/* 7zCrc.c -- CRC32 init
2015-03-10 : Igor Pavlov : Public domain */

#include "Precomp.h"

#include "7zCrc.h"
#include "CpuArch.h"

#define kCrcPoly 0xEDB88320

#ifdef MY_CPU_LE
#define CRC_NUM_TABLES 8
#else
#define CRC_NUM_TABLES 9

#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);
UInt32 MY_FAST_CALL CrcUpdateT1_BeT8(UInt32 v, const void* data, size_t size, const UInt32* table);
#endif

#ifndef MY_CPU_BE
UInt32 MY_FAST_CALL CrcUpdateT4(UInt32 v, const void* data, size_t size, const UInt32* table);
UInt32 MY_FAST_CALL CrcUpdateT8(UInt32 v, const void* data, size_t size, const UInt32* table);
#endif

typedef UInt32(MY_FAST_CALL* CRC_FUNC)(UInt32 v, const void* data, size_t size, const UInt32* table);

CRC_FUNC g_CrcUpdateT4;
CRC_FUNC g_CrcUpdateT8;
CRC_FUNC g_CrcUpdate;

UInt32 g_CrcTable[256 * CRC_NUM_TABLES];

UInt32 MY_FAST_CALL CrcUpdate(UInt32 v, const void* data, size_t size)
{
    return g_CrcUpdate(v, data, size, g_CrcTable);
}

UInt32 MY_FAST_CALL CrcCalc(const void* data, size_t size)
{
    return g_CrcUpdate(CRC_INIT_VAL, data, size, g_CrcTable) ^ CRC_INIT_VAL;
}

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

UInt32 MY_FAST_CALL CrcUpdateT1(UInt32 v, const void* data, size_t size, const UInt32* table)
{
    const Byte* p = (const Byte*)data;
    const Byte* pEnd = p + size;
    for (; p != pEnd; p++)
        v = CRC_UPDATE_BYTE_2(v, *p);
    return v;
}

void MY_FAST_CALL CrcGenerateTable()
{
    UInt32 i;
    for (i = 0; i < 256; i++)
    {
        UInt32 r = i;
        unsigned j;
        for (j = 0; j < 8; j++)
            r = (r >> 1) ^ (kCrcPoly & ~((r & 1) - 1));
        g_CrcTable[i] = r;
    }
    for (; i < 256 * CRC_NUM_TABLES; i++)
    {
        UInt32 r = g_CrcTable[i - 256];
        g_CrcTable[i] = g_CrcTable[r & 0xFF] ^ (r >> 8);
    }

#if CRC_NUM_TABLES < 4

    g_CrcUpdate = CrcUpdateT1;

#else

#ifdef MY_CPU_LE

    g_CrcUpdateT4 = CrcUpdateT4;
    g_CrcUpdate = CrcUpdateT4;

#if CRC_NUM_TABLES >= 8
    g_CrcUpdateT8 = CrcUpdateT8;

#ifdef MY_CPU_X86_OR_AMD64
    if (!CPU_Is_InOrder())
        g_CrcUpdate = CrcUpdateT8;
#endif
#endif

#else
    {
#ifndef MY_CPU_BE
        UInt32 k = 0x01020304;
        const Byte* p = (const Byte*)&k;
        if (p[0] == 4 && p[1] == 3)
        {
            g_CrcUpdateT4 = CrcUpdateT4;
            g_CrcUpdate = CrcUpdateT4;
#if CRC_NUM_TABLES >= 8
            g_CrcUpdateT8 = CrcUpdateT8;
            // g_CrcUpdate = CrcUpdateT8;
#endif
        }
        else if (p[0] != 1 || p[1] != 2)
            g_CrcUpdate = CrcUpdateT1;
        else
#endif
        {
            for (i = 256 * CRC_NUM_TABLES - 1; i >= 256; i--)
            {
                UInt32 x = g_CrcTable[i - 256];
                g_CrcTable[i] = CRC_UINT32_SWAP(x);
            }
            g_CrcUpdateT4 = CrcUpdateT1_BeT4;
            g_CrcUpdate = CrcUpdateT1_BeT4;
#if CRC_NUM_TABLES >= 8
            g_CrcUpdateT8 = CrcUpdateT1_BeT8;
            // g_CrcUpdate = CrcUpdateT1_BeT8;
#endif
        }
    }
#endif

#endif
}
