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1 // Copyright (c) 2017 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_HTTP_HTTP_CACHE_WRITERS_H_ | |
6 #define NET_HTTP_HTTP_CACHE_WRITERS_H_ | |
7 | |
8 #include <list> | |
9 #include <memory> | |
10 | |
11 #include "base/memory/weak_ptr.h" | |
12 #include "net/base/completion_callback.h" | |
13 #include "net/http/http_cache.h" | |
14 | |
15 namespace net { | |
16 | |
17 // If multiple HttpCache::Transactions are accessing the same cache entry | |
18 // simultaneously, their access to the data read from network is synchronized | |
19 // by HttpCache::Writers. This enables each of those transactions to drive | |
20 // reading the response body from the network ensuring a slow consumer does not | |
21 // starve other consumers of the same resource. | |
22 | |
jkarlin
2017/07/06 18:50:04
Add a // on this line since it's part of the same
shivanisha
2017/07/11 02:10:26
done
| |
23 // Writers represents the set of all HttpCache::Transactions that are | |
24 // reading from the network using the same network transaction and writing to | |
25 // the same cache entry. It is owned by the ActiveEntry. | |
26 class NET_EXPORT_PRIVATE HttpCache::Writers { | |
27 public: | |
28 // |*disk_entry| must outlive this object. | |
jkarlin
2017/07/06 18:50:04
s/|*disk_entry|/|entry|/
shivanisha
2017/07/11 02:10:26
done
| |
29 Writers(disk_cache::Entry* entry); | |
30 ~Writers(); | |
31 | |
32 // Retrieves data from the network transaction associated with the Writers | |
33 // object. This may be done directly (via a network read into |*buf->data()|) | |
34 // or indirectly (by copying from another transactions buffer into | |
35 // |*buf->data()| on network read completion) depending on whether or not a | |
36 // read is currently in progress. May return the result synchronously or | |
37 // return ERR_IO_PENDING: if ERR_IO_PENDING is returned, |callback| will be | |
38 // run to inform the consumer of the result of the Read(). | |
39 // |transaction| may be removed while Read() is ongoing. In that case Writers | |
40 // will still complete the Read() processing but will not invoke the | |
41 // |callback|. | |
42 int Read(scoped_refptr<IOBuffer> buf, | |
43 int buf_len, | |
44 const CompletionCallback& callback, | |
45 Transaction* transaction); | |
46 | |
47 // Invoked when StopCaching is called on a member transaction. | |
48 // It stops caching only if there are no other transactions. Returns true if | |
49 // caching can be stopped. | |
50 // TODO(shivanisha@) Also document this conditional stopping in | |
51 // HttpTransaction on integration. | |
52 bool StopCaching(Transaction* transaction); | |
53 | |
54 // Adds an HttpCache::Transaction to Writers and if it's the first transaction | |
55 // added, transfers the ownership of the network transaction to Writers. | |
56 // Should only be invoked if CanAddWriters() returns true. | |
57 // |network_transaction| should be non-null only for the first transaction | |
58 // and it will be assigned to |network_transaction_|. If |is_exclusive| is | |
59 // true, it makes writing an exclusive operation implying that Writers can | |
60 // contain at most one transaction till the completion of the response body. | |
61 // |transaction| can be destroyed at any point and it should invoke | |
62 // RemoveTransaction() during its destruction. | |
63 void AddTransaction(Transaction* transaction, | |
64 std::unique_ptr<HttpTransaction> network_transaction, | |
65 bool is_exclusive); | |
66 | |
67 // Removes a transaction. Should be invoked when this transaction is | |
68 // destroyed. | |
69 void RemoveTransaction(Transaction* transaction); | |
70 | |
71 // Invoked when there is a change in a member transaction's priority or a | |
72 // member transaction is removed. | |
73 void UpdatePriority(); | |
74 | |
75 // Returns true if this object is empty. | |
76 bool IsEmpty() const { return all_writers_.empty(); } | |
77 | |
78 // Returns true if |transaction| is part of writers. | |
79 bool HasTransaction(Transaction* transaction) const { | |
80 return all_writers_.count(transaction) > 0; | |
81 } | |
82 | |
83 // Remove and return any idle writers. Should only be invoked when a | |
84 // response is completely written and when ContainesOnlyIdleWriters() | |
85 // returns true. | |
86 TransactionSet RemoveAllIdleWriters(); | |
87 | |
88 // Returns true if more writers can be added for shared writing. | |
89 bool CanAddWriters(); | |
90 | |
91 // TODO(shivanisha), Check if this function gets invoked in the integration | |
92 // CL. Remove if not. | |
93 HttpTransaction* network_transaction() { return network_transaction_.get(); } | |
94 | |
95 // Invoked to mark an entry as truncated. This must only be invoked when there | |
96 // is no ongoing Read() call. | |
97 void TruncateEntry(); | |
98 | |
99 // Should be invoked only when writers has transactions attached to it and | |
100 // thus has a valid network transaction. | |
101 LoadState GetWriterLoadState(); | |
102 | |
103 // For testing. | |
