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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_BLOCKFILE_SPARSE_CONTROL_H_ | |
6 #define NET_DISK_CACHE_BLOCKFILE_SPARSE_CONTROL_H_ | |
7 | |
8 #include <string> | |
9 #include <vector> | |
10 | |
11 #include "base/basictypes.h" | |
12 #include "base/compiler_specific.h" | |
13 #include "net/base/completion_callback.h" | |
14 #include "net/disk_cache/blockfile/bitmap.h" | |
15 #include "net/disk_cache/blockfile/disk_format.h" | |
16 | |
17 namespace net { | |
18 class IOBuffer; | |
19 class DrainableIOBuffer; | |
20 } | |
21 | |
22 namespace disk_cache { | |
23 | |
24 class Entry; | |
25 class EntryImpl; | |
26 | |
27 // This class provides support for the sparse capabilities of the disk cache. | |
28 // Basically, sparse IO is directed from EntryImpl to this class, and we split | |
29 // the operation into multiple small pieces, sending each one to the | |
30 // appropriate entry. An instance of this class is asociated with each entry | |
31 // used directly for sparse operations (the entry passed in to the constructor). | |
32 class SparseControl { | |
33 public: | |
34 typedef net::CompletionCallback CompletionCallback; | |
35 | |
36 // The operation to perform. | |
37 enum SparseOperation { | |
38 kNoOperation, | |
39 kReadOperation, | |
40 kWriteOperation, | |
41 kGetRangeOperation | |
42 }; | |
43 | |
44 explicit SparseControl(EntryImpl* entry); | |
45 ~SparseControl(); | |
46 | |
47 // Initializes the object for the current entry. If this entry already stores | |
48 // sparse data, or can be used to do it, it updates the relevant information | |
49 // on disk and returns net::OK. Otherwise it returns a net error code. | |
50 int Init(); | |
51 | |
52 // Performs a quick test to see if the entry is sparse or not, without | |
53 // generating disk IO (so the answer provided is only a best effort). | |
54 bool CouldBeSparse() const; | |
55 | |
56 // Performs an actual sparse read or write operation for this entry. |op| is | |
57 // the operation to perform, |offset| is the desired sparse offset, |buf| and | |
58 // |buf_len| specify the actual data to use and |callback| is the callback | |
59 // to use for asynchronous operations. See the description of the Read / | |
60 // WriteSparseData for details about the arguments. The return value is the | |
61 // number of bytes read or written, or a net error code. | |
62 int StartIO(SparseOperation op, int64 offset, net::IOBuffer* buf, | |
63 int buf_len, const CompletionCallback& callback); | |
64 | |
65 // Implements Entry::GetAvailableRange(). | |
66 int GetAvailableRange(int64 offset, int len, int64* start); | |
67 | |
68 // Cancels the current sparse operation (if any). | |
69 void CancelIO(); | |
70 | |
71 // Returns OK if the entry can be used for new IO or ERR_IO_PENDING if we are | |
72 // busy. If the entry is busy, we'll invoke the callback when we are ready | |
73 // again. See disk_cache::Entry::ReadyToUse() for more info. | |
74 int ReadyToUse(const CompletionCallback& completion_callback); | |
75 | |
76 // Deletes the children entries of |entry|. | |
77 static void DeleteChildren(EntryImpl* entry); | |
78 | |
79 private: | |
80 // Creates a new sparse entry or opens an aready created entry from disk. | |
81 // These methods just read / write the required info from disk for the current | |
82 // entry, and verify that everything is correct. The return value is a net | |
83 // error code. | |
84 int CreateSparseEntry(); | |
85 int OpenSparseEntry(int data_len); | |
86 | |
87 // Opens and closes a child entry. A child entry is a regular EntryImpl object | |
88 // with a key derived from the key of the resource to store and the range | |
89 // stored by that child. | |
90 bool OpenChild(); | |
91 void CloseChild(); | |
92 std::string GenerateChildKey(); | |
93 | |
94 // Deletes the current child and continues the current operation (open). | |
95 bool KillChildAndContinue(const std::string& key, bool fatal); | |
96 | |
97 // Continues the current operation (open) without a current child. | |
98 bool ContinueWithoutChild(const std::string& key); | |
99 | |
100 // Returns true if the required child is tracked by the parent entry, i.e. it | |
101 // was already created. | |
102 bool ChildPresent(); | |
103 | |
104 // Sets the bit for the current child to the provided |value|. In other words, | |
105 // starts or stops tracking this child. | |
106 void SetChildBit(bool value); | |
107 | |
108 // Writes to disk the tracking information for this entry. | |
109 void WriteSparseData(); | |
110 | |
111 // Verify that the range to be accessed for the current child is appropriate. | |
112 // Returns false if an error is detected or there is no need to perform the | |
113 // current IO operation (for instance if the required range is not stored by | |
114 // the child). | |
115 bool VerifyRange(); | |
116 | |
117 // Updates the contents bitmap for the current range, based on the result of | |
118 // the current operation. | |
119 void UpdateRange(int result); | |
120 | |
121 // Returns the number of bytes stored at |block_index|, if its allocation-bit | |
122 // is off (because it is not completely filled). | |
123 int PartialBlockLength(int block_index) const; | |
124 | |
125 // Initializes the sparse info for the current child. | |
126 void InitChildData(); | |
127 | |
128 // Iterates through all the children needed to complete the current operation. | |
129 void DoChildrenIO(); | |
130 | |
131 // Performs a single operation with the current child. Returns true when we | |
132 // should move on to the next child and false when we should interrupt our | |
133 // work. | |
134 bool DoChildIO(); | |
135 | |
136 // Performs the required work for GetAvailableRange for one child. | |
137 int DoGetAvailableRange(); | |
138 | |
139 // Performs the required work after a single IO operations finishes. | |
140 void DoChildIOCompleted(int result); | |
141 | |
142 // Invoked by the callback of asynchronous operations. | |
143 void OnChildIOCompleted(int result); | |
144 | |
145 // Reports to the user that we are done. | |
146 void DoUserCallback(); | |
147 void DoAbortCallbacks(); | |
148 | |
149 EntryImpl* entry_; // The sparse entry. | |
150 EntryImpl* child_; // The current child entry. | |
151 SparseOperation operation_; | |
152 bool pending_; // True if any child IO operation returned pending. | |
153 bool finished_; | |
154 bool init_; | |
155 bool range_found_; // True if GetAvailableRange found something. | |
156 bool abort_; // True if we should abort the current operation ASAP. | |
157 | |
158 SparseHeader sparse_header_; // Data about the children of entry_. | |
159 Bitmap children_map_; // The actual bitmap of children. | |
160 SparseData child_data_; // Parent and allocation map of child_. | |
161 Bitmap child_map_; // The allocation map as a bitmap. | |
162 | |
163 CompletionCallback user_callback_; | |
164 std::vector<CompletionCallback> abort_callbacks_; | |
165 int64 offset_; // Current sparse offset. | |
166 scoped_refptr<net::DrainableIOBuffer> user_buf_; | |
167 int buf_len_; // Bytes to read or write. | |
168 int child_offset_; // Offset to use for the current child. | |
169 int child_len_; // Bytes to read or write for this child. | |
170 int result_; | |
171 | |
172 DISALLOW_COPY_AND_ASSIGN(SparseControl); | |
173 }; | |
174 | |
175 } // namespace disk_cache | |
176 | |
177 #endif // NET_DISK_CACHE_BLOCKFILE_SPARSE_CONTROL_H_ | |
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