAGE UNIT SEPARATOR>", [1]
 //   "7.4.1.2 Encoding Syntax", [1]
 //   "7.5 <PROGRAM MESSAGE TERMINATOR>", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseEndOfCommand( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_need_data;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                            // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
              pObj->parseEndOfCommand.sepFound = false;                  
         }

         // walk til the end of the buffer
         while( pObj->str != pObj->tail )
         {
              char character = *(pObj->str++);

              if( !pObj->parseEndOfCommand.sepFound )
              {
                  // check for white-character
                  if( scpi_iswhite( character ) )
                  {
                      continue; // skip character
                  }

                  // check for message-separator-character
                  if( scpi_ismsgsep( character ) )
                  {
                      pObj->parseEndOfCommand.sepFound = true;
                      pObj->head = (pObj->str - 1);
                      pObj->tail = pObj->str;
                      pObj->type = eScpiEntityType_Service_MsgSep;
                      break; // separator found
                  }

                  // check for message-terminator-character
                  if( scpi_isnl( character ) )
                  {
                      pObj->parseEndOfCommand.sepFound = true;
                      pObj->head = (pObj->str - 1);
                      pObj->tail = pObj->str;
                      pObj->type = eScpiEntityType_Service_MsgTerm;
                      break; // separator found
                  }
              }

              pObj->head = (pObj->str - 1);
              pObj->tail = pObj->str;
              status = eScpiParserStatus_failed; // unexpected character
              pObj->error = SCPI_ERROR_INVSEP_ERROR;
              pObj->pErrorMsg = SCPI_ERROR_INVSEP_ERROR_MSG;
              break;
         }

         if( eScpiParserStatus_need_data == status )
         {
             if( pObj->parseEndOfCommand.sepFound )
             {
                 status = eScpiParserStatus_success; // separator found 

                 pObj->type = eScpiEntityType_Service_MsgTerm;

                 // reset error code/status
                 pObj->error = SCPI_ERROR_SUCCESS;
                 pObj->pErrorMsg = NULL;
             }
         }
     }

     return status;
 } 
 // =================================================================================================================   
 // @parseWhiteSequence
 // "Parser-function", searches for white characters sequence or NL-terminator
 // References:
 //   "7.4.1.2 Encoding Syntax", [1] 
 //   "7.5 <PROGRAM MESSAGE TERMINATOR>", [1]
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 // Note: this function does not modify @str iterator if no white character found
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseWhiteSequence( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 != ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head)
         && (0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str)) )
     {
         status = eScpiParserStatus_need_data;  // forward status set: the default 'eScpiParserStatus_invalid' shall
                                            // ... not be returned due to the context will be changed.

         // if the context has been cleaned up
         if( ! pObj->bContextKept )  
         {
              pObj->parseWhiteSequence.whiteFound = false;
              pObj->parseWhiteSequence.nlFound = false;
         }

         // walk til the end of the buffer
         while( pObj->str != pObj->tail )
         {
              char character = *(pObj->str);

              // check for white-character
              if( scpi_iswhite( character ) )
              {
                  pObj->parseWhiteSequence.whiteFound = true;
                  pObj->str++; // skip white character
                  (void)pObj->head; // keep @head pointer to point to the start of white-sequence
                  continue; // skip character
              }

              // check for white-character
              if( scpi_isnl( character ) )
              {
                  pObj->parseWhiteSequence.nlFound = true;
                  (void)pObj->str++; // skip NL-character
                  (void)pObj->head; // keep @head pointer to point to the start of white-sequence
                  break; // stop searching
              }

              if( !pObj->parseWhiteSequence.whiteFound )
              {
                  pObj->head = (pObj->str - 1);
                  pObj->tail = pObj->str;
                  status = eScpiParserStatus_failed; // unexpected character
                  pObj->error = SCPI_ERROR_INVALID_CHARACTER;
                  pObj->pErrorMsg = SCPI_ERROR_INVALID_CHARACTER_MSG;
              }

              break; // non-white character found
         }

         if( eScpiParserStatus_need_data == status )
         {
             if( pObj->parseWhiteSequence.whiteFound )
             {
                 if( pObj->bEndMessage )
                 {
                     // reset error code/status
                     pObj->error = SCPI_ERROR_SUCCESS;
                     pObj->pErrorMsg = NULL;
                     pObj->tail = pObj->str; // update the tail pointer
                     pObj->type = eScpiEntityType_Service_White;

