Index: net/http/http_cache_writers.h |
diff --git a/net/http/http_cache_writers.h b/net/http/http_cache_writers.h |
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+++ b/net/http/http_cache_writers.h |
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+// Copyright (c) 2017 The Chromium Authors. All rights reserved. |
+// Use of this source code is governed by a BSD-style license that can be |
+// found in the LICENSE file. |
+ |
+#ifndef NET_HTTP_HTTP_CACHE_WRITERS_H_ |
+#define NET_HTTP_HTTP_CACHE_WRITERS_H_ |
+ |
+#include <list> |
+#include <memory> |
+ |
+#include "base/memory/weak_ptr.h" |
+#include "net/base/completion_callback.h" |
+#include "net/http/http_cache.h" |
+ |
+namespace net { |
+ |
+// If multiple HttpCache::Transactions are accessing the same cache entry |
+// simultaneously, their access to the data read from network is synchronized |
+// by HttpCache::Writers. This enables each of those transactions to drive |
+// reading the response body from the network ensuring a slow consumer does not |
+// starve other consumers of the same resource. |
+// |
+// Writers represents the set of all HttpCache::Transactions that are |
+// reading from the network using the same network transaction and writing to |
+// the same cache entry. It is owned by the ActiveEntry. |
+class NET_EXPORT_PRIVATE HttpCache::Writers { |
+ public: |
+ // |entry| must outlive this object. |
+ Writers(disk_cache::Entry* entry); |
+ ~Writers(); |
+ |
+ // Retrieves data from the network transaction associated with the Writers |
+ // object. This may be done directly (via a network read into |*buf->data()|) |
+ // or indirectly (by copying from another transactions buffer into |
+ // |*buf->data()| on network read completion) depending on whether or not a |
+ // read is currently in progress. May return the result synchronously or |
+ // return ERR_IO_PENDING: if ERR_IO_PENDING is returned, |callback| will be |
+ // run to inform the consumer of the result of the Read(). |
+ // |transaction| may be removed while Read() is ongoing. In that case Writers |
+ // will still complete the Read() processing but will not invoke the |
+ // |callback|. |
+ int Read(scoped_refptr<IOBuffer> buf, |
+ int buf_len, |
+ const CompletionCallback& callback, |
+ Transaction* transaction); |
+ |
+ // Invoked when StopCaching is called on a member transaction. |
+ // It stops caching only if there are no other transactions. Returns true if |
+ // caching can be stopped. |
+ // TODO(shivanisha@) Also document this conditional stopping in |
+ // HttpTransaction on integration. |
+ bool StopCaching(Transaction* transaction); |
+ |
+ // Adds an HttpCache::Transaction to Writers and if it's the first transaction |
+ // added, transfers the ownership of the network transaction to Writers. |
+ // Should only be invoked if CanAddWriters() returns true. |
+ // |network_transaction| should be non-null only for the first transaction |
+ // and it will be assigned to |network_transaction_|. If |is_exclusive| is |
+ // true, it makes writing an exclusive operation implying that Writers can |
+ // contain at most one transaction till the completion of the response body. |
+ // |transaction| can be destroyed at any point and it should invoke |
+ // RemoveTransaction() during its destruction. |
+ void AddTransaction(Transaction* transaction, |
+ std::unique_ptr<HttpTransaction> network_transaction, |
+ bool is_exclusive); |
+ |
+ // Removes a transaction. Should be invoked when this transaction is |
+ // destroyed. |
+ void RemoveTransaction(Transaction* transaction); |
+ |
+ // Invoked when there is a change in a member transaction's priority or a |
+ // member transaction is removed. |
+ void UpdatePriority(); |
+ |
+ // Returns true if this object is empty. |
+ bool IsEmpty() const { return all_writers_.empty(); } |
+ |
+ // Returns true if |transaction| is part of writers. |
+ bool HasTransaction(Transaction* transaction) const { |
+ return all_writers_.count(transaction) > 0; |
+ } |
+ |
+ // Remove and return any idle writers. Should only be invoked when a |
+ // response is completely written and when ContainesOnlyIdleWriters() |
+ // returns true. |
+ TransactionSet RemoveAllIdleWriters(); |
+ |
+ // Returns true if more writers can be added for shared writing. |
+ bool CanAddWriters(); |
+ |
+ // TODO(shivanisha), Check if this function gets invoked in the integration |
+ // CL. Remove if not. |
+ HttpTransaction* network_transaction() { return network_transaction_.get(); } |
+ |
+ // Invoked to mark an entry as truncated. This must only be invoked when there |
+ // is no ongoing Read() call. |
