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1 // Copyright (c) 2012 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 #ifndef NET_DISK_CACHE_MEMORY_MEM_ENTRY_IMPL_H_ | |
6 #define NET_DISK_CACHE_MEMORY_MEM_ENTRY_IMPL_H_ | |
7 | |
8 #include "base/containers/hash_tables.h" | |
9 #include "base/gtest_prod_util.h" | |
10 #include "base/memory/scoped_ptr.h" | |
11 #include "net/base/net_log.h" | |
12 #include "net/disk_cache/disk_cache.h" | |
13 | |
14 namespace disk_cache { | |
15 | |
16 class MemBackendImpl; | |
17 | |
18 // This class implements the Entry interface for the memory-only cache. An | |
19 // object of this class represents a single entry on the cache. We use two | |
20 // types of entries, parent and child to support sparse caching. | |
21 // | |
22 // A parent entry is non-sparse until a sparse method is invoked (i.e. | |
23 // ReadSparseData, WriteSparseData, GetAvailableRange) when sparse information | |
24 // is initialized. It then manages a list of child entries and delegates the | |
25 // sparse API calls to the child entries. It creates and deletes child entries | |
26 // and updates the list when needed. | |
27 // | |
28 // A child entry is used to carry partial cache content, non-sparse methods like | |
29 // ReadData and WriteData cannot be applied to them. The lifetime of a child | |
30 // entry is managed by the parent entry that created it except that the entry | |
31 // can be evicted independently. A child entry does not have a key and it is not | |
32 // registered in the backend's entry map. It is registered in the backend's | |
33 // ranking list to enable eviction of a partial content. | |
34 // | |
35 // A sparse entry has a fixed maximum size and can be partially filled. There | |
36 // can only be one continous filled region in a sparse entry, as illustrated by | |
37 // the following example: | |
38 // | xxx ooooo | | |
39 // x = unfilled region | |
40 // o = filled region | |
41 // It is guranteed that there is at most one unfilled region and one filled | |
42 // region, and the unfilled region (if there is one) is always before the filled | |
43 // region. The book keeping for filled region in a sparse entry is done by using | |
44 // the variable |child_first_pos_| (inclusive). | |
45 | |
46 class MemEntryImpl : public Entry { | |
47 public: | |
48 enum EntryType { | |
49 kParentEntry, | |
50 kChildEntry, | |
51 }; | |
52 | |
53 explicit MemEntryImpl(MemBackendImpl* backend); | |
54 | |
55 // Performs the initialization of a EntryImpl that will be added to the | |
56 // cache. | |
57 bool CreateEntry(const std::string& key, net::NetLog* net_log); | |
58 | |
59 // Permanently destroys this entry. | |
60 void InternalDoom(); | |
61 | |
62 void Open(); | |
63 bool InUse(); | |
64 | |
65 MemEntryImpl* next() const { | |
66 return next_; | |
67 } | |
68 | |
69 MemEntryImpl* prev() const { | |
70 return prev_; | |
71 } | |
72 | |
73 void set_next(MemEntryImpl* next) { | |
74 next_ = next; | |
75 } | |
76 | |
77 void set_prev(MemEntryImpl* prev) { | |
78 prev_ = prev; | |
79 } | |
80 | |
81 EntryType type() const { | |
82 return parent_ ? kChildEntry : kParentEntry; | |
83 } | |
84 | |
85 const net::BoundNetLog& net_log() { | |
86 return net_log_; | |
87 } | |
88 | |
89 // Entry interface. | |
90 void Doom() override; | |
91 void Close() override; | |
92 std::string GetKey() const override; | |
93 base::Time GetLastUsed() const override; | |
94 base::Time GetLastModified() const override; | |
95 int32 GetDataSize(int index) const override; | |
96 int ReadData(int index, | |
97 int offset, | |
98 IOBuffer* buf, | |
99 int buf_len, | |
100 const CompletionCallback& callback) override; | |
101 int WriteData(int index, | |
102 int offset, | |
103 IOBuffer* buf, | |
104 int buf_len, | |
105 const CompletionCallback& callback, | |