104 int CountTransactionsForTesting() const { return all_writers_.size(); } | |
105 bool IsTruncatedForTesting() const { return truncated_; } | |
106 | |
107 private: | |
108 friend class WritersTest; | |
109 | |
110 enum class State { | |
111 UNSET, | |
112 NONE, | |
113 NETWORK_READ, | |
114 NETWORK_READ_COMPLETE, | |
115 CACHE_WRITE_DATA, | |
116 CACHE_WRITE_DATA_COMPLETE, | |
117 CACHE_WRITE_TRUNCATED_RESPONSE, | |
118 CACHE_WRITE_TRUNCATED_RESPONSE_COMPLETE, | |
119 }; | |
120 | |
121 // These transactions are waiting on Read. After the active transaction | |
122 // completes writing the data to the cache, their buffer would be filled with | |
123 // the data and their callback will be invoked. | |
124 struct WaitingForRead { | |
125 Transaction* transaction; | |
126 scoped_refptr<IOBuffer> read_buf; | |
127 int read_buf_len; | |
128 int write_len; | |
129 const CompletionCallback callback; | |
130 WaitingForRead(Transaction* transaction, | |
131 scoped_refptr<IOBuffer> read_buf, | |
132 int len, | |
133 const CompletionCallback& consumer_callback); | |
134 ~WaitingForRead(); | |
135 WaitingForRead(const WaitingForRead&); | |
136 }; | |
137 using WaitingForReadList = std::list<WaitingForRead>; | |
138 | |
139 // Runs the state transition loop. Resets and calls |callback_| on exit, | |
140 // unless the return value is ERR_IO_PENDING. | |
141 int DoLoop(int result); | |
142 | |
143 // State machine functions. | |
144 int DoNetworkRead(); | |
145 int DoNetworkReadComplete(int result); | |
146 int DoCacheWriteData(int num_bytes); | |
147 int DoCacheWriteDataComplete(int result); | |
148 int DoCacheWriteTruncatedResponse(); | |
149 int DoCacheWriteTruncatedResponseComplete(int result); | |
150 | |
151 // Helper functions for callback. | |
152 | |
jkarlin
2017/07/06 18:50:04
Remove newline, the comment will apply to all meth
shivanisha
2017/07/11 02:10:26
done
| |
153 void OnNetworkReadFailure(int result); | |
154 void OnCacheWriteFailure(); | |
155 void OnDataReceived(int result); | |
156 | |
157 // Notifies the transactions waiting on Read of the result, by posting a task | |
158 // for each of them. | |
159 void ProcessWaitingForReadTransactions(int result); | |
160 | |
161 // Sets the state to FAIL_READ so that any subsequent Read on an idle | |
162 // transaction fails. | |
163 void SetIdleWritersFailState(int result); | |
164 | |
165 // Called to reset state when all transaction references are removed from | |
166 // |this|. | |
167 void ResetStateForEmptyWriters(); | |
168 | |
169 // Invoked when |active_transaction_| fails to read from network or write to | |
170 // cache. |error| indicates network read error code or cache write error. | |
171 void ProcessFailure(Transaction* transaction, int error); | |
172 | |
173 // Returns true if |this| only contains idle writers. | |
174 bool ContainsOnlyIdleWriters() const; | |
jkarlin
2017/07/06 18:50:04
Define what idle writers are.
shivanisha
2017/07/11 02:10:26
done
| |
175 | |
176 // IO Completion callback function. | |
177 void OnIOComplete(int result); | |
178 | |
179 State next_state_ = State::NONE; | |
180 | |
181 // True if only reading from network and not writing to cache. | |
182 bool network_read_only_ = false; | |
183 | |
184 // TODO(shivanisha) Add HttpCache* cache_ = nullptr; on integration. | |
185 | |
186 disk_cache::Entry* disk_entry_ = nullptr; | |
187 | |
188 std::unique_ptr<HttpTransaction> network_transaction_ = nullptr; | |
189 | |
190 scoped_refptr<IOBuffer> read_buf_ = nullptr; | |
191 | |
192 int io_buf_len_ = 0; | |
193 int write_len_ = 0; | |
194 | |
195 // The cache transaction that is the current consumer of network_transaction_ | |
196 // ::Read or writing to the entry and is waiting for the operation to be | |
197 // completed. This is used to ensure there is at most one consumer of | |
198 // network_transaction_ at a time. | |
199 Transaction* active_transaction_ = nullptr; | |
200 | |
201 // Transactions whose consumers have invoked Read, but another transaction is | |
202 // currently the |active_transaction_|. After the network read and cache write | |
203 // is complete, the waiting transactions will be notified. | |
204 WaitingForReadList waiting_for_read_; | |
205 | |
206 // Includes all transactions. ResetStateForEmptyWriters should be invoked | |
207 // whenever all_writers_ becomes empty. | |
208 TransactionSet all_writers_; | |
209 | |
210 // True if multiple transactions are not allowed e.g. for partial requests. | |
211 bool is_exclusive_ = false; | |
212 | |
213 // Current priority of the request. It is always the maximum of all the writer | |
214 // transactions. | |
215 RequestPriority priority_ = MINIMUM_PRIORITY; | |
216 | |
217 bool truncated_ = false; // used for testing. | |
218 | |
219 CompletionCallback callback_; // Callback for active_transaction_. | |
220 | |
221 base::WeakPtrFactory<Writers> weak_factory_; | |
222 DISALLOW_COPY_AND_ASSIGN(Writers); | |
223 }; | |
224 | |
225 } // namespace net | |
226 | |
227 #endif // NET_HTTP_HTTP_CACHE_WRITERS_H_ | |
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