Initial version of new file wrapper

webrtc/base/file.h

+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_BASE_FILE_H_
+#define WEBRTC_BASE_FILE_H_
+
+#include <stdint.h>
+
+#include "webrtc/base/platform_file.h"
+#include "webrtc/base/constructormagic.h"
+
+namespace rtc {
+
+// This class wraps the platform specific APIs for simple file interactions.
+//
+// The regular read and write methods (Write|Read)(At)? are best effort, i.e.
+// if an underlying call does not manage to read/write all the data more calls
+// will be performed, until an error is detected or all data is read/written.
+// The NoBestEffort variants do not do this.

[sprang_webrtc, 2016/08/15 09:43:07]

I'm thinking we should switch this naming around, making synchronous write the
default and naming the other WriteBestEffort. Feels like you normally want the
WriteAll version. WDYT?

[palmkvist, 2016/08/16 08:55:35]

I agree that WriteAll should be the default, but I figured the best way to do
that was to give that the simplest name; Write is equivalent to the previous
WriteAll, WriteNoBestEffort is the version that might not write everything.

After thinking some more on it though I think that the NoBestEffort versions are
probably not very useful, my assumption is that you either want to write
everything in a blocking fashion, or you want some stronger asynchronous
guarantees. 

I vote removing the NoBestEffort versions and later adding some proper async
versions.

[sprang, 2016/08/16 09:27:44]

Agreed, let's only add a best-effort method if we actually have a use case for
it.

+class File {
+ public:
+  // Wraps the given PlatformFile. This class is then responsible for closing
+  // the file, which will be done in the destructor if Close is never called.
+  explicit File(PlatformFile);
+  ~File();
+
+  size_t Write(const uint8_t* data, size_t length);
+  size_t Read(uint8_t* buffer, size_t length);
+
+  size_t WriteAt(const uint8_t* data, size_t length, size_t offset);
+  size_t ReadAt(uint8_t* buffer, size_t length, size_t offset);
+
+  size_t WriteNoBestEffort(const uint8_t* data, size_t length);
+  size_t ReadNoBestEffort(uint8_t* buffer, size_t length);
+
+  size_t WriteAtNoBestEffort(const uint8_t* data, size_t length, size_t offset);
+  size_t ReadAtNoBestEffort(uint8_t* buffer, size_t length, size_t offset);
+
+  // Attempt to position the file at the given offset from the start.
+  // Returns true if successful, false otherwise.
+  bool Seek(size_t offset);
+
+  // Attempt to close the file. Returns true if successful, false otherwise,
+  // most notably when the file is already closed.
+  bool Close();
+
+ private:
+  rtc::PlatformFile file_;
+  RTC_DISALLOW_COPY_AND_ASSIGN(File);
+};
+
+}  // namespace rtc
+
+#endif  // WEBRTC_BASE_FILE_H_