Introduce USB MIDI descriptor parser

media/midi/usb_midi_descriptor_parser.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 MEDIA_MIDI_USB_MIDI_DESCRIPTOR_PARSER_H_
+#define MEDIA_MIDI_USB_MIDI_DESCRIPTOR_PARSER_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/containers/hash_tables.h"
+#include "media/base/media_export.h"
+#include "media/midi/usb_midi_jack.h"
+
+namespace media {
+
+class UsbMidiDevice;
+
+// UsbMidiDescriptorParser parses USB descriptors and
+// generates input / output lists of MIDIPortInfo.
+class MEDIA_EXPORT UsbMidiDescriptorParser {
+ public:
+  UsbMidiDescriptorParser();
+  ~UsbMidiDescriptorParser();
+
+  // Returns true if the operation succeeds.
+  // When an incorrect input is given, this method may return true but
+  // never crashes.

[Takashi Toyoshima, 2013/12/19 05:54:23]

So, when does it return false? Or why it may return against invalid inputs?
That may be a common question when someone read this comment.
Can you elaborate it?

[yhirano, 2013/12/19 07:15:05]

It may return false when the input is not correct.
I wanted to say that this function does not fully check the descriptor.
For example, it doesn't check the content of DEVICE descriptor.

+  bool Parse(UsbMidiDevice* device, const uint8* data, size_t size);
+
+  const std::vector<UsbMidiJack>& jacks() const { return jacks_; }
+
+ private:
+  bool ParseInternal(UsbMidiDevice* device, const uint8* data, size_t size);
+  bool ParseInterface(UsbMidiDevice* device, const uint8* data, size_t size);
+  bool ParseCSInterface(UsbMidiDevice* device, const uint8* data, size_t size);
+  bool ParseEndpoint(UsbMidiDevice* device, const uint8* data, size_t size);
+  bool ParseCSEndpoint(UsbMidiDevice* device, const uint8* data, size_t size);
+  void Clear();
+  void ClearExceptJacks();
+
+  bool is_parsing_usb_midi_interface_;
+  uint8 current_endpoint_address_;
+  uint8 current_cable_number_;
+
+  std::vector<UsbMidiJack> jacks_;

[Takashi Toyoshima, 2013/12/19 05:54:23]

Some comments? They are not trivial, and comments will be helpful to understand
how this class parse  inputs.

[yhirano, 2013/12/19 07:15:05]

Done.

+  base::hash_map<uint8, UsbMidiJack> incomplete_jacks_;

[Takashi Toyoshima, 2013/12/19 05:54:23]

DISALLOW_COPY_AND_ASSIGN()

[yhirano, 2013/12/19 07:15:05]

Done.

+};
+
+
+}  // namespace media
+
+#endif  // MEDIA_MIDI_USB_MIDI_DESCRIPTOR_PARSER_H_