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/*
Cyclic Redundancy Code (CRC) functions
by Rafael Vuijk (aka DarkFader)
*/
#ifndef __CRC_H
#define __CRC_H
//#include "little.h" // FixCrc is not yet big endian compatible
/*
* Data
*/
extern unsigned short ccitt16tab[];
extern unsigned short crc16tab[];
extern unsigned long crc32tab[];
/*
* Defines
*/
#define CRC_TEMPLATE template <typename CrcType, CrcType *crcTable>
/*
* CalcCcitt
* Does not perform final inversion.
*/
#define CalcCcitt_ CalcCcitt<CrcType, crcTable>
#define CalcCcitt16 CalcCcitt<typeof(*ccitt16tab), ccitt16tab>
CRC_TEMPLATE inline CrcType CalcCcitt(unsigned char *data, unsigned int length, CrcType crc = (CrcType)0)
{
for (unsigned int i=0; i<length; i++)
{
crc = (crc << 8) ^ crcTable[(crc >> 8) ^ data[i]];
}
return crc;
}
/*
* CalcCrc
* Does not perform final inversion.
*/
#define CalcCrc_ CalcCrc<CrcType, crcTable>
#define CalcCrc16 CalcCrc<typeof(*crc16tab), crc16tab>
#define CalcCrc32 CalcCrc<typeof(*crc32tab), crc32tab>
CRC_TEMPLATE inline CrcType CalcCrc(unsigned char *data, unsigned int length, CrcType crc = (CrcType)~0)
{
for (unsigned int i=0; i<length; i++)
{
crc = (crc >> 8) ^ crcTable[(crc ^ data[i]) & 0xFF];
}
return crc;
}
/*
* FCalcCrc
* Does not perform final inversion.
*/
#define FCalcCrc_ FCalcCrc<CrcType, crcTable>
#define FCalcCrc16 FCalcCrc<typeof(*crc16tab), crc16tab>
#define FCalcCrc32 FCalcCrc<typeof(*crc32tab), crc32tab>
CRC_TEMPLATE inline CrcType FCalcCrc(FILE *f, unsigned int offset, unsigned int length, CrcType crc = (CrcType)~0)
{
fseek(f, offset, SEEK_SET);
for (unsigned int i=0; i<length; i++)
{
crc = (crc >> 8) ^ crcTable[(crc ^ fgetc(f)) & 0xFF];
}
return crc;
}
/*
* RevCrc
* Reverse table lookup.
*/
#define RevCrc_ RevCrc<CrcType, crcTable>
CRC_TEMPLATE inline unsigned char RevCrc(unsigned char x, CrcType *value = 0)
{
for (int y=0; y<256; y++)
{
if ((crcTable[y] >> (8*sizeof(CrcType)-8)) == x)
{
if (value) *value = crcTable[y];
return y;
}
}
return 0;
}
/*
* FixCrc
*/
#define FixCrc_ FixCrc<CrcType, crcTable>
#define FixCrc16 FixCrc<typeof(*crc16tab), crc16tab>
#define FixCrc32 FixCrc<typeof(*crc32tab), crc32tab>
CRC_TEMPLATE void FixCrc
(
unsigned char *data, // data to be patched
unsigned int patch_offset, unsigned char *patch_data, unsigned int patch_length, // patch data
unsigned int fix_offset = 0, // position to write the fix. by default, it is immediately after the patched data
CrcType initial_crc = (CrcType)~0 // useful when manually calculating leading data
)
{
if (!fix_offset) fix_offset = patch_offset + patch_length;
// calculate CRC after leading data
initial_crc = CalcCrc_(data, patch_offset, initial_crc);
// calculate CRC before fix
unsigned char buf[2*sizeof(CrcType)];
CrcType crc_before_fix = CalcCrc_(data + patch_offset, fix_offset - patch_offset);
*(CrcType *)(buf + 0) = crc_before_fix;
// patch
memcpy(data + patch_offset, patch_data, patch_length);
// calculate CRC after unfixed
CrcType crc_after_unfix = CalcCrc_(data + patch_offset, fix_offset - patch_offset + sizeof(CrcType));
*(CrcType *)(buf + sizeof(CrcType)) = crc_after_unfix;
// fix it
for (int i=sizeof(CrcType); i>=1; i--)
{
CrcType value;
unsigned char index = RevCrc_(buf[i + sizeof(CrcType) - 1], &value);
*(CrcType *)(buf + i) ^= value;
buf[i - 1] ^= index;
}
memcpy(data + fix_offset, buf, sizeof(CrcType));
}
/*
* FFixCrc
*/
#define FFixCrc_ FFixCrc<CrcType, crcTable>
#define FFixCrc16 FFixCrc<typeof(*crc16tab), crc16tab>
#define FFixCrc32 FFixCrc<typeof(*crc32tab), crc32tab>
CRC_TEMPLATE void FFixCrc
(
FILE *f, // file to be patched
unsigned int patch_offset, unsigned char *patch_data, unsigned int patch_length, // patch data
unsigned int fix_offset = 0, // position to write the fix. by default, it is immediately after the patched data
CrcType initial_crc = (CrcType)~0 // useful when manually calculating leading data
)
{
if (!fix_offset) fix_offset = patch_offset + patch_length;
// calculate CRC after leading data
initial_crc = FCalcCrc_(f, 0, patch_offset, initial_crc);
// calculate CRC before fix
unsigned char buf[2*sizeof(CrcType)];
CrcType crc_before_fix = FCalcCrc_(f, patch_offset, fix_offset - patch_offset);
*(CrcType *)(buf + 0) = crc_before_fix;
// patch
fseek(f, patch_offset, SEEK_SET);
fwrite(patch_data, 1, patch_length, f);
// calculate CRC after unfixed
CrcType crc_after_unfix = FCalcCrc_(f, patch_offset, fix_offset - patch_offset + sizeof(CrcType));
*(CrcType *)(buf + sizeof(CrcType)) = crc_after_unfix;
// fix it
for (int i=sizeof(CrcType); i>=1; i--)
{
CrcType value;
unsigned char index = RevCrc_(buf[i + sizeof(CrcType) - 1], &value);
*(CrcType *)(buf + i) ^= value;
buf[i - 1] ^= index;
}
fseek(f, fix_offset, SEEK_SET);
fwrite(buf, sizeof(CrcType), 1, f);
}
#endif // __CRC_H
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