                     status = eScpiParserStatus_success;
                 }
             }
             else
             if( pObj->parseWhiteSequence.nlFound )
             {
                 // reset error code/status
                 pObj->error = SCPI_ERROR_SUCCESS;
                 pObj->pErrorMsg = NULL;
                 pObj->tail = pObj->str; // update the tail pointer
                 pObj->type = eScpiEntityType_Service_MsgTerm;

                 status = eScpiParserStatus_success;
             }
         }
     }

     return status;
 }
 // =================================================================================================================   
 // @checkNotEndOfString
 // "Parser-function", checks if the parser context not reached the end of string
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'. 
 // Returns:
 //   eScpiParserStatus_failed - error, end-of-string is reached
 //   eScpiParserStatus_success - success, end-of-string is not reached
 //   eScpiParserStatus_invalid - error, invalid parameters
 eScpiParserStatus_t checkNotEndOfString( xParseEntry_t * xObj )
 {
     sParseEntry_t * pObj = (sParseEntry_t*)xObj;

     eScpiParserStatus_t status = eScpiParserStatus_invalid;
   
     if( NULL != pObj && NULL != pObj->str && 0 <= ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->head) 
         && 0 <= ((ptrdiff_t)pObj->str - (ptrdiff_t)pObj->head) )
     {
         if( 0 < ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str) )
         {
             status = eScpiParserStatus_success;
         }
         else if( 0 == ((ptrdiff_t)pObj->tail - (ptrdiff_t)pObj->str) )
         {
             status = eScpiParserStatus_failed;
         }
     }

     return status;
 }
 // =================================================================================================================  
 #pragma pack(push,1)
 static const struct
 {
   eScpiParserStatus_t (*f)( xParseEntry_t * xObj );
   uint8_t type;
 } 
 parseArgumentsMap[] = 
 {
   { parseCharacter, eScpiArg_Character },
   { parseString, eScpiArg_String },
   { parseArbitraryBlock, eScpiArg_Datablock },
   { parseNumber, eScpiArg_Numeric },
   { parseDemicalNumber, eScpiArg_Numeric_Demical },
   { parseNonDemicalNumber, eScpiArg_Numeric_NonDemical },
   { parseDemicalNumber , eScpiArg_Array_Decimal }
 }; 
 #pragma pack(pop)
 // =================================================================================================================  
 // @parseArguments
 // Common parser function to analyze and recognize command arguments using the
 // template preassigned by @DECLARE_SCPI_ARGS macro.
 // Parameters:
 //     @xObj - parser context, must be prepared by @prepareParserContext
 // ... before each call. If it is needed to continue the processing, the
 // ... @bKeepContext parameter duing the call @prepareParserContext must 
 // ... be set to 'true', and otherwise, to restart parsing the parameter
 // ... must be set to 'false'.
 //     @argTokens - array of argument string tokens to store parameters iterators;
 //     @argTypes - array of argument types [eScpiArgType_t] to set the parameters parsing methods;
 //     @entityTypes - array of entity types [eScpiEntityType_t] to be written after successful call; optional;
 //     @argN - number of arguments (including optional and mandatory ones);
 //     @argOptionalN - number of optional only arguments;
 //     @pArgParsed - pointer to the variable to store the number of successfully 
 // ... parsed arguments, valid only if eScpiParserStatus_success status is returned,
 // ... Otherwise, if the status is eScpiParserStatus_failed this value indicates
 // ... the index of erroneous parameter. Can not be NULL.
 // Returns:
 //   eScpiParserStatus_failed - error, can not parse data;
 //   eScpiParserStatus_invalid - error, invalid parameters;
 //   eScpiParserStatus_success - success, the string has been successfully parsed;
 //   eScpiParserStatus_need_data - warning, the string can not be parsed due to
 //                             there no enough data to process.
 eScpiParserStatus_t parseArguments( xParseEntry_t * xObj,
                                     sStrToken_t * argTokens,
                                     const uint8_t * argTypes,
                                     uint8_t * entityTypes,
                                     size_t argN,
                                     size_t argOptionalN, 
                                     uint8_t * pArgParsed )
 {
     my_assert( xObj );
     my_assert( argTokens );
     my_assert( pArgParsed );
     my_assert( argN >= argOptionalN );
     my_assert( argTypes || argN == 0 );

     sParseEntry_t * pObj = (sParseEntry_t*)xObj;
     eScpiParserStatus_t status = eScpiParserStatus_invalid;

     pObj->error = SCPI_ERROR_SYNTAX_ERROR;
     pObj->pErrorMsg = SCPI_ERROR_SYNTAX_ERROR_PARAM_MSG; 

