c_equiv.c

#include <stdio.h>
#include <Windows.h>
#include <mmsystem.h>

int main() {
    unsigned int numDevices, i;
    MMRESULT result;
    LPWAVEOUTCAPSW caps = malloc(sizeof(WAVEOUTCAPSW));
    memset(caps, 0, sizeof(WAVEOUTCAPSW));

    numDevices = waveOutGetNumDevs();

    for (i = 0; i < numDevices; i++) {
        result = waveOutGetDevCapsW(i, caps, sizeof(WAVEOUTCAPSW));
        printf("getCaps() result: %d\n", result);
        printf("getCaps() name: %S\n", caps->szPname);
    }

    printf("Device count: %d\n", numDevices);
    return 0;
}

usage.go

dev_count := waveOutDeviceCount()

for i := 0; i < dev_count; i++ {
    caps, err := waveOutGetDeviceCaps(i)
    _ = caps // just to suppress unused error
    fmt.Printf("err: %s.\n", err)
}

winmm_windows.go

// ...

var procWaveOutGetNumDevs = winmm.NewProc("waveOutGetNumDevs")
var procWaveOutGetDevCaps = winmm.NewProc("waveOutGetDevCapsW")

// ...

type waveoutcaps struct {
	wMid           uint16
	wPid           uint16
	vDriverVersion uint32
	szPname        [32]uint16
	dwFormats      uint32
	wChannels      uint16
	wReserved1     uint16
	dwSupport      uint32
}

// ...

func waveOutDeviceCount() int {
	r, _, _ := procWaveOutGetNumDevs.Call()
	return int(r)
}

func waveOutGetDeviceCaps(id int) (*waveoutcaps, error) {
	var caps *waveoutcaps

	r, _, e := procWaveOutGetDevCaps.Call(uintptr(id), uintptr(unsafe.Pointer(caps)), unsafe.Sizeof(waveoutcaps{}))
	if e.(windows.Errno) != 0 {
		return nil, &winmmError{
			fname: "waveOutGetDeviceCaps",
			errno: e.(windows.Errno),
		}
	}
	if mmresult(r) != mmsyserrNoerror {
		return nil, &winmmError{
			fname:    "waveOutGetDeviceCaps",
			mmresult: mmresult(r),
		}
	}

	return caps, nil
}