Reverse Engineering References

[Skarma]

Reversed from Halo CE 1.08 using OllyDbg, IDA Pro, Hexrays, and msdn.

Calculates a Crc32 from the inputed buffer, the buffer length, and the current Crc32 value. It first checks if a Crc32 lookup table has been created, then uses it in calculating the Crc32.

//----- (004D37E0) --------------------------------------------------------
bool *Crc32TableInit = (bool *)0x006B4CA0;
DWORD *Crc32Table = (DWORD *)0x00652968; // 256 dwords
 
void CalcCrc32(DWORD *Crc32, constchar *Buffer, DWORD Length)
{
 DWORD Crc = *Crc32;
 
 if(!*Crc32TableInit)
 {
   InitCrc32Table(Crc32Table);
   *Crc32TableInit = true;
 }
 
 for(DWORD i = 0; i < Length; i++)
 {
   Crc = (*Crc32 >> 8) ^ Crc32Table[(*Buffer++ ^ *Crc32) & 0xFF];
 }
 
 *Crc32 = Crc;
}