I need script that will calculate crc32 with the same output for both Python and C.
I'm using right now zlib.crc32, but for C there is no such library and we are writing it on our own basing on Wikipedia. But it doesn't return the same value.
This is our code of C script (copied from wikipedia, based on RFC):
unsigned int crc32( unsigned char *message, unsigned int n )
{
//int i, crc;
unsigned int crc;
unsigned int i;
unsigned int byte, c;
const unsigned int g0 = 0xEDB88320, g1 = g0>>1,
g2 = g0>>2, g3 = g0>>3, g4 = g0>>4, g5 = g0>>5,
g6 = (g0>>6)^g0, g7 = ((g0>>6)^g0)>>1;
i = 0;
crc = 0xFFFFFFFF;
//while ((byte = message[i]) != 0)
while( i != n)
{
byte = message[i]; // Get next byte.
// byte = FrmReadByte( i ); // Get next byte.
crc = crc ^ byte;
c = ((crc<<31>>31) & g7) ^ ((crc<<30>>31) & g6) ^
((crc<<29>>31) & g5) ^ ((crc<<28>>31) & g4) ^
((crc<<27>>31) & g3) ^ ((crc<<26>>31) & g2) ^
((crc<<25>>31) & g1) ^ ((crc<<24>>31) & g0);
crc = ((unsigned)crc >> 8) ^ c;
i = i + 1;
}
return ~crc;
}
EDIT:
RAM メモリは 4KB しかありません。プログラム自体はそこにはありません。crc32 スクリプトで 1KB のメモリを使用するのは、おそらく多すぎて収まりません。CにもZLIBライブラリが存在することを指摘してくれてありがとう。