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 <iostream>
+#include <string>
+
+#include "base/debug/trace_event.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/sys_string_conversions.h"
+#include <CoreAudio/HostTime.h>
+
+using base::IntToString;
+using base::SysCFStringRefToUTF8;
+using std::string;
+
+namespace media {
+
+MIDIManager* MIDIManager::Create() {
+  return new MIDIManagerMac();
+}
+
+MIDIManagerMac::MIDIManagerMac()
+    : midi_client_(NULL),
+      coremidi_input_(NULL),
+      coremidi_output_(NULL),
+      packet_list_(NULL),
+      midi_packet_(NULL) {
+}
+
+bool MIDIManagerMac::Initialize() {
+  TRACE_EVENT0("midi", "MIDIManagerMac::Initialize");
+
+  // CoreMIDI registration.
+  midi_client_ = NULL;
+  OSStatus result = MIDIClientCreate(
+      CFSTR("Google Chrome"),
+      NULL,
+      NULL,
+      &midi_client_);
+
+  if (result != noErr)
+    return false;
+
+  coremidi_input_ = NULL;
+
+  // Create input and output port.
+  result = MIDIInputPortCreate(
+      midi_client_,
+      CFSTR("MIDI Input"),
+      ReadMidiDispatch,
+      this,
+      &coremidi_input_);
+  if (result != noErr)
+    return false;
+
+  result = MIDIOutputPortCreate(
+      midi_client_,
+      CFSTR("MIDI Output"),
+      &coremidi_output_);
+  if (result != noErr)
+    return false;
+
+  int destination_count = MIDIGetNumberOfDestinations();
+  destinations_.reserve(destination_count);
+
+  for (int i = 0; i < destination_count ; i++) {
+    MIDIEndpointRef destination = MIDIGetDestination(i);
+
+    // Keep track of all destinations (known as outputs by the Web MIDI API).
+    // Cache to avoid any possible overhead in calling MIDIGetDestination().
+    destinations_[i] = destination;
+
+    MIDIPortInfo info = GetPortInfoFromEndpoint(destination);
+    AddOutputPort(info);
+  }
+
+  // Open connections from all sources.
+  int source_count = MIDIGetNumberOfSources();
+
+  for (int i = 0; i < source_count; ++i)  {
+    // Receive from all sources.
+    MIDIEndpointRef src = MIDIGetSource(i);
+    MIDIPortConnectSource(coremidi_input_, src, src);
+
+    // Keep track of all sources (known as inputs in Web MIDI API terminology).
+    source_map_[src] = i;
+
+    MIDIPortInfo info = GetPortInfoFromEndpoint(src);
+    AddInputPort(info);
+  }
+
+  // TODO(crogers): Fix the memory management here!
+  packet_list_ = reinterpret_cast<MIDIPacketList*>(midi_buffer_);
+  midi_packet_ = MIDIPacketListInit(packet_list_);
+
+  return true;
+}
+
+MIDIManagerMac::~MIDIManagerMac() {
+  if (coremidi_input_)
+    MIDIPortDispose(coremidi_input_);
+  if (coremidi_output_)
+    MIDIPortDispose(coremidi_output_);
+}
+
+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];
+
+  // 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);
+
+    ReceiveMIDIData(
+        port_index,
+        packet.data,
+        packet.length,
+        timestamp_seconds);
+  }
+}
+
+void MIDIManagerMac::SendMIDIData(int port_index,
+                                  const uint8* data,
+                                  size_t length,
+                                  double timestamp) {
+  // TODO(crogers): Filter out sysex.
+
+  MIDITimeStamp coremidi_timestamp = SecondsToMIDITimeStamp(timestamp);
+
+  midi_packet_ = MIDIPacketListAdd(
+      packet_list_,
+      kMaxPacketListSize,
+      midi_packet_,
+      coremidi_timestamp,
+      length,
+      data);
+
+  // Lookup the destination based on the port index.
+  if (port_index < 0 ||

[palmer, 2013/06/19 21:39:15]

Funny, I saw the same pattern in my previous (unrelated) code review. This code
is OK as-is, but for cleanliness You could either change post_index to be a
size_t or other unsigned type (thus obviating the port_index < 0 part of the
check), or use the range-checked std::vector::at function instead of operator[].

[Chris Rogers, 2013/06/20 17:41:33]

Agreed that unsigned is better.  For now adding TODO,since this propagates all
the way through the Blink API, so will take some re-factoring...

+      static_cast<size_t>(port_index) >= destinations_.size())
+    return;
+
+  MIDIEndpointRef destination = destinations_[port_index];
+
+  MIDISend(coremidi_output_, destination, packet_list_);
+
+  // Re-initialize for next time.
+  midi_packet_ = MIDIPacketListInit(packet_list_);
+}
+
+MIDIPortInfo MIDIManagerMac::GetPortInfoFromEndpoint(
+    MIDIEndpointRef endpoint) {
+  SInt32 id_number = 0;
+  MIDIObjectGetIntegerProperty(endpoint, kMIDIPropertyUniqueID, &id_number);
+  string id = IntToString(id_number);
+
+  CFStringRef manufacturer_ref = NULL;
+  MIDIObjectGetStringProperty(
+      endpoint, kMIDIPropertyManufacturer, &manufacturer_ref);
+  string manufacturer = SysCFStringRefToUTF8(manufacturer_ref);
+
+  CFStringRef name_ref = NULL;
+  MIDIObjectGetStringProperty(endpoint, kMIDIPropertyName, &name_ref);
+  string name = SysCFStringRefToUTF8(name_ref);
+
+  SInt32 version_number = 0;
+  MIDIObjectGetIntegerProperty(
+      endpoint, kMIDIPropertyDriverVersion, &version_number);
+  string version = IntToString(version_number);
+
+  return MIDIPortInfo(id, manufacturer, name, version);
+}
+
+double MIDIManagerMac::MIDITimeStampToSeconds(MIDITimeStamp timestamp) {
+  UInt64 nanoseconds = AudioConvertHostTimeToNanos(timestamp);
+  return static_cast<double>(nanoseconds) / 1.0e9;
+}
+
+MIDITimeStamp MIDIManagerMac::SecondsToMIDITimeStamp(double seconds) {
+  UInt64 nanos = UInt64(seconds * 1.0e9);
+  return AudioConvertNanosToHostTime(nanos);
+}
+
+}  // namespace media