/*
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* Copyright 2016 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkLRUCache_DEFINED
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#define SkLRUCache_DEFINED
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#include "SkChecksum.h"
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#include "SkTHash.h"
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#include "SkTInternalLList.h"
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/**
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* A generic LRU cache.
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*/
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template <typename K, typename V, typename HashK = SkGoodHash>
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class SkLRUCache : public SkNoncopyable {
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private:
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struct Entry {
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Entry(const K& key, V&& value)
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: fKey(key)
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, fValue(std::move(value)) {}
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K fKey;
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V fValue;
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SK_DECLARE_INTERNAL_LLIST_INTERFACE(Entry);
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};
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public:
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explicit SkLRUCache(int maxCount)
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: fMaxCount(maxCount) {}
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~SkLRUCache() {
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Entry* node = fLRU.head();
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while (node) {
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fLRU.remove(node);
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delete node;
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node = fLRU.head();
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}
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}
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V* find(const K& key) {
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Entry** value = fMap.find(key);
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if (!value) {
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return nullptr;
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}
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Entry* entry = *value;
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if (entry != fLRU.head()) {
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fLRU.remove(entry);
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fLRU.addToHead(entry);
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} // else it's already at head position, don't need to do anything
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return &entry->fValue;
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}
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V* insert(const K& key, V value) {
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Entry* entry = new Entry(key, std::move(value));
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fMap.set(entry);
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fLRU.addToHead(entry);
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while (fMap.count() > fMaxCount) {
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this->remove(fLRU.tail()->fKey);
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}
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return &entry->fValue;
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}
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int count() {
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return fMap.count();
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}
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template <typename Fn> // f(V*)
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void foreach(Fn&& fn) {
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typename SkTInternalLList<Entry>::Iter iter;
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for (Entry* e = iter.init(fLRU, SkTInternalLList<Entry>::Iter::kHead_IterStart); e;
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e = iter.next()) {
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fn(&e->fValue);
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}
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}
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void reset() {
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fMap.reset();
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for (Entry* e = fLRU.head(); e; e = fLRU.head()) {
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fLRU.remove(e);
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delete e;
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}
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}
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private:
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struct Traits {
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static const K& GetKey(Entry* e) {
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return e->fKey;
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}
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static uint32_t Hash(const K& k) {
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return HashK()(k);
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}
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};
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void remove(const K& key) {
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Entry** value = fMap.find(key);
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SkASSERT(value);
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Entry* entry = *value;
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SkASSERT(key == entry->fKey);
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fMap.remove(key);
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fLRU.remove(entry);
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delete entry;
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}
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int fMaxCount;
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SkTHashTable<Entry*, K, Traits> fMap;
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SkTInternalLList<Entry> fLRU;
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};
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#endif
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