citra/src/common/hash.cpp

// Copyright 2013 Dolphin Emulator Project
// Licensed under GPLv2
// Refer to the license.txt file included.


#include "common/hash.h"
#if _M_SSE >= 0x402
#include "common/cpu_detect.h"
#include <nmmintrin.h>
#endif

static u64 (*ptrHashFunction)(const u8 *src, int len, u32 samples) = &GetMurmurHash3;

// uint32_t
// WARNING - may read one more byte!
// Implementation from Wikipedia.
u32 HashFletcher(const u8* data_u8, size_t length)
{
    const u16* data = (const u16*)data_u8; /* Pointer to the data to be summed */
    size_t len = (length + 1) / 2; /* Length in 16-bit words */
    u32 sum1 = 0xffff, sum2 = 0xffff;

    while (len)
    {
        size_t tlen = len > 360 ? 360 : len;
        len -= tlen;

        do {
            sum1 += *data++;
            sum2 += sum1;
        }
        while (--tlen);

        sum1 = (sum1 & 0xffff) + (sum1 >> 16);
        sum2 = (sum2 & 0xffff) + (sum2 >> 16);
    }

    // Second reduction step to reduce sums to 16 bits
    sum1 = (sum1 & 0xffff) + (sum1 >> 16);
    sum2 = (sum2 & 0xffff) + (sum2 >> 16);
    return(sum2 << 16 | sum1);
}


// Implementation from Wikipedia
// Slightly slower than Fletcher above, but slightly more reliable.
#define MOD_ADLER 65521
// data: Pointer to the data to be summed; len is in bytes
u32 HashAdler32(const u8* data, size_t len)
{
    u32 a = 1, b = 0;

    while (len)
    {
        size_t tlen = len > 5550 ? 5550 : len;
        len -= tlen;

        do
        {
            a += *data++;
            b += a;
        }
        while (--tlen);

        a = (a & 0xffff) + (a >> 16) * (65536 - MOD_ADLER);
        b = (b & 0xffff) + (b >> 16) * (65536 - MOD_ADLER);
    }

    // It can be shown that a <= 0x1013a here, so a single subtract will do.
    if (a >= MOD_ADLER)
    {
        a -= MOD_ADLER;
    }

    // It can be shown that b can reach 0xfff87 here.
    b = (b & 0xffff) + (b >> 16) * (65536 - MOD_ADLER);

    if (b >= MOD_ADLER)
    {
        b -= MOD_ADLER;
    }

    return((b << 16) | a);
}

// Stupid hash - but can't go back now :)
// Don't use for new things. At least it's reasonably fast.
u32 HashEctor(const u8* ptr, int length)
{
    u32 crc = 0;

    for (int i = 0; i < length; i++)
    {
        crc ^= ptr[i];
        crc = (crc << 3) | (crc >> 29);
    }

    return(crc);
}


#ifdef _M_X64

//-----------------------------------------------------------------------------
// Block read - if your platform needs to do endian-swapping or can only
// handle aligned reads, do the conversion here

inline u64 getblock(const u64 * p, int i)
{
    return p[i];
}

//----------
// Block mix - combine the key bits with the hash bits and scramble everything

inline void bmix64(u64 & h1, u64 & h2, u64 & k1, u64 & k2, u64 & c1, u64 & c2)
{
    k1 *= c1; 
    k1  = _rotl64(k1,23); 
    k1 *= c2;
    h1 ^= k1;
    h1 += h2;

    h2 = _rotl64(h2,41);

    k2 *= c2; 
    k2  = _rotl64(k2,23);
    k2 *= c1;
    h2 ^= k2;
    h2 += h1;

    h1 = h1*3+0x52dce729;
    h2 = h2*3+0x38495ab5;

    c1 = c1*5+0x7b7d159c;
    c2 = c2*5+0x6bce6396;
}

//----------
// Finalization mix - avalanches all bits to within 0.05% bias

inline u64 fmix64(u64 k)
{
    k ^= k >> 33;
    k *= 0xff51afd7ed558ccd;
    k ^= k >> 33;
    k *= 0xc4ceb9fe1a85ec53;
    k ^= k >> 33;

    return k;
}

u64 GetMurmurHash3(const u8 *src, int len, u32 samples)
{
    const u8 * data = (const u8*)src;
    const int nblocks = len / 16;
    u32 Step = (len / 8);
    if(samples == 0) samples = max(Step, 1u);
    Step = Step / samples;
    if(Step < 1) Step = 1;

    u64 h1 = 0x9368e53c2f6af274;
    u64 h2 = 0x586dcd208f7cd3fd;

    u64 c1 = 0x87c37b91114253d5;
    u64 c2 = 0x4cf5ad432745937f;