+ void TruncateEntry(); |
+ |
+ // Should be invoked only when writers has transactions attached to it and |
+ // thus has a valid network transaction. |
+ LoadState GetWriterLoadState(); |
+ |
+ // For testing. |
+ int CountTransactionsForTesting() const { return all_writers_.size(); } |
+ bool IsTruncatedForTesting() const { return truncated_; } |
+ |
+ private: |
+ friend class WritersTest; |
+ |
+ enum class State { |
+ UNSET, |
+ NONE, |
+ NETWORK_READ, |
+ NETWORK_READ_COMPLETE, |
+ CACHE_WRITE_DATA, |
+ CACHE_WRITE_DATA_COMPLETE, |
+ CACHE_WRITE_TRUNCATED_RESPONSE, |
+ CACHE_WRITE_TRUNCATED_RESPONSE_COMPLETE, |
+ }; |
+ |
+ // These transactions are waiting on Read. After the active transaction |
+ // completes writing the data to the cache, their buffer would be filled with |
+ // the data and their callback will be invoked. |
+ struct WaitingForRead { |
+ Transaction* transaction; |
+ scoped_refptr<IOBuffer> read_buf; |
+ int read_buf_len; |
+ int write_len; |
+ const CompletionCallback callback; |
+ WaitingForRead(Transaction* transaction, |
+ scoped_refptr<IOBuffer> read_buf, |
+ int len, |
+ const CompletionCallback& consumer_callback); |
+ ~WaitingForRead(); |
+ WaitingForRead(const WaitingForRead&); |
+ }; |
+ using WaitingForReadList = std::list<WaitingForRead>; |
+ |
+ // Runs the state transition loop. Resets and calls |callback_| on exit, |
+ // unless the return value is ERR_IO_PENDING. |
+ int DoLoop(int result); |
+ |
+ // State machine functions. |
+ int DoNetworkRead(); |
+ int DoNetworkReadComplete(int result); |
+ int DoCacheWriteData(int num_bytes); |
+ int DoCacheWriteDataComplete(int result); |
+ int DoCacheWriteTruncatedResponse(); |
+ int DoCacheWriteTruncatedResponseComplete(int result); |
+ |
+ // Helper functions for callback. |
+ void OnNetworkReadFailure(int result); |
+ void OnCacheWriteFailure(); |
+ void OnDataReceived(int result); |
+ |
+ // Notifies the transactions waiting on Read of the result, by posting a task |
+ // for each of them. |
+ void ProcessWaitingForReadTransactions(int result); |
+ |
+ // Sets the state to FAIL_READ so that any subsequent Read on an idle |
+ // transaction fails. |
+ void SetIdleWritersFailState(int result); |
+ |
+ // Called to reset state when all transaction references are removed from |
+ // |this|. |
+ void ResetStateForEmptyWriters(); |
+ |
+ // Invoked when |active_transaction_| fails to read from network or write to |
+ // cache. |error| indicates network read error code or cache write error. |
+ void ProcessFailure(Transaction* transaction, int error); |
+ |
+ // Returns true if |this| only contains idle writers. Idle writers are those |
+ // that are waiting for Read to be invoked by the consumer. |
+ bool ContainsOnlyIdleWriters() const; |
+ |
+ // IO Completion callback function. |
+ void OnIOComplete(int result); |
+ |
+ State next_state_ = State::NONE; |
+ |
+ // True if only reading from network and not writing to cache. |
+ bool network_read_only_ = false; |
+ |
+ // TODO(shivanisha) Add HttpCache* cache_ = nullptr; on integration. |
+ |
+ disk_cache::Entry* disk_entry_ = nullptr; |
+ |
+ std::unique_ptr<HttpTransaction> network_transaction_ = nullptr; |
+ |
+ scoped_refptr<IOBuffer> read_buf_ = nullptr; |
+ |
+ int io_buf_len_ = 0; |
+ int write_len_ = 0; |
+ |
+ // The cache transaction that is the current consumer of network_transaction_ |
+ // ::Read or writing to the entry and is waiting for the operation to be |
+ // completed. This is used to ensure there is at most one consumer of |
+ // network_transaction_ at a time. |
+ Transaction* active_transaction_ = nullptr; |
+ |
+ // Transactions whose consumers have invoked Read, but another transaction is |
+ // currently the |active_transaction_|. After the network read and cache write |
+ // is complete, the waiting transactions will be notified. |
+ WaitingForReadList waiting_for_read_; |
+ |
+ // Includes all transactions. ResetStateForEmptyWriters should be invoked |
+ // whenever all_writers_ becomes empty. |
+ TransactionSet all_writers_; |
+ |
+ // True if multiple transactions are not allowed e.g. for partial requests. |
+ bool is_exclusive_ = false; |
+ |
+ // Current priority of the request. It is always the maximum of all the writer |
+ // transactions. |
+ RequestPriority priority_ = MINIMUM_PRIORITY; |
+ |
+ bool truncated_ = false; // used for testing. |
+ |
+ CompletionCallback callback_; // Callback for active_transaction_. |
+ |
+ base::WeakPtrFactory<Writers> weak_factory_; |
+ DISALLOW_COPY_AND_ASSIGN(Writers); |
+}; |
+ |
+} // namespace net |
+ |
+#endif // NET_HTTP_HTTP_CACHE_WRITERS_H_ |