/* (C) 2003 XDA Developers  itsme@xs4all.nl
 *
 * $Header$
 */
#include "crc32.h"

#include <windows.h>
#include "vectorutils.h"

static class CRCCalc {
public:
    CRCCalc() {
        initcrc(0xEDB88320L);
    }

    DWORD crc32(DWORD prev, BYTE c) const
    {
       return (prev>>8) ^ crc32tab[(int)((prev&0xff)^c)];
    }

private:
        DWORD crc32tab[256];
 
    /* crcBase = 0xEDB88320L */
    DWORD calccrc32tab(BYTE c, DWORD crcBase)
    {  
       DWORD val = c;
       int i;
       for (i=0 ; i<8 ; i++)
       {
          if (val&1)
            val = (val>>1)^crcBase;
          else
            val = (val>>1);
       }
       return val;
    }

    void initcrc(DWORD crcBase)
    {
       DWORD val;
       int i;
       for (i=0 ; i<256 ; i++)
       {
          val = calccrc32tab(i, crcBase);
          crc32tab[i]=val;
       }
    }
} g_crccalc;

DWORD add_to_crc32(DWORD prev, BYTE c)
{
    return g_crccalc.crc32(prev, c);
}

DWORD calccrc32(const ByteVector& buf)
{
    DWORD crc= 0;
    for (ByteVector::const_iterator i= buf.begin() ; i!=buf.end() ; ++i)
        crc= add_to_crc32(crc, *i);

    return crc;
}
DWORD calccrc32(const BYTE*buf, DWORD len)
{
    DWORD crc= 0;
    while (len--)
        crc= add_to_crc32(crc, *buf++);

    return crc;
}