Problem with OFCRC32::compute method

[Leonid]

Hello!
I have following problem: when I tried to calculate CRC32 for file 1.txt with content "ABCDEFGHIJKLMNOPQRSTUVWXYZ" using OFCRC32::compute method I received unexpected result 0x041BC610. But when I calc CRC32 for this file by another program I had 0xABF77822
Here is my code:

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FILE* f = NULL;
	OFCRC32 crc32;
	USES_CONVERSION;
	const char* fname = OLE2A(filename);
	unsigned long res = 0;
	f = fopen(fname, "rb");
	fseek(f, 0L, SEEK_END);
	unsigned long size = ftell(f);
	rewind(f);
	char *buf = new char[size];
	memset(buf, 0, (size_t)size);
	fread(buf, 1, size, f);
	res = crc32.compute(buf,size); // res = 0x041BC610 instead of 0xABF77822
	
	fclose(f);
	delete [] buf;

Please help me. What I'm doing wrong?

[Jörg Riesmeier]

Are you sure that the other program uses the same algorithm?

[Leonid]

Are you sure that the other program uses the same algorithm?

But CRC32 should have the same value for all algorithms? Or I'm wrong?

Here is algorithm used by another program (crc_tab is the same as in OFCRC32 class) :

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unsigned long update_crc_32( unsigned long crc, char c ) {
    unsigned long tmp, long_c;
    long_c = 0x000000ffL & (unsigned long) c;
    tmp = crc ^ long_c;
    crc = (crc >> 8) ^ crc_tab[ tmp & 0xff ];
    return crc;
}

sample of usage:

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FILE* f = NULL;
f = fopen(fname, "rb")
crc_32         = 0xffffffffL;
while( ( ch=fgetc( f ) ) != EOF )
  {
      crc_32 = update_crc_32(crc_32,  (char) ch);
  }
fclose( fp );
crc_32    ^= 0xffffffffL;

As I can see, algorithm of CRC32 calculation is the same.