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102 lines
3.1 KiB
C++
102 lines
3.1 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// See net/disk_cache/disk_cache.h for the public interface.
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#ifndef NET_DISK_CACHE_BLOCKFILE_STORAGE_BLOCK_H_
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#define NET_DISK_CACHE_BLOCKFILE_STORAGE_BLOCK_H_
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#include <stddef.h>
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#include <stdint.h>
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#include "base/macros.h"
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#include "net/disk_cache/blockfile/addr.h"
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#include "net/disk_cache/blockfile/mapped_file.h"
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namespace disk_cache {
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// This class encapsulates common behavior of a single "block" of data that is
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// stored on a block-file. It implements the FileBlock interface, so it can be
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// serialized directly to the backing file.
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// This object provides a memory buffer for the related data, and it can be used
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// to actually share that memory with another instance of the class.
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//
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// The following example shows how to share storage with another object:
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// StorageBlock<TypeA> a(file, address);
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// StorageBlock<TypeB> b(file, address);
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// a.Load();
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// DoSomething(a.Data());
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// b.SetData(a.Data());
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// ModifySomething(b.Data());
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// // Data modified on the previous call will be saved by b's destructor.
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// b.set_modified();
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template<typename T>
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class StorageBlock : public FileBlock {
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public:
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StorageBlock(MappedFile* file, Addr address);
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virtual ~StorageBlock();
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// FileBlock interface.
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void* buffer() const override;
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size_t size() const override;
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int offset() const override;
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// Allows the overide of dummy values passed on the constructor.
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bool LazyInit(MappedFile* file, Addr address);
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// Sets the internal storage to share the memory provided by other instance.
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void SetData(T* other);
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// Deletes the data, even if it was modified and not saved. This object must
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// own the memory buffer (it cannot be shared).
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void Discard();
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// Stops sharing the data with another object.
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void StopSharingData();
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// Sets the object to lazily save the in-memory data on destruction.
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void set_modified();
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// Forgets that the data was modified, so it's not lazily saved.
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void clear_modified();
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// Gets a pointer to the internal storage (allocates storage if needed).
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T* Data();
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// Returns true if there is data associated with this object.
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bool HasData() const;
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// Returns true if the internal hash is correct.
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bool VerifyHash() const;
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// Returns true if this object owns the data buffer, false if it is shared.
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bool own_data() const;
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const Addr address() const;
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// Loads and store the data.
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bool Load();
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bool Store();
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bool Load(FileIOCallback* callback, bool* completed);
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bool Store(FileIOCallback* callback, bool* completed);
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private:
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void AllocateData();
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void DeleteData();
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uint32_t CalculateHash() const;
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T* data_;
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MappedFile* file_;
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Addr address_;
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bool modified_;
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bool own_data_; // Is data_ owned by this object or shared with someone else.
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bool extended_; // Used to store an entry of more than one block.
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DISALLOW_COPY_AND_ASSIGN(StorageBlock);
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};
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} // namespace disk_cache
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#endif // NET_DISK_CACHE_BLOCKFILE_STORAGE_BLOCK_H_
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