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

media/midi/usb_midi_input_stream.cc

Index: media/midi/usb_midi_input_stream.cc
diff --git a/media/midi/usb_midi_input_stream.cc b/media/midi/usb_midi_input_stream.cc
new file mode 100644
index 0000000000000000000000000000000000000000..703e221c54e5fac4eb55f5f9ffbbd8d8555ce2a4
--- /dev/null
+++ b/media/midi/usb_midi_input_stream.cc
@@ -0,0 +1,100 @@
+// 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.
+
+#include "media/midi/usb_midi_input_stream.h"
+

[Takashi Toyoshima, 2013/12/24 04:19:32]

string.h for memcpy ?

[yhirano, 2013/12/24 05:57:01]

Done.

+#include <vector>
+
+#include "base/logging.h"
+#include "media/midi/usb_midi_device.h"
+#include "media/midi/usb_midi_jack.h"
+
+namespace media {
+
+UsbMidiInputStream::JackUniqueKey::JackUniqueKey(UsbMidiDevice* device,
+                                                 int endpoint_number,
+                                                 int cable_number)
+    : device(device),
+      endpoint_number(endpoint_number),
+      cable_number(cable_number) {}
+
+bool UsbMidiInputStream::JackUniqueKey::operator==(
+    const JackUniqueKey& that) const {
+  return device == that.device &&
+      endpoint_number == that.endpoint_number &&
+      cable_number == that.cable_number;
+}
+
+size_t UsbMidiInputStream::JackHash::operator()
+    (const JackUniqueKey& key) const {
+  return std::hash<UsbMidiDevice*>()(key.device) * 17 +
+      std::hash<int>()(key.endpoint_number) * 19 +
+      std::hash<int>()(key.cable_number) * 31;
+}
+
+UsbMidiInputStream::UsbMidiInputStream(const std::vector<UsbMidiJack>& jacks,
+                                       Delegate* delegate)
+    : jacks_(jacks), delegate_(delegate), pending_size_(0) {
+  for (size_t i = 0; i < jacks.size(); ++i) {
+    jack_dictionary_.insert(
+        std::make_pair(JackUniqueKey(jacks[i].device,
+                                     jacks[i].GetEndpointNumber(),
+                                     jacks[i].cable_number),
+                       i));
+  }
+}
+
+UsbMidiInputStream::~UsbMidiInputStream() {}
+
+void UsbMidiInputStream::OnReceivedData(UsbMidiDevice* device,
+                                        int endpoint_number,
+                                        const uint8* data,
+                                        size_t size,
+                                        double timestamp) {
+  size_t current = 0;
+  if (pending_size_ > 0) {
+    if (pending_size_ + size < kPacketSize) {
+      for (size_t i = 0; i < size; ++i)
+        pending_data_[i + pending_size_] = data[i];
+      pending_size_ += size;
+      return;
+    }
+    for (current = 0; current < kPacketSize - pending_size_; ++current)
+      pending_data_[current + pending_size_] = data[current];
+    ProcessOnePacket(device, endpoint_number, pending_data_, timestamp);
+    pending_size_ = 0;
+  }
+  while (current + kPacketSize <= size) {
+    ProcessOnePacket(device, endpoint_number, &data[current], timestamp);
+    current += kPacketSize;
+  }
+  pending_size_ = size - current;
+  DCHECK_LT(pending_size_, arraysize(pending_data_));
+  memcpy(pending_data_, &data[current], pending_size_);
+}
+
+void UsbMidiInputStream::ProcessOnePacket(UsbMidiDevice* device,
+                                          int endpoint_number,
+                                          const uint8* packet,
+                                          double timestamp) {
+  // packet[0:4] is accessible here.

[Takashi Toyoshima, 2013/12/24 04:19:32]

It's nice to have some information about USB MIDI spec. E.g., section number of
the spec is useful information here. So, see also Universal Serial Bus Device
Class Definition for MIDI Devices Release 1.0 "4 USB-MIDI Event Packets" or
something like that.

If possible, please add spec reference here and there. It's useful to read these
source code and review this change.

[yhirano, 2013/12/24 05:57:01]

Added comments in headers.

+  uint8 cin = packet[0] & 0x0f;
+  uint8 cable_number = packet[0] >> 4;
+  const size_t packet_size_table[16] = {
+    0, 0, 2, 3, 3, 1, 2, 3, 3, 3, 3, 3, 2, 2, 3, 1,
+  };
+  size_t packet_size = packet_size_table[cin];
+  if (packet_size == 0) {
+    // The CINs are reserved. Ignore them.
+    return;
+  }
+  base::hash_map<JackUniqueKey, size_t, JackHash>::const_iterator it =
+      jack_dictionary_.find(JackUniqueKey(device,
+                                          endpoint_number,
+                                          cable_number));
+  if (it != jack_dictionary_.end())
+    delegate_->OnReceivedData(it->second, &packet[1], packet_size, timestamp);
+}
+
+}  // namespace media