[WebMIDI] Introduce UsbMidi{Input, Output}Stream.

media/midi/usb_midi_input_stream.h

Index: media/midi/usb_midi_input_stream.h
diff --git a/media/midi/usb_midi_input_stream.h b/media/midi/usb_midi_input_stream.h
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index 0000000000000000000000000000000000000000..70ed306699a8e16dd4ab4cb55ae2b070d4317685
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+// Copyright 2014 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_INPUT_STREAM_H_
+#define MEDIA_MIDI_USB_MIDI_INPUT_STREAM_H_
+
+#include <map>
+#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;
+
+// UsbMidiInputStream converts USB-MIDI data to MIDI data.
+// See "USB Device Class Definition for MIDI Devices" Release 1.0,
+// Section 4 "USB-MIDI Event Packets" for details.
+class MEDIA_EXPORT UsbMidiInputStream {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+    // This function is called when some data arrives to a USB-MIDI jack.
+    // An input USB-MIDI jack corresponds to an input MIDIPortInfo.
+    virtual void OnReceivedData(size_t jack_index,
+                                const uint8* data,
+                                size_t size,
+                                double timestamp) = 0;
+  };
+
+  UsbMidiInputStream(const std::vector<UsbMidiJack>& jacks,
+                     Delegate* delegate);
+  ~UsbMidiInputStream();
+
+  // This function should be called when some data arrives to a USB-MIDI
+  // endpoint. This function converts the data to MIDI data and call
+  // |delegate->OnReceivedData| with it.
+  // |size| must be a multiple of |kPacketSize|.
+  void OnReceivedData(UsbMidiDevice* device,
+                      int endpoint_number,
+                      const uint8* data,
+                      size_t size,
+                      double timestamp);
+
+ private:
+  static const size_t kPacketSize = 4;
+  struct JackUniqueKey {
+    JackUniqueKey(UsbMidiDevice* device, int endpoint_number, int cable_number);
+    bool operator==(const JackUniqueKey& that) const;
+    bool operator<(const JackUniqueKey& that) const;
+
+    UsbMidiDevice* device;
+    int endpoint_number;
+    int cable_number;
+  };
+
+  // Processes a USB-MIDI Event Packet.
+  // The first |kPacketSize| bytes of |packet| must be accessible.
+  void ProcessOnePacket(UsbMidiDevice* device,
+                        int endpoint_number,
+                        const uint8* packet,
+                        double timestamp);
+
+  // A map from UsbMidiJack to its index in |jacks_|.
+  std::map<JackUniqueKey, size_t> jack_dictionary_;
+
+  // Not owned
+  Delegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(UsbMidiInputStream);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_MIDI_USB_MIDI_INPUT_STREAM_H_