backend/runloop.c - platform/external/libcups - Git at Google

 /*
  * Common run loop APIs for CUPS backends.
  *
  * Copyright © 2007-2014 by Apple Inc.
  * Copyright © 2006-2007 by Easy Software Products, all rights reserved.
  *
  * Licensed under Apache License v2.0.  See the file "LICENSE" for more
  * information.
  */

 /*
  * Include necessary headers.
  */

 #include "backend-private.h"
 #include <limits.h>
 #include <sys/select.h>


 /*
  * 'backendDrainOutput()' - Drain pending print data to the device.
  */

 int					/* O - 0 on success, -1 on error */
 backendDrainOutput(int print_fd,	/* I - Print file descriptor */
                    int device_fd)	/* I - Device file descriptor */
 {
   int		nfds;			/* Maximum file descriptor value + 1 */
   fd_set	input;			/* Input set for reading */
   ssize_t	print_bytes,		/* Print bytes read */
 		bytes;			/* Bytes written */
   char		print_buffer[8192],	/* Print data buffer */
 		*print_ptr;		/* Pointer into print data buffer */
   struct timeval timeout;		/* Timeout for read... */


   fprintf(stderr, "DEBUG: backendDrainOutput(print_fd=%d, device_fd=%d)\n",
           print_fd, device_fd);

  /*
   * Figure out the maximum file descriptor value to use with select()...
   */

   nfds = (print_fd > device_fd ? print_fd : device_fd) + 1;

  /*
   * Now loop until we are out of data from print_fd...
   */

   for (;;)
   {
    /*
     * Use select() to determine whether we have data to copy around...
     */

     FD_ZERO(&input);
     FD_SET(print_fd, &input);

     timeout.tv_sec  = 0;
     timeout.tv_usec = 0;

     if (select(nfds, &input, NULL, NULL, &timeout) < 0)
       return (-1);

     if (!FD_ISSET(print_fd, &input))
       return (0);

     if ((print_bytes = read(print_fd, print_buffer,
 			    sizeof(print_buffer))) < 0)
     {
      /*
       * Read error - bail if we don't see EAGAIN or EINTR...
       */

       if (errno != EAGAIN && errno != EINTR)
       {
 	fprintf(stderr, "DEBUG: Read failed: %s\n", strerror(errno));
 	_cupsLangPrintFilter(stderr, "ERROR", _("Unable to read print data."));
 	return (-1);
       }

       print_bytes = 0;
     }
     else if (print_bytes == 0)
     {
      /*
       * End of file, return...
       */

       return (0);
     }

     fprintf(stderr, "DEBUG: Read %d bytes of print data...\n",
 	    (int)print_bytes);

     for (print_ptr = print_buffer; print_bytes > 0;)
     {
       if ((bytes = write(device_fd, print_ptr, (size_t)print_bytes)) < 0)
       {
        /*
         * Write error - bail if we don't see an error we can retry...
 	*/

         if (errno != ENOSPC && errno != ENXIO && errno != EAGAIN &&
 	    errno != EINTR && errno != ENOTTY)
 	{
 	  _cupsLangPrintError("ERROR", _("Unable to write print data"));
 	  return (-1);
 	}
       }
       else
       {
         fprintf(stderr, "DEBUG: Wrote %d bytes of print data...\n", (int)bytes);

