visualboyadvance-m/fex/7z_C/7zCrcOpt.c

/* 7zCrcOpt.c -- CRC32 calculation
2010-12-01 : Igor Pavlov : Public domain */

#include "CpuArch.h"

#define CRC_UPDATE_BYTE_2(crc, b) (table[((crc) ^ (b)) & 0xFF] ^ ((crc) >> 8))

#ifndef MY_CPU_BE

UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void* data, size_t size, const UInt32* table)
{
    const Byte* p = (const Byte*)data;
    for (; size > 0 && ((unsigned)(ptrdiff_t)p & 3) != 0; size--, p++)
        v = CRC_UPDATE_BYTE_2(v, *p);
    for (; size >= 4; size -= 4, p += 4) {
        v ^= *(const UInt32*)p;
        v = table[0x300 + (v & 0xFF)] ^ table[0x200 + ((v >> 8) & 0xFF)] ^ table[0x100 + ((v >> 16) & 0xFF)] ^ table[0x000 + ((v >> 24))];
    }
    for (; size > 0; size--, p++)
        v = CRC_UPDATE_BYTE_2(v, *p);
    return v;
}

UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void* data, size_t size, const UInt32* table)
{
    return CrcUpdateT4(v, data, size, table);
}

#endif

#ifndef MY_CPU_LE

#define CRC_UINT32_SWAP(v) ((v >> 24) | ((v >> 8) & 0xFF00) | ((v << 8) & 0xFF0000) | (v << 24))

UInt32 MY_FAST_CALL CrcUpdateT1_BeT4(UInt32 v, const void* data, size_t size, const UInt32* table)
{
    const Byte* p = (const Byte*)data;
    for (; size > 0 && ((unsigned)(ptrdiff_t)p & 3) != 0; size--, p++)
        v = CRC_UPDATE_BYTE_2(v, *p);
    v = CRC_UINT32_SWAP(v);
    table += 0x100;
    for (; size >= 4; size -= 4, p += 4) {
        v ^= *(const UInt32*)p;
        v = table[0x000 + (v & 0xFF)] ^ table[0x100 + ((v >> 8) & 0xFF)] ^ table[0x200 + ((v >> 16) & 0xFF)] ^ table[0x300 + ((v >> 24))];
    }
    table -= 0x100;
    v = CRC_UINT32_SWAP(v);
    for (; size > 0; size--, p++)
        v = CRC_UPDATE_BYTE_2(v, *p);
    return v;
}

#endif