dom/midi/MIDIUtils.cpp
author L10n Bumper Bot <release+l10nbumper@mozilla.com>
Thu, 08 Nov 2018 03:00:11 -0800
changeset 501100 1cd4f2d571554c4dc89cf1be1d98683c0d14f797
parent 460148 6464e4c6f27f4280ede1753aa3a125595b3a845c
child 508163 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
no bug - Bumping Fennec l10n changesets r=release a=l10n-bump DONTBUILD an -> 336e061995b9 ar -> f6834a7d7374 as -> d2c76e616a66 ast -> fcb8f3455237 az -> c4caf3b07cf2 be -> 697eb1022498 bg -> 7bf1f448f743 bn-BD -> 5f7a87adee06 bn-IN -> 49ce3195c4c2 br -> 41cf35b7c5b5 bs -> 4a14aee27904 ca -> 9373e8ce86d4 cak -> a40d767541ba cs -> 4b99defb0525 cy -> 4c948fed2584 de -> 017a7e7a267a dsb -> aadebeccf5ba el -> 2d28a78dcef5 en-CA -> 55ad9171a9f0 en-GB -> 296422b495e9 en-ZA -> c1b5d2128914 eo -> c68e87667d9f es-AR -> bff0a788c711 es-CL -> 1d3efd2532ea es-ES -> 4d1feb70b0e2 es-MX -> fceda607d0f4 et -> 58a8262a0cc7 eu -> 7cebfd46208b fa -> cbc040d58476 ff -> 46f5aec275ea fi -> 235ab13d261e fr -> 8ee417b64f99

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/dom/MIDITypes.h"
#include "mozilla/dom/MIDIUtils.h"

// Taken from MIDI IMPLEMENTATION CHART INSTRUCTIONS, MIDI Spec v1.0, Pg. 97
static const uint8_t kCommandByte = 0x80;
static const uint8_t kSysexMessageStart = 0xF0;
static const uint8_t kSystemMessage = 0xF0;
static const uint8_t kSysexMessageEnd = 0xF7;
static const uint8_t kSystemRealtimeMessage = 0xF8;
// Represents the length of all possible command messages.
// Taken from MIDI Spec, Pg. 101v 1.0, Table 2
static const uint8_t kCommandLengths[] = {3, 3, 3, 3, 2, 2, 3};
// Represents the length of all possible system messages. The length of sysex
// messages is variable, so we just put zero since it won't be checked anyways.
// Taken from MIDI Spec v1.0, Pg. 105, Table 5
static const uint8_t kSystemLengths[] = {0, 2, 3, 2, 1, 1, 1, 1};

namespace mozilla {
namespace dom {
namespace MIDIUtils {

// Checks validity of MIDIMessage passed to it. Throws debug warnings and
// returns false if message is not valid.
bool
IsValidMessage(const MIDIMessage* aMsg)
{
  if (NS_WARN_IF(!aMsg)) {
    return false;
  }
  // Assert on parser problems
  MOZ_ASSERT(aMsg->data().Length() > 0,
             "Created a MIDI Message of Length 0. This should never happen!");
  uint8_t cmd = aMsg->data()[0];
  // If first byte isn't a command, something is definitely wrong.
  MOZ_ASSERT((cmd & kCommandByte) == kCommandByte,
             "Constructed a MIDI packet where first byte is not command!");
  if (cmd == kSysexMessageStart) {
    // All we can do with sysex is make sure it starts and  ends with the correct
    // command bytes.
    if (aMsg->data()[aMsg->data().Length() - 1] != kSysexMessageEnd) {
      NS_WARNING("Last byte of Sysex Message not 0xF7!");
      return false;
    }
    return true;
  }
  // For system realtime messages, the length should always be 1.
  if ((cmd & kSystemRealtimeMessage) == kSystemRealtimeMessage) {
    return aMsg->data().Length() == 1;
  }
  // Otherwise, just use the correct array for testing lengths. We can't tell
  // much about message validity other than that.
  if ((cmd & kSystemMessage) == kSystemMessage) {
    if (cmd - kSystemMessage >= static_cast<uint8_t>(ArrayLength(kSystemLengths))) {
      NS_WARNING("System Message Command byte not valid!");
      return false;
    }
    return aMsg->data().Length() == kSystemLengths[cmd - kSystemMessage];
  }
  // For non system commands, we only care about differences in the high nibble
  // of the first byte. Shift this down to give the index of the expected packet
  // length.
  uint8_t cmdIndex = (cmd - kCommandByte) >> 4;
  if (cmdIndex >= ArrayLength(kCommandLengths)) {
    // If our index is bigger than our array length, command byte is unknown;
    NS_WARNING("Unknown MIDI command!");
    return false;
  }
  return aMsg->data().Length() == kCommandLengths[cmdIndex];
}

uint32_t
ParseMessages(const nsTArray<uint8_t>& aByteBuffer,
              const TimeStamp& aTimestamp,
              nsTArray<MIDIMessage>& aMsgArray)
{
  uint32_t bytesRead = 0;
  bool inSysexMessage = false;
  nsAutoPtr<MIDIMessage> currentMsg;
  for (auto& byte : aByteBuffer) {
    bytesRead++;
    if ((byte & kSystemRealtimeMessage) == kSystemRealtimeMessage) {
      MIDIMessage rt_msg;
      rt_msg.data().AppendElement(byte);
      rt_msg.timestamp() = aTimestamp;
      aMsgArray.AppendElement(rt_msg);
      continue;
    }
    if (byte == kSysexMessageEnd) {
      if (!inSysexMessage) {
        MOZ_ASSERT(inSysexMessage);
        NS_WARNING("Got sysex message end with no sysex message being processed!");
      }
      inSysexMessage = false;
    } else if (byte & kCommandByte) {
      if (currentMsg && IsValidMessage(currentMsg)) {
        aMsgArray.AppendElement(*currentMsg);
      }
      currentMsg = new MIDIMessage();
      currentMsg->timestamp() = aTimestamp;
    }
    currentMsg->data().AppendElement(byte);
    if (byte == kSysexMessageStart) {
      inSysexMessage = true;
    }
  }
  if (currentMsg && IsValidMessage(currentMsg)) {
    aMsgArray.AppendElement(*currentMsg);
  }
  return bytesRead;
}

bool
IsSysexMessage(const MIDIMessage& aMsg)
{
  if (aMsg.data().Length() == 0) {
    return false;
  }
  if (aMsg.data()[0] == kSysexMessageStart) {
    return true;
  }
  return false;
}
}
} // namespace dom
} // namespace mozilla