C API not working for MIDI input

[jg-854]

Hi,

I am trying to use the C API and I have built a rudimentary program that listens to the MIDI messages from a keyboard. I know my keyboard works (tested in Garageband, as well as using the testing with qmidiin.cpp). Even though the length of the message after calling the function is 3, the message array doesn't seem to be updated. Why is this?

I tried the C API test function provided in the repo, and that works. Moreover, I am able to retrieve the name of of the device that I am connected to. It is just reading the message that seems to not work.

`

#include <stdio.h>
#include<stdlib.h>
#include "rtmidi_c.h"

struct RtMidiWrapper *midiin;
                                
int main() {
    
    midiin = rtmidi_in_create_default();
    unsigned int ports = rtmidi_get_port_count(midiin);
    rtmidi_in_ignore_types(midiin,false,false,false);
    printf("MIDI input ports found: %u \n", ports);

    if (ports != 0)
    {
        printf("Connecting to device \n ");
        rtmidi_open_port(midiin,0,"Midi Keyboard");
    }   
    else{
        printf("Could not find a device!");
        goto cleanup;
    }


    unsigned char message[1024] ;
    size_t length;
    double td;

    while (true)
    {
        td = rtmidi_in_get_message(midiin,message,&length);
        if (length > 0)
        {
            printf("\n Length of message received: %zu ",length);
            for (int i =0 ; i< length ; i++)
            {
                printf("Byte %d: %u  ", i,message[i]);
            }
        }
    }

    cleanup:

        rtmidi_close_port(midiin);
        rtmidi_in_free(midiin);
        return 0;
}

`

I am running on a M1 MBP using Monterey
Thanks!

[garyscavone]

Did you try the programs in the tests directory?

[jg-854]

Thanks for the reply -no I did not. I ran the programs in a separate directory. This directory contains rtmidi_c.h and the dynamic libraries as well as my source code.

[jg-854]

Did you try the programs in the tests directory?

Sorry, I misread your question. I did run the programs in test directory. They all work. However, the C API test doesn't cover the 'get message' function. that is what I am interested in.

[koppi]

@jg-854 replace size_t length; with size_t length = 1024; in the above code and it should work as expected.

[garyscavone]

Great! Can you submit a PR?