    //----------
    // body

    const u64 * blocks = (const u64 *)(data);

    for(int i = 0; i < nblocks; i+=Step)
    {
        u64 k1 = getblock(blocks,i*2+0);
        u64 k2 = getblock(blocks,i*2+1);

        bmix64(h1,h2,k1,k2,c1,c2);
    }

    //----------
    // tail

    const u8 * tail = (const u8*)(data + nblocks*16);

    u64 k1 = 0;
    u64 k2 = 0;

    switch(len & 15)
    {
    case 15: k2 ^= u64(tail[14]) << 48;
    case 14: k2 ^= u64(tail[13]) << 40;
    case 13: k2 ^= u64(tail[12]) << 32;
    case 12: k2 ^= u64(tail[11]) << 24;
    case 11: k2 ^= u64(tail[10]) << 16;
    case 10: k2 ^= u64(tail[ 9]) << 8;
    case  9: k2 ^= u64(tail[ 8]) << 0;

    case  8: k1 ^= u64(tail[ 7]) << 56;
    case  7: k1 ^= u64(tail[ 6]) << 48;
    case  6: k1 ^= u64(tail[ 5]) << 40;
    case  5: k1 ^= u64(tail[ 4]) << 32;
    case  4: k1 ^= u64(tail[ 3]) << 24;
    case  3: k1 ^= u64(tail[ 2]) << 16;
    case  2: k1 ^= u64(tail[ 1]) << 8;
    case  1: k1 ^= u64(tail[ 0]) << 0;
            bmix64(h1,h2,k1,k2,c1,c2);
    };

    //----------
    // finalization

    h2 ^= len;

    h1 += h2;
    h2 += h1;

    h1 = fmix64(h1);
    h2 = fmix64(h2);

    h1 += h2;

    return h1;
}


// CRC32 hash using the SSE4.2 instruction
u64 GetCRC32(const u8 *src, int len, u32 samples)
{
#if _M_SSE >= 0x402
    u64 h = len;
    u32 Step = (len / 8);
    const u64 *data = (const u64 *)src;
    const u64 *end = data + Step;
    if(samples == 0) samples = max(Step, 1u);
    Step = Step / samples;
    if(Step < 1) Step = 1;
    while(data < end)
    {
        h = _mm_crc32_u64(h, data[0]);
        data += Step;
    }

    const u8 *data2 = (const u8*)end;
    return _mm_crc32_u64(h, u64(data2[0]));
#else
    return 0;
#endif
}


/* 
 * NOTE: This hash function is used for custom texture loading/dumping, so
 * it should not be changed, which would require all custom textures to be
 * recalculated for their new hash values. If the hashing function is
 * changed, make sure this one is still used when the legacy parameter is
 * true.
 */
u64 GetHashHiresTexture(const u8 *src, int len, u32 samples)
{
    const u64 m = 0xc6a4a7935bd1e995;
    u64 h = len * m;
    const int r = 47;
    u32 Step = (len / 8);
    const u64 *data = (const u64 *)src;
    const u64 *end = data + Step;
    if(samples == 0) samples = max(Step, 1u);
    Step = Step / samples;
    if(Step < 1) Step = 1;
    while(data < end)
    {
        u64 k = data[0];
        data+=Step;
        k *= m;
        k ^= k >> r; 
        k *= m;
        h ^= k;
        h *= m;
    }

    const u8 * data2 = (const u8*)end;

    switch(len & 7)
    {
    case 7: h ^= u64(data2[6]) << 48;
    case 6: h ^= u64(data2[5]) << 40;
    case 5: h ^= u64(data2[4]) << 32;
    case 4: h ^= u64(data2[3]) << 24;
    case 3: h ^= u64(data2[2]) << 16;
    case 2: h ^= u64(data2[1]) << 8;
    case 1: h ^= u64(data2[0]);
            h *= m;
    };
 
    h ^= h >> r;
    h *= m;
    h ^= h >> r;

    return h;
} 
#else
// CRC32 hash using the SSE4.2 instruction
u64 GetCRC32(const u8 *src, int len, u32 samples)
{
#if _M_SSE >= 0x402
    u32 h = len;
    u32 Step = (len/4);
    const u32 *data = (const u32 *)src;
    const u32 *end = data + Step;
    if(samples == 0) samples = max(Step, 1u);
    Step  = Step / samples;
    if(Step < 1) Step = 1;
    while(data < end)
    {
        h = _mm_crc32_u32(h, data[0]);
        data += Step;
    }

    const u8 *data2 = (const u8*)end;
    return (u64)_mm_crc32_u32(h, u32(data2[0]));
#else
    return 0;
#endif
}

