//---------------------------------------------------------------------------
/* crc32.c -- compute the CRC-32 of a data stream 
* Copyright (C) 1995-2002 Mark Adler 
* For conditions of distribution and use, see copyright notice in zlib.h 
*/ 
//Подпрограмма формирования контрольной суммы блока 
// На входе: 
// crc - начальная контрольная сумма( делать её так: crc=crc32(0,NULL,0); ) 
// buf - адрес блока 
// len - размер блока в байтах 
// На выходе: 
//  Контрольная сумма блока с учётом начальной 
// Использовать так: 
// unsigned long crc=crc32(0,NULL,0); //Инициализация начального значения 
// for(...) //цикл если buf содержит не все данные 
// { 
//  crc=crc32(crc,buf,len); 
// } 

#include "crc32.h"

static __root const unsigned long crc_table[256] =
{
0x00000000,0x77073096,0xee0e612c,0x990951ba,0x076dc419,0x706af48f,0xe963a535,0x9e6495a3,
0x0edb8832,0x79dcb8a4,0xe0d5e91e,0x97d2d988,0x09b64c2b,0x7eb17cbd,0xe7b82d07,0x90bf1d91,
0x1db71064,0x6ab020f2,0xf3b97148,0x84be41de,0x1adad47d,0x6ddde4eb,0xf4d4b551,0x83d385c7,
0x136c9856,0x646ba8c0,0xfd62f97a,0x8a65c9ec,0x14015c4f,0x63066cd9,0xfa0f3d63,0x8d080df5,
0x3b6e20c8,0x4c69105e,0xd56041e4,0xa2677172,0x3c03e4d1,0x4b04d447,0xd20d85fd,0xa50ab56b,
0x35b5a8fa,0x42b2986c,0xdbbbc9d6,0xacbcf940,0x32d86ce3,0x45df5c75,0xdcd60dcf,0xabd13d59,
0x26d930ac,0x51de003a,0xc8d75180,0xbfd06116,0x21b4f4b5,0x56b3c423,0xcfba9599,0xb8bda50f,
0x2802b89e,0x5f058808,0xc60cd9b2,0xb10be924,0x2f6f7c87,0x58684c11,0xc1611dab,0xb6662d3d,
0x76dc4190,0x01db7106,0x98d220bc,0xefd5102a,0x71b18589,0x06b6b51f,0x9fbfe4a5,0xe8b8d433,
0x7807c9a2,0x0f00f934,0x9609a88e,0xe10e9818,0x7f6a0dbb,0x086d3d2d,0x91646c97,0xe6635c01,
0x6b6b51f4,0x1c6c6162,0x856530d8,0xf262004e,0x6c0695ed,0x1b01a57b,0x8208f4c1,0xf50fc457,
0x65b0d9c6,0x12b7e950,0x8bbeb8ea,0xfcb9887c,0x62dd1ddf,0x15da2d49,0x8cd37cf3,0xfbd44c65,
0x4db26158,0x3ab551ce,0xa3bc0074,0xd4bb30e2,0x4adfa541,0x3dd895d7,0xa4d1c46d,0xd3d6f4fb,
0x4369e96a,0x346ed9fc,0xad678846,0xda60b8d0,0x44042d73,0x33031de5,0xaa0a4c5f,0xdd0d7cc9,
0x5005713c,0x270241aa,0xbe0b1010,0xc90c2086,0x5768b525,0x206f85b3,0xb966d409,0xce61e49f,
0x5edef90e,0x29d9c998,0xb0d09822,0xc7d7a8b4,0x59b33d17,0x2eb40d81,0xb7bd5c3b,0xc0ba6cad,
0xedb88320,0x9abfb3b6,0x03b6e20c,0x74b1d29a,0xead54739,0x9dd277af,0x04db2615,0x73dc1683,
0xe3630b12,0x94643b84,0x0d6d6a3e,0x7a6a5aa8,0xe40ecf0b,0x9309ff9d,0x0a00ae27,0x7d079eb1,
0xf00f9344,0x8708a3d2,0x1e01f268,0x6906c2fe,0xf762575d,0x806567cb,0x196c3671,0x6e6b06e7,
0xfed41b76,0x89d32be0,0x10da7a5a,0x67dd4acc,0xf9b9df6f,0x8ebeeff9,0x17b7be43,0x60b08ed5,
0xd6d6a3e8,0xa1d1937e,0x38d8c2c4,0x4fdff252,0xd1bb67f1,0xa6bc5767,0x3fb506dd,0x48b2364b,
0xd80d2bda,0xaf0a1b4c,0x36034af6,0x41047a60,0xdf60efc3,0xa867df55,0x316e8eef,0x4669be79,
0xcb61b38c,0xbc66831a,0x256fd2a0,0x5268e236,0xcc0c7795,0xbb0b4703,0x220216b9,0x5505262f,
0xc5ba3bbe,0xb2bd0b28,0x2bb45a92,0x5cb36a04,0xc2d7ffa7,0xb5d0cf31,0x2cd99e8b,0x5bdeae1d,
0x9b64c2b0,0xec63f226,0x756aa39c,0x026d930a,0x9c0906a9,0xeb0e363f,0x72076785,0x05005713,
0x95bf4a82,0xe2b87a14,0x7bb12bae,0x0cb61b38,0x92d28e9b,0xe5d5be0d,0x7cdcefb7,0x0bdbdf21,
0x86d3d2d4,0xf1d4e242,0x68ddb3f8,0x1fda836e,0x81be16cd,0xf6b9265b,0x6fb077e1,0x18b74777,
0x88085ae6,0xff0f6a70,0x66063bca,0x11010b5c,0x8f659eff,0xf862ae69,0x616bffd3,0x166ccf45,
0xa00ae278,0xd70dd2ee,0x4e048354,0x3903b3c2,0xa7672661,0xd06016f7,0x4969474d,0x3e6e77db,
0xaed16a4a,0xd9d65adc,0x40df0b66,0x37d83bf0,0xa9bcae53,0xdebb9ec5,0x47b2cf7f,0x30b5ffe9,
0xbdbdf21c,0xcabac28a,0x53b39330,0x24b4a3a6,0xbad03605,0xcdd70693,0x54de5729,0x23d967bf,
0xb3667a2e,0xc4614ab8,0x5d681b02,0x2a6f2b94,0xb40bbe37,0xc30c8ea1,0x5a05df1b,0x2d02ef8d
};