         print_bytes -= bytes;
 	print_ptr   += bytes;
       }
     }
   }
 }


 /*
  * 'backendRunLoop()' - Read and write print and back-channel data.
  */

 ssize_t					/* O - Total bytes on success, -1 on error */
 backendRunLoop(
     int          print_fd,		/* I - Print file descriptor */
     int          device_fd,		/* I - Device file descriptor */
     int          snmp_fd,		/* I - SNMP socket or -1 if none */
     http_addr_t  *addr,			/* I - Address of device */
     int          use_bc,		/* I - Use back-channel? */
     int          update_state,		/* I - Update printer-state-reasons? */
     _cups_sccb_t side_cb)		/* I - Side-channel callback */
 {
   int		nfds;			/* Maximum file descriptor value + 1 */
   fd_set	input,			/* Input set for reading */
 		output;			/* Output set for writing */
   ssize_t	print_bytes,		/* Print bytes read */
 		bc_bytes,		/* Backchannel bytes read */
 		total_bytes,		/* Total bytes written */
 		bytes;			/* Bytes written */
   int		paperout;		/* "Paper out" status */
   int		offline;		/* "Off-line" status */
   char		print_buffer[8192],	/* Print data buffer */
 		*print_ptr,		/* Pointer into print data buffer */
 		bc_buffer[1024];	/* Back-channel data buffer */
   struct timeval timeout;		/* Timeout for select() */
   time_t	curtime,		/* Current time */
 		snmp_update = 0;
 #if defined(HAVE_SIGACTION) && !defined(HAVE_SIGSET)
   struct sigaction action;		/* Actions for POSIX signals */
 #endif /* HAVE_SIGACTION && !HAVE_SIGSET */


   fprintf(stderr,
           "DEBUG: backendRunLoop(print_fd=%d, device_fd=%d, snmp_fd=%d, "
 	  "addr=%p, use_bc=%d, side_cb=%p)\n",
           print_fd, device_fd, snmp_fd, addr, use_bc, side_cb);

  /*
   * If we are printing data from a print driver on stdin, ignore SIGTERM
   * so that the driver can finish out any page data, e.g. to eject the
   * current page.  We only do this for stdin printing as otherwise there
   * is no way to cancel a raw print job...
   */

   if (!print_fd)
   {
 #ifdef HAVE_SIGSET /* Use System V signals over POSIX to avoid bugs */
     sigset(SIGTERM, SIG_IGN);
 #elif defined(HAVE_SIGACTION)
     memset(&action, 0, sizeof(action));

     sigemptyset(&action.sa_mask);
     action.sa_handler = SIG_IGN;
     sigaction(SIGTERM, &action, NULL);
 #else
     signal(SIGTERM, SIG_IGN);
 #endif /* HAVE_SIGSET */
   }
   else if (print_fd < 0)
   {
    /*
     * Copy print data from stdin, but don't mess with the signal handlers...
     */

     print_fd = 0;
   }

  /*
   * Figure out the maximum file descriptor value to use with select()...
   */

   nfds = (print_fd > device_fd ? print_fd : device_fd) + 1;

  /*
   * Now loop until we are out of data from print_fd...
   */

   for (print_bytes = 0, print_ptr = print_buffer, offline = -1,
            paperout = -1, total_bytes = 0;;)
   {
    /*
     * Use select() to determine whether we have data to copy around...
     */

     FD_ZERO(&input);
     if (!print_bytes)
       FD_SET(print_fd, &input);
     if (use_bc)
       FD_SET(device_fd, &input);
     if (!print_bytes && side_cb)
       FD_SET(CUPS_SC_FD, &input);

     FD_ZERO(&output);
     if (print_bytes || (!use_bc && !side_cb))
       FD_SET(device_fd, &output);

     if (use_bc || side_cb)
     {
       timeout.tv_sec  = 5;
       timeout.tv_usec = 0;

       if (select(nfds, &input, &output, NULL, &timeout) < 0)
       {
        /*
 	* Pause printing to clear any pending errors...
 	*/

 	if (errno == ENXIO && offline != 1 && update_state)
 	{
 	  fputs("STATE: +offline-report\n", stderr);
 	  _cupsLangPrintFilter(stderr, "INFO",
 	                       _("The printer is not connected."));
 	  offline = 1;
 	}
 	else if (errno == EINTR && total_bytes == 0)
 	{
 	  fputs("DEBUG: Received an interrupt before any bytes were "
 	        "written, aborting.\n", stderr);
           return (0);
 	}

 	sleep(1);
 	continue;
       }
     }

    /*
     * Check if we have a side-channel request ready...
     */

     if (side_cb && FD_ISSET(CUPS_SC_FD, &input))
     {
      /*
       * Do the side-channel request, then start back over in the select
       * loop since it may have read from print_fd...
       */

       if ((*side_cb)(print_fd, device_fd, snmp_fd, addr, use_bc))
         side_cb = NULL;
       continue;
     }

