The following very simple low level C-function simply sets the mixer volume. How to convert this simple function to dlang ?

void mixer_setlevel_stereo(int mixfd,int dev,int left,int right)
{
left+=256*right;
#int_ioctl(int fd, unsigned long request, ...);
ioctl(mixfd,
((unsigned long) (((0x80000000UL|0x40000000UL)) | (((sizeof(int)) & ((1 << 13) - 1)) << 16) | ((('M')) << 8) | ((dev)))),
&left);
}

On Friday, 16 April 2021 at 17:50:13 UTC, Alain De Vos wrote:

import core.stdc.config;
import core.sys.posix.sys.ioctl;
void mixer_setlevel_stereo(int mixfd,int dev,int left,int right)
{
left+=256*right;
ioctl(mixfd,
(cast(c_ulong) (((0x80000000UL|0x40000000UL)) | (((int.sizeof) & ((1 << 13) - 1)) << 16) | ((('M')) << 8) | ((dev)))),
&left);
}

something like that it is almost identical

On Friday, 16 April 2021 at 17:50:13 UTC, Alain De Vos wrote:

void mixer_setlevel_stereo(int mixfd,int dev,int left,int right)
{
left+=256*right;
#int_ioctl(int fd, unsigned long request, ...);
ioctl(mixfd,
((unsigned long) (((0x80000000UL|0x40000000UL)) | (((sizeof(int)) & ((1 << 13) - 1)) << 16) | ((('M')) << 8) | ((dev)))),
&left);
}

You could change sizeof(int) to int.sizeof and (unsigned long) to cast(uint) in this case, but it seems you expanded the IOWR macro resulting in the ugly mess of bitwise operations.

I did a search for your function name and found what I think is the original C code:

void mixer_setlevel_stereo(int mixfd,int dev,int left,int right)
{
  left+=256*right;
  ioctl(mixfd,MIXER_WRITE(dev),&left);
}

Looking at my /usr/include/linux/soundcard.h:

#define MIXER_WRITE(dev)		_SIOWR('M', dev, int)

And _SIOWR looks identical to IOWR, so I think this is a correct translation:

import core.sys.posix.sys.ioctl: ioctl, _IOWR;

void mixer_setlevel_stereo(int mixfd, int dev, int left, int right)
{
	left += 256 * right;
	ioctl(mixfd, _IOWR!int('M', dev), &left);
}

I had to copy over a downloaded ioctl.d to the directory ./core/sys/posix/
I don't know why. But with this dub seems to work. Weird ???

I had forgotten I needed also an integer file handle to provide to ioctrl; cfr this code which puts the volume on maximum on my PC.
So I need if fact this to dlang ... somehow ...

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/soundcard.h>
char *mixerdev="/dev/mixer";
int main(int argc,char *argv[])
{
int mixfd=open(mixerdev,O_RDWR);
int left=255*255+255;
unsigned int x=3221507328U;
ioctl(mixfd,x,&left);
close(mixfd);
exit(0);
}

I tried :

import std.stdio;
import core.sys.posix.ioctl;
import core.stdc.config;
import core.stdc.stdio;

void main() {
	writeln("Set vol to min");
	char *mixerdev=cast(char *)"/dev/mixer";
	char *mode=cast(char *)"rw";
	int mixfd=cast(int)fopen(mixerdev,mode);
	writeln(mixfd);
	c_ulong x=3221507328;
	int left=0;
	ioctl(mixfd,x, &left);
}

But I think I did here a mysterious cast of a FILE* handle to int , which is probably rubbish ....

After some fiddling i finally got it.
A d-lang program which sets my volume to zero.

import std.stdio;
import core.sys.posix.ioctl;
import core.stdc.config;
import core.stdc.stdio;
void main() {
writeln("Set vol to min");
char *mixerdev=cast(char *)"/dev/mixer";
char *mode=cast(char *)"rw";
int mixfd=(fopen(mixerdev,mode)).fileno;
writeln(mixfd);
c_ulong x=3221507328;
int left=0;
ioctl(mixfd,x, &left);
}

The function .fileno returns the "underlying handle" of the FILE "object".

On Saturday, 17 April 2021 at 00:05:41 UTC, Alain De Vos wrote:

import std.stdio;
import core.sys.posix.ioctl;
import core.stdc.config;
import core.stdc.stdio;
void main() {
writeln("Set vol to min");
char *mixerdev=cast(char *)"/dev/mixer";
char *mode=cast(char *)"rw";
int mixfd=(fopen(mixerdev,mode)).fileno;
writeln(mixfd);
c_ulong x=3221507328;
int left=0;
ioctl(mixfd,x, &left);
}

Here you could avoid C stdio and just use posix functions like core.sys.posix.fcntl : open that returns a file descriptor directly.

Correct, then i have :

import std.stdio: writeln;
import core.sys.posix.fcntl: open,O_RDWR;
import core.sys.posix.unistd : close;
import core.sys.posix.ioctl: ioctl;
import core.stdc.config: c_ulong;

void main() {
	writeln("Set vol to max");
	char *mixerdev=cast(char *)"/dev/mixer";
	int mode=O_RDWR;
	int mixfd=open(mixerdev,mode);
	writeln(mixfd);
	c_ulong fun=3221507328;
	int vol=255*255+255;
	ioctl(mixfd,fun, &vol);
	close(mixfd);
}