/* Unix pty slave program -- David Decotigny 2005
   License: GNU GPL version 2
   Most of it taken from the GNU C library doc examples */
#include <utmp.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <termios.h>

/**
 * @file termslave.c
 *
 * Linux pseudo-TTY slave program. To be used with "qemu -monitor pty"
 * to access qemu's monitor from any linux terminal. To use it, launch
 * a "qemu -monitor pty" in one terminal, take a look at the first
 * line stating "char device redirected to /dev/pts/4" for example,
 * and lauch the termslave program as "./termslave /dev/pts/4" in
 * another terminal.
 *
 * To make this correctly work, one has to apply the
 * patch-qemu-pty.diff patch to qemu < 0.8.0 (qemu 0.8.0 and beyond
 * already includes this patch).
 *
 * This program also works with the "-serial pty" flag of qemu. It can
 * be used to send commands to the SOS serial-line shell (article 9).
 */


/* Use this variable to remember original terminal attributes. */
struct termios saved_attributes;

static void
reset_input_mode (void)
{
  tcsetattr (STDIN_FILENO, TCSANOW, &saved_attributes);
}

static void
set_input_mode (void)
{
  struct termios tattr;
  
  /* Make sure stdin is a terminal. */
  if (!isatty (STDIN_FILENO))
    {
      fprintf (stderr, "Not a terminal.\n");
      exit (EXIT_FAILURE);
    }
  
  /* Save the terminal attributes so we can restore them later. */
  tcgetattr (STDIN_FILENO, &saved_attributes);
  atexit (reset_input_mode);
  
  /* Set the funny terminal modes. */
  tcgetattr (STDIN_FILENO, &tattr);
  tattr.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP
		       |INLCR|IGNCR|ICRNL|IXON);
  tattr.c_lflag &= ~(ICANON|ECHO);
  tattr.c_cflag |= CLOCAL;
  tattr.c_cc[VMIN] = 1;
  tattr.c_cc[VTIME] = 0;
  tcsetattr (STDIN_FILENO, TCSAFLUSH, &tattr);
}

int main (int argc, char *argv[])
{
  int term;

  if (argc < 2)
    {
      fprintf(stderr, "Usage: %s /dev/pts/number\n", argv[0]);
      return -1;
    }

  term = open(argv[1], O_RDWR);
  if (term < 0)
    {
      perror("open");
      return -1;
    }
  if (! isatty(term))
    {
      fprintf(stderr, "%s is not a valid terminal\n", argv[1]);
      return -1;
    }

  set_input_mode();

  while (1)
    {
      fd_set cur_set;
      FD_ZERO(& cur_set);
      FD_SET(STDIN_FILENO, & cur_set);
      FD_SET(term, & cur_set);
      if (select(FD_SETSIZE, & cur_set, NULL, NULL, NULL) < 1)
	continue;

      if (FD_ISSET(term, & cur_set))
	{
	  char buf[1024];
	  int len = read(term, buf, sizeof(buf));

	  if (len >= 1)
	    write(STDOUT_FILENO, buf, len);
	  else
	    {
	      fprintf(stderr, "Master exitted\n");
	      break;
	    }
	}

      if (FD_ISSET(STDIN_FILENO, & cur_set))
	{
	  char c;
	  if (read(STDIN_FILENO, &c, 1) == 1)
	    {
	      if (c == 0x4) /* ctrl-D */
		break;
	      write(term, &c, 1);
	    }
	  else
	    break;
	}
    }
  
  return 0;
}