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// Copyright 2008, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// See net/disk_cache/disk_cache.h for the public interface.
#ifndef NET_DISK_CACHE_STORAGE_BLOCK_H__
#define NET_DISK_CACHE_STORAGE_BLOCK_H__
#include "net/disk_cache/addr.h"
#include "net/disk_cache/mapped_file.h"
namespace disk_cache {
class EntryImpl;
// This class encapsulates common behavior of a single "block" of data that is
// stored on a block-file. It implements the FileBlock interface, so it can be
// serialized directly to the backing file.
// This object provides a memory buffer for the related data, and it can be used
// to actually share that memory with another instance of the class.
//
// The following example shows how to share storage with another object:
// StorageBlock<TypeA> a(file, address);
// StorageBlock<TypeB> b(file, address);
// a.Load();
// DoSomething(a.Data());
// b.SetData(a.Data());
// ModifySomething(b.Data());
// // Data modified on the previous call will be saved by b's destructor.
// b.set_modified();
template<typename T>
class StorageBlock : public FileBlock {
public:
StorageBlock(MappedFile* file, Addr address);
virtual ~StorageBlock();
// FileBlock interface.
virtual void* buffer() const;
virtual size_t size() const;
virtual DWORD offset() const;
// Allows the overide of dummy values passed on the constructor.
bool LazyInit(MappedFile* file, Addr address);
// Sets the internal storage to share the momory provided by other instance.
void SetData(T* other);
// Sets the object to lazily save the in-memory data on destruction.
void set_modified();
// Gets a pointer to the internal storage (allocates storage if needed).
T* Data();
// Returns true if there is data associated with this object.
bool HasData() const;
const Addr address() const;
// Loads and store the data.
bool Load();
bool Store();
private:
void AllocateData();
T* data_;
MappedFile* file_;
Addr address_;
bool modified_;
bool own_data_; // Is data_ owned by this object or shared with someone else.
bool extended_; // Used to store an entry of more than one block.
DISALLOW_EVIL_CONSTRUCTORS(StorageBlock);
};
typedef StorageBlock<EntryStore> CacheEntryBlock;
typedef StorageBlock<RankingsNode> CacheRankingsBlock;
} // namespace disk_cache
#endif // NET_DISK_CACHE_STORAGE_BLOCK_H__
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