     // check parameters
     if( NULL == xObj && NULL == argTokens && (NULL == argTypes && 0 != argN) && NULL == pArgParsed && (argN < argOptionalN) )
     {
         return eScpiParserStatus_invalid;
     }

     // special condition: no parameters are allowed
     if( 0 == argN )
     {
         status = parseEndOfCommand( xObj );

         if( status != eScpiParserStatus_success )
         {
             pObj->error = SCPI_ERROR_PARAMETER_NOTALLOWED;
             pObj->pErrorMsg = SCPI_ERROR_PARAMETER_NOTALLOWED_MSG; 
         }

         // no break, no return, 'for' will not be executed due to argN==0
     }

     bool parseBreak = false;
     bool trailingDataSep = false;
     size_t nArgs = 0;
     for( size_t a = 0; (a < argN) && (!parseBreak); ++a )
     {
        *pArgParsed = a; // indicate current parameter index (failed case)

        eScpiParserStatus_t (*fParser)( xParseEntry_t * xObj ) = NULL;

        // search for parser routine by the specified argument type
        for( size_t f = 0; f < sizeof(parseArgumentsMap)/sizeof(*parseArgumentsMap); ++f )
        {
              if( parseArgumentsMap[f].type == argTypes[a] )
              {
                  // parser found
                  fParser = parseArgumentsMap[f].f;
                  break;
              }
        }

        if( NULL == fParser )
        {
            // parser not found
            status = eScpiParserStatus_failed;
            break;
        }

        // keep tail pointer before searching for white characters        
        const char * _tail = pObj->tail;

        // skip white characters
        status = parseWhiteSequence( xObj );

        // check if NL-character found
        if( status == eScpiParserStatus_success )
        {
            if( eScpiEntityType_Service_MsgTerm == pObj->type )
            {
                goto L_parseArguments_TERM;
            }
        }

        // restore tail pointer before searching for parameter        
        pObj->tail = _tail;

        // move forward @head pointer to skip white sequence
        pObj->head = pObj->str;

        // check for end-of-string
        if( eScpiParserStatus_success == checkNotEndOfString( xObj ) )
        {
            // call the parser
            status = fParser( xObj );

            // check result
            if( status != eScpiParserStatus_success )
            {
                // parsing error

                // check for specific error case: message separator (intercept)
                if( SCPI_ERROR_INVALID_CHARACTER == pObj->error && scpi_ismsgsep( *pObj->head ) )
                {   
                    // replace "error condition" -> "message termination"       
                    pObj->type = eScpiEntityType_Service_MsgTerm;
                    status = eScpiParserStatus_success;
                    goto L_parseArguments_TERM;
                }

                break;
            }
            else
            {
                trailingDataSep = false;
            }
        }
        else
        {
            // end of string: error condition
            pObj->type = eScpiEntityType_Service_MsgTerm;
            goto L_parseArguments_TERM;
        }

        argTokens[nArgs].shead = pObj->head;
        argTokens[nArgs].stail = pObj->tail;

        if( NULL != entityTypes )
        {
            // write entity type to the output buffer
            entityTypes[nArgs] = pObj->type;
        }

        nArgs++; // increment number of parsed parameters

        // restore tail pointer before searching for separator        
        pObj->tail = _tail;

        // move forward @head pointer to skip the separator
        pObj->head = pObj->str;

