[Pstreams-users] out_avail

[Eric O. <e_p...@sb...>]

I had an issue with pstream.h that showed up in Linux. I opened a 
pstream (in,out,stderr).  While reading stdout, the read would 
eventually block because the stderr filled some buffer. I needed a way 
to check if a character is available on stdout (or stderr) - or a nice 
way to make the readline non-blocking. (if I have lots of stderr from 
the cmd)

I added a function to the pstreambuff class. I don't know it this was 
the best way, but it worked
 /**
   *  @return  Report if characters available to be read
   */
  template <typename C, typename T>
    inline bool
    basic_pstreambuf<C,T>::out_avail()
    {
       // setup select structures
      fd_set rfds;
      FD_ZERO(&rfds); // clear
      FD_SET(rpipe_[rsrc_out],&rfds);

      struct timeval tv;
      tv.tv_sec = 0;
      tv.tv_usec = 1;
     
      int maxfd = rpipe_[rsrc_out];
      
      ::select(maxfd+1,&rfds,NULL,NULL,&tv);

      if (FD_ISSET(rpipe_[rsrc_out],&rfds)) {
        return(true);
      } else {
        return (false);
      }
    }

//////////////////////////
Then I can just:
redi::pstream
    parse(cmd,std::ios_base::in|std::ios_base::app);
bool oav;
while (getline(parse.out(),line)) {
   oav = parse.rdbuf()->out_avail();
   process(line);
   while (!oav && (getline(parse.err(),line))) {
       process_error(line);
       oav = parse.rdbuf()->out_avail();
   }
}
while ((getline(parse.err(),line))) {
       process_error(line);
}
parse.close();

///////////////////
very nice package BTW.  Exactly what I needed
 - Eric Olson, eo...@ci...