Sending a system exclusive message using CoreMIDI

I'm working on a MacOS app where I'm utilizing MIDI. What I'd like to do is send s SysEx message to a MIDI device. Now, I've done this once in Java, but never in Swift.

And since the coremidi library is almost totally new to me, i have no idea how this would work. What I've figured out so far is that I have to compose a MIDISysexSendRequest, and I've come this far:

let SysEx = MIDISysexSendRequest(destination: self.endpointRef, data: UnsafePointer<UInt8>, bytesToSend: 8, complete: complete, reserved: (UInt8, UInt8, UInt8), completionProc: completionProc, completionRefCon: nil)

In this, there are a few things that confuse me:

In what way am i supposed to compose the data variable? I know what bytes i want to send, just not how to format this for Swift
What is reserved supposed to be?

I couldn't find any examples or reference on these that i could use. Could someone help me/

Thanks in advance.

Solution

Reserved means you can't use it, as in: "reserved for internal use"

struct MIDISysexSendRequest
{
    MIDIEndpointRef     destination;
    const Byte *        data;
    UInt32              bytesToSend;
    Boolean             complete;
    Byte                reserved[3];
    MIDICompletionProc  completionProc;
    void * __nullable   completionRefCon;
};

/*!
    @struct         MIDISysexSendRequest
    @abstract       A request to transmit a system-exclusive event.

    @field          destination
                        The endpoint to which the event is to be sent.
    @field          data
                        Initially, a pointer to the sys-ex event to be sent.
                        MIDISendSysex will advance this pointer as bytes are
                        sent.
    @field          bytesToSend
                        Initially, the number of bytes to be sent.  MIDISendSysex
                        will decrement this counter as bytes are sent.
    @field          complete
                        The client may set this to true at any time to abort
                        transmission.  The implementation sets this to true when
                        all bytes have been sent.
    @field          completionProc
                        Called when all bytes have been sent, or after the client
                        has set complete to true.
    @field          completionRefCon
                        Passed as a refCon to completionProc.

    @discussion
        This represents a request to send a single system-exclusive MIDI event to
        a MIDI destination asynchronously.
*/

Notice how the reserved variable doesn't even show up in the header.

A quick google shows many projects written in swift that use MIDI. Browse through some of these to see working examples.

The first one I looked at seemed perfect for seeing how things are done. It even has quite a few .java files, so it might be easier for you to see how it relates to swift (or how to connect them).

Take a look here: MIDI in Swift

In the CoreMIDI framework there is a file called "MIDIServices.h" (finder will find it for you). It has a LOT of information regarding MIDI.

Best of luck!! 🍀