    /*
     * Check if we have back-channel data ready...
     */

     if (FD_ISSET(device_fd, &input))
     {
       if ((bc_bytes = read(device_fd, bc_buffer, sizeof(bc_buffer))) > 0)
       {
 	fprintf(stderr,
 	        "DEBUG: Received " CUPS_LLFMT " bytes of back-channel data\n",
 	        CUPS_LLCAST bc_bytes);
         cupsBackChannelWrite(bc_buffer, (size_t)bc_bytes, 1.0);
       }
       else if (bc_bytes < 0 && errno != EAGAIN && errno != EINTR)
       {
         fprintf(stderr, "DEBUG: Error reading back-channel data: %s\n",
 	        strerror(errno));
 	use_bc = 0;
       }
       else if (bc_bytes == 0)
         use_bc = 0;
     }

    /*
     * Check if we have print data ready...
     */

     if (FD_ISSET(print_fd, &input))
     {
       if ((print_bytes = read(print_fd, print_buffer,
                               sizeof(print_buffer))) < 0)
       {
        /*
         * Read error - bail if we don't see EAGAIN or EINTR...
 	*/

 	if (errno != EAGAIN && errno != EINTR)
 	{
 	  fprintf(stderr, "DEBUG: Read failed: %s\n", strerror(errno));
 	  _cupsLangPrintFilter(stderr, "ERROR",
 	                       _("Unable to read print data."));
 	  return (-1);
 	}

         print_bytes = 0;
       }
       else if (print_bytes == 0)
       {
        /*
         * End of file, break out of the loop...
 	*/

         break;
       }

       print_ptr = print_buffer;

       fprintf(stderr, "DEBUG: Read %d bytes of print data...\n",
               (int)print_bytes);
     }

    /*
     * Check if the device is ready to receive data and we have data to
     * send...
     */

     if (print_bytes && FD_ISSET(device_fd, &output))
     {
       if ((bytes = write(device_fd, print_ptr, (size_t)print_bytes)) < 0)
       {
        /*
         * Write error - bail if we don't see an error we can retry...
 	*/

         if (errno == ENOSPC)
 	{
 	  if (paperout != 1 && update_state)
 	  {
 	    fputs("STATE: +media-empty-warning\n", stderr);
 	    fputs("DEBUG: Out of paper\n", stderr);
 	    paperout = 1;
 	  }
         }
 	else if (errno == ENXIO)
 	{
 	  if (offline != 1 && update_state)
 	  {
 	    fputs("STATE: +offline-report\n", stderr);
 	    _cupsLangPrintFilter(stderr, "INFO",
 	                         _("The printer is not connected."));
 	    offline = 1;
 	  }
 	}
 	else if (errno != EAGAIN && errno != EINTR && errno != ENOTTY)
 	{
 	  _cupsLangPrintError("ERROR", _("Unable to write print data"));
 	  return (-1);
 	}
       }
       else
       {
         if (paperout && update_state)
 	{
 	  fputs("STATE: -media-empty-warning\n", stderr);
 	  paperout = 0;
 	}

 	if (offline && update_state)
 	{
 	  fputs("STATE: -offline-report\n", stderr);
 	  _cupsLangPrintFilter(stderr, "INFO",
 	                       _("The printer is now connected."));
 	  offline = 0;
 	}

         fprintf(stderr, "DEBUG: Wrote %d bytes of print data...\n", (int)bytes);

         print_bytes -= bytes;
 	print_ptr   += bytes;
 	total_bytes += bytes;
       }
     }

