Support overlapping operations on the SimpleEntryImpl.

net/disk_cache/simple/simple_entry_impl.h

 // Copyright (c) 2013 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_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_IMPL_H_
 #define NET_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_IMPL_H_
 
+#include <queue>
 #include <string>
 
 #include "base/files/file_path.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "net/disk_cache/disk_cache.h"
 #include "net/disk_cache/simple/simple_entry_format.h"
 #include "net/disk_cache/simple/simple_index.h"
 
 
@@ skipping 60 matching lines @@
   virtual bool CouldBeSparse() const OVERRIDE;
   virtual void CancelSparseIO() OVERRIDE;
   virtual int ReadyForSparseIO(const CompletionCallback& callback) OVERRIDE;
 
  private:
   SimpleEntryImpl(SimpleSynchronousEntry* synchronous_entry,
                   base::WeakPtr<SimpleIndex> index);
 
   virtual ~SimpleEntryImpl();
 
+  // Runs next operation in the queue, if any and if there is no other operation

[gavinp, 2013/04/17 13:13:45]

Nit: "Runs _the_ next", and also "if and _only_ if".

[felipeg, 2013/04/17 13:34:18]

Done.

+  // running at the moment. Returns true if a operation has run.

[gavinp, 2013/04/17 13:13:45]

What is this return value used for?

[felipeg, 2013/04/17 13:34:18]

It will be used to implement the optimistic writes, you will see.

+  bool RunNextOperationIfNeeded();
+
+  void ReadDataInternal(int index,
+                        int offset,
+                        scoped_refptr<net::IOBuffer> buf,
+                        int buf_len,
+                        const CompletionCallback& callback);
+
+  void WriteDataInternal(int index,
+                         int offset,
+                         scoped_refptr<net::IOBuffer> buf,
+                         int buf_len,
+                         const CompletionCallback& callback,
+                         bool truncate);
+
   // Called after a SimpleSynchronousEntry has completed CreateEntry() or
   // OpenEntry(). Constructs the new SimpleEntryImpl (if |result| is net::OK)
   // and passes it back to the caller via |out_entry|. Also runs
   // |completion_callback|.
   static void CreationOperationComplete(
       base::WeakPtr<SimpleIndex> index,
       const CompletionCallback& completion_callback,
       const std::string& key,
       Entry** out_entry,
       SimpleSynchronousEntry* sync_entry);
@@ skipping 25 matching lines @@
   const base::FilePath path_;
   const std::string key_;
 
   // |last_used_|, |last_modified_| and |data_size_| are copied from the
   // synchronous entry at the completion of each item of asynchronous IO.
   base::Time last_used_;
   base::Time last_modified_;
   int32 data_size_[kSimpleEntryFileCount];
 
   // The |synchronous_entry_| is the worker thread object that performs IO on
-  // entries. It's owned by this SimpleEntryImpl whenever
-  // |synchronous_entry_in_use_by_worker_| is false (i.e. when an operation
-  // is not pending on the worker pool). When an operation is pending on the
-  // worker pool, the |synchronous_entry_| is owned by itself.
+  // entries. It's owned by this SimpleEntryImpl whenever |operation_running_|
+  // is false (i.e. when an operation is not pending on the worker pool). When
+  // an operation is pending on the worker pool, the |synchronous_entry_| is

[gavinp, 2013/04/17 13:13:45]

While we're here, the last sentence of this comment doesn't make sense anymore.

[felipeg, 2013/04/17 13:34:18]

Done.

+  // owned by itself.
   SimpleSynchronousEntry* synchronous_entry_;
 
   // Set to true when a worker operation is posted on the |synchronous_entry_|,
   // and false after. Used to ensure thread safety by not allowing multiple
   // threads to access the |synchronous_entry_| simultaneously.
-  bool synchronous_entry_in_use_by_worker_;
+  bool operation_running_;
+  std::queue<base::Closure> operations_;

[gavinp, 2013/04/17 13:13:45]

pending_operations_ ?

[felipeg, 2013/04/17 13:34:18]

Done.

 
   base::WeakPtr<SimpleIndex> index_;
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_ENTRY_IMPL_H_