Add new simple disk cache backend.

net/disk_cache/simple/simple_backend_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_BACKEND_IMPL_H_
+#define NET_DISK_CACHE_SIMPLE_SIMPLE_BACKEND_IMPL_H_
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "base/compiler_specific.h"
+#include "base/file_path.h"
+#include "base/task_runner.h"
+#include "base/threading/thread_checker.h"
+#include "net/base/cache_type.h"
+#include "net/disk_cache/disk_cache.h"
+
+namespace disk_cache {
+
+// SimpleBackendImpl is a new cache backend that stores entries in individual
+// files.
+
+// It is currently a work in progress, missing many features of a real cache,
+// such as eviction.
+
+// See http://www.chromium.org/developers/design-documents/network-stack/disk-cache/very-simple-backend
+
+class SimpleBackendImpl : public Backend {
+ public:
+  virtual ~SimpleBackendImpl();
+
+  static int CreateBackend(const base::FilePath& full_path,
+                           bool force,
+                           int max_bytes,
+                           net::CacheType type,
+                           uint32 flags,
+                           scoped_refptr<base::TaskRunner> thread,
+                           net::NetLog* net_log,
+                           Backend** backend,
+                           const CompletionCallback& callback);
+
+  // From Backend:
+  virtual net::CacheType GetCacheType() const OVERRIDE;
+  virtual int32 GetEntryCount() const OVERRIDE;
+  virtual int OpenEntry(const std::string& key, Entry** entry,
+                        const CompletionCallback& callback) OVERRIDE;
+  virtual int CreateEntry(const std::string& key, Entry** entry,
+                          const CompletionCallback& callback) OVERRIDE;
+  virtual int DoomEntry(const std::string& key,
+                        const CompletionCallback& callback) OVERRIDE;
+  virtual int DoomAllEntries(const CompletionCallback& callback) OVERRIDE;
+  virtual int DoomEntriesBetween(base::Time initial_time,
+                                 base::Time end_time,
+                                 const CompletionCallback& callback) OVERRIDE;
+  virtual int DoomEntriesSince(base::Time initial_time,
+                               const CompletionCallback& callback) OVERRIDE;
+  virtual int OpenNextEntry(void** iter, Entry** next_entry,
+                            const CompletionCallback& callback) OVERRIDE;
+  virtual void EndEnumeration(void** iter) OVERRIDE;
+  virtual void GetStats(
+      std::vector<std::pair<std::string, std::string> >* stats) OVERRIDE;
+  virtual void OnExternalCacheHit(const std::string& key) OVERRIDE;
+
+ private:
+  explicit SimpleBackendImpl(const base::FilePath& path);
+
+  static void EnsureCachePathExistsOnWorkerThread(

[felipeg, 2013/02/12 13:25:20]

No need to have "OnWorkerThread" on the name of the function.
If you want you can add a comment such as "May run on a worker thread."

[gavinp, 2013/02/12 15:45:57]

Done. I added documentation to both methods.

+      const base::FilePath& path,
+      const scoped_refptr<base::TaskRunner>& callback_runner,
+      const CompletionCallback& callback,
+      Backend** backend);
+
+  static void OnCachePathCreated(int result,
+                                 const base::FilePath& path,
+                                 const CompletionCallback& callback,
+                                 Backend** backend);
+
+  base::ThreadChecker thread_checker_;
+  const base::FilePath path_;
+};
+
+}  // namespace disk_cache
+
+#endif  // NET_DISK_CACHE_SIMPLE_SIMPLE_BACKEND_IMPL_H_