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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 #include <list> | |
jkarlin
2017/06/12 18:30:32
newline above
shivanisha
2017/06/14 02:33:17
Added
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8 #include <memory> | |
9 #include "base/memory/weak_ptr.h" | |
jkarlin
2017/06/12 18:30:32
newline above
shivanisha
2017/06/14 02:33:17
added
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10 #include "net/base/completion_callback.h" | |
11 #include "net/http/http_cache.h" | |
12 | |
13 // If multiple HttpCache::Transactions are accessing the same cache entry | |
14 // simultaneously, their access to the data read from network is synchronized | |
15 // by HttpCache::Writers. This enables each of those transactions to drive | |
16 // reading the response body from the network ensuring a slow consumer does not | |
17 // starve other consumers of the same resource. | |
18 | |
19 namespace net { | |
20 | |
21 // Writer represents the set of all HttpCache::Transactions that are | |
22 // reading from the network using the same network transaction and writing to | |
23 // the same cache entry. It is owned by the ActiveEntry. | |
24 class NET_EXPORT_PRIVATE HttpCache::Writers { | |
25 public: | |
26 // |*entry| and |*cache| must outlive this object. | |
27 Writers(HttpCache* cache, ActiveEntry* entry); | |
28 ~Writers(); | |
29 | |
30 // Retrieves data from the network transaction associated with the Writers | |
31 // object. This may be done directly (via a network read into |*buf->data()|) | |
32 // or indirectly (by copying from another transactions buffer into | |
33 // |*buf->data()| on network read completion) depending on whether or not a | |
34 // read is currently in progress. May return the result synchronously or | |
35 // return ERR_IO_PENDING: if ERR_IO_PENDING is returned, |callback| will be | |
36 // run to inform the consumer of the result of the Read(). | |
37 int Read(scoped_refptr<IOBuffer> buf, | |
38 int buf_len, | |
39 const CompletionCallback& callback, | |
40 Transaction* transaction); | |
41 | |
42 // Invoked when StopCaching is called on a member transaction. | |
43 // It stops caching only if there are no other transactions. Returns true if | |
44 // caching can be stopped. | |
45 bool StopCaching(Transaction* transaction); | |
46 | |
47 // Membership functions. | |
48 | |
49 // Adds an HttpCache::Transaction to Writers and if its the first transaction | |
jkarlin
2017/06/12 18:30:32
s/its/it's/
shivanisha
2017/06/14 02:33:17
done
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50 // added, transfers the ownership of the network transaction to Writers. | |
51 // Should only be invoked if CanAddTransaction() returns true. | |
52 // |network_transaction| should be non-null only for the first transaction | |
53 // and it will be assigned to |network_transaction_|. If |is_exclusive| is | |
54 // true, it makes writing an exclusine operation implying that Writers can | |
Randy Smith (Not in Mondays)
2017/06/08 17:10:01
nit: exclusive
shivanisha
2017/06/12 18:51:14
done
| |
55 // contain at most one transaction till the completion of the response body. | |
56 // |transaction| can be destroyed at any point and it should invoke | |
57 // RemoveTransaction() during its destruction. | |
58 void AddTransaction(Transaction* transaction, | |
59 std::unique_ptr<HttpTransaction> network_transaction, | |
60 bool is_exclusive); | |
Randy Smith (Not in Mondays)
2017/06/08 17:10:01
The current implementation requires the consumer t
shivanisha
2017/06/12 18:51:14
ok, let's come back to this in the integration CL
| |
61 | |
62 // Removes a transaction. | |
63 void RemoveTransaction(Transaction* transaction); | |
64 | |
65 // Invoked when there is a change in a member transaction's priority or a | |
66 // member transaction is removed. | |
67 void PriorityChanged(); | |
68 | |
69 // Returns true if this object is empty. | |
70 bool IsEmpty() const { return all_writers_.empty(); } | |
71 | |
72 // Returns true is |transaction| is part of writers. | |
73 bool IsPresent(Transaction* transaction) const { | |
74 return all_writers_.count(transaction) > 0; | |
75 } | |
76 | |
77 // Returns true if |this| only contains idle writers. | |
78 bool ContainsOnlyIdleWriters() const; | |
79 | |
80 // Move any idle writers to entry_->readers. Should only be invoked when a | |
81 // response is completely written and when ContainesOnlyIdleWriters() | |
82 // returns true. | |
83 void MoveIdleWritersToReaders(); | |
84 | |
85 // Returns true if more writers can be added for shared writing. | |
86 bool CanAddWriters(); | |
87 | |
88 HttpTransaction* network_transaction() { return network_transaction_.get(); } | |
89 | |
90 // Invoked from HttpCache when it is notified of a transaction failing to | |
91 // write. |error| indicates network read error code or cache write error. | |
92 void ProcessFailure(Transaction* transaction, int error); | |
93 | |
94 // Invoked to mark an entry as truncated. | |
95 void TruncateEntry(); | |
96 | |
97 // Should be invoked only when writers has transactions attached to it and | |
