7zCrc.c
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/* 7zCrc.c */
#include "7zCrc.h"
#define kCrcPoly 0xEDB88320
UInt32 g_CrcTable[256];
void InitCrcTable()
{
UInt32 i;
for (i = 0; i < 256; i++)
{
UInt32 r = i;
int j;
for (j = 0; j < 8; j++)
if (r & 1)
r = (r >> 1) ^ kCrcPoly;
else
r >>= 1;
g_CrcTable[i] = r;
}
}
void CrcInit(UInt32 *crc) { *crc = 0xFFFFFFFF; }
UInt32 CrcGetDigest(UInt32 *crc) { return *crc ^ 0xFFFFFFFF; }
void CrcUpdateByte(UInt32 *crc, Byte b)
{
*crc = g_CrcTable[((Byte)(*crc)) ^ b] ^ (*crc >> 8);
}
void CrcUpdateUInt16(UInt32 *crc, UInt16 v)
{
CrcUpdateByte(crc, (Byte)v);
CrcUpdateByte(crc, (Byte)(v >> 8));
}
void CrcUpdateUInt32(UInt32 *crc, UInt32 v)
{
int i;
for (i = 0; i < 4; i++)
CrcUpdateByte(crc, (Byte)(v >> (8 * i)));
}
void CrcUpdateUInt64(UInt32 *crc, UInt64 v)
{
int i;
for (i = 0; i < 8; i++)
{
CrcUpdateByte(crc, (Byte)(v));
v >>= 8;
}
}
void CrcUpdate(UInt32 *crc, const void *data, size_t size)
{
UInt32 v = *crc;
const Byte *p = (const Byte *)data;
for (; size > 0 ; size--, p++)
v = g_CrcTable[((Byte)(v)) ^ *p] ^ (v >> 8);
*crc = v;
}
UInt32 CrcCalculateDigest(const void *data, size_t size)
{
UInt32 crc;
CrcInit(&crc);
CrcUpdate(&crc, data, size);
return CrcGetDigest(&crc);
}
int CrcVerifyDigest(UInt32 digest, const void *data, size_t size)
{
return (CrcCalculateDigest(data, size) == digest);
}