pagespeed/kernel/cache/threadsafe_cache.h

/*
 * Copyright 2010 Google Inc.
 *
 * 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.
 */

// Author: jmarantz@google.com (Joshua Marantz)

#ifndef PAGESPEED_KERNEL_CACHE_THREADSAFE_CACHE_H_
#define PAGESPEED_KERNEL_CACHE_THREADSAFE_CACHE_H_

#include "pagespeed/kernel/base/abstract_mutex.h"
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/scoped_ptr.h"
#include "pagespeed/kernel/base/shared_string.h"
#include "pagespeed/kernel/base/string.h"
#include "pagespeed/kernel/base/string_util.h"
#include "pagespeed/kernel/base/thread_annotations.h"
#include "pagespeed/kernel/cache/cache_interface.h"

namespace net_instaweb {

// Composes a cache with a Mutex to form a threadsafe cache.  Note
// that cache callbacks will be run in a thread that is dependent
// on the cache implementation.  This wrapper class just guarantees
// the thread safety of the cache itself, not the callbacks.
//
// WARNING: THIS IMPLEMENTATION HOLDS A LOCK ACROSS THE VALIDATOR.
// TODO(jmarantz): redesign the interface between this class and
// the cache it protects.
class ThreadsafeCache : public CacheInterface {
 public:
  // Does not takes ownership of cache.  Takes ownership of mutex.
  ThreadsafeCache(CacheInterface* cache, AbstractMutex* mutex)
      : cache_(cache),
        mutex_(mutex) {
  }
  virtual ~ThreadsafeCache();

  virtual void Get(const GoogleString& key, Callback* callback);
  virtual void Put(const GoogleString& key, const SharedString& value)
      LOCKS_EXCLUDED(mutex_);
  virtual void Delete(const GoogleString& key) LOCKS_EXCLUDED(mutex_);
  virtual CacheInterface* Backend() { return cache_; }
  virtual bool IsBlocking() const { return cache_->IsBlocking(); }
  virtual bool IsHealthy() const LOCKS_EXCLUDED(mutex_);
  virtual void ShutDown() LOCKS_EXCLUDED(mutex_);

  static GoogleString FormatName(StringPiece cache);
  virtual GoogleString Name() const { return FormatName(cache_->Name()); }

 private:
  CacheInterface* cache_;
  scoped_ptr<AbstractMutex> mutex_;

  DISALLOW_COPY_AND_ASSIGN(ThreadsafeCache);
};

}  // namespace net_instaweb

#endif  // PAGESPEED_KERNEL_CACHE_THREADSAFE_CACHE_H_