        // check for end-of-string
        if( eScpiParserStatus_success == checkNotEndOfString( xObj ) )
        {
            status = parseProgramDataSeparator( xObj );
            
            if( eScpiParserStatus_success != status )
            {
                // check for specific error case: message separator (intercept)
                if( SCPI_ERROR_INVSEP_ERROR == pObj->error && scpi_ismsgsep( *pObj->head ) )
                {   
                    // replace "error condition" -> "message termination"
                    pObj->type = eScpiEntityType_Service_MsgTerm;
                    pObj->error = SCPI_ERROR_SUCCESS;
                    status = eScpiParserStatus_success;
                    goto L_parseArguments_TERM;
                }

                break;
            }
        }
        else
        {
            pObj->type = eScpiEntityType_Service_MsgTerm;

            goto L_parseArguments_TERM;
        }
L_parseArguments_TERM:
        switch( pObj->type )
        {
           case eScpiEntityType_Service_MsgTerm:
           case eScpiEntityType_Service_MsgSep:
           {
              if( (nArgs) < argN - argOptionalN ) // not all mandatory parameters parsed
              {
                  // error: missing parameter
                  status = eScpiParserStatus_failed;
                  pObj->head = pObj->tail = pObj->str = _tail; // reset all the token stats to not point to any token
                  pObj->error = SCPI_ERROR_MISSING_PARAMETER;
                  pObj->pErrorMsg = SCPI_ERROR_MISSING_PARAMETER_MSG; 
              }
              else
              {
                  // Check for trailing data separator
                  if( trailingDataSep )
                  {
                      // error: extra parameter
                      status = eScpiParserStatus_failed;
                      pObj->error = SCPI_ERROR_INVSEP_ERROR;
                      pObj->pErrorMsg = SCPI_ERROR_INVSEP_ERROR_MSG;
                      
                      // reset all the token stats to not point to any token                  
                      pObj->head = pObj->tail = pObj->str = _tail;
                  }
              }
 
              (void)status;
              parseBreak = true; // message terminator faced
           }
           break;

           case eScpiEntityType_Service_DataSep:
           {
              if( nArgs >= argN ) // all parameters already parsed
              {
                  // error: extra parameter
                  status = eScpiParserStatus_failed;
                  pObj->error = SCPI_ERROR_PARAMETER_NOTALLOWED;
                  pObj->pErrorMsg = SCPI_ERROR_PARAMETER_NOTALLOWED_MSG;

                  // reset all the token stats to not point to any token due to it is impossible
                  // to get know where is the end of extra parameter in general case (e.g. if the string is passed).
                  pObj->head = pObj->tail = pObj->str = _tail;
                  parseBreak = true;
              }

              trailingDataSep = true;
           }
           break;

           default:
              status = eScpiParserStatus_failed;
              pObj->error = SCPI_ERROR_SYNTAX_ERROR;
              pObj->pErrorMsg = SCPI_ERROR_SYNTAX_ERROR_PARAM_MSG;
        }

        // Restore iterators only if parsing is continuing.
        // Otherwise it is required to leave @head/@tail pointing to the
        // ... last found entity to search next command correctly.
        if( ! parseBreak )
        {
            // restore iterators before searching next entity
            pObj->head = pObj->str;
            pObj->tail = _tail;
        }

        *pArgParsed = (nArgs); // indicate number of parameters parsed (success state)
     }

     return status;
 }
 
 eScpiParserStatus_t parseArrayArguments( xParseEntry_t * xObj,
                                          uint8_t * argTokens,
                                          size_t * argNumber,
                                          const uint8_t * argTypes,
                                          uint8_t * entityTypes,
                                          size_t argN,
                                          size_t argOptionalN, 
                                          uint8_t * pArgParsed )
 {
     my_assert( xObj );
     my_assert( argTokens );
     my_assert( pArgParsed );
     my_assert( argN >= argOptionalN );
     my_assert( argTypes || argN == 0 );
     my_assert( argNumber );

     sParseEntry_t * pObj = (sParseEntry_t*)xObj;
     eScpiParserStatus_t status = eScpiParserStatus_invalid;

     pObj->error = SCPI_ERROR_SYNTAX_ERROR;
     pObj->pErrorMsg = SCPI_ERROR_SYNTAX_ERROR_PARAM_MSG;

     // check parameters
     if( NULL == xObj && NULL == argTokens && (NULL == argTypes && 0 != argN) && NULL == pArgParsed && (argN < argOptionalN) )
     {
         return eScpiParserStatus_invalid;
     }

     // special condition: no parameters are allowed
     if( 0 == argN )
     {
         status = parseEndOfCommand( xObj );

         if( status != eScpiParserStatus_success )
         {
             pObj->error = SCPI_ERROR_PARAMETER_NOTALLOWED;
             pObj->pErrorMsg = SCPI_ERROR_PARAMETER_NOTALLOWED_MSG; 
         }

