Basic MP3 Player using mpg123 and ao

music.go

package mp3

// #cgo LDFLAGS: -lmpg123 -lao -ldl -lm
/*
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include "mpg123.h"
#include <ao/ao.h>

char* get_list_at(char **list, int idx) { return list[idx]; }

*/
import "C"

import (
        "fmt"
	"unsafe"
)

func DecodeTrack(file string) {

        var v1 *C.mpg123_id3v1
        var v2 *C.mpg123_id3v2

        C.mpg123_init()
        defer C.mpg123_exit()

        m := C.mpg123_new(nil, nil)
        defer C.mpg123_delete(m)

        f := C.CString(file)

        if err := C.mpg123_open(m, f); err != C.MPG123_OK {
                panic("Error reading file")
        }
        defer C.mpg123_close(m)

        C.mpg123_scan(m)
        meta := C.mpg123_meta_check(m)

        if meta == C.MPG123_ID3 && C.mpg123_id3(m, &v1, &v2) == C.MPG123_OK {
                var title, artist, album, genre string
                switch false {
                case v2 == nil:
                        fmt.Println("ID3V2 tag found")
                        title = C.GoString(v2.title.p)
                        artist = C.GoString(v2.artist.p)
                        album = C.GoString(v2.album.p)
                        genre = C.GoString(v2.genre.p)

                case v1 == nil:
                        fmt.Println("ID3V2 tag found")
                        title = C.GoString(&v1.title[0])
                        artist = C.GoString(&v1.artist[0])
                        album = C.GoString(&v1.album[0])
                        genre = "Unknown" // FIXME convert int to string
                }

                fmt.Println(title)
                fmt.Println(artist)
                fmt.Println(album)
                fmt.Println(genre)
        }


	C.ao_initialize()
	defer C.ao_shutdown()

	default_driver := C.ao_default_driver_id()
	var format C.ao_sample_format
	var device *C.ao_device

	//C.memset(&format,0,unsafe.Sizeof(format))
	var channels, encoding C.int
	var rate C.long
	C.mpg123_getformat(m, &rate, &channels, &encoding)
	format.bits = 16
	format.channels = channels
	format.rate = C.int(rate)
	format.byte_format = C.AO_FMT_LITTLE

	device = C.ao_open_live(default_driver, &format, nil)
	if device == nil {
		fmt.Println("Error opening device")
		return
	}
	defer C.ao_close(device)

	var ret C.int
	var fill C.size_t
	buf := make([]C.uchar,1024*16)

        for {
                ret = C.mpg123_read(m, (*C.uchar)(unsafe.Pointer(&buf)), 16*1024, &fill)
		if ret == C.MPG123_DONE {
			break
		}
		C.ao_play(device,(*C.char)(unsafe.Pointer(&buf)),16*1024)
        }
}