98 // thus has a valid network transaction. | |
99 LoadState GetWriterLoadState(); | |
100 | |
101 // For testing. | |
102 | |
103 int CountTransactionsForTesting() const { return all_writers_.size(); } | |
104 bool IsTruncatedForTesting() const { return truncated_; } | |
105 | |
106 private: | |
107 enum class State { | |
108 NONE, | |
109 NETWORK_READ, | |
110 NETWORK_READ_COMPLETE, | |
111 CACHE_WRITE_DATA, | |
112 CACHE_WRITE_DATA_COMPLETE, | |
113 CACHE_WRITE_TRUNCATED_RESPONSE, | |
114 CACHE_WRITE_TRUNCATED_RESPONSE_COMPLETE, | |
115 FAIL_READ | |
Randy Smith (Not in Mondays)
2017/06/08 17:10:01
My personal preference would be to keep the invari
jkarlin
2017/06/12 18:30:32
+1
shivanisha
2017/06/12 18:51:14
Deferring this comment since the follow up CL anyw
| |
116 }; | |
117 | |
118 // These transactions are waiting on Read. After the active transaction | |
119 // completes writing the data to the cache, their buffer would be filled with | |
120 // the data and their callback will be invoked. | |
121 struct WaitingForRead { | |
122 Transaction* transaction; | |
123 scoped_refptr<IOBuffer> read_buf; | |
124 int read_buf_len; | |
125 int write_len; | |
126 const CompletionCallback callback; | |
127 WaitingForRead(Transaction* transaction, | |
128 scoped_refptr<IOBuffer> read_buf, | |
129 int len, | |
130 const CompletionCallback& consumer_callback); | |
131 ~WaitingForRead(); | |
132 WaitingForRead(const WaitingForRead&); | |
133 }; | |
134 using WaitingForReadList = std::list<WaitingForRead>; | |
135 | |
136 // Runs the state transition loop. Resets and calls |callback_| on exit, | |
137 // unless the return value is ERR_IO_PENDING. | |
138 int DoLoop(int result); | |
139 | |
140 // State machine functions. | |
141 int DoNetworkRead(); | |
142 int DoNetworkReadComplete(int result); | |
143 int DoCacheWriteData(int num_bytes); | |
144 int DoCacheWriteDataComplete(int result); | |
145 int DoCacheWriteTruncatedResponse(); | |
146 int DoCacheWriteTruncatedResponseComplete(int result); | |
147 | |
148 // Helper functions for callback. | |
149 | |
jkarlin
2017/06/12 18:30:32
Remove newline?
shivanisha
2017/06/14 02:33:17
Comment applies to all 3 following functions.
jkarlin
2017/06/14 20:03:14
Right, for group comments I typically see the comm
| |
150 void OnNetworkReadFailure(int result); | |
151 void OnCacheWriteFailure(); | |
152 void OnDataReceived(int result); | |
153 | |
154 // Helper function for writing to cache. | |
155 int WriteToEntry(int offset, | |
156 IOBuffer* data, | |
157 int data_len, | |
158 const CompletionCallback& callback); | |
159 | |
160 // Notifies the transactions waiting on Read of the result, by posting a task | |
161 // for each of them. | |
162 void ProcessWaitingForReadTransactions(int result); | |
163 | |
164 // Sets the state to FAIL_READ so that any subsequent Read on an idle | |
165 // transaction fails. | |
166 void SetIdleWritersFailState(int result); | |
167 | |
168 // Called to reset state when all transaction references are removed from | |
169 // |this|. | |
170 void ResetStateForEmptyWriters(); | |
171 | |
172 // IO Completion callback function. | |
173 void OnIOComplete(int result); | |
174 | |
175 State next_state_ = State::NONE; | |
176 | |
177 // True if only reading from network and not writing to cache. | |
178 bool network_read_only_ = false; | |
179 | |
180 // Http Cache. | |
181 HttpCache* cache_ = nullptr; | |
182 | |
183 // Owner of this object. | |
184 ActiveEntry* entry_ = nullptr; | |
185 | |
186 std::unique_ptr<HttpTransaction> network_transaction_ = nullptr; | |
187 | |
188 scoped_refptr<IOBuffer> read_buf_ = nullptr; | |
189 | |
190 int io_buf_len_ = 0; | |
191 int write_len_ = 0; | |
192 | |
193 // The cache transaction that is the current consumer of network_transaction_ | |
194 // ::Read or writing to the entry and is waiting for the operation to be | |
195 // completed. This is used to ensure there is at most one consumer of | |
196 // network_transaction_ at a time. | |
197 Transaction* active_transaction_ = nullptr; | |
198 | |
199 // Transactions whose consumers have invoked Read, but another transaction is | |
200 // currently the |active_transaction_|. After the network read and cache write | |
201 // is complete, the waiting transactions will be notified. | |
202 WaitingForReadList waiting_for_read_; | |
203 | |
204 // Includes all transactions. | |
205 TransactionSet all_writers_; | |
206 | |
207 // True if multiple transactions are not allowed e.g. for partial requests. | |
208 bool is_exclusive_ = false; | |
209 | |
210 // Current priority of the request. It is always the maximum of all the writer | |
211 // transactions. | |
212 RequestPriority priority_ = MINIMUM_PRIORITY; | |
213 | |
214 // Error to be returned on a future Read when state is FAIL_READ. | |
215 int error_code_ = 0; | |
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 #endif // NET_HTTP_HTTP_CACHE_WRITERS_H_ | |
jkarlin
2017/06/12 18:30:32
newline above
shivanisha
2017/06/14 02:33:17
Added
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OLD | NEW |