dolphin/Source/Core/Common/Src/Hash.cpp

// Copyright (C) 2003 Dolphin Project.

// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, version 2.0.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License 2.0 for more details.

// A copy of the GPL 2.0 should have been included with the program.
// If not, see http://www.gnu.org/licenses/

// Official SVN repository and contact information can be found at
// http://code.google.com/p/dolphin-emu/

#include "Hash.h"
#if _M_SSE >= 0x402
#include "CPUDetect.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 slighly 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, const int len, u32 samples)
{
    const u8 * data = (const u8*)src;
    const int nblocks = len / 16;

    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++)
    {
        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 = Step;
	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 = Step;
	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 = Step;
	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;
	const int nblocks = len / 8;
	u32 out[2];

	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; i++)
	{
		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 = 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 = Step;
	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;
	}
}