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// 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"
// 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
u64 GetHash64(const u8 *src, int len, u32 samples)
{
const u64 m = 0xc6a4a7935bd1e995;
const int r = 47;
u64 h = len * m;
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
u64 GetHash64(const u8 *src, int len, u32 samples)
{
const u32 m = 0x5bd1e995;
const int r = 24;
u32 h1 = len;
u32 h2 = 0;
u32 Step = (len / 4);
const u32 * data = (const u32 *)src;
const u32 * end = data + Step;
const u8 * uEnd = (const u8 *)end;
if(samples == 0) samples = Step;
Step = Step / samples;
if(Step < 2) Step = 2;
while(data < end)
{
u32 k1 = data[0];
k1 *= m;
k1 ^= k1 >> r;
k1 *= m;
h1 *= m;
h1 ^= k1;
u32 k2 = data[1];
k2 *= m;
k2 ^= k2 >> r;
k2 *= m;
h2 *= m;
h2 ^= k2;
data+=Step;
}
if((len & 7) > 3)
{
u32 k1 = *(end - 1);
k1 *= m;
k1 ^= k1 >> r;
k1 *= m;
h1 *= m;
h1 ^= k1;
len -= 4;
}
switch(len & 3)
{
case 3: h2 ^= uEnd[2] << 16;
case 2: h2 ^= uEnd[1] << 8;
case 1: h2 ^= uEnd[0];
h2 *= m;
};
h1 ^= h2 >> 18; h1 *= m;
h2 ^= h1 >> 22; h2 *= m;
h1 ^= h2 >> 17; h1 *= m;
h2 ^= h1 >> 19; h2 *= m;
u64 h = h1;
h = (h << 32) | h2;
return h;
}
#endif
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