106 bool truncate) override; | |
107 int ReadSparseData(int64 offset, | |
108 IOBuffer* buf, | |
109 int buf_len, | |
110 const CompletionCallback& callback) override; | |
111 int WriteSparseData(int64 offset, | |
112 IOBuffer* buf, | |
113 int buf_len, | |
114 const CompletionCallback& callback) override; | |
115 int GetAvailableRange(int64 offset, | |
116 int len, | |
117 int64* start, | |
118 const CompletionCallback& callback) override; | |
119 bool CouldBeSparse() const override; | |
120 void CancelSparseIO() override {} | |
121 int ReadyForSparseIO(const CompletionCallback& callback) override; | |
122 | |
123 private: | |
124 typedef base::hash_map<int, MemEntryImpl*> EntryMap; | |
125 | |
126 enum { | |
127 NUM_STREAMS = 3 | |
128 }; | |
129 | |
130 ~MemEntryImpl() override; | |
131 | |
132 // Do all the work for corresponding public functions. Implemented as | |
133 // separate functions to make logging of results simpler. | |
134 int InternalReadData(int index, int offset, IOBuffer* buf, int buf_len); | |
135 int InternalWriteData(int index, int offset, IOBuffer* buf, int buf_len, | |
136 bool truncate); | |
137 int InternalReadSparseData(int64 offset, IOBuffer* buf, int buf_len); | |
138 int InternalWriteSparseData(int64 offset, IOBuffer* buf, int buf_len); | |
139 | |
140 // Old Entry interface. | |
141 int GetAvailableRange(int64 offset, int len, int64* start); | |
142 | |
143 // Grows and cleans up the data buffer. | |
144 void PrepareTarget(int index, int offset, int buf_len); | |
145 | |
146 // Updates ranking information. | |
147 void UpdateRank(bool modified); | |
148 | |
149 // Initializes the children map and sparse info. This method is only called | |
150 // on a parent entry. | |
151 bool InitSparseInfo(); | |
152 | |
153 // Performs the initialization of a MemEntryImpl as a child entry. | |
154 // |parent| is the pointer to the parent entry. |child_id| is the ID of | |
155 // the new child. | |
156 bool InitChildEntry(MemEntryImpl* parent, int child_id, net::NetLog* net_log); | |
157 | |
158 // Returns an entry responsible for |offset|. The returned entry can be a | |
159 // child entry or this entry itself if |offset| points to the first range. | |
160 // If such entry does not exist and |create| is true, a new child entry is | |
161 // created. | |
162 MemEntryImpl* OpenChild(int64 offset, bool create); | |
163 | |
164 // Finds the first child located within the range [|offset|, |offset + len|). | |
165 // Returns the number of bytes ahead of |offset| to reach the first available | |
166 // bytes in the entry. The first child found is output to |child|. | |
167 int FindNextChild(int64 offset, int len, MemEntryImpl** child); | |
168 | |
169 // Removes child indexed by |child_id| from the children map. | |
170 void DetachChild(int child_id); | |
171 | |
172 std::string key_; | |
173 std::vector<char> data_[NUM_STREAMS]; // User data. | |
174 int32 data_size_[NUM_STREAMS]; | |
175 int ref_count_; | |
176 | |
177 int child_id_; // The ID of a child entry. | |
178 int child_first_pos_; // The position of the first byte in a child | |
179 // entry. | |
180 MemEntryImpl* next_; // Pointers for the LRU list. | |
181 MemEntryImpl* prev_; | |
182 MemEntryImpl* parent_; // Pointer to the parent entry. | |
183 scoped_ptr<EntryMap> children_; | |
184 | |
185 base::Time last_modified_; // LRU information. | |
186 base::Time last_used_; | |
187 MemBackendImpl* backend_; // Back pointer to the cache. | |
188 bool doomed_; // True if this entry was removed from the cache. | |
189 | |
190 net::BoundNetLog net_log_; | |
191 | |
192 DISALLOW_COPY_AND_ASSIGN(MemEntryImpl); | |
193 }; | |
194 | |
195 } // namespace disk_cache | |
196 | |
197 #endif // NET_DISK_CACHE_MEMORY_MEM_ENTRY_IMPL_H_ | |
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