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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 // |
| 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 // |entry| must outlive this object. |
| 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 void OnNetworkReadFailure(int result); |
| 153 void OnCacheWriteFailure(); |
| 154 void OnDataReceived(int result); |
| 155 |
| 156 // Notifies the transactions waiting on Read of the result, by posting a task |
| 157 // for each of them. |
| 158 void ProcessWaitingForReadTransactions(int result); |
| 159 |
| 160 // Sets the state to FAIL_READ so that any subsequent Read on an idle |
| 161 // transaction fails. |
| 162 void SetIdleWritersFailState(int result); |
| 163 |
| 164 // Called to reset state when all transaction references are removed from |
| 165 // |this|. |
| 166 void ResetStateForEmptyWriters(); |
| 167 |
| 168 // Invoked when |active_transaction_| fails to read from network or write to |
| 169 // cache. |error| indicates network read error code or cache write error. |
| 170 void ProcessFailure(Transaction* transaction, int error); |
| 171 |
| 172 // Returns true if |this| only contains idle writers. Idle writers are those |
| 173 // that are waiting for Read to be invoked by the consumer. |
| 174 bool ContainsOnlyIdleWriters() const; |
| 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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