    /*
     * Do SNMP updates periodically...
     */

     if (snmp_fd >= 0 && time(&curtime) >= snmp_update)
     {
       if (backendSNMPSupplies(snmp_fd, addr, NULL, NULL))
         snmp_update = INT_MAX;
       else
         snmp_update = curtime + 5;
     }
   }

  /*
   * Return with success...
   */

   return (total_bytes);
 }


 /*
  * 'backendWaitLoop()' - Wait for input from stdin while handling side-channel
  *                       queries.
  */

 int					/* O - 1 if data is ready, 0 if not */
 backendWaitLoop(
     int          snmp_fd,		/* I - SNMP socket or -1 if none */
     http_addr_t  *addr,			/* I - Address of device */
     int          use_bc,		/* I - Use back-channel? */
     _cups_sccb_t side_cb)		/* I - Side-channel callback */
 {
   int			nfds;		/* Number of file descriptors */
   fd_set		input;		/* Input set for reading */
   time_t		curtime = 0,	/* Current time */
 			snmp_update = 0;/* Last SNMP status update */
   struct timeval	timeout;	/* Timeout for select() */


   fprintf(stderr, "DEBUG: backendWaitLoop(snmp_fd=%d, addr=%p, side_cb=%p)\n",
 	  snmp_fd, addr, side_cb);

  /*
   * Now loop until we receive data from stdin...
   */

   if (snmp_fd >= 0)
     snmp_update = time(NULL) + 5;

   for (;;)
   {
    /*
     * Use select() to determine whether we have data to copy around...
     */

     FD_ZERO(&input);
     FD_SET(0, &input);
     if (side_cb)
       FD_SET(CUPS_SC_FD, &input);

     if (snmp_fd >= 0)
     {
       curtime         = time(NULL);
       timeout.tv_sec  = curtime >= snmp_update ? 0 : snmp_update - curtime;
       timeout.tv_usec = 0;

       nfds = select(CUPS_SC_FD + 1, &input, NULL, NULL, &timeout);
     }
     else
       nfds = select(CUPS_SC_FD + 1, &input, NULL, NULL, NULL);

     if (nfds < 0)
     {
      /*
       * Pause printing to clear any pending errors...
       */

       if (errno == EINTR)
       {
 	fputs("DEBUG: Received an interrupt before any bytes were "
 	      "written, aborting.\n", stderr);
 	return (0);
       }

       sleep(1);
       continue;
     }

    /*
     * Check for input on stdin...
     */

     if (FD_ISSET(0, &input))
       break;

    /*
     * Check if we have a side-channel request ready...
     */

     if (side_cb && FD_ISSET(CUPS_SC_FD, &input))
     {
      /*
       * Do the side-channel request, then start back over in the select
       * loop since it may have read from print_fd...
       */

       if ((*side_cb)(0, -1, snmp_fd, addr, use_bc))
         side_cb = NULL;
       continue;
     }

    /*
     * Do SNMP updates periodically...
     */

     if (snmp_fd >= 0 && curtime >= snmp_update)
     {
       if (backendSNMPSupplies(snmp_fd, addr, NULL, NULL))
         snmp_fd = -1;
       else
         snmp_update = curtime + 5;
     }
   }

  /*
   * Return with success...
   */

   return (1);
 }
	/*
	* Common run loop APIs for CUPS backends.
	*
	* Copyright © 2007-2014 by Apple Inc.
	* Copyright © 2006-2007 by Easy Software Products, all rights reserved.
	*
	* Licensed under Apache License v2.0. See the file "LICENSE" for more
	* information.
	*/

