On Fri, 27 Oct 2023 11:10:45 GMT, Alec Su <d...@openjdk.org> wrote:
> JVM attempts to reuse the buffer for sending MIDI out data when the buffer
> size is enough. It use `dwBytesRecorded` in `MIDIHDR` structure to indicate
> the actual size of the data. However, `midiOutLongMsg()` ignores
> `dwBytesRecorded`, although it did not mentioned in the documentation. I've
> tested on Windows 7, 10 and 11. All of them have the same behavior.
>
> The bug cannot be easily reproduced because some MIDI drivers filter out any
> malformed MIDI data. The example code below create a special case to make
> sure all MIDI data are legally when the bug is triggered.
>
>
> import javax.sound.midi.*;
>
> public class MidiTest {
> public static class RawMidiMessage extends MidiMessage {
> public RawMidiMessage(byte[] data) {
> super(data);
> }
>
> @Override
> public Object clone() {
> return new RawMidiMessage(this.getMessage());
> }
> }
>
> public static void main(String[] args) {
> var deviceInfos = MidiSystem.getMidiDeviceInfo();
> for (var info : deviceInfos) {
> try (MidiDevice device = MidiSystem.getMidiDevice(info)) {
> if (device.getMaxReceivers() != 0) {
> System.out.println("Open MIDI port: " + info.getName());
> device.open();
> Receiver receiver = device.getReceiver();
> // Send two sysex messages at once
> receiver.send(new RawMidiMessage(new byte[]{
> (byte) 0xF0, 0x7D, 0x01, (byte) 0xF7,
> (byte) 0xF0, 0x7D, 0x02, (byte) 0xF7
> }), -1);
> // Send another sysex message
> receiver.send(new RawMidiMessage(new byte[]{(byte) 0xF0,
> 0x7D, 0x03, (byte) 0xF7}), -1);
> }
> } catch (MidiUnavailableException e) {
> e.printStackTrace();
> }
> }
> }
> }
>
>
> The expected messages received should be the following three messages
>
> F0 7D 01 F7
> F0 7D 02 F7
> F0 7D 03 F7
>
>
> But acually four messages was received with the second message repeated twice.
>
> F0 7D 01 F7
> F0 7D 02 F7
> F0 7D 03 F7
> F0 7D 02 F7
>
>
> To resolve the issue, I add a new variable to backup the actual buffer size
> and set `dwBufferLength` of `MIDIHDR` structure to the size of MIDI data.
> After calling `midiOutLongMsg()`, I restore the original buffer size if the
> buffer hasn't been freed due to an error.
>
> It seems that the patch may also resolve JDK-8250667. The extra bytes in the
> s...
I think the java code in the description can be added as a testcase, even if it
works fine before the patch, it is useful that the affected code will be
triggered.
As an example you can use the tests in the next folder:
https://github.com/openjdk/jdk/tree/master/test/jdk/javax/sound
-------------
PR Comment: https://git.openjdk.org/jdk/pull/16399#issuecomment-1783346826