//-----------------------------------------------------------------------------
// Block read - if your platform needs to do endian-swapping or can only
// handle aligned reads, do the conversion here

inline u32 getblock(const u32 * p, int i)
{
    return p[i];
}

//----------
// Finalization mix - force all bits of a hash block to avalanche

// avalanches all bits to within 0.25% bias

inline u32 fmix32(u32 h)
{
    h ^= h >> 16;
    h *= 0x85ebca6b;
    h ^= h >> 13;
    h *= 0xc2b2ae35;
    h ^= h >> 16;

    return h;
}

inline void bmix32(u32 & h1, u32 & h2, u32 & k1, u32 & k2, u32 & c1, u32 & c2)
{
    k1 *= c1; 
    k1  = _rotl(k1,11); 
    k1 *= c2;
    h1 ^= k1;
    h1 += h2;

    h2 = _rotl(h2,17);

    k2 *= c2; 
    k2  = _rotl(k2,11);
    k2 *= c1;
    h2 ^= k2;
    h2 += h1;

    h1 = h1*3+0x52dce729;
    h2 = h2*3+0x38495ab5;

    c1 = c1*5+0x7b7d159c;
    c2 = c2*5+0x6bce6396;
}

//----------

u64 GetMurmurHash3(const u8* src, int len, u32 samples)
{
    const u8 * data = (const u8*)src;
    u32 out[2];
    const int nblocks = len / 8;
    u32 Step = (len / 4);
    if(samples == 0) samples = max(Step, 1u);
    Step = Step / samples;
    if(Step < 1) Step = 1;

    u32 h1 = 0x8de1c3ac;
    u32 h2 = 0xbab98226;

    u32 c1 = 0x95543787;
    u32 c2 = 0x2ad7eb25;

    //----------
    // body

    const u32 * blocks = (const u32 *)(data + nblocks*8);

    for(int i = -nblocks; i < 0; i+=Step)
    {
        u32 k1 = getblock(blocks,i*2+0);
        u32 k2 = getblock(blocks,i*2+1);

        bmix32(h1,h2,k1,k2,c1,c2);
    }

    //----------
    // tail
    
    const u8 * tail = (const u8*)(data + nblocks*8);

    u32 k1 = 0;
    u32 k2 = 0;

    switch(len & 7)
    {
    case 7: k2 ^= tail[6] << 16;
    case 6: k2 ^= tail[5] << 8;
    case 5: k2 ^= tail[4] << 0;
    case 4: k1 ^= tail[3] << 24;
    case 3: k1 ^= tail[2] << 16;
    case 2: k1 ^= tail[1] << 8;
    case 1: k1 ^= tail[0] << 0;
            bmix32(h1,h2,k1,k2,c1,c2);
    };

    //----------
    // finalization

    h2 ^= len;

    h1 += h2;
    h2 += h1;

    h1 = fmix32(h1);
    h2 = fmix32(h2);

    h1 += h2;
    h2 += h1;

    out[0] = h1;
    out[1] = h2;
    
    return *((u64 *)&out);
}

/*
 * FIXME: The old 32-bit version of this hash made different hashes than the
 * 64-bit version. Until someone can make a new version of the 32-bit one that
 * makes identical hashes, this is just a c/p of the 64-bit one.
 */
u64 GetHashHiresTexture(const u8 *src, int len, u32 samples)
{
    const u64 m = 0xc6a4a7935bd1e995ULL;
    u64 h = len * m;
    const int r = 47;
    u32 Step = (len / 8);
    const u64 *data = (const u64 *)src;
    const u64 *end = data + Step;
    if(samples == 0) samples = max(Step, 1u);
    Step = Step / samples;
    if(Step < 1) Step = 1;
    while(data < end)
    {
        u64 k = data[0];
        data+=Step;
        k *= m; 
        k ^= k >> r; 
        k *= m;
        h ^= k;
        h *= m; 
    }

    const u8 * data2 = (const u8*)end;

    switch(len & 7)
    {
    case 7: h ^= u64(data2[6]) << 48;
    case 6: h ^= u64(data2[5]) << 40;
    case 5: h ^= u64(data2[4]) << 32;
    case 4: h ^= u64(data2[3]) << 24;
    case 3: h ^= u64(data2[2]) << 16;
    case 2: h ^= u64(data2[1]) << 8;
    case 1: h ^= u64(data2[0]);
            h *= m;
    };
 
    h ^= h >> r;
    h *= m;
    h ^= h >> r;

    return h;
}
#endif

u64 GetHash64(const u8 *src, int len, u32 samples)
{
    return ptrHashFunction(src, len, samples);
}

// sets the hash function used for the texture cache
void SetHash64Function(bool useHiresTextures)
{
    if (useHiresTextures)
    {
        ptrHashFunction = &GetHashHiresTexture;
    }
#if _M_SSE >= 0x402
    else if (cpu_info.bSSE4_2 && !useHiresTextures) // sse crc32 version
    {
        ptrHashFunction = &GetCRC32;
    }
#endif
    else
    {
        ptrHashFunction = &GetMurmurHash3;
    }
}