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/*
* Copyright 2011 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef GrBinHashKey_DEFINED
#define GrBinHashKey_DEFINED
#include "GrTypes.h"
/**
* Hash function class that can take a data chunk of any predetermined length. The hash function
* used is the One-at-a-Time Hash (http://burtleburtle.net/bob/hash/doobs.html).
*
* Keys are computed from Entry objects. Entry must be fully ordered by a member:
* int compare(const GrTBinHashKey<Entry, ..>& k);
* which returns negative if the Entry < k, 0 if it equals k, and positive if k < the Entry.
* Additionally, Entry must be flattenable into the key using setKeyData.
*
* This class satisfies the requirements to be a key for a GrTHashTable.
*/
template<typename Entry, size_t KeySize>
class GrTBinHashKey {
public:
GrTBinHashKey() {
this->reset();
}
GrTBinHashKey(const GrTBinHashKey<Entry, KeySize>& other) {
*this = other;
}
GrTBinHashKey<Entry, KeySize>& operator=(const GrTBinHashKey<Entry, KeySize>& other) {
memcpy(this, &other, sizeof(*this));
return *this;
}
~GrTBinHashKey() {
}
void reset() {
fHash = 0;
#if GR_DEBUG
fIsValid = false;
#endif
}
void setKeyData(const uint32_t* SK_RESTRICT data) {
GrAssert(GrIsALIGN4(KeySize));
memcpy(&fData, data, KeySize);
uint32_t hash = 0;
size_t len = KeySize;
while (len >= 4) {
hash += *data++;
hash += (fHash << 10);
hash ^= (hash >> 6);
len -= 4;
}
hash += (fHash << 3);
hash ^= (fHash >> 11);
hash += (fHash << 15);
#if GR_DEBUG
fIsValid = true;
#endif
fHash = hash;
}
int compare(const GrTBinHashKey<Entry, KeySize>& key) const {
GrAssert(fIsValid && key.fIsValid);
return memcmp(fData, key.fData, KeySize);
}
static bool EQ(const Entry& entry, const GrTBinHashKey<Entry, KeySize>& key) {
GrAssert(key.fIsValid);
return 0 == entry.compare(key);
}
static bool LT(const Entry& entry, const GrTBinHashKey<Entry, KeySize>& key) {
GrAssert(key.fIsValid);
return entry.compare(key) < 0;
}
uint32_t getHash() const {
GrAssert(fIsValid);
return fHash;
}
private:
uint32_t fHash;
uint8_t fData[KeySize]; // Buffer for key storage
#if GR_DEBUG
public:
bool fIsValid;
#endif
};
#endif
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