	/*
	* Include necessary headers.
	*/

	#include "backend-private.h"
	#include <limits.h>
	#include <sys/select.h>


	/*
	* 'backendDrainOutput()' - Drain pending print data to the device.
	*/

	int /* O - 0 on success, -1 on error */
	backendDrainOutput(int print_fd, /* I - Print file descriptor */
	int device_fd) /* I - Device file descriptor */
	{
	int nfds; /* Maximum file descriptor value + 1 */
	fd_set input; /* Input set for reading */
	ssize_t print_bytes, /* Print bytes read */
	bytes; /* Bytes written */
	char print_buffer[8192], /* Print data buffer */
	print_ptr; / Pointer into print data buffer */
	struct timeval timeout; /* Timeout for read... */


	fprintf(stderr, "DEBUG: backendDrainOutput(print_fd=%d, device_fd=%d)\n",
	print_fd, device_fd);

	/*
	* Figure out the maximum file descriptor value to use with select()...
	*/

	nfds = (print_fd > device_fd ? print_fd : device_fd) + 1;

	/*
	* Now loop until we are out of data from print_fd...
	*/

	for (;;)
	{
	/*
	* Use select() to determine whether we have data to copy around...
	*/

	FD_ZERO(&input);
	FD_SET(print_fd, &input);

	timeout.tv_sec = 0;
	timeout.tv_usec = 0;

	if (select(nfds, &input, NULL, NULL, &timeout) < 0)
	return (-1);

	if (!FD_ISSET(print_fd, &input))
	return (0);

	if ((print_bytes = read(print_fd, print_buffer,
	sizeof(print_buffer))) < 0)
	{
	/*
	* Read error - bail if we don't see EAGAIN or EINTR...
	*/

	if (errno != EAGAIN && errno != EINTR)
	{
	fprintf(stderr, "DEBUG: Read failed: %s\n", strerror(errno));
	_cupsLangPrintFilter(stderr, "ERROR", _("Unable to read print data."));
	return (-1);
	}

	print_bytes = 0;
	}
	else if (print_bytes == 0)
	{
	/*
	* End of file, return...
	*/

	return (0);
	}

	fprintf(stderr, "DEBUG: Read %d bytes of print data...\n",
	(int)print_bytes);

	for (print_ptr = print_buffer; print_bytes > 0;)
	{
	if ((bytes = write(device_fd, print_ptr, (size_t)print_bytes)) < 0)
	{
	/*
	* Write error - bail if we don't see an error we can retry...
	*/

	if (errno != ENOSPC && errno != ENXIO && errno != EAGAIN &&
	errno != EINTR && errno != ENOTTY)
	{
	_cupsLangPrintError("ERROR", _("Unable to write print data"));
	return (-1);
	}
	}
	else
	{
	fprintf(stderr, "DEBUG: Wrote %d bytes of print data...\n", (int)bytes);

	print_bytes -= bytes;
	print_ptr += bytes;
	}
	}
	}
	}


	/*
	* 'backendRunLoop()' - Read and write print and back-channel data.
	*/

	ssize_t /* O - Total bytes on success, -1 on error */
	backendRunLoop(
	int print_fd, /* I - Print file descriptor */
	int device_fd, /* I - Device file descriptor */
	int snmp_fd, /* I - SNMP socket or -1 if none */
	http_addr_t addr, / I - Address of device */
	int use_bc, /* I - Use back-channel? */
	int update_state, /* I - Update printer-state-reasons? */
	_cups_sccb_t side_cb) /* I - Side-channel callback */
	{
	int nfds; /* Maximum file descriptor value + 1 */
	fd_set input, /* Input set for reading */
	output; /* Output set for writing */
	ssize_t print_bytes, /* Print bytes read */
	bc_bytes, /* Backchannel bytes read */
	total_bytes, /* Total bytes written */
	bytes; /* Bytes written */
	int paperout; /* "Paper out" status */
	int offline; /* "Off-line" status */
	char print_buffer[8192], /* Print data buffer */
	print_ptr, / Pointer into print data buffer */
	bc_buffer[1024]; /* Back-channel data buffer */
	struct timeval timeout; /* Timeout for select() */
	time_t curtime, /* Current time */
	snmp_update = 0;
	#if defined(HAVE_SIGACTION) && !defined(HAVE_SIGSET)
	struct sigaction action; /* Actions for POSIX signals */
	#endif /* HAVE_SIGACTION && !HAVE_SIGSET */


