mojo leveldb: Remove the created file thread.

components/leveldb/leveldb_mojo_proxy.h

+// Copyright 2016 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 COMPONENTS_LEVELDB_LEVELDB_MOJO_PROXY_H_
+#define COMPONENTS_LEVELDB_LEVELDB_MOJO_PROXY_H_
+
+#include <map>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "base/files/file.h"
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/waitable_event.h"
+#include "base/threading/thread.h"
+#include "components/filesystem/public/interfaces/directory.mojom.h"
+
+namespace leveldb {
+
+// A proxy for thread safe access to mojo objects from multiple threads.
+//
+// MojoEnv is an object passed to the leveldb implementation which can be

[jam, 2016/03/29 05:58:00]

nit: just to be consistent with how these projects are named: mojo->Mojo,
leveldb->LevelDB

+// called from multiple threads. mojo pipes are bound to a single
+// thread. Because of this mismatch, we create a proxy object which will
+// redirect calls to the thread which owns the mojo pipe, sends and receives
+// messages.
+//
+// All public methods can be accessed from any thread.
+class LevelDBMojoProxy : public base::RefCountedThreadSafe<LevelDBMojoProxy> {
+ public:
+  explicit LevelDBMojoProxy(
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+
+  // A private struct to hide the underlying file that holds the lock from our
+  // callers, forcing them to go through our LockFile()/UnlockFile() interface
+  // so that they don't try to use the underlying pointer from an unsafe thread.
+  struct OpaqueLock;
+
+  // A private struct to hide the underlying root directory that we're
+  // operating in. LevelDBMojoProxy will want to own all the directory
+  // pointers, so while opening a database, we pass the directory to the thread
+  // it will be operated on.
+  struct OpaqueDir;
+
+  // Passes ownership of a |directory| to the other thread, giving a reference
+  // handle back to the caller.
+  OpaqueDir* RegisterDirectory(filesystem::DirectoryPtr directory);
+  void UnregisterDirectory(OpaqueDir* dir);
+
+  // Synchronously calls Directory.OpenFileHandle().
+  base::File OpenFileHandle(OpaqueDir* dir,
+                            const std::string& name,
+                            uint32_t open_flags);
+
+  // Synchronously flushes |directory_|.

[jam, 2016/03/29 05:58:00]

nit: s/flushes/sync

+  filesystem::FileError SyncDirectory(OpaqueDir* dir, const std::string& name);
+
+  // Synchronously checks whether |name| exists.
+  bool FileExists(OpaqueDir* dir, const std::string& name);
+
+  // Synchronously returns the filenames of all files in |path|.
+  filesystem::FileError GetChildren(OpaqueDir* dir,
+                                    const std::string& path,
+                                    std::vector<std::string>* result);
+
+  // Synchronously deletes |path|.
+  filesystem::FileError Delete(OpaqueDir* dir,
+                               const std::string& path,
+                               uint32_t delete_flags);
+
+  // Synchronously creates |path|.
+  filesystem::FileError CreateDir(OpaqueDir* dir, const std::string& path);
+
+  // Synchronously gets the size of a file.
+  filesystem::FileError GetFileSize(OpaqueDir* dir,
+                                    const std::string& path,
+                                    uint64_t* file_size);
+
+  // Synchronously renames a file.
+  filesystem::FileError RenameFile(OpaqueDir* dir,
+                                   const std::string& old_path,
+                                   const std::string& new_path);
+
+  // Synchronously locks a file. Returns both the file return code, and if OK,
+  // an opaque object to the lock to enforce going through this interface to
+  // unlock the file so that unlocking happens on the correct thread.
+  std::pair<filesystem::FileError, OpaqueLock*> LockFile(
+      OpaqueDir* dir,
+      const std::string& path);
+
+  // Unlocks a file. LevelDBMojoProxy takes ownership of lock. (We don't make
+  // this a scoped_ptr because exporting the ctor/dtor for this struct publicly
+  // defeats the purpose of the struct.)
+  filesystem::FileError UnlockFile(OpaqueLock* lock);
+
+ private:
+  friend class base::RefCountedThreadSafe<LevelDBMojoProxy>;
+  ~LevelDBMojoProxy();
+
+  void SignalIfNeeded(base::WaitableEvent* done_event);
+
+  // Implementation methods of the public interface. Depending on whether they
+  // were called from the thread that |task_runner_| is, these might be called
+  // directly or through PostTask().
+  void RegisterDirectoryImpl(
+      mojo::InterfacePtrInfo<filesystem::Directory> directory_info,
+      base::WaitableEvent* done_event,
+      OpaqueDir** out_dir);
+  void UnregisterDirectoryImpl(OpaqueDir* dir, base::WaitableEvent* done_event);
+  void OpenFileHandleImpl(OpaqueDir* dir,
+                          std::string name,
+                          uint32_t open_flags,
+                          base::WaitableEvent* done_event,
+                          base::File* out_file);
+  void SyncDirectoryImpl(OpaqueDir* dir,
+                         std::string name,
+                         base::WaitableEvent* done_event,
+                         filesystem::FileError* out_error);
+  void FileExistsImpl(OpaqueDir* dir,
+                      std::string name,
+                      base::WaitableEvent* done_event,
+                      bool* exists);
+  void GetChildrenImpl(OpaqueDir* dir,
+                       std::string name,
+                       std::vector<std::string>* contents,
+                       base::WaitableEvent* done_event,
+                       filesystem::FileError* out_error);
+  void DeleteImpl(OpaqueDir* dir,
+                  std::string name,
+                  uint32_t delete_flags,
+                  base::WaitableEvent* done_event,
+                  filesystem::FileError* out_error);
+  void CreateDirImpl(OpaqueDir* dir,
+                     std::string name,
+                     base::WaitableEvent* done_event,
+                     filesystem::FileError* out_error);
+  void GetFileSizeImpl(OpaqueDir* dir,
+                       const std::string& path,
+                       uint64_t* file_size,
+                       base::WaitableEvent* done_event,
+                       filesystem::FileError* out_error);
+  void RenameFileImpl(OpaqueDir* dir,
+                      const std::string& old_path,
+                      const std::string& new_path,
+                      base::WaitableEvent* done_event,
+                      filesystem::FileError* out_error);
+  void LockFileImpl(OpaqueDir* dir,
+                    const std::string& path,
+                    base::WaitableEvent* done_event,
+                    filesystem::FileError* out_error,
+                    OpaqueLock** out_lock);
+  void UnlockFileImpl(scoped_ptr<OpaqueLock> lock,
+                      base::WaitableEvent* done_event,
+                      filesystem::FileError* out_error);
+
+  // The task runner which represents the thread that all mojo objects are
+  // bound to.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  int outstanding_opaque_dirs_;
+
+  DISALLOW_COPY_AND_ASSIGN(LevelDBMojoProxy);
+};
+
+}  // namespace leveldb
+
+#endif  // COMPONENTS_LEVELDB_LEVELDB_MOJO_PROXY_H_