         // no break, no return, 'for' will not be executed due to argN==0
     }

     bool parseBreak = false;
     bool trailingDataSep = false;
     size_t nArgs = 0;
     
     for( size_t a = 0; (!parseBreak); ++a )
     {
        *pArgParsed = a; // indicate current parameter index (failed case)

        eScpiParserStatus_t (*fParser)( xParseEntry_t * xObj ) = NULL;

        // search for parser routine by the specified argument type
        for( size_t f = 0; f < sizeof(parseArgumentsMap)/sizeof(*parseArgumentsMap); ++f )
        {
              if( parseArgumentsMap[f].type == argTypes[0] )
              {
                  // parser found
                  fParser = parseArgumentsMap[f].f;
                  break;
              }
        }

        if( NULL == fParser )
        {
            // parser not found
            status = eScpiParserStatus_failed;
            break;
        }

        // keep tail pointer before searching for white characters        
        const char * _tail = pObj->tail;

        // skip white characters
        status = parseWhiteSequence( xObj );

        // check if NL-character found
        if( status == eScpiParserStatus_success )
        {
            if( eScpiEntityType_Service_MsgTerm == pObj->type )
            {
                goto L_parseArguments_TERM;
            }
        }

        // restore tail pointer before searching for parameter        
        pObj->tail = _tail;

        // move forward @head pointer to skip white sequence
        pObj->head = pObj->str;

        // check for end-of-string
        if( eScpiParserStatus_success == checkNotEndOfString( xObj ) )
        {
            // call the parser
            status = fParser( xObj );

            // check result
            if( status != eScpiParserStatus_success )
            {
                // parsing error

                // check for specific error case: message separator (intercept)
                if( SCPI_ERROR_INVALID_CHARACTER == pObj->error && scpi_ismsgsep( *pObj->head ) )
                {   
                    // replace "error condition" -> "message termination"       
                    pObj->type = eScpiEntityType_Service_MsgTerm;
                    status = eScpiParserStatus_success;
                    goto L_parseArguments_TERM;
                }

                break;
            }
            else
            {
                trailingDataSep = false;
            }
        }
        else
        {
            // end of string: error condition
            pObj->type = eScpiEntityType_Service_MsgTerm;
            goto L_parseArguments_TERM;
        }
        
        {
            sStrToken_t currentToken = {
                .shead = pObj->head,
                .stail = pObj->tail
            };
            
            sProcessNumericEntry_t Entry;
            sNumericRange_t range = 
            {
                .max.demicalInteger = 99,
                .min.demicalInteger = 0,
                .type = SCPI_NUMERIC_LIMIT_TYPE_I32
            };
            
            if(processNumericArgument( &Entry, &currentToken, pObj->type, &range )
               && *argNumber > nArgs)
            {
                argTokens[nArgs] = Entry.valueEntry.Value.demicalInteger;
            }
            else
            {
                parseBreak = true;
                goto L_parseArguments_TERM;
            }
        }

        if( NULL != entityTypes )
        {
            // write entity type to the output buffer
            entityTypes[nArgs] = pObj->type;
        }

        nArgs++; // increment number of parsed parameters

        // restore tail pointer before searching for separator        
        pObj->tail = _tail;

        // move forward @head pointer to skip the separator
        pObj->head = pObj->str;

        // check for end-of-string
        if( eScpiParserStatus_success == checkNotEndOfString( xObj ) )
        {
            status = parseProgramDataSeparator( xObj );
            
            if( eScpiParserStatus_success != status )
            {
                // check for specific error case: message separator (intercept)
                if( SCPI_ERROR_INVSEP_ERROR == pObj->error && scpi_ismsgsep( *pObj->head ) )
                {   
                    // replace "error condition" -> "message termination"
                    pObj->type = eScpiEntityType_Service_MsgTerm;
                    pObj->error = SCPI_ERROR_SUCCESS;
                    status = eScpiParserStatus_success;
                    goto L_parseArguments_TERM;
                }

                break;
            }
        }
        else
        {
            pObj->type = eScpiEntityType_Service_MsgTerm;