	fprintf(stderr,
	"DEBUG: backendRunLoop(print_fd=%d, device_fd=%d, snmp_fd=%d, "
	"addr=%p, use_bc=%d, side_cb=%p)\n",
	print_fd, device_fd, snmp_fd, addr, use_bc, side_cb);

	/*
	* If we are printing data from a print driver on stdin, ignore SIGTERM
	* so that the driver can finish out any page data, e.g. to eject the
	* current page. We only do this for stdin printing as otherwise there
	* is no way to cancel a raw print job...
	*/

	if (!print_fd)
	{
	#ifdef HAVE_SIGSET /* Use System V signals over POSIX to avoid bugs */
	sigset(SIGTERM, SIG_IGN);
	#elif defined(HAVE_SIGACTION)
	memset(&action, 0, sizeof(action));

	sigemptyset(&action.sa_mask);
	action.sa_handler = SIG_IGN;
	sigaction(SIGTERM, &action, NULL);
	#else
	signal(SIGTERM, SIG_IGN);
	#endif /* HAVE_SIGSET */
	}
	else if (print_fd < 0)
	{
	/*
	* Copy print data from stdin, but don't mess with the signal handlers...
	*/

	print_fd = 0;
	}

	/*
	* Figure out the maximum file descriptor value to use with select()...
	*/

	nfds = (print_fd > device_fd ? print_fd : device_fd) + 1;

	/*
	* Now loop until we are out of data from print_fd...
	*/

	for (print_bytes = 0, print_ptr = print_buffer, offline = -1,
	paperout = -1, total_bytes = 0;;)
	{
	/*
	* Use select() to determine whether we have data to copy around...
	*/

	FD_ZERO(&input);
	if (!print_bytes)
	FD_SET(print_fd, &input);
	if (use_bc)
	FD_SET(device_fd, &input);
	if (!print_bytes && side_cb)
	FD_SET(CUPS_SC_FD, &input);

	FD_ZERO(&output);
	if (print_bytes \|\| (!use_bc && !side_cb))
	FD_SET(device_fd, &output);

	if (use_bc \|\| side_cb)
	{
	timeout.tv_sec = 5;
	timeout.tv_usec = 0;

	if (select(nfds, &input, &output, NULL, &timeout) < 0)
	{
	/*
	* Pause printing to clear any pending errors...
	*/

	if (errno == ENXIO && offline != 1 && update_state)
	{
	fputs("STATE: +offline-report\n", stderr);
	_cupsLangPrintFilter(stderr, "INFO",
	_("The printer is not connected."));
	offline = 1;
	}
	else if (errno == EINTR && total_bytes == 0)
	{
	fputs("DEBUG: Received an interrupt before any bytes were "
	"written, aborting.\n", stderr);
	return (0);
	}

	sleep(1);
	continue;
	}
	}

	/*
	* Check if we have a side-channel request ready...
	*/

	if (side_cb && FD_ISSET(CUPS_SC_FD, &input))
	{
	/*
	* Do the side-channel request, then start back over in the select
	* loop since it may have read from print_fd...
	*/

	if ((*side_cb)(print_fd, device_fd, snmp_fd, addr, use_bc))
	side_cb = NULL;
	continue;
	}

