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