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music_cmd.c

/*
    SDL_mixer:  An audio mixer library based on the SDL library
    Copyright (C) 1997-2004 Sam Lantinga

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the Free
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    Sam Lantinga
    slouken@libsdl.org
*/

/* $Id: music_cmd.c,v 1.6 2004/01/04 17:37:04 slouken Exp $ */

/* This file supports an external command for playing music */

#ifdef unix       /* This is a UNIX-specific hack */

#include <sys/types.h>
#include <sys/wait.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <ctype.h>

#include "SDL_mixer.h"
#include "music_cmd.h"

/* Unimplemented */
void MusicCMD_SetVolume(int volume)
{
      Mix_SetError("No way to modify external player volume");
}

/* Load a music stream from the given file */
MusicCMD *MusicCMD_LoadSong(const char *cmd, const char *file)
{
      MusicCMD *music;

      /* Allocate and fill the music structure */
      music = (MusicCMD *)malloc(sizeof *music);
      if ( music == NULL ) {
            Mix_SetError("Out of memory");
            return(NULL);
      }
      strncpy(music->file, file, (sizeof music->file)-1);
      music->file[(sizeof music->file)-1] = '\0';
      strncpy(music->cmd, cmd, (sizeof music->cmd)-1);
      music->cmd[(sizeof music->cmd)-1] = '\0';
      music->pid = 0;

      /* We're done */
      return(music);
}

/* Parse a command line buffer into arguments */
static int ParseCommandLine(char *cmdline, char **argv)
{
      char *bufp;
      int argc;

      argc = 0;
      for ( bufp = cmdline; *bufp; ) {
            /* Skip leading whitespace */
            while ( isspace(*bufp) ) {
                  ++bufp;
            }
            /* Skip over argument */
            if ( *bufp == '"' ) {
                  ++bufp;
                  if ( *bufp ) {
                        if ( argv ) {
                              argv[argc] = bufp;
                        }
                        ++argc;
                  }
                  /* Skip over word */
                  while ( *bufp && (*bufp != '"') ) {
                        ++bufp;
                  }
            } else {
                  if ( *bufp ) {
                        if ( argv ) {
                              argv[argc] = bufp;
                        }
                        ++argc;
                  }
                  /* Skip over word */
                  while ( *bufp && ! isspace(*bufp) ) {
                        ++bufp;
                  }
            }
            if ( *bufp ) {
                  if ( argv ) {
                        *bufp = '\0';
                  }
                  ++bufp;
            }
      }
      if ( argv ) {
            argv[argc] = NULL;
      }
      return(argc);
}

static char **parse_args(char *command, char *last_arg)
{
      int argc;
      char **argv;

      /* Parse the command line */
      argc = ParseCommandLine(command, NULL);
      if ( last_arg ) {
            ++argc;
      }
      argv = (char **)malloc((argc+1)*(sizeof *argv));
      if ( argv == NULL ) {
            return(NULL);
      }
      argc = ParseCommandLine(command, argv);

      /* Add last command line argument */
      if ( last_arg ) {
            argv[argc++] = last_arg;
      }
      argv[argc] = NULL;

      /* We're ready! */
      return(argv);
}

/* Start playback of a given music stream */
void MusicCMD_Start(MusicCMD *music)
{
      music->pid = fork();
      switch(music->pid) {
          /* Failed fork() system call */
          case -1:
            Mix_SetError("fork() failed");
            return;

          /* Child process - executes here */
          case 0: {
                char command[PATH_MAX];
                char **argv;

                /* Execute the command */
                strcpy(command, music->cmd);
                argv = parse_args(command, music->file);
                if ( argv != NULL ) {
                  execvp(argv[0], argv);
                }

                /* exec() failed */
                perror(argv[0]);
                _exit(-1);
            }
            break;

          /* Parent process - executes here */
          default:
            break;
      }
      return;
}

/* Stop playback of a stream previously started with MusicCMD_Start() */
void MusicCMD_Stop(MusicCMD *music)
{
      int status;

      if ( music->pid > 0 ) {
            while ( kill(music->pid, 0) == 0 ) {
                  kill(music->pid, SIGTERM);
                  sleep(1);
                  waitpid(music->pid, &status, WNOHANG);
            }
            music->pid = 0;
      }
}

/* Pause playback of a given music stream */
void MusicCMD_Pause(MusicCMD *music)
{
      if ( music->pid > 0 ) {
            kill(music->pid, SIGSTOP);
      }
}

/* Resume playback of a given music stream */
void MusicCMD_Resume(MusicCMD *music)
{
      if ( music->pid > 0 ) {
            kill(music->pid, SIGCONT);
      }
}

/* Close the given music stream */
void MusicCMD_FreeSong(MusicCMD *music)
{
      free(music);
}

/* Return non-zero if a stream is currently playing */
int MusicCMD_Active(MusicCMD *music)
{
      int status;
      int active;

      active = 0;
      if ( music->pid > 0 ) {
            waitpid(music->pid, &status, WNOHANG);
            if ( kill(music->pid, 0) == 0 ) {
                  active = 1;
            }
      }
      return(active);
}

#endif /* unix */

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