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88 lines
2.5 KiB
C++
88 lines
2.5 KiB
C++
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "CacheHashUtils.h"
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#include "plstr.h"
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namespace mozilla {
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namespace net {
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/**
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* CacheHashUtils::Hash(const char * key, uint32_t initval)
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*
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* See http://burtleburtle.net/bob/hash/evahash.html for more information
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* about this hash function.
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*
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* This algorithm is used to check the data integrity.
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*/
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static inline void hashmix(uint32_t& a, uint32_t& b, uint32_t& c)
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{
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a -= b; a -= c; a ^= (c>>13);
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b -= c; b -= a; b ^= (a<<8);
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c -= a; c -= b; c ^= (b>>13);
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a -= b; a -= c; a ^= (c>>12);
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b -= c; b -= a; b ^= (a<<16);
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c -= a; c -= b; c ^= (b>>5);
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a -= b; a -= c; a ^= (c>>3);
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b -= c; b -= a; b ^= (a<<10);
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c -= a; c -= b; c ^= (b>>15);
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}
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CacheHashUtils::Hash32_t
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CacheHashUtils::Hash(const char *aData, uint32_t aSize, uint32_t aInitval)
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{
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const uint8_t *k = reinterpret_cast<const uint8_t*>(aData);
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uint32_t a, b, c, len/*, length*/;
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// length = PL_strlen(key);
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/* Set up the internal state */
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len = aSize;
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a = b = 0x9e3779b9; /* the golden ratio; an arbitrary value */
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c = aInitval; /* variable initialization of internal state */
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/*---------------------------------------- handle most of the key */
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while (len >= 12)
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{
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a += k[0] + (uint32_t(k[1])<<8) + (uint32_t(k[2])<<16) + (uint32_t(k[3])<<24);
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b += k[4] + (uint32_t(k[5])<<8) + (uint32_t(k[6])<<16) + (uint32_t(k[7])<<24);
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c += k[8] + (uint32_t(k[9])<<8) + (uint32_t(k[10])<<16) + (uint32_t(k[11])<<24);
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hashmix(a, b, c);
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k += 12; len -= 12;
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}
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/*------------------------------------- handle the last 11 bytes */
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c += aSize;
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switch(len) { /* all the case statements fall through */
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case 11: c += (uint32_t(k[10])<<24);
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case 10: c += (uint32_t(k[9])<<16);
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case 9 : c += (uint32_t(k[8])<<8);
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/* the low-order byte of c is reserved for the length */
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case 8 : b += (uint32_t(k[7])<<24);
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case 7 : b += (uint32_t(k[6])<<16);
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case 6 : b += (uint32_t(k[5])<<8);
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case 5 : b += k[4];
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case 4 : a += (uint32_t(k[3])<<24);
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case 3 : a += (uint32_t(k[2])<<16);
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case 2 : a += (uint32_t(k[1])<<8);
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case 1 : a += k[0];
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/* case 0: nothing left to add */
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}
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hashmix(a, b, c);
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return c;
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}
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CacheHashUtils::Hash16_t
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CacheHashUtils::Hash16(const char *aData, uint32_t aSize, uint32_t aInitval)
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{
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Hash32_t hash = Hash(aData, aSize, aInitval);
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return (hash & 0xFFFF);
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}
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} // net
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} // mozilla
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