/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef ANDROID_HARDWARE_HIDL_CACHE_H
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#define ANDROID_HARDWARE_HIDL_CACHE_H
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#include <utils/Log.h>
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namespace android {
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namespace hardware {
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// A generic cache to map Key to sp<Value>. The cache records are kept with
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// wp<Value>, so that it does not block the Value to be garbage collected
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// when there's no other sp<> externally.
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template <class Key, class Value, class Compare = std::less<Key>>
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class HidlCache : public virtual RefBase {
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using Mutex = std::mutex;
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using Lock = std::lock_guard<Mutex>;
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public:
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// A RAII class to manage lock/unlock HidlCache.
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class HidlCacheLock : public virtual RefBase {
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public:
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HidlCacheLock(sp<HidlCache> cache, const Key& key) : mCache(cache), mKey(key) {
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mCache->lock(mKey);
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}
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~HidlCacheLock() { mCache->unlock(mKey); }
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private:
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sp<HidlCache> mCache;
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const Key mKey;
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};
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// lock the IMemory refered by key and keep it alive even if there's no
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// other memory block refers to.
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virtual bool lock(const Key& key);
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virtual sp<Value> unlock(const Key& key);
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virtual bool flush(const Key& key);
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// fetch the sp<Value> with key from cache,
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// make a new instance with fill() if it does not present currently.
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virtual sp<Value> fetch(const Key& key);
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virtual sp<HidlCacheLock> lockGuard(const Key& key) { return new HidlCacheLock(this, key); }
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virtual ~HidlCache() {}
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protected:
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friend void HidlCacheWhiteBoxTest();
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// This method shall be called with a lock held
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virtual sp<Value> fillLocked(const Key& key) = 0;
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// @return nullptr if it does not present currently.
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// @note This method shall be called with a lock held
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virtual sp<Value> getCachedLocked(const Key& key);
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bool cached(Key key) const { return mCached.count(key) > 0; }
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bool locked(Key key) const { return mLocked.count(key) > 0; }
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Mutex mMutex;
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std::map<Key, wp<Value>, Compare> mCached;
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std::map<Key, sp<Value>, Compare> mLocked;
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};
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template <class Key, class Value, class Compare>
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bool HidlCache<Key, Value, Compare>::lock(const Key& key) {
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{
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Lock lock(mMutex);
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if (cached(key)) {
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sp<Value> im = mCached[key].promote();
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if (im != nullptr) {
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mLocked[key] = im;
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return true;
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} else {
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mCached.erase(key);
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}
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}
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}
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sp<Value> value = fetch(key);
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if (value == nullptr) {
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return false;
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} else {
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Lock lock(mMutex);
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mLocked[key] = value;
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return true;
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}
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}
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template <class Key, class Value, class Compare>
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sp<Value> HidlCache<Key, Value, Compare>::unlock(const Key& key) {
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Lock lock(mMutex);
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if (locked(key)) {
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sp<Value> v = mLocked[key];
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mLocked.erase(key);
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return v;
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}
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return nullptr;
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}
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template <class Key, class Value, class Compare>
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bool HidlCache<Key, Value, Compare>::flush(const Key& key) {
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Lock lock(mMutex);
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bool contain = cached(key);
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mCached.erase(key);
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return contain;
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}
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template <class Key, class Value, class Compare>
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sp<Value> HidlCache<Key, Value, Compare>::getCachedLocked(const Key& key) {
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if (cached(key)) {
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wp<Value> cache = mCached[key];
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sp<Value> mem = cache.promote();
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if (mem != nullptr) {
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return mem;
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} else {
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mCached.erase(key);
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}
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}
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return nullptr;
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}
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template <class Key, class Value, class Compare>
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sp<Value> HidlCache<Key, Value, Compare>::fetch(const Key& key) {
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Lock lock(mMutex);
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sp<Value> value = getCachedLocked(key);
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if (value == nullptr) {
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value = fillLocked(key);
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}
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return value;
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}
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} // namespace hardware
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} // namespace android
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#endif
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