Add new simple disk cache backend.

net/disk_cache/very_simple/very_simple_synchronous_entry.h

Index: net/disk_cache/very_simple/very_simple_synchronous_entry.h
diff --git a/net/disk_cache/very_simple/very_simple_synchronous_entry.h b/net/disk_cache/very_simple/very_simple_synchronous_entry.h
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index 0000000000000000000000000000000000000000..7b4a0253671cbc8aae595e08b82d8ddcfd478b02
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+++ b/net/disk_cache/very_simple/very_simple_synchronous_entry.h
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+// 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_VERY_SIMPLE_VERY_SIMPLE_SYNCHRONOUS_ENTRY_H_
+#define NET_DISK_CACHE_VERY_SIMPLE_VERY_SIMPLE_SYNCHRONOUS_ENTRY_H_
+
+#include <string>
+
+#include "base/callback_forward.h"
+#include "base/file_path.h"
+#include "base/memory/ref_counted.h"
+#include "base/platform_file.h"
+#include "base/task_runner.h"
+#include "base/time.h"
+#include "net/base/completion_callback.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace net {
+class IOBuffer;
+}
+
+namespace disk_cache {
+
+// Worker thread interface to the very simple cache. This interface is not
+// thread safe, and callers must insure that it is only ever accessed from
+// a single thread between synchronization points.
+class VerySimpleSynchronousEntry {
+ public:
+  // All callbacks include the pointer to the SynchronousEntry being operated on
+  // if it is valid after the operation.
+  typedef base::Callback<void(VerySimpleSynchronousEntry*, int)>
+      SynchronousEntryCallback;
+
+  static void OpenEntry(
+      const FilePath& path,
+      const std::string& key,
+      const scoped_refptr<base::TaskRunner>& callback_runner,
+      const SynchronousEntryCallback& callback);
+
+  static void CreateEntry(
+      const FilePath& path,
+      const std::string& key,
+      const scoped_refptr<base::TaskRunner>& callback_runner,
+      const SynchronousEntryCallback& callback);
+
+  // Deletes an entry without first Opening it. Does not check if there is
+  // already an Entry object in memory holding the open files. Be careful! This
+  // is meant to be used by the Backend::DoomEntry() call. |callback| will be
+  // run by |callback_runner|.
+  static void DoomEntry(const FilePath& path,
+                        const std::string& key,
+                        scoped_refptr<base::TaskRunner> callback_runner,
+                        const net::CompletionCallback& callback);
+
+  // N.B. DoomAndClose(), Close(), ReadData() and WriteData() may block on IO.
+  void DoomAndClose();
+  void Close();
+  void ReadData(int index,
+                int offset,
+                net::IOBuffer* buf,
+                int buf_len,
+                const SynchronousEntryCallback& callback);
+  void WriteData(int index,
+                 int offset,
+                 net::IOBuffer* buf,
+                 int buf_len,
+                 const SynchronousEntryCallback& callback,
+                 bool truncate);
+
+  std::string key() const { return key_; }
+  base::Time last_used() const { return last_used_; }
+  base::Time last_modified() const { return last_modified_; }
+  int32 data_size(int index) const { return data_size_[index]; }
+
+ private:
+  static const int kIndexCount = 3;
+
+  struct EntryStatus {
+    enum Mode {
+      ENTRY_UNINITIALIZED,
+      ENTRY_READER,
+      ENTRY_WRITER,
+    };
+
+    EntryStatus();
+
+    Mode mode;
+    int64 data_offset;
+  };
+
+  VerySimpleSynchronousEntry(
+      const scoped_refptr<base::TaskRunner>& callback_runner,
+      const FilePath& path,
+      const std::string& key);
+
+  // Like Entry, the VerySimpleSynchronousEntry self releases when Close() is
+  // called.
+  ~VerySimpleSynchronousEntry();
+
+  bool OpenOrCreateFiles(bool create);
+  bool InitializeForOpen();
+  bool InitializeForCreate();
+
+  scoped_refptr<base::TaskRunner> callback_runner_;
+  const FilePath path_;
+  const std::string key_;
+
+  bool initialized_;
+
+  base::Time last_used_;
+  base::Time last_modified_;
+  int32 data_size_[kIndexCount];
+
+  base::PlatformFile files_[kIndexCount];
+  EntryStatus status_[kIndexCount];
+};
+
+}  // namespace disk_cache
+
+#endif  // NET_DISK_CACHE_VERY_SIMPLE_VERY_SIMPLE_SYNCHRONOUS_ENTRY_H_