Base: Introduce a new version of FileUtilProxy that works with File.

base/files/file_proxy.h

 // Copyright (c) 2012 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 BASE_FILES_FILE_UTIL_PROXY_H_
-#define BASE_FILES_FILE_UTIL_PROXY_H_
+#ifndef BASE_FILES_FILE_PROXY_H_
+#define BASE_FILES_FILE_PROXY_H_
 
 #include "base/base_export.h"
 #include "base/callback_forward.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
-#include "base/platform_file.h"
+#include "base/memory/weak_ptr.h"
 
 namespace tracked_objects {
 class Location;
 };
 
 namespace base {
 
 class TaskRunner;
 class Time;
 
-// This class provides asynchronous access to common file routines.
-class BASE_EXPORT FileUtilProxy {
+// This class provides asynchronous access to a File. All methods follow the
+// same rules of the equivalent File method, as they are implemented by bouncing
+// the operation to File using a TaskRunner.
+//
+// This class does NOT perform automatic proxying to close the underlying file
+// at destruction, which means that it may potentially close the file in the
+// wrong thread (the current thread). If that is not appropriate, the caller
+// must ensure that Close() is called, so that the operation happens on the
+// desired thread.
+//
+// The TaskRunner is in charge of any sequencing of the operations, but a single
+// operation can be proxied at a time, regardless of the use of a callback.
+// In other words, having a sequence like
+//
+//   proxy.Write(...);
+//   delete proxy;
+//
+// will keep the file valid during the Write operation but will cause the file
+// to be closed in the current thread, when the operation finishes. If Close is
+// called right away after Write, the second call will fail because there is an
+// operation in progress.
+class BASE_EXPORT FileProxy : public SupportsWeakPtr<FileProxy> {
  public:
-  // This callback is used by methods that report only an error code.  It is
-  // valid to pass a null callback to any function that takes a StatusCallback,
-  // in which case the operation will complete silently.
+  // This callback is used by methods that report only an error code. It is
+  // valid to pass a null callback to some functions that takes a
+  // StatusCallback, in which case the operation will complete silently.
   typedef Callback<void(File::Error)> StatusCallback;
 
   typedef Callback<void(File::Error,
-                        PassPlatformFile,
-                        bool /* created */)> CreateOrOpenCallback;
-  typedef Callback<void(File::Error,
-                        PassPlatformFile,
                         const FilePath&)> CreateTemporaryCallback;
   typedef Callback<void(File::Error,
                         const File::Info&)> GetFileInfoCallback;
   typedef Callback<void(File::Error,
-                        const char* /* data */,
-                        int /* bytes read */)> ReadCallback;
+                        const char* data,
+                        int bytes_read)> ReadCallback;
   typedef Callback<void(File::Error,
-                        int /* bytes written */)> WriteCallback;
+                        int bytes_written)> WriteCallback;
 
-  typedef Callback<File::Error(PlatformFile*, bool*)> CreateOrOpenTask;
-  typedef Callback<File::Error(PlatformFile)> CloseTask;
-  typedef Callback<File::Error(void)> FileTask;
+  FileProxy();
+  explicit FileProxy(TaskRunner* task_runner);
+  ~FileProxy();
 
   // Creates or opens a file with the given flags. It is invalid to pass a null
-  // callback. If PLATFORM_FILE_CREATE is set in |file_flags| it always tries to
-  // create a new file at the given |file_path| and calls back with
-  // PLATFORM_FILE_ERROR_FILE_EXISTS if the |file_path| already exists.
+  // callback. If File::FLAG_CREATE is set in |file_flags| it always tries to
+  // create a new file at the given |file_path| and fails if the file already
+  // exists.
   //
   // This returns false if task posting to |task_runner| has failed.
-  static bool CreateOrOpen(TaskRunner* task_runner,
-                           const FilePath& file_path,
-                           int file_flags,
-                           const CreateOrOpenCallback& callback);
+  bool CreateOrOpen(const FilePath& file_path,
+                    uint32 file_flags,
+                    const StatusCallback& callback);
 
-  // Creates a temporary file for writing. The path and an open file handle are
+  // Creates a temporary file for writing. The path and an open file are
   // returned. It is invalid to pass a null callback. The additional file flags
   // will be added on top of the default file flags which are:
-  //   base::PLATFORM_FILE_CREATE_ALWAYS
-  //   base::PLATFORM_FILE_WRITE
-  //   base::PLATFORM_FILE_TEMPORARY.
-  // Set |additional_file_flags| to 0 for synchronous writes and set to
-  // base::PLATFORM_FILE_ASYNC to support asynchronous file operations.
+  //   File::FLAG_CREATE_ALWAYS
+  //   File::FLAG_WRITE
+  //   File::FLAG_TEMPORARY.
   //
   // This returns false if task posting to |task_runner| has failed.
-  static bool CreateTemporary(
-      TaskRunner* task_runner,
-      int additional_file_flags,
-      const CreateTemporaryCallback& callback);
+  bool CreateTemporary(uint32 additional_file_flags,
+                       const CreateTemporaryCallback& callback);
 
-  // Close the given file handle.
+  // Returns true if the underlying |file_| is valid.
+  bool IsValid() const;
+
+  // Returns true if a new file was created (or an old one truncated to zero
+  // length to simulate a new file), and false otherwise.
+  bool created() const { return file_.created(); }
+
+  File TakeFile();
+
+  // Proxies File::Close. The callback can be null.
   // This returns false if task posting to |task_runner| has failed.
-  static bool Close(TaskRunner* task_runner,
-                    PlatformFile,
-                    const StatusCallback& callback);
+  bool Close(const StatusCallback& callback);
 
