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annotate libs/assimp/Hash.h @ 0:b2f14e535253

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author John Tsiombikas <nuclear@member.fsf.org>
date Sat, 01 Feb 2014 19:58:19 +0200
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nuclear@0 1 /*
nuclear@0 2 Open Asset Import Library (assimp)
nuclear@0 3 ----------------------------------------------------------------------
nuclear@0 4
nuclear@0 5 Copyright (c) 2006-2012, assimp team
nuclear@0 6 All rights reserved.
nuclear@0 7
nuclear@0 8 Redistribution and use of this software in source and binary forms,
nuclear@0 9 with or without modification, are permitted provided that the
nuclear@0 10 following conditions are met:
nuclear@0 11
nuclear@0 12 * Redistributions of source code must retain the above
nuclear@0 13 copyright notice, this list of conditions and the
nuclear@0 14 following disclaimer.
nuclear@0 15
nuclear@0 16 * Redistributions in binary form must reproduce the above
nuclear@0 17 copyright notice, this list of conditions and the
nuclear@0 18 following disclaimer in the documentation and/or other
nuclear@0 19 materials provided with the distribution.
nuclear@0 20
nuclear@0 21 * Neither the name of the assimp team, nor the names of its
nuclear@0 22 contributors may be used to endorse or promote products
nuclear@0 23 derived from this software without specific prior
nuclear@0 24 written permission of the assimp team.
nuclear@0 25
nuclear@0 26 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
nuclear@0 27 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
nuclear@0 28 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
nuclear@0 29 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
nuclear@0 30 OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
nuclear@0 31 SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
nuclear@0 32 LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
nuclear@0 33 DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
nuclear@0 34 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
nuclear@0 35 (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
nuclear@0 36 OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
nuclear@0 37
nuclear@0 38 ----------------------------------------------------------------------
nuclear@0 39 */
nuclear@0 40
nuclear@0 41 #ifndef AI_HASH_H_INCLUDED
nuclear@0 42 #define AI_HASH_H_INCLUDED
nuclear@0 43
nuclear@0 44 // ------------------------------------------------------------------------------------------------
nuclear@0 45 // Hashing function taken from
nuclear@0 46 // http://www.azillionmonkeys.com/qed/hash.html
nuclear@0 47 // (incremental version)
nuclear@0 48 //
nuclear@0 49 // This code is Copyright 2004-2008 by Paul Hsieh. It is used here in the belief that
nuclear@0 50 // Assimp's license is considered compatible with Pauls's derivative license as specified
nuclear@0 51 // on his web page.
nuclear@0 52 //
nuclear@0 53 // (stdint.h should have been been included here)
nuclear@0 54 // ------------------------------------------------------------------------------------------------
nuclear@0 55 #undef get16bits
nuclear@0 56 #if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
nuclear@0 57 || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
nuclear@0 58 #define get16bits(d) (*((const uint16_t *) (d)))
nuclear@0 59 #endif
nuclear@0 60
nuclear@0 61 #if !defined (get16bits)
nuclear@0 62 #define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
nuclear@0 63 +(uint32_t)(((const uint8_t *)(d))[0]) )
nuclear@0 64 #endif
nuclear@0 65
nuclear@0 66 // ------------------------------------------------------------------------------------------------
nuclear@0 67 inline uint32_t SuperFastHash (const char * data, uint32_t len = 0, uint32_t hash = 0) {
nuclear@0 68 uint32_t tmp;
nuclear@0 69 int rem;
nuclear@0 70
nuclear@0 71 if (!data) return 0;
nuclear@0 72 if (!len)len = (uint32_t)::strlen(data);
nuclear@0 73
nuclear@0 74 rem = len & 3;
nuclear@0 75 len >>= 2;
nuclear@0 76
nuclear@0 77 /* Main loop */
nuclear@0 78 for (;len > 0; len--) {
nuclear@0 79 hash += get16bits (data);
nuclear@0 80 tmp = (get16bits (data+2) << 11) ^ hash;
nuclear@0 81 hash = (hash << 16) ^ tmp;
nuclear@0 82 data += 2*sizeof (uint16_t);
nuclear@0 83 hash += hash >> 11;
nuclear@0 84 }
nuclear@0 85
nuclear@0 86 /* Handle end cases */
nuclear@0 87 switch (rem) {
nuclear@0 88 case 3: hash += get16bits (data);
nuclear@0 89 hash ^= hash << 16;
nuclear@0 90 hash ^= data[sizeof (uint16_t)] << 18;
nuclear@0 91 hash += hash >> 11;
nuclear@0 92 break;
nuclear@0 93 case 2: hash += get16bits (data);
nuclear@0 94 hash ^= hash << 11;
nuclear@0 95 hash += hash >> 17;
nuclear@0 96 break;
nuclear@0 97 case 1: hash += *data;
nuclear@0 98 hash ^= hash << 10;
nuclear@0 99 hash += hash >> 1;
nuclear@0 100 }
nuclear@0 101
nuclear@0 102 /* Force "avalanching" of final 127 bits */
nuclear@0 103 hash ^= hash << 3;
nuclear@0 104 hash += hash >> 5;
nuclear@0 105 hash ^= hash << 4;
nuclear@0 106 hash += hash >> 17;
nuclear@0 107 hash ^= hash << 25;
nuclear@0 108 hash += hash >> 6;
nuclear@0 109
nuclear@0 110 return hash;
nuclear@0 111 }
nuclear@0 112
nuclear@0 113 #endif // !! AI_HASH_H_INCLUDED