mirror of https://github.com/tongzx/nt5src
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
79 lines
1.5 KiB
79 lines
1.5 KiB
/*
|
|
* CRC32.C -- CRC32 computation
|
|
*/
|
|
|
|
#include "crc32.h"
|
|
|
|
long crc32Table[256];
|
|
|
|
/*
|
|
* GenerateCRC32Table - Construct CRC-32 constant table
|
|
*
|
|
* We construct the table on-the-fly because the code needed
|
|
* to do build it is much smaller than the table it creates.
|
|
*/
|
|
|
|
void GenerateCRC32Table(void)
|
|
{
|
|
int iIndex;
|
|
int cBit;
|
|
long shiftIn;
|
|
long shiftOut;
|
|
|
|
for (iIndex = 0; iIndex < 256; iIndex++)
|
|
{
|
|
shiftOut = iIndex;
|
|
shiftIn = 0;
|
|
|
|
for (cBit = 0; cBit < 8; cBit++)
|
|
{
|
|
shiftIn <<= 1;
|
|
shiftIn |= (shiftOut & 1);
|
|
shiftOut >>= 1;
|
|
}
|
|
|
|
shiftIn <<= 24;
|
|
|
|
for (cBit = 0; cBit < 8; cBit++)
|
|
{
|
|
if (shiftIn & 0x80000000L)
|
|
{
|
|
shiftIn = (shiftIn << 1) ^ 0x04C11DB7L;
|
|
}
|
|
else
|
|
{
|
|
shiftIn <<= 1;
|
|
}
|
|
}
|
|
|
|
for (cBit = 0; cBit < 32; cBit++)
|
|
{
|
|
shiftOut <<= 1;
|
|
shiftOut |= (shiftIn & 1);
|
|
shiftIn >>= 1;
|
|
}
|
|
|
|
crc32Table[iIndex] = shiftOut;
|
|
}
|
|
}
|
|
|
|
|
|
/*
|
|
* update CRC32 accumulator from contents of a buffer
|
|
*/
|
|
|
|
void CRC32Update(unsigned long *pCRC32,void *p,unsigned long cb)
|
|
{
|
|
unsigned char *pb = p;
|
|
unsigned long crc32;
|
|
|
|
crc32 = (-1L - *pCRC32);
|
|
|
|
while (cb--)
|
|
{
|
|
crc32 = crc32Table[(unsigned char)crc32 ^ *pb++] ^
|
|
((crc32 >> 8) & 0x00FFFFFFL);
|
|
}
|
|
|
|
*pCRC32 = (-1L - crc32);
|
|
}
|