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Diffstat (limited to '')
| -rw-r--r-- | dom/midi/MIDIUtils.cpp | 172 |
1 files changed, 172 insertions, 0 deletions
diff --git a/dom/midi/MIDIUtils.cpp b/dom/midi/MIDIUtils.cpp new file mode 100644 index 0000000000..645889a167 --- /dev/null +++ b/dom/midi/MIDIUtils.cpp @@ -0,0 +1,172 @@ +/* -*- 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" +#include "mozilla/UniquePtr.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}; +static const uint8_t kReservedStatuses[] = {0xf4, 0xf5, 0xf9, 0xfd}; + +namespace mozilla::dom::MIDIUtils { + +static bool IsSystemRealtimeMessage(uint8_t aByte) { + return (aByte & kSystemRealtimeMessage) == kSystemRealtimeMessage; +} + +static bool IsCommandByte(uint8_t aByte) { + return (aByte & kCommandByte) == kCommandByte; +} + +static bool IsReservedStatus(uint8_t aByte) { + for (const auto& msg : kReservedStatuses) { + if (aByte == msg) { + return true; + } + } + + return false; +} + +// Checks validity of MIDIMessage passed to it. Throws debug warnings and +// returns false if message is not valid. +bool IsValidMessage(const MIDIMessage* aMsg) { + if (aMsg->data().Length() == 0) { + return false; + } + + uint8_t cmd = aMsg->data()[0]; + // If first byte isn't a command, something is definitely wrong. + if (!IsCommandByte(cmd)) { + NS_WARNING("Constructed a MIDI packet where first byte is not command!"); + return false; + } + + if (IsReservedStatus(cmd)) { + NS_WARNING("Using a reserved message"); + return false; + } + + if (cmd == kSysexMessageStart) { + // All we can do with sysex is make sure it starts and ends with the + // correct command bytes and that it does not contain other command bytes. + if (aMsg->data()[aMsg->data().Length() - 1] != kSysexMessageEnd) { + NS_WARNING("Last byte of Sysex Message not 0xF7!"); + return false; + } + + for (size_t i = 1; i < aMsg->data().Length() - 2; i++) { + if (IsCommandByte(aMsg->data()[i])) { + return false; + } + } + + return true; + } + // For system realtime messages, the length should always be 1. + if (IsSystemRealtimeMessage(cmd)) { + 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]; +} + +bool ParseMessages(const nsTArray<uint8_t>& aByteBuffer, + const TimeStamp& aTimestamp, + nsTArray<MIDIMessage>& aMsgArray) { + bool inSysexMessage = false; + UniquePtr<MIDIMessage> currentMsg = nullptr; + for (const auto& byte : aByteBuffer) { + if (IsSystemRealtimeMessage(byte)) { + MIDIMessage rt_msg; + rt_msg.data().AppendElement(byte); + rt_msg.timestamp() = aTimestamp; + if (!IsValidMessage(&rt_msg)) { + return false; + } + aMsgArray.AppendElement(rt_msg); + continue; + } + + if (byte == kSysexMessageEnd) { + if (!inSysexMessage) { + NS_WARNING( + "Got sysex message end with no sysex message being processed!"); + return false; + } + inSysexMessage = false; + } else if (IsCommandByte(byte)) { + if (currentMsg) { + if (!IsValidMessage(currentMsg.get())) { + return false; + } + + aMsgArray.AppendElement(*currentMsg); + } + + currentMsg = MakeUnique<MIDIMessage>(); + currentMsg->timestamp() = aTimestamp; + } + + if (!currentMsg) { + NS_WARNING("No command byte has been encountered yet!"); + return false; + } + + currentMsg->data().AppendElement(byte); + + if (byte == kSysexMessageStart) { + inSysexMessage = true; + } + } + + if (currentMsg) { + if (!IsValidMessage(currentMsg.get())) { + return false; + } + aMsgArray.AppendElement(*currentMsg); + } + + return true; +} + +bool IsSysexMessage(const MIDIMessage& aMsg) { + if (aMsg.data().Length() == 0) { + return false; + } + return aMsg.data()[0] == kSysexMessageStart; +} +} // namespace mozilla::dom::MIDIUtils |