Web MIDI API back-end (work-in-progress)

media/midi/midi_manager_mac.cc

+// 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/midi_manager_mac.h"
+
+#include "base/time.h"
+#include <CoreAudio/HostTime.h>
+
+namespace media {
+
+MIDIManager* MIDIManager::Create() {
+  return new MIDIManagerMac();
+}
+
+MIDIManagerMac::MIDIManagerMac() {

[scherkus (not reviewing), 2013/06/03 22:44:59]

FYI this will be executed on the main UI thread when Chrome launches

do you have #s on what the impact of running this code is?

can we do it lazily e.g., the first time we successfully approve MIDI access?

+  OSStatus result = noErr;
+
+  // Create client and ports.
+  midi_client_ = NULL;
+  result = MIDIClientCreate(CFSTR("Google Chrome"), NULL, NULL, &midi_client_);
+
+  input_port_ = NULL;
+
+  result = MIDIInputPortCreate(midi_client_,
+                               CFSTR("MIDI Input"),
+                               ReadMidiDispatch,
+                               this,
+                               &input_port_);
+
+  result = MIDIOutputPortCreate(midi_client_,
+                                CFSTR("MIDI Output"),
+                                &output_port_);
+
+  int m = MIDIGetNumberOfDestinations();
+
+  for (int i = 0; i < m ; i++) {
+    MIDIEndpointRef  destination = MIDIGetDestination(i);
+    CFStringRef deviceName = GetDeviceNameFromEndpoint(destination);
+
+    printf("%d: ", i);
+    CFShow(deviceName);
+  }
+
+  // Use first destination as default.
+  destination_ = MIDIGetDestination(0);
+
+  // Open connections from all sources
+  int n = MIDIGetNumberOfSources();
+
+  for (int i = 0; i < n; ++i)  {
+    // Receive from all sources
+    MIDIEndpointRef src = MIDIGetSource(i);
+    MIDIPortConnectSource(input_port_, src, src);
+    
+    // Keep track of all sources (known as inputs in Web MIDI API terminology).
+    source_map_[src] = i;
+
+    // CFStringRef deviceName = GetDeviceNameFromEndpoint(src);
+
+    CFStringRef midiSourceNameRef;
+    MIDIObjectGetStringProperty(src, kMIDIPropertyName, &midiSourceNameRef);
+
+    CFShow(midiSourceNameRef);
+  }
+
+  // init MIDIPacketList
+  packet_list_ = reinterpret_cast<MIDIPacketList*>(mMIDIBuffer);
+  midi_packet_ = MIDIPacketListInit(packet_list_);
+}
+
+MIDIManagerMac::~MIDIManagerMac() {
+    MIDIPortDispose(input_port_);
+    MIDIPortDispose(output_port_);
+}
+
+void MIDIManagerMac::ReadMidiDispatch(const MIDIPacketList* packet_list,
+                                      void* read_proc_refcon,
+                                      void* src_conn_refcon) {
+  MIDIManagerMac* manager = static_cast<MIDIManagerMac*>(read_proc_refcon);
+  MIDIEndpointRef source = static_cast<MIDIEndpointRef>(src_conn_refcon);
+
+  // Dispatch to class method.
+  manager->ReadMidi(source, packet_list);
+}
+
+void MIDIManagerMac::ReadMidi(MIDIEndpointRef source,
+                              const MIDIPacketList* packet_list) {
+  // Lookup the port index based on the source.
+  SourceMap::iterator j = source_map_.find(source);
+  if (j == source_map_.end())
+    return;
+  int port_index = source_map_[source];
+  // printf("port_index = %d\n", port_index);
+
+  // Go through each packet and process separately.
+  for(size_t i = 0; i < packet_list->numPackets; i++) {
+    // Each packet contains MIDI data for one or more messages (like note-on).
+    const MIDIPacket &packet = packet_list->packet[i];
+    double timestamp_seconds = MIDITimeStampToSeconds(packet.timeStamp);
+
+    // TODO(crogers): handle port index properly at Blink layer.
+    // Right now it only allows a value of 0.
+    port_index = 0;
+
+    ReceiveMIDIData(
+        port_index,
+        packet.data,
+        packet.length,
+        timestamp_seconds);
+  }
+}
+
+void MIDIManagerMac::SendMIDI(UInt8 *midi_data,
+                              UInt32 length,
+                              MIDITimeStamp timestamp) {
+  midi_packet_ = MIDIPacketListAdd(
+      packet_list_,
+      kMaxPacketListSize,
+      midi_packet_,
+      timestamp,
+      length,
+      midi_data);
+
+  MIDISend(output_port_, destination_, packet_list_);
+
+  // Re-initialize for next time.
+  midi_packet_ = MIDIPacketListInit(packet_list_);
+}
+
+double MIDIManagerMac::MIDITimeStampToSeconds(MIDITimeStamp timestamp)
+{
+  UInt64 nanos = AudioConvertHostTimeToNanos(timestamp );
+
+  double seconds = double(nanos) / 1.0e9;
+  return seconds;
+}
+
+MIDITimeStamp MIDIManagerMac::SecondsToMIDITimeStamp(double seconds) {
+  UInt64 nanos = UInt64(seconds * 1.0e9);
+  MIDITimeStamp timeStamp = AudioConvertNanosToHostTime(nanos);
+  return timeStamp;
+}
+
+CFStringRef MIDIManagerMac::GetDeviceNameFromEndpoint(
+    MIDIEndpointRef endpoint) {
+  MIDIEntityRef entity;
+  MIDIEndpointGetEntity(endpoint, &entity);
+
+  MIDIDeviceRef device;
+  MIDIEntityGetDevice(entity, &device);
+
+  CFStringRef device_name_ref;
+  MIDIObjectGetStringProperty(device, kMIDIPropertyName, &device_name_ref);
+
+  return device_name_ref;
+}
+
+}  // namespace media
+