            goto L_parseArguments_TERM;
        }
L_parseArguments_TERM:
        switch( pObj->type )
        {
           case eScpiEntityType_Service_MsgTerm:
           case eScpiEntityType_Service_MsgSep:
           {
              if( (nArgs) < argN - argOptionalN ) // not all mandatory parameters parsed
              {
                  // error: missing parameter
                  status = eScpiParserStatus_failed;
                  pObj->head = pObj->tail = pObj->str = _tail; // reset all the token stats to not point to any token
                  pObj->error = SCPI_ERROR_MISSING_PARAMETER;
                  pObj->pErrorMsg = SCPI_ERROR_MISSING_PARAMETER_MSG; 
              }
              else
              {
                  // Check for trailing data separator
                  if( trailingDataSep )
                  {
                      // error: extra parameter
                      status = eScpiParserStatus_failed;
                      pObj->error = SCPI_ERROR_INVSEP_ERROR;
                      pObj->pErrorMsg = SCPI_ERROR_INVSEP_ERROR_MSG;
                      
                      // reset all the token stats to not point to any token                  
                      pObj->head = pObj->tail = pObj->str = _tail;
                  }
              }
 
              (void)status;
              parseBreak = true; // message terminator faced
           }
           break;

           case eScpiEntityType_Service_DataSep:
           {
              //if( nArgs >= argN ) // all parameters already parsed
              //{
                  // error: extra parameter
                  //status = eScpiParserStatus_failed;
                  //pObj->error = SCPI_ERROR_PARAMETER_NOTALLOWED;
                  //pObj->pErrorMsg = SCPI_ERROR_PARAMETER_NOTALLOWED_MSG;

                  // reset all the token stats to not point to any token due to it is impossible
                  // to get know where is the end of extra parameter in general case (e.g. if the string is passed).
                  //pObj->head = pObj->tail = pObj->str = _tail;
                  //parseBreak = true;
              //}

              trailingDataSep = true;
           }
           break;

           default:
              status = eScpiParserStatus_failed;
              pObj->error = SCPI_ERROR_SYNTAX_ERROR;
              pObj->pErrorMsg = SCPI_ERROR_SYNTAX_ERROR_PARAM_MSG;
        }

        // Restore iterators only if parsing is continuing.
        // Otherwise it is required to leave @head/@tail pointing to the
        // ... last found entity to search next command correctly.
        if( ! parseBreak )
        {
            // restore iterators before searching next entity
            pObj->head = pObj->str;
            pObj->tail = _tail;
        }

        *pArgParsed = (nArgs); // indicate number of parameters parsed (success state)
     }

     return status;
 }
 // ================================================================================================================= 
 static xParseEntry_t ctx;
 static char scpi_test_buffer[128] = {0};   
 static volatile bool scpi_test_exit = false;

 void scpi_test_buf_example( size_t scpi_test_id,
                             size_t scpi_test_subid,
                             char ** _scpi_buffer_ptr,
                             size_t * _scpi_buffer_len,
                             size_t * _scpi_message_len,
                             bool * _scpi_end_of_message,
                             bool * _scpi_keep_ctx,
                             const char *  * _entity_start,
                             size_t * _entity_length )
 {
     *_scpi_buffer_ptr = scpi_test_buffer;
     *_scpi_buffer_len = 1;
     *_scpi_end_of_message = false;
     *_scpi_keep_ctx = false;
     *_entity_start = NULL;
     *_entity_length = 0;
     *_scpi_message_len = 0;
     switch( scpi_test_id )
     {
        case 3: // Numbers:
        {
            switch( scpi_test_subid )
            {
              // Correct examples:
                case 0: strcpy( scpi_test_buffer, "3" ); break;
                case 1: strcpy( scpi_test_buffer, "-3" ); break;
                case 2: strcpy( scpi_test_buffer, ".3" ); break;
                case 3: strcpy( scpi_test_buffer, "3.e+1" ); break;
                case 4: strcpy( scpi_test_buffer, "3e14" ); break;
                case 5: strcpy( scpi_test_buffer, "+3 e-1" ); break;
                case 6: strcpy( scpi_test_buffer, "3 E 14" ); break;
                case 7: strcpy( scpi_test_buffer, "-3.14e-159" ); break;
                case 8: strcpy( scpi_test_buffer, "+3. E -14159" ); break;
                case 9: strcpy( scpi_test_buffer, "3 E15 " ); break;
                case 10: strcpy( scpi_test_buffer, "-.3 E -15 " ); break;

