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/*
* Copyright 2010 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef GrTHashCache_DEFINED
#define GrTHashCache_DEFINED
#include "GrTDArray.h"
/**
* Key needs
* static bool EQ(const Entry&, const HashKey&);
* static bool LT(const Entry&, const HashKey&);
* uint32_t getHash() const;
*
* Allows duplicate key entries but on find you may get
* any of the duplicate entries returned.
*/
template <typename T, typename Key, size_t kHashBits> class GrTHashTable {
public:
GrTHashTable() { Gr_bzero(fHash, sizeof(fHash)); }
~GrTHashTable() {}
int count() const { return fSorted.count(); }
T* find(const Key&) const;
// return true if key was unique when inserted.
bool insert(const Key&, T*);
void remove(const Key&, const T*);
T* removeAt(int index, uint32_t hash);
void removeAll();
void deleteAll();
void unrefAll();
/**
* Return the index for the element, using a linear search.
*/
int slowFindIndex(T* elem) const { return fSorted.find(elem); }
#if GR_DEBUG
void validate() const;
bool contains(T*) const;
#endif
// testing
const GrTDArray<T*>& getArray() const { return fSorted; }
private:
enum {
kHashCount = 1 << kHashBits,
kHashMask = kHashCount - 1
};
static unsigned hash2Index(uint32_t hash) {
hash ^= hash >> 16;
if (kHashBits <= 8) {
hash ^= hash >> 8;
}
return hash & kHashMask;
}
mutable T* fHash[kHashCount];
GrTDArray<T*> fSorted;
// search fSorted, and return the found index, or ~index of where it
// should be inserted
int searchArray(const Key&) const;
};
///////////////////////////////////////////////////////////////////////////////
template <typename T, typename Key, size_t kHashBits>
int GrTHashTable<T, Key, kHashBits>::searchArray(const Key& key) const {
int count = fSorted.count();
if (0 == count) {
// we should insert it at 0
return ~0;
}
const T* const* array = fSorted.begin();
int high = count - 1;
int low = 0;
while (high > low) {
int index = (low + high) >> 1;
if (Key::LT(*array[index], key)) {
low = index + 1;
} else {
high = index;
}
}
// check if we found it
if (Key::EQ(*array[high], key)) {
// above search should have found the first occurrence if there
// are multiple.
GrAssert(0 == high || Key::LT(*array[high - 1], key));
return high;
}
// now return the ~ of where we should insert it
if (Key::LT(*array[high], key)) {
high += 1;
}
return ~high;
}
template <typename T, typename Key, size_t kHashBits>
T* GrTHashTable<T, Key, kHashBits>::find(const Key& key) const {
int hashIndex = hash2Index(key.getHash());
T* elem = fHash[hashIndex];
if (NULL == elem || !Key::EQ(*elem, key)) {
// bsearch for the key in our sorted array
int index = this->searchArray(key);
if (index < 0) {
return NULL;
}
elem = fSorted[index];
// update the hash
fHash[hashIndex] = elem;
}
return elem;
}
template <typename T, typename Key, size_t kHashBits>
bool GrTHashTable<T, Key, kHashBits>::insert(const Key& key, T* elem) {
int index = this->searchArray(key);
bool first = index < 0;
if (first) {
// turn it into the actual index
index = ~index;
}
// add it to our array
*fSorted.insert(index) = elem;
// update our hash table (overwrites any dupe's position in the hash)
fHash[hash2Index(key.getHash())] = elem;
return first;
}
template <typename T, typename Key, size_t kHashBits>
void GrTHashTable<T, Key, kHashBits>::remove(const Key& key, const T* elem) {
int index = hash2Index(key.getHash());
if (fHash[index] == elem) {
fHash[index] = NULL;
}
// remove from our sorted array
index = this->searchArray(key);
GrAssert(index >= 0);
// if there are multiple matches searchArray will give us the first match
// march forward until we find elem.
while (elem != fSorted[index]) {
++index;
GrAssert(index < fSorted.count());
}
GrAssert(elem == fSorted[index]);
fSorted.remove(index);
}
template <typename T, typename Key, size_t kHashBits>
T* GrTHashTable<T, Key, kHashBits>::removeAt(int elemIndex, uint32_t hash) {
int hashIndex = hash2Index(hash);
if (fHash[hashIndex] == fSorted[elemIndex]) {
fHash[hashIndex] = NULL;
}
// remove from our sorted array
T* elem = fSorted[elemIndex];
fSorted.remove(elemIndex);
return elem;
}
template <typename T, typename Key, size_t kHashBits>
void GrTHashTable<T, Key, kHashBits>::removeAll() {
fSorted.reset();
Gr_bzero(fHash, sizeof(fHash));
}
template <typename T, typename Key, size_t kHashBits>
void GrTHashTable<T, Key, kHashBits>::deleteAll() {
fSorted.deleteAll();
Gr_bzero(fHash, sizeof(fHash));
}
template <typename T, typename Key, size_t kHashBits>
void GrTHashTable<T, Key, kHashBits>::unrefAll() {
fSorted.unrefAll();
Gr_bzero(fHash, sizeof(fHash));
}
#if GR_DEBUG
template <typename T, typename Key, size_t kHashBits>
void GrTHashTable<T, Key, kHashBits>::validate() const {
for (size_t i = 0; i < GR_ARRAY_COUNT(fHash); i++) {
if (fHash[i]) {
unsigned hashIndex = hash2Index(Key::GetHash(*fHash[i]));
GrAssert(hashIndex == i);
}
}
int count = fSorted.count();
for (int i = 1; i < count; i++) {
GrAssert(Key::LT(*fSorted[i - 1], *fSorted[i]) ||
Key::EQ(*fSorted[i - 1], *fSorted[i]));
}
}
template <typename T, typename Key, size_t kHashBits>
bool GrTHashTable<T, Key, kHashBits>::contains(T* elem) const {
int index = fSorted.find(elem);
return index >= 0;
}
#endif
#endif
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