mirror of
https://github.com/dolphin-emu/dolphin.git
synced 2024-11-15 13:57:57 -07:00
775dc8a9c0
git-svn-id: https://dolphin-emu.googlecode.com/svn/trunk@4 8ced0084-cf51-0410-be5f-012b33b47a6e
139 lines
3.0 KiB
C++
139 lines
3.0 KiB
C++
// Copyright (C) 2003-2008 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);
|
|
}
|
|
|
|
|
|
// Another fast and decent hash
|
|
u32 HashFNV(const u8* ptr, int length)
|
|
{
|
|
u32 hash = 0x811c9dc5;
|
|
|
|
for (int i = 0; i < length; i++)
|
|
{
|
|
hash *= 1677761;
|
|
hash ^= ptr[i];
|
|
}
|
|
|
|
return(hash);
|
|
}
|
|
|
|
|
|
// Another fast and decent hash
|
|
u32 HashFNV1(const u8* ptr, int length)
|
|
{
|
|
u32 hash = 0x811c9dc5;
|
|
|
|
for (int i = 0; i < length; i++)
|
|
{
|
|
hash *= 1677761;
|
|
hash ^= ptr[i];
|
|
}
|
|
|
|
return(hash);
|
|
}
|
|
|
|
|
|
// Terribly stupid hash - but can't go back now :)
|
|
// Don't use for new things. At least it's 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);
|
|
}
|
|
|
|
|