发送WindowsPriview :: Device :: Midi :: MidiSystemExclusiveMessage消息时出现问题

问题描述

在Microsoft提供的示例应用程序和我的应用程序（在示例之后建模）中，应用程序在发送MidiSystemExclusiveMessage后挂起。以下是示例应用的摘录。在我的应用程序中，发送
的数据是在Platform :: Array< unsigned char>中。阵列。我正在尝试将数据发送到LoopBe虚拟端口。我发现如果我发送长度超过4个字节的sysex消息，则会发生挂起。 可能导致此问题的原因是什么？

In both the sample application provided by Microsoft and my application, which is modeled after the sample, the application hangs after a MidiSystemExclusiveMessage is sent. Below is a snippet from the sample app. In my application the data being sent is in a Platform::Array<unsigned char> array. I'm trying to send data to a LoopBe virtual port. I find that if I send a sysex message that is more than 4 bytes in length then the hang occurs. What could be causing this?

            DataWriter^ dataWriter = ref new DataWriter();

            // expecting a string of format "NN NN NN NN...." where NN is a byte in hex
            int len = _sendMessageTextBox->Text->Length();
            if (0 == len)
            {
                return;
            }

            const wchar_t* startPointer = _sendMessageTextBox->Text->Data();
            wchar_t* endPointer = nullptr;

            do
            {
                byte midiByte = (byte)wcstoul(startPointer, &endPointer, 16);
                if (endPointer == startPointer)
                {
                    // conversion failed, bail out
                    break;
                }

                dataWriter->WriteByte(midiByte);

                // prep for next iteration
                startPointer = endPointer;
            } while (nullptr != endPointer);

            midiMessage = ref new MidiSystemExclusiveMessage(dataWriter->DetachBuffer());
            break;

推荐答案

这看起来很可疑。我不知道wcstoul如何处理内部空间，但我会从这开始作为调查的基础。

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