-  // Retrieves the information about a file. It is invalid to pass a null
-  // callback.
+  // Proxies File::GetInfo. The callback can't be null.
   // This returns false if task posting to |task_runner| has failed.
-  static bool GetFileInfo(
-      TaskRunner* task_runner,
-      const FilePath& file_path,
-      const GetFileInfoCallback& callback);
+  bool GetInfo(const GetFileInfoCallback& callback);
 
-  // Does the same as GetFileInfo but takes PlatformFile instead of FilePath.
-  // This returns false if task posting to |task_runner| has failed.
-  static bool GetFileInfoFromPlatformFile(
-      TaskRunner* task_runner,
-      PlatformFile file,
-      const GetFileInfoCallback& callback);
-
-  // Deletes a file or a directory.
-  // It is an error to delete a non-empty directory with recursive=false.
-  // This returns false if task posting to |task_runner| has failed.
-  static bool DeleteFile(TaskRunner* task_runner,
-                         const FilePath& file_path,
-                         bool recursive,
-                         const StatusCallback& callback);
-
-  // Reads from a file. On success, the file pointer is moved to position
-  // |offset + bytes_to_read| in the file. The callback can be null.
-  //
+  // Proxies File::Read. The callback can't be null.
   // This returns false if |bytes_to_read| is less than zero, or
   // if task posting to |task_runner| has failed.
-  static bool Read(
-      TaskRunner* task_runner,
-      PlatformFile file,
-      int64 offset,
-      int bytes_to_read,
-      const ReadCallback& callback);
+  bool Read(int64 offset, int bytes_to_read, const ReadCallback& callback);
 
-  // Writes to a file. If |offset| is greater than the length of the file,
-  // |false| is returned. On success, the file pointer is moved to position
-  // |offset + bytes_to_write| in the file. The callback can be null.
-  // |bytes_to_write| must be greater than zero.
-  //
+  // Proxies File::Write. The callback can be null.
   // This returns false if |bytes_to_write| is less than or equal to zero,
   // if |buffer| is NULL, or if task posting to |task_runner| has failed.
-  static bool Write(
-      TaskRunner* task_runner,
-      PlatformFile file,
-      int64 offset,
-      const char* buffer,
-      int bytes_to_write,
-      const WriteCallback& callback);
+  bool Write(int64 offset,
+             const char* buffer,
+             int bytes_to_write,
+             const WriteCallback& callback);
 
-  // Touches a file. The callback can be null.
+  // Proxies File::SetTimes. The callback can be null.
   // This returns false if task posting to |task_runner| has failed.
-  static bool Touch(
-      TaskRunner* task_runner,
-      PlatformFile file,
-      const Time& last_access_time,
-      const Time& last_modified_time,
-      const StatusCallback& callback);
+  bool SetTimes(Time last_access_time,
+                Time last_modified_time,
+                const StatusCallback& callback);
 
-  // Touches a file. The callback can be null.
+  // Proxies File::SetLength. The callback can be null.
   // This returns false if task posting to |task_runner| has failed.
-  static bool Touch(
-      TaskRunner* task_runner,
-      const FilePath& file_path,
-      const Time& last_access_time,
-      const Time& last_modified_time,
-      const StatusCallback& callback);
+  bool SetLength(int64 length, const StatusCallback& callback);
 
-  // Truncates a file to the given length. If |length| is greater than the
-  // current length of the file, the file will be extended with zeroes.
-  // The callback can be null.
+  // Proxies File::Flush. The callback can be null.
   // This returns false if task posting to |task_runner| has failed.
-  static bool Truncate(
-      TaskRunner* task_runner,
-      PlatformFile file,
-      int64 length,
-      const StatusCallback& callback);
-
-  // Truncates a file to the given length. If |length| is greater than the
-  // current length of the file, the file will be extended with zeroes.
-  // The callback can be null.
-  // This returns false if task posting to |task_runner| has failed.
-  static bool Truncate(
-      TaskRunner* task_runner,
-      const FilePath& path,
-      int64 length,
-      const StatusCallback& callback);
-
-  // Flushes a file. The callback can be null.
-  // This returns false if task posting to |task_runner| has failed.
-  static bool Flush(
-      TaskRunner* task_runner,
-      PlatformFile file,
-      const StatusCallback& callback);
-
-  // Relay helpers.
-  // They return false if posting a given task to |task_runner| has failed.
-  static bool RelayCreateOrOpen(
-      TaskRunner* task_runner,
-      const CreateOrOpenTask& open_task,
-      const CloseTask& close_task,
-      const CreateOrOpenCallback& callback);
-  static bool RelayClose(
-      TaskRunner* task_runner,
-      const CloseTask& close_task,
-      PlatformFile,
-      const StatusCallback& callback);
+  bool Flush(const StatusCallback& callback);
 
  private:
-  DISALLOW_IMPLICIT_CONSTRUCTORS(FileUtilProxy);
+  friend class FileHelper;
+  void SetFile(File file);
+
+  scoped_refptr<TaskRunner> task_runner_;
+  File file_;
+  DISALLOW_COPY_AND_ASSIGN(FileProxy);
 };
 
 }  // namespace base
 
-#endif  // BASE_FILES_FILE_UTIL_PROXY_H_
+#endif  // BASE_FILES_FILE_PROXY_H_