              // Incorrect examples:
                case 11: strcpy( scpi_test_buffer, "-3.1.e-1" ); break; // pass: 4 chars returned => actually succeeded 
                case 12: strcpy( scpi_test_buffer, "3e1.4" ); break;  // pass: 3 chars returned => actually succeeded 
                case 13: strcpy( scpi_test_buffer, "+3. E -14159." ); break; // pass: 12 chars returned => actually succeeded
                case 14: strcpy( scpi_test_buffer, "3 E15 E15" ); break;  // pass: 5 chars returned => actually succeeded
                case 15: strcpy( scpi_test_buffer, "-3.1-E -15 " ); break; // pass: 4 chars returned => actually succeeded                
                case 16: strcpy( scpi_test_buffer, " 3" ); break; // pass
                case 17: strcpy( scpi_test_buffer, "+-3" ); break; // pass
                case 18: strcpy( scpi_test_buffer, ". 3" ); break; // pass
                case 19: strcpy( scpi_test_buffer, "3.e++1" ); break; // pass                
                case 20: strcpy( scpi_test_buffer, "3 E E 14" ); break; // pass
                case 21: strcpy( scpi_test_buffer, "-3e.14e-159" ); break; // pass                
                case 22: strcpy( scpi_test_buffer, "3.e+e+1" ); break; // pass
                case 23: strcpy( scpi_test_buffer, "3. E-E 14" ); break; // pass
                case 24: strcpy( scpi_test_buffer, "-3e..1-159" ); break; // pass
                case 25: strcpy( scpi_test_buffer, "3-.e+1" ); break; // pass: 1 chars returned => actually succeeded 
                case 26: strcpy( scpi_test_buffer, "3.E.+1E2" ); break; // pass
                case 27: strcpy( scpi_test_buffer, "-3e.e1-159" ); break; // pass
              
            }

            *_scpi_message_len = strlen( scpi_test_buffer );
        }
        break;

        case 4: // Non-demical numbers:
        {
            switch( scpi_test_subid )
            {
              // Correct examples:
                case 0: strcpy( scpi_test_buffer, "#b00110001" ); break;  // CORRECT  : passed
                case 1: strcpy( scpi_test_buffer, "#Haf020ffc" ); break;  // CORRECT  : passed
                case 2: strcpy( scpi_test_buffer, "#Q7777111" ); break;   // CORRECT  : passed
                case 3: strcpy( scpi_test_buffer, "b0011000" ); break;    // INCORRECT: passed
                case 4: strcpy( scpi_test_buffer, "Haf020ff" ); break;    // INCORRECT: passed
                case 5: strcpy( scpi_test_buffer, "q7777111" ); break;    // INCORRECT: passed
                case 6: strcpy( scpi_test_buffer, "0011000" ); break;     // INCORRECT: passed
                case 7: strcpy( scpi_test_buffer, "af020ff" ); break;     // INCORRECT: passed
                case 8: strcpy( scpi_test_buffer, "7777111" ); break;     // INCORRECT: passed   
                case 9: strcpy( scpi_test_buffer, "##b0011000" ); break;  // INCORRECT: passed
                case 10:strcpy( scpi_test_buffer, "##haf020ff" ); break;  // INCORRECT: passed
                case 11:strcpy( scpi_test_buffer, "##q7777111" ); break;  // INCORRECT: passed
                case 12:strcpy( scpi_test_buffer, "#bb0011000" ); break;  // INCORRECT: passed
                case 13:strcpy( scpi_test_buffer, "#hhaf020ff" ); break;  // INCORRECT: passed
                case 14:strcpy( scpi_test_buffer, "#qq7777111" ); break;  // INCORRECT: passed
            }

            *_scpi_message_len = strlen( scpi_test_buffer );
        }
        break;
     }
 }

 void scpi_parser_test()
 {
     size_t scpi_test_id = 4; 
     // 0 = string
     // 1 = arbitrary block
     // 2 = command program header
     // 3 = demical numbers
     // 4 = non-demical numbers
     
     eScpiParserStatus_t scpi_status = eScpiParserStatus_invalid;
     size_t scpi_buffer_len = 1;// sizeof( scpi_test_buffer );
     size_t scpi_message_len = sizeof(scpi_test_buffer);
     char * scpi_buffer_ptr = scpi_test_buffer;
     bool   scpi_end_of_message = false;
     bool   scpi_keep_ctx = false;
     const char * entity_start = NULL;
     size_t entity_length = 0;
     size_t scpi_test_subid = 0;
     
