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/*
* Copyright (C) 2016 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_HARDWARE_HIDL_CACHE_H
#define ANDROID_HARDWARE_HIDL_CACHE_H
#include <utils/Log.h>
namespace android {
namespace hardware {
// A generic cache to map Key to sp<Value>. The cache records are kept with
// wp<Value>, so that it does not block the Value to be garbage collected
// when there's no other sp<> externally.
template <class Key, class Value, class Compare = std::less<Key>>
class HidlCache : public virtual RefBase {
using Mutex = std::mutex;
using Lock = std::lock_guard<Mutex>;
public:
// A RAII class to manage lock/unlock HidlCache.
class HidlCacheLock : public virtual RefBase {
public:
HidlCacheLock(sp<HidlCache> cache, const Key& key) : mCache(cache), mKey(key) {
mCache->lock(mKey);
}
~HidlCacheLock() { mCache->unlock(mKey); }
private:
sp<HidlCache> mCache;
const Key mKey;
};
// lock the IMemory refered by key and keep it alive even if there's no
// other memory block refers to.
virtual bool lock(const Key& key);
virtual sp<Value> unlock(const Key& key);
virtual bool flush(const Key& key);
// fetch the sp<Value> with key from cache,
// make a new instance with fill() if it does not present currently.
virtual sp<Value> fetch(const Key& key);
virtual sp<HidlCacheLock> lockGuard(const Key& key) { return new HidlCacheLock(this, key); }
virtual ~HidlCache() {}
protected:
friend void HidlCacheWhiteBoxTest();
// This method shall be called with a lock held
virtual sp<Value> fillLocked(const Key& key) = 0;
// @return nullptr if it does not present currently.
// @note This method shall be called with a lock held
virtual sp<Value> getCachedLocked(const Key& key);
bool cached(Key key) const { return mCached.count(key) > 0; }
bool locked(Key key) const { return mLocked.count(key) > 0; }
Mutex mMutex;
std::map<Key, wp<Value>, Compare> mCached;
std::map<Key, sp<Value>, Compare> mLocked;
};
template <class Key, class Value, class Compare>
bool HidlCache<Key, Value, Compare>::lock(const Key& key) {
{
Lock lock(mMutex);
if (cached(key)) {
sp<Value> im = mCached[key].promote();
if (im != nullptr) {
mLocked[key] = im;
return true;
} else {
mCached.erase(key);
}
}
}
sp<Value> value = fetch(key);
if (value == nullptr) {
return false;
} else {
Lock lock(mMutex);
mLocked[key] = value;
return true;
}
}
template <class Key, class Value, class Compare>
sp<Value> HidlCache<Key, Value, Compare>::unlock(const Key& key) {
Lock lock(mMutex);
if (locked(key) > 0) {
sp<Value> v = mLocked[key];
mLocked.erase(key);
return v;
}
return nullptr;
}
template <class Key, class Value, class Compare>
bool HidlCache<Key, Value, Compare>::flush(const Key& key) {
Lock lock(mMutex);
bool contain = cached(key);
mCached.erase(key);
return contain;
}
template <class Key, class Value, class Compare>
sp<Value> HidlCache<Key, Value, Compare>::getCachedLocked(const Key& key) {
if (cached(key)) {
wp<Value> cache = mCached[key];
sp<Value> mem = cache.promote();
if (mem != nullptr) {
return mem;
} else {
mCached.erase(key);
}
}
return nullptr;
}
template <class Key, class Value, class Compare>
sp<Value> HidlCache<Key, Value, Compare>::fetch(const Key& key) {
Lock lock(mMutex);
sp<Value> value = getCachedLocked(key);
if (value == nullptr) {
value = fillLocked(key);
}
return value;
}
} // namespace hardware
} // namespace android
#endif
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