1 2 /* 3 * Copyright 2011 Google Inc. 4 * 5 * Use of this source code is governed by a BSD-style license that can be 6 * found in the LICENSE file. 7 */ 8 9 10 #ifndef GrBinHashKey_DEFINED 11 #define GrBinHashKey_DEFINED 12 13 #include "GrTypes.h" 14 15 /** 16 * Hash function class that can take a data chunk of any predetermined 17 * length. The hash function used is the One-at-a-Time Hash 18 * (http://burtleburtle.net/bob/hash/doobs.html). 19 */ 20 template<typename Entry, size_t KeySize> 21 class GrBinHashKey { 22 public: GrBinHashKey()23 GrBinHashKey() 24 : fHash(0) 25 #if GR_DEBUG 26 , fIsValid(false) 27 #endif 28 {} 29 GrBinHashKey(const GrBinHashKey<Entry,KeySize> & other)30 GrBinHashKey(const GrBinHashKey<Entry, KeySize>& other) { 31 *this = other; 32 } 33 GrBinHashKey<Entry, KeySize>& operator=(const GrBinHashKey<Entry, 34 KeySize>& other) { 35 memcpy(this, &other, sizeof(*this)); 36 return *this; 37 } 38 ~GrBinHashKey()39 ~GrBinHashKey() { 40 } 41 setKeyData(const uint32_t * SK_RESTRICT data)42 void setKeyData(const uint32_t* SK_RESTRICT data) { 43 GrAssert(GrIsALIGN4(KeySize)); 44 memcpy(&fData, data, KeySize); 45 46 uint32_t hash = 0; 47 size_t len = KeySize; 48 while (len >= 4) { 49 hash += *data++; 50 hash += (fHash << 10); 51 hash ^= (hash >> 6); 52 len -= 4; 53 } 54 hash += (fHash << 3); 55 hash ^= (fHash >> 11); 56 hash += (fHash << 15); 57 #if GR_DEBUG 58 fIsValid = true; 59 #endif 60 fHash = hash; 61 } 62 compare(const GrBinHashKey<Entry,KeySize> & key)63 int compare(const GrBinHashKey<Entry, KeySize>& key) const { 64 GrAssert(fIsValid && key.fIsValid); 65 return memcmp(fData, key.fData, KeySize); 66 } 67 68 static bool EQ(const Entry & entry,const GrBinHashKey<Entry,KeySize> & key)69 EQ(const Entry& entry, const GrBinHashKey<Entry, KeySize>& key) { 70 GrAssert(key.fIsValid); 71 return 0 == entry.compare(key); 72 } 73 74 static bool LT(const Entry & entry,const GrBinHashKey<Entry,KeySize> & key)75 LT(const Entry& entry, const GrBinHashKey<Entry, KeySize>& key) { 76 GrAssert(key.fIsValid); 77 return entry.compare(key) < 0; 78 } 79 getHash()80 uint32_t getHash() const { 81 GrAssert(fIsValid); 82 return fHash; 83 } 84 85 private: 86 uint32_t fHash; 87 uint8_t fData[KeySize]; //Buffer for key storage 88 89 #if GR_DEBUG 90 public: 91 bool fIsValid; 92 #endif 93 }; 94 95 #endif 96