pagespeed/kernel/base/null_shared_mem.h

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 PAGESPEED_KERNEL_BASE_NULL_SHARED_MEM_H_
#define PAGESPEED_KERNEL_BASE_NULL_SHARED_MEM_H_

#include <cstddef>
#include "pagespeed/kernel/base/abstract_shared_mem.h"
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/string.h"

namespace net_instaweb {

class MessageHandler;

// A stub implementation of shared memory for systems where we do not
// have a real one. Fails all the operations.
class NullSharedMem : public AbstractSharedMem {
 public:
  NullSharedMem();
  virtual ~NullSharedMem();

  virtual size_t SharedMutexSize() const;

  virtual AbstractSharedMemSegment* CreateSegment(
      const GoogleString& name, size_t size, MessageHandler* handler);

  // Attaches to an existing segment, which must have been created already.
  // May return NULL on failure
  virtual AbstractSharedMemSegment* AttachToSegment(
      const GoogleString& name, size_t size, MessageHandler* handler);

  virtual void DestroySegment(const GoogleString& name,
                              MessageHandler* handler);

  // Does not actually support any operations.
  virtual bool IsDummy() { return true; }

 private:
  DISALLOW_COPY_AND_ASSIGN(NullSharedMem);
};

}  // namespace net_instaweb

#endif  // PAGESPEED_KERNEL_BASE_NULL_SHARED_MEM_H_