Introduce USB MIDI descriptor parser

media/midi/usb_midi_jack.h

+// Copyright 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_JACK_H_
+#define MEDIA_MIDI_USB_MIDI_JACK_H_
+
+#include "base/basictypes.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class UsbMidiDevice;
+
+// UsbMidiJack represents an EMBEDDED MIDI jack.
+struct MEDIA_EXPORT UsbMidiJack {

[DaleCurtis, 2014/01/10 01:55:57]

Class?  If you think other classes will use your JackMatcher, just add an
operator== here instead.

[yhirano, 2014/01/10 02:30:32]

A jack is fully identified with (device, endpoint_address, jack_id), since
endpoint address is unique in a USB device and jack ID is unique in a USB
interface.
Hence JackMatcher is not a generic matcher and I want to define it there.
(note: We find an jack with JackMatcher in incomplete jacks that the current
parsing interface contains.)

+  // The direction of the endpoint associated with an EMBEDDED MIDI jack.
+  // Note that an IN MIDI jack associated with an OUT endpoint has
+  // ***OUT*** direction.
+  enum Direction {
+    IN,
+    OUT,
+  };
+  UsbMidiJack(UsbMidiDevice* device,
+              uint8 jack_id,
+              uint8 cable_number,
+              uint8 endpoint_address)
+      : device(device),
+        jack_id(jack_id),
+        cable_number(cable_number),
+        endpoint_address(endpoint_address) {}
+  // Not owned
+  UsbMidiDevice* device;
+  // The id of this jack unique in the interface.
+  uint8 jack_id;
+  // The cable number of this jack in the associated endpoint.
+  uint8 cable_number;
+  // The address of the endpoint that this jack is associated with.
+  uint8 endpoint_address;
+
+  Direction direction() const {
+    return (endpoint_address & 0x80) ? IN : OUT;
+  }
+  uint8 endpoint_number() const {
+    return (endpoint_address & 0xf);
+  }
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MIDI_USB_MIDI_JACK_H_