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/*
* Copyright (C) 2010 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ANDROID_UTILS_GENERATION_CACHE_H
#define ANDROID_UTILS_GENERATION_CACHE_H
#include <utils/KeyedVector.h>
#include <utils/RefBase.h>
namespace android {
/**
* GenerationCache callback used when an item is removed
*/
template<typename EntryKey, typename EntryValue>
class OnEntryRemoved {
public:
virtual ~OnEntryRemoved() { };
virtual void operator()(EntryKey& key, EntryValue& value) = 0;
}; // class OnEntryRemoved
template<typename EntryKey, typename EntryValue>
struct Entry: public LightRefBase<Entry<EntryKey, EntryValue> > {
Entry(const Entry<EntryKey, EntryValue>& e) :
key(e.key), value(e.value),
parent(e.parent), child(e.child) { }
Entry(const EntryKey& key, const EntryValue& value) :
key(key), value(value) { }
EntryKey key;
EntryValue value;
sp<Entry<EntryKey, EntryValue> > parent; // next older entry
sp<Entry<EntryKey, EntryValue> > child; // next younger entry
}; // struct Entry
/**
* A LRU type cache
*/
template<typename K, typename V>
class GenerationCache {
public:
GenerationCache(uint32_t maxCapacity);
virtual ~GenerationCache();
enum Capacity {
kUnlimitedCapacity,
};
void setOnEntryRemovedListener(OnEntryRemoved<K, V>* listener);
size_t size() const;
void clear();
bool contains(const K& key) const;
const K& getKeyAt(size_t index) const;
const V& getValueAt(size_t index) const;
const V& get(const K& key);
bool put(const K& key, const V& value);
void removeAt(ssize_t index);
bool remove(const K& key);
bool removeOldest();
private:
KeyedVector<K, sp<Entry<K, V> > > mCache;
uint32_t mMaxCapacity;
OnEntryRemoved<K, V>* mListener;
sp<Entry<K, V> > mOldest;
sp<Entry<K, V> > mYoungest;
void attachToCache(const sp<Entry<K, V> >& entry);
void detachFromCache(const sp<Entry<K, V> >& entry);
}; // class GenerationCache
template<typename K, typename V>
GenerationCache<K, V>::GenerationCache(uint32_t maxCapacity): mMaxCapacity(maxCapacity),
mListener(NULL) {
};
template<typename K, typename V>
GenerationCache<K, V>::~GenerationCache() {
clear();
};
template<typename K, typename V>
uint32_t GenerationCache<K, V>::size() const {
return mCache.size();
}
/**
* Should be set by the user of the Cache so that the callback is called whenever an item is
* removed from the cache
*/
template<typename K, typename V>
void GenerationCache<K, V>::setOnEntryRemovedListener(OnEntryRemoved<K, V>* listener) {
mListener = listener;
}
template<typename K, typename V>
void GenerationCache<K, V>::clear() {
if (mListener) {
for (uint32_t i = 0; i < mCache.size(); i++) {
sp<Entry<K, V> > entry = mCache.valueAt(i);
if (mListener) {
(*mListener)(entry->key, entry->value);
}
}
}
mCache.clear();
mYoungest.clear();
mOldest.clear();
}
template<typename K, typename V>
bool GenerationCache<K, V>::contains(const K& key) const {
return mCache.indexOfKey(key) >= 0;
}
template<typename K, typename V>
const K& GenerationCache<K, V>::getKeyAt(size_t index) const {
return mCache.keyAt(index);
}
template<typename K, typename V>
const V& GenerationCache<K, V>::getValueAt(size_t index) const {
return mCache.valueAt(index)->value;
}
template<typename K, typename V>
const V& GenerationCache<K, V>::get(const K& key) {
ssize_t index = mCache.indexOfKey(key);
if (index >= 0) {
const sp<Entry<K, V> >& entry = mCache.valueAt(index);
detachFromCache(entry);
attachToCache(entry);
return entry->value;
}
return NULL;
}
template<typename K, typename V>
bool GenerationCache<K, V>::put(const K& key, const V& value) {
if (mMaxCapacity != kUnlimitedCapacity && mCache.size() >= mMaxCapacity) {
removeOldest();
}
ssize_t index = mCache.indexOfKey(key);
if (index < 0) {
sp<Entry<K, V> > entry = new Entry<K, V>(key, value);
mCache.add(key, entry);
attachToCache(entry);
return true;
}
return false;
}
template<typename K, typename V>
bool GenerationCache<K, V>::remove(const K& key) {
ssize_t index = mCache.indexOfKey(key);
if (index >= 0) {
removeAt(index);
return true;
}
return false;
}
template<typename K, typename V>
void GenerationCache<K, V>::removeAt(ssize_t index) {
sp<Entry<K, V> > entry = mCache.valueAt(index);
if (mListener) {
(*mListener)(entry->key, entry->value);
}
mCache.removeItemsAt(index, 1);
detachFromCache(entry);
}
template<typename K, typename V>
bool GenerationCache<K, V>::removeOldest() {
if (mOldest.get()) {
ssize_t index = mCache.indexOfKey(mOldest->key);
if (index >= 0) {
removeAt(index);
return true;
}
LOGE("GenerationCache: removeOldest failed to find the item in the cache "
"with the given key, but we know it must be in there. "
"Is the key comparator kaput?");
}
return false;
}
template<typename K, typename V>
void GenerationCache<K, V>::attachToCache(const sp<Entry<K, V> >& entry) {
if (!mYoungest.get()) {
mYoungest = mOldest = entry;
} else {
entry->parent = mYoungest;
mYoungest->child = entry;
mYoungest = entry;
}
}
template<typename K, typename V>
void GenerationCache<K, V>::detachFromCache(const sp<Entry<K, V> >& entry) {
if (entry->parent.get()) {
entry->parent->child = entry->child;
} else {
mOldest = entry->child;
}
if (entry->child.get()) {
entry->child->parent = entry->parent;
} else {
mYoungest = entry->parent;
}
entry->parent.clear();
entry->child.clear();
}
}; // namespace android
#endif // ANDROID_UTILS_GENERATION_CACHE_H
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