problem with c++, mplayer interface.

anyone with c++ and mplayer knowledge know whats wrong with this?

Code:

#include <string.h>
#include <iostream>
#include <fstream>

class mplayer_interface
{
    private:

    FILE *mp_pipe;

    public:
    void setup()
    {
        mp_pipe = popen("mplayer -slave -quiet -idle &> /dev/null", "w");
    }
    void close()
    {
        pclose(mp_pipe);
    }
    void play( )
    {
        fputs("loadlist ./data/.currentplaylist\n", mp_pipe);
    }
    void stop()
    {
        fputs("stop\n", mp_pipe);
    }
};

void cd_to_exe_dir( char *argv[] )
{
    std::string path = argv[0];
    int ii = path.length();
    while ( !( path[ii] == '/' || path[ii] == '\\' ) )
    {
        ii--;
    }
    path.erase( ii, 100 );
    chdir( path.c_str() );
}

int main( int argc, char *argv[] )
{
    cd_to_exe_dir( argv );
    mplayer_interface mplayer;
    mplayer.setup();
    mplayer.play();
    std::string userI;
    while ( strcmp( userI.c_str(), "exit") != 0 )
    {
        std::cout<<'>';
        std::cin>>userI;
    }
    mplayer.stop();
    mplayer.close();
    return(0);
}

nothing plays until i type exit, then mplayer plays the first half second of the first file in ./data/.currentplaylist. i want it to play until exit is typed.

It may need to be in its own thread, and the while loop is basically choking it out. I don't know if mplayer.play() creates its own thread or not, but worth a shot.

So i would have to create a thread for that, darn im not so good at that.
I'd use boost::thread for that but thread() only accepts void functions so i would have to create a new function, somthing like:

Code:

void mplayer_thread( int &mpipe ) 
{
       mpipe = popen("mplayer -slave -quiet -idle" , "w");
}

and that would have to be outside of the class. is thair any better whay to do it?

why dose this now segfault?

Code:

#include <string.h>
#include <iostream>
#include <fstream>
#include <boost/thread.hpp>

void mplayer_thread( FILE *&mpipe )
{
       mpipe = popen("mplayer -slave -quiet -idle" , "w");
}

class mplayer_interface
{
    private:

    FILE *mp_pipe;
    boost::thread thread_mp;

    public:
    void setup()
    {
        thread_mp =  boost::thread(mplayer_thread , mp_pipe  );
        //mp_pipe = popen("mplayer -slave -quiet -idle" , "w");
    }
    void close()
    {
        pclose(mp_pipe);
        thread_mp.join();
    }
    void play( )
    {
        fputs("loadlist ./data/.currentplaylist\n", mp_pipe); //segfaults here
    }
    void stop()
    {
        fputs("stop\n", mp_pipe);
    }
};

void cd_to_exe_dir( char *argv[] )
{
    std::string path = argv[0];
    int ii = path.length();
    while ( !( path[ii] == '/' || path[ii] == '\\' ) )
    {
        ii--;
    }
    path.erase( ii, 100 );
    chdir( path.c_str() );
}

int main( int argc, char *argv[] )
{
    cd_to_exe_dir( argv );
    mplayer_interface mplayer;
    mplayer.setup();
    mplayer.play();
    mplayer.stop();
    std::string userI;
    while ( strcmp( userI.c_str(), "exit") != 0 )
    {
        std::cout<<'>';
        std::cin>>userI;
    }
    mplayer.stop();
    mplayer.close();
    return(0);
}

Do you really mean those periods to be in that order? Why not just remove them since . means current directory. The only thing worth worry about is .. since it means parent directory.

you mean the "." in ./data/.currentplaylist? you need it. this is on linux, so /data/.currentplaylist means that data is a folder in root (wrong). and the "." in .currentplaylist is allso neaded, in unix "." before a file/folder means thats its hidden .currentplaylist is the name of the file. this also has nothing to do with the segfault.

