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Addition new function for crc32 checksum!

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git-svn-id: svn://kolibrios.org@7740 a494cfbc-eb01-0410-851d-a64ba20cac60
This commit is contained in:
pavelyakov 2020-03-21 10:59:27 +00:00
parent 0cee7aa77a
commit eed7aee495
1 changed files with 58 additions and 0 deletions
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58
programs/cmm/lib/crc32.h Executable file
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/* CRC32 function; Author PaulCodeman */
:dword crc32Table = 0;
:dword makeCRCTable(void)
{
dword i = 0;
dword c = 0;
dword ii = 0;
dword crcTable = 0;
IF (crc32Table) RETURN 0;
crc32Table = malloc(4*256);
crcTable = crc32Table;
WHILE (i < 256)
{
c = i;
ii = 0;
WHILE (ii < 8)
{
IF (c&1)
{
c >>= 1;
c ^= 0xEDB88320;
}
ELSE c >>= 1;
ii++;
}
DSDWORD[crcTable] = c;
crcTable += 4;
i++;
}
}
:dword crc32(dword bytes, length)
{
dword crc = 0;
dword i = 0;
byte b = 0;
IF (!crc32Table) makeCRCTable();
crc = 0xFFFFFFFF;
WHILE (i < length)
{
b = DSBYTE[bytes];
bytes++;
EDX = crc^b;
EDX &= 0xFF;
EDX <<= 2;
EDX += crc32Table;
crc >>= 8;
crc ^= DSDWORD[EDX];
i++;
}
RETURN crc ^ 0xFFFFFFFF;
}
/* EXAMPLE
dword str = 0;
str = "Kevin van Zonneveld";
crc32(str, strlen(str));
IF (EAX == 1249991249) ExitProcess();
*/