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

media/midi/usb_midi_output_stream.cc

+// 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.
+
+#include "media/midi/usb_midi_output_stream.h"
+
+#include "base/logging.h"
+#include "media/midi/midi_message_util.h"
+#include "media/midi/usb_midi_device.h"
+
+namespace media {
+
+void UsbMidiOutputStream::Send(const std::vector<uint8>& data) {
+  // To prevent link errors caused by DCHECK_*.
+  const size_t kPacketContentSize = UsbMidiOutputStream::kPacketContentSize;
+  DCHECK_LT(jack_.cable_number, 16u);
+  DCHECK_EQ(3u, kPacketContentSize);

[scherkus (not reviewing), 2014/01/16 21:55:52]

what is this DCHECK() protecting against?

UsbMidiOutputStream::kPacketContentSize is a constant -- do we really need a
run-time check to make sure the constant is still 3?

[yhirano, 2014/01/20 09:12:19]

I added it for readability, but OK, I deleted.

+
+  std::vector<uint8> data_to_send;
+  size_t current = 0;
+  size_t size = GetSize(data);
+  while (current < size) {
+    uint8 first_byte = Get(data, current);
+    if (first_byte == kSysExByte || is_sending_sysex_) {
+      // System Exclusive messages
+      if (!PushSysExMessage(data, &current, &data_to_send))
+        break;
+    } else if ((first_byte & kSysMessageBitMask) == kSysMessageBitPattern) {
+      if (first_byte & 0x08) {
+        // System Real-Time messages
+        PushSysRTMessage(data, &current, &data_to_send);
+      } else {
+        // System Common messages
+        if (!PushSysCommonMessage(data, &current, &data_to_send))
+          break;
+      }
+    } else if (first_byte & 0x80) {
+      if (!PushChannelMessage(data, &current, &data_to_send))
+        break;
+    } else {
+      // Unknown messages
+      DVLOG(1) << "Unknown byte: " << static_cast<unsigned int>(first_byte);
+      ++current;
+    }
+  }
+
+  if (data_to_send.size() > 0)
+    jack_.device->Send(jack_.endpoint_number(), data_to_send);
+
+  DCHECK_LE(current, size);
+  DCHECK_LE(size - current, kPacketContentSize);
+  // Note that this can be a self-copying and the iteration order is important.
+  for (size_t i = current; i < size; ++i)
+    pending_data_[i - current] = Get(data, i);
+  pending_size_ = size - current;
+}
+
+size_t UsbMidiOutputStream::GetSize(const std::vector<uint8>& data) const {
+  return data.size() + pending_size_;
+}
+
+uint8_t UsbMidiOutputStream::Get(const std::vector<uint8>& data,
+                               size_t index) const {
+  DCHECK_LT(index, GetSize(data));
+  if (index < pending_size_)
+    return pending_data_[index];
+  return data[index - pending_size_];
+}
+
+bool UsbMidiOutputStream::PushSysExMessage(const std::vector<uint8>& data,
+                                           size_t* current,
+                                           std::vector<uint8>* data_to_send) {
+  size_t index = *current;
+  size_t message_size = 0;
+  const size_t kMessageSizeMax = 3;
+  uint8 message[kMessageSizeMax] = {};
+
+  while (index < GetSize(data)) {
+    if (message_size == kMessageSizeMax) {
+      // We can't find the end-of-message mark in the three bytes.
+      *current = index;
+      data_to_send->push_back((jack_.cable_number << 4) | 0x4);
+      data_to_send->insert(data_to_send->end(),
+                           message,
+                           message + arraysize(message));
+      is_sending_sysex_ = true;
+      return true;
+    }
+    uint8 byte = Get(data, index);
+    if ((byte & kSysRTMessageBitMask) == kSysRTMessageBitPattern) {
+      // System Real-Time messages interleaved in a SysEx message
+      PushSysRTMessage(data, &index, data_to_send);
+      continue;
+    }
+
+    message[message_size] = byte;
+    ++message_size;
+    if (byte == kEndOfSysExByte) {
+      uint8 code_index = message_size + 0x4;
+      DCHECK(code_index == 0x5 || code_index == 0x6 || code_index == 0x7);
+      data_to_send->push_back((jack_.cable_number << 4) | code_index);
+      data_to_send->insert(data_to_send->end(),
+                           message,
+                           message + arraysize(message));
+      *current = index + 1;
+      is_sending_sysex_ = false;
+      return true;
+    }
+    ++index;
+  }
+  return false;
+}
+
+bool UsbMidiOutputStream::PushSysCommonMessage(
+    const std::vector<uint8>& data,
+    size_t* current,
+    std::vector<uint8>* data_to_send) {
+  size_t index = *current;
+  uint8 first_byte = Get(data, index);
+  DCHECK_LE(0xf1, first_byte);
+  DCHECK_LE(first_byte, 0xf7);
+  const size_t message_size_table[8] = {
+    0, 2, 3, 2, 1, 1, 1, 0,
+  };
+  size_t message_size = message_size_table[first_byte & 0x0f];
+  DCHECK_NE(0u, message_size);
+  DCHECK_LE(message_size, 3u);
+
+  if (GetSize(data) < index + message_size) {
+    // The message is incomplete.
+    return false;
+  }
+
+  uint8 code_index = message_size == 1 ? 0x5 : static_cast<uint8>(message_size);
+  data_to_send->push_back((jack_.cable_number << 4) | code_index);
+  for (size_t i = index; i < index + 3; ++i)
+    data_to_send->push_back(i < index + message_size ? Get(data, i) : 0);
+  *current += message_size;
+  return true;
+}
+
+void UsbMidiOutputStream::PushSysRTMessage(const std::vector<uint8>& data,
+                                           size_t* current,
+                                           std::vector<uint8>* data_to_send) {
+  size_t index = *current;
+  uint8 first_byte = Get(data, index);
+  DCHECK_LE(0xf8, first_byte);
+  DCHECK_LE(first_byte, 0xff);
+
+  data_to_send->push_back((jack_.cable_number << 4) | 0x5);
+  data_to_send->push_back(first_byte);
+  data_to_send->push_back(0);
+  data_to_send->push_back(0);
+  *current += 1;
+}
+
+bool UsbMidiOutputStream::PushChannelMessage(const std::vector<uint8>& data,
+                                           size_t* current,
+                                           std::vector<uint8>* data_to_send) {
+  size_t index = *current;
+  uint8 first_byte = Get(data, index);
+  DCHECK_LE(0x80, (first_byte & 0xf0));
+  DCHECK_LE((first_byte & 0xf0), 0xe0);
+
+  const size_t message_size_table[8] = {
+    3, 3, 3, 3, 2, 3, 3, 0,
+  };
+  uint8 code_index = first_byte >> 4;
+  size_t message_size = message_size_table[code_index & 0x7];
+  DCHECK_NE(0u, message_size);
+  DCHECK_LE(message_size, 3u);
+
+  if (GetSize(data) < index + message_size) {
+    // The message is incomplete.
+    return false;
+  }
+
+  data_to_send->push_back((jack_.cable_number << 4) | code_index);
+  for (size_t i = index; i < index + 3; ++i)
+    data_to_send->push_back(i < index + message_size ? Get(data, i) : 0);
+  *current += message_size;
+  return true;
+}
+
+}  // namespace media