129 lines
2.5 KiB
C++
129 lines
2.5 KiB
C++
/* Copyright (C) 2009 Wildfire Games.
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* This file is part of 0 A.D.
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*
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* 0 A.D. is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* 0 A.D. is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* Fowler/Noll/Vo string hash
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*/
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#include "precompiled.h"
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// FNV1-A hash - good for strings.
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// if len = 0 (default), treat buf as a C-string;
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// otherwise, hash <len> bytes of buf.
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u32 fnv_hash(const void* buf, size_t len)
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{
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u32 h = 0x811c9dc5u;
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// give distinct values for different length 0 buffers.
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// value taken from FNV; it has no special significance.
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const u8* p = (const u8*)buf;
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// expected case: string
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if(!len)
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{
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while(*p)
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{
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h ^= *p++;
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h *= 0x01000193u;
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}
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}
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else
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{
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size_t bytes_left = len;
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while(bytes_left != 0)
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{
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h ^= *p++;
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h *= 0x01000193u;
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bytes_left--;
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}
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}
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return h;
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}
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// FNV1-A hash - good for strings.
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// if len = 0 (default), treat buf as a C-string;
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// otherwise, hash <len> bytes of buf.
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u64 fnv_hash64(const void* buf, size_t len)
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{
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u64 h = 0xCBF29CE484222325ull;
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// give distinct values for different length 0 buffers.
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// value taken from FNV; it has no special significance.
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const u8* p = (const u8*)buf;
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// expected case: string
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if(!len)
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{
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while(*p)
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{
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h ^= *p++;
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h *= 0x100000001B3ull;
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}
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}
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else
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{
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size_t bytes_left = len;
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while(bytes_left != 0)
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{
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h ^= *p++;
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h *= 0x100000001B3ull;
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bytes_left--;
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}
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}
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return h;
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}
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// special version for strings: first converts to lowercase
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// (useful for comparing mixed-case filenames).
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// note: still need <len>, e.g. to support non-0-terminated strings
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u32 fnv_lc_hash(const char* str, size_t len)
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{
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u32 h = 0x811c9dc5u;
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// give distinct values for different length 0 buffers.
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// value taken from FNV; it has no special significance.
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// expected case: string
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if(!len)
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{
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while(*str)
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{
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h ^= tolower(*str++);
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h *= 0x01000193u;
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}
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}
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else
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{
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size_t bytes_left = len;
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while(bytes_left != 0)
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{
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h ^= tolower(*str++);
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h *= 0x01000193u;
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bytes_left--;
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}
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}
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return h;
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}
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