/* 
  Generate a table for a byte-wise 32-bit CRC calculation on the polynomial: 
  x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1. 

  Polynomials over GF(2) are represented in binary, one bit per coefficient, 
  with the lowest powers in the most significant bit.  Then adding polynomials 
  is just exclusive-or, and multiplying a polynomial by x is a right shift by 
  one.  If we call the above polynomial p, and represent a byte as the 
  polynomial q, also with the lowest power in the most significant bit (so the 
  byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p, 
  where a mod b means the remainder after dividing a by b. 

  This calculation is done using the shift-register method of multiplying and 
  taking the remainder.  The register is initialized to zero, and for each 
  incoming bit, x^32 is added mod p to the register if the bit is a one (where 
  x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by 
  x (which is shifting right by one and adding x^32 mod p if the bit shifted 
  out is a one).  We start with the highest power (least significant bit) of 
  q and repeat for all eight bits of q. 

  The table is simply the CRC of all possible eight bit values.  This is all 
  the information needed to generate CRC's on data a byte at a time for all 
  combinations of CRC register values and incoming bytes. 
*/ 

unsigned long __ICRC32(void)
{
 return CRC32(0,0,0);
}

/* ========================================================================= */
#define DO1(buf) crc = crc_table[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8); 
#define DO2(buf)  DO1(buf); DO1(buf); 
#define DO4(buf)  DO2(buf); DO2(buf); 
#define DO8(buf)  DO4(buf); DO4(buf); 

/* ========================================================================= */
unsigned long CRC32(unsigned long crc, const unsigned char *buf, unsigned long len)
{ 
    if (buf == 0) return 0L;
    
    crc = crc ^ 0xffffffffL; 
    while (len >= 8) 
    { 
      DO8(buf); 
      len -= 8; 
    } 
    while (len >= 4)
    {
      DO4(buf);
      len -= 4;
    }
    if (len) do {
      DO1(buf); 
    } while (--len); 
    return crc ^ 0xffffffffL; 
}