1// Copyright (c) 2010 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5// See net/disk_cache/disk_cache.h for the public interface. 6 7#ifndef NET_DISK_CACHE_STORAGE_BLOCK_H__ 8#define NET_DISK_CACHE_STORAGE_BLOCK_H__ 9#pragma once 10 11#include "net/disk_cache/addr.h" 12#include "net/disk_cache/mapped_file.h" 13 14namespace disk_cache { 15 16// This class encapsulates common behavior of a single "block" of data that is 17// stored on a block-file. It implements the FileBlock interface, so it can be 18// serialized directly to the backing file. 19// This object provides a memory buffer for the related data, and it can be used 20// to actually share that memory with another instance of the class. 21// 22// The following example shows how to share storage with another object: 23// StorageBlock<TypeA> a(file, address); 24// StorageBlock<TypeB> b(file, address); 25// a.Load(); 26// DoSomething(a.Data()); 27// b.SetData(a.Data()); 28// ModifySomething(b.Data()); 29// // Data modified on the previous call will be saved by b's destructor. 30// b.set_modified(); 31template<typename T> 32class StorageBlock : public FileBlock { 33 public: 34 StorageBlock(MappedFile* file, Addr address); 35 virtual ~StorageBlock(); 36 37 // FileBlock interface. 38 virtual void* buffer() const; 39 virtual size_t size() const; 40 virtual int offset() const; 41 42 // Allows the overide of dummy values passed on the constructor. 43 bool LazyInit(MappedFile* file, Addr address); 44 45 // Sets the internal storage to share the memory provided by other instance. 46 void SetData(T* other); 47 48 // Deletes the data, even if it was modified and not saved. This object must 49 // own the memory buffer (it cannot be shared). 50 void Discard(); 51 52 // Stops sharing the data with another object. 53 void StopSharingData(); 54 55 // Sets the object to lazily save the in-memory data on destruction. 56 void set_modified(); 57 58 // Gets a pointer to the internal storage (allocates storage if needed). 59 T* Data(); 60 61 // Returns true if there is data associated with this object. 62 bool HasData() const; 63 64 // Returns true if this object owns the data buffer, false if it is shared. 65 bool own_data() const; 66 67 const Addr address() const; 68 69 // Loads and store the data. 70 bool Load(); 71 bool Store(); 72 73 private: 74 void AllocateData(); 75 void DeleteData(); 76 77 T* data_; 78 MappedFile* file_; 79 Addr address_; 80 bool modified_; 81 bool own_data_; // Is data_ owned by this object or shared with someone else. 82 bool extended_; // Used to store an entry of more than one block. 83 84 DISALLOW_COPY_AND_ASSIGN(StorageBlock); 85}; 86 87typedef StorageBlock<EntryStore> CacheEntryBlock; 88typedef StorageBlock<RankingsNode> CacheRankingsBlock; 89 90} // namespace disk_cache 91 92#endif // NET_DISK_CACHE_STORAGE_BLOCK_H__ 93