Code:

void play( )
{
    fputs("loadlist ./data/.currentplaylist\n", mp_pipe); //segfaults here
}

You are not testing if mp_pipe is a valid pointer before trying to write to it. It's possible your main thread calls play() before mplayer_thread() has been executed.

Are you sure the working directory is what you think it is?

I thought popen will start a new shell and run your command in there.

Have you tried using absolute paths for everything?

Code:

void mplayer_thread( FILE *&mpipe )
{
       mpipe = popen("mplayer -slave -quiet -idle &> /dev/null" , "w");
}

class mplayer_interface
{
    private:
    FILE *mp_pipe;
    boost::mutex io_mutex;
    boost::thread thread_mp;

    public:
    void setup()
    {
        mp_pipe = NULL;
        thread_mp =  boost::thread(mplayer_thread , mp_pipe  );
        while ( mp_pipe == NULL ) std::cout<<"whaiting for pipe\n";
        //mp_pipe = popen("mplayer -slave -quiet -idle" , "w");
    }
    void close()
    {
        pclose(mp_pipe);
        thread_mp.join();
    }
    void play( )
    {
        fputs("loadlist ./data/.currentplaylist\n", mp_pipe);
    }
    void stop()
    {
        fputs("stop\n", mp_pipe);
    }
};

//other functions unchainged

now its at an endless loop at

Code:

while ( mp_pipe == NULL ) std::cout<<"whaiting for pipe\n";

Originally Posted by cyberfish

Are you sure the working directory is what you think it is?
I thought popen will start a new shell and run your command in there.
Have you tried using absolute paths for everything?

I donsent work with absolute paths either. and the code in the fist post worked somewhat:

nothing plays until i type exit, then mplayer plays the first half second of the first file in ./data/.currentplaylist. i want it to play until exit is typed.

it plays for a short time while the program exits, that means that the path must be correct, and that mplayer recived the loadlist command.

the commands are correct, because this works in bash:

[user@localhost ~]$ mplayer -slave -quiet -idle
MPlayer SVN-r30040-4.4.1 (C) 2000-2009 MPlayer Team

loadlist /home/user/C++/scratchpad/bin/Debug/data/.currentplaylist

I'm really at a loss here.

Originally Posted by IM back!

it plays for a short time while the program exits, that means that the path must be correct, and that mplayer recived the loadlist command.

Ah, I missed that part of your first post Sounds like the loadlist command to mplayer is being delayed because of output buffering. Try adding
fflush(mp_pipe);
after the fputs in play() and stop()

Originally Posted by _Mike

Ah, I missed that part of your first post Sounds like the loadlist command to mplayer is being delayed because of output buffering. Try adding
fflush(mp_pipe);
after the fputs in play() and stop()

that worked! Thank you.

heres the final code just in case someone has the same problem:

Code:

#include <string.h>
#include <iostream>
#include <fstream>

class mplayer_interface
{
    private:

    FILE *mp_pipe;

    public:
    void setup()
    {
        mp_pipe = popen("mplayer -slave -quiet -idle &> /dev/null", "w");
    }
    void close()
    {
        pclose(mp_pipe);
    }
    void play( )
    {
        fputs("loadlist ./data/.currentplaylist\n", mp_pipe);
        fflush(mp_pipe);
    }
    void stop()
    {
        fputs("stop\n", mp_pipe);
        fflush(mp_pipe);
    }
};

void cd_to_exe_dir( char *argv[] )
{
    std::string path = argv[0];
    int ii = path.length();
    while ( !( path[ii] == '/' || path[ii] == '\\' ) )
    {
        ii--;
    }
    path.erase( ii, 100 );
    chdir( path.c_str() );
}

int main( int argc, char *argv[] )
{
    cd_to_exe_dir( argv );
    mplayer_interface mplayer;
    mplayer.setup();
    mplayer.play();
    std::string userI;
    while ( strcmp( userI.c_str(), "exit") != 0 )
    {
        std::cout<<'>';
        std::cin>>userI;
    }
    mplayer.stop();
    mplayer.close();
    return(0);
}