     switch( scpi_test_id ) {
            case 0: strcpy( scpi_test_buffer, "\"Test string with a \"\"quotted\"\" part.\"" ); break; //30

            case 1: strcpy( scpi_test_buffer, "#2160123456789abcdef-----" ); break; //25

            case 2: strcpy( scpi_test_buffer, ":MEM:TABLE:DATA PARAM" ); break; //26
                                              
            case 3: scpi_test_buf_example ( scpi_test_id, scpi_test_subid,
                             &scpi_buffer_ptr,
                             &scpi_buffer_len,
                             &scpi_message_len,
                             &scpi_end_of_message,
                             &scpi_keep_ctx,
                             &entity_start,
                             &entity_length );
            break; 

            case 4: scpi_test_buf_example ( scpi_test_id, scpi_test_subid,
                             &scpi_buffer_ptr,
                             &scpi_buffer_len,
                             &scpi_message_len,
                             &scpi_end_of_message,
                             &scpi_keep_ctx,
                             &entity_start,
                             &entity_length );
            break;
     }     

     asm( "bkpt #0" );
     while( !scpi_test_exit )
     {
         scpi_end_of_message = ( scpi_buffer_ptr >= scpi_test_buffer + scpi_message_len - 1 );

         if( ! prepareParserContext( &ctx, 
                                      scpi_buffer_ptr, 
                                      scpi_buffer_len,
                                      scpi_end_of_message,
                                      scpi_keep_ctx ) )
         {
             asm( "bkpt #0" );
             break;
         }
         else
         {
           //asm( "bkpt #0" );
         }

         switch( scpi_test_id ) {
            case 0: scpi_status = parseString( &ctx ); break;

            case 1: scpi_status = parseArbitraryBlock( &ctx ); break;

            case 2: scpi_status = parseCommandProgramHeader( &ctx ); break;

            case 3: scpi_status = parseDemicalNumber( &ctx ); break;

            case 4: scpi_status = parseNonDemicalNumber( &ctx ); break;

            default: scpi_status = eScpiParserStatus_invalid;
         }

         switch( scpi_status )
         {
            case eScpiParserStatus_invalid:
            {
               scpi_keep_ctx = false;
               asm( "bkpt #0" );
            }
            break;

            case eScpiParserStatus_failed:
            {
               scpi_keep_ctx = false;
               asm( "bkpt #0" );

               scpi_test_buf_example ( scpi_test_id, ++scpi_test_subid,
                             &scpi_buffer_ptr,
                             &scpi_buffer_len,
                             &scpi_message_len,
                             &scpi_end_of_message,
                             &scpi_keep_ctx,
                             &entity_start,
                             &entity_length );
            }
            break;

            case eScpiParserStatus_success:
            {
               const char * pEntityBegin = NULL;
               const char * pEntityEnd = NULL;
               uint8_t eEntityType;
               scpi_keep_ctx = false;
               getParsedEntityDetails( &ctx,
                         (void const**)&pEntityBegin,
                         (void const**)&pEntityEnd,
                                       &eEntityType );

               if( NULL == entity_start )
               {
                   entity_start = pEntityBegin;
               }

               entity_length = (pEntityEnd - entity_start);
               asm( "bkpt #0" );
               

               scpi_test_buf_example ( scpi_test_id, ++scpi_test_subid,
                             &scpi_buffer_ptr,
                             &scpi_buffer_len,
                             &scpi_message_len,
                             &scpi_end_of_message,
                             &scpi_keep_ctx,
                             &entity_start,
                             &entity_length );
            }
            break;

            case eScpiParserStatus_need_data:
            {                 
               const char * pEntityBegin = NULL;
               const char * pEntityEnd = NULL;
               scpi_keep_ctx = true;
               getParsedEntityDetails( &ctx,
                         (void const**)&pEntityBegin,
                         (void const**)&pEntityEnd,
                                       NULL );


               scpi_buffer_ptr += (pEntityEnd - pEntityBegin);
             //asm( "bkpt #0" );
               if( NULL == entity_start )
               {
                   entity_start = pEntityBegin;
               }
            }
            break;
         }
     }
     asm( "bkpt #0" );
 }