	/*
	* Check if we have back-channel data ready...
	*/

	if (FD_ISSET(device_fd, &input))
	{
	if ((bc_bytes = read(device_fd, bc_buffer, sizeof(bc_buffer))) > 0)
	{
	fprintf(stderr,
	"DEBUG: Received " CUPS_LLFMT " bytes of back-channel data\n",
	CUPS_LLCAST bc_bytes);
	cupsBackChannelWrite(bc_buffer, (size_t)bc_bytes, 1.0);
	}
	else if (bc_bytes < 0 && errno != EAGAIN && errno != EINTR)
	{
	fprintf(stderr, "DEBUG: Error reading back-channel data: %s\n",
	strerror(errno));
	use_bc = 0;
	}
	else if (bc_bytes == 0)
	use_bc = 0;
	}

	/*
	* Check if we have print data ready...
	*/

	if (FD_ISSET(print_fd, &input))
	{
	if ((print_bytes = read(print_fd, print_buffer,
	sizeof(print_buffer))) < 0)
	{
	/*
	* Read error - bail if we don't see EAGAIN or EINTR...
	*/

	if (errno != EAGAIN && errno != EINTR)
	{
	fprintf(stderr, "DEBUG: Read failed: %s\n", strerror(errno));
	_cupsLangPrintFilter(stderr, "ERROR",
	_("Unable to read print data."));
	return (-1);
	}

	print_bytes = 0;
	}
	else if (print_bytes == 0)
	{
	/*
	* End of file, break out of the loop...
	*/

	break;
	}

	print_ptr = print_buffer;

	fprintf(stderr, "DEBUG: Read %d bytes of print data...\n",
	(int)print_bytes);
	}

	/*
	* Check if the device is ready to receive data and we have data to
	* send...
	*/

	if (print_bytes && FD_ISSET(device_fd, &output))
	{
	if ((bytes = write(device_fd, print_ptr, (size_t)print_bytes)) < 0)
	{
	/*
	* Write error - bail if we don't see an error we can retry...
	*/

	if (errno == ENOSPC)
	{
	if (paperout != 1 && update_state)
	{
	fputs("STATE: +media-empty-warning\n", stderr);
	fputs("DEBUG: Out of paper\n", stderr);
	paperout = 1;
	}
	}
	else if (errno == ENXIO)
	{
	if (offline != 1 && update_state)
	{
	fputs("STATE: +offline-report\n", stderr);
	_cupsLangPrintFilter(stderr, "INFO",
	_("The printer is not connected."));
	offline = 1;
	}
	}
	else if (errno != EAGAIN && errno != EINTR && errno != ENOTTY)
	{
	_cupsLangPrintError("ERROR", _("Unable to write print data"));
	return (-1);
	}
	}
	else
	{
	if (paperout && update_state)
	{
	fputs("STATE: -media-empty-warning\n", stderr);
	paperout = 0;
	}

	if (offline && update_state)
	{
	fputs("STATE: -offline-report\n", stderr);
	_cupsLangPrintFilter(stderr, "INFO",
	_("The printer is now connected."));
	offline = 0;
	}

	fprintf(stderr, "DEBUG: Wrote %d bytes of print data...\n", (int)bytes);

	print_bytes -= bytes;
	print_ptr += bytes;
	total_bytes += bytes;
	}
	}

	/*
	* Do SNMP updates periodically...
	*/

	if (snmp_fd >= 0 && time(&curtime) >= snmp_update)
	{
	if (backendSNMPSupplies(snmp_fd, addr, NULL, NULL))
	snmp_update = INT_MAX;
	else
	snmp_update = curtime + 5;
	}
	}

	/*
	* Return with success...
	*/

	return (total_bytes);
	}


	/*
	* 'backendWaitLoop()' - Wait for input from stdin while handling side-channel
	* queries.
	*/

	int /* O - 1 if data is ready, 0 if not */
	backendWaitLoop(
	int snmp_fd, /* I - SNMP socket or -1 if none */
	http_addr_t addr, / I - Address of device */
	int use_bc, /* I - Use back-channel? */
	_cups_sccb_t side_cb) /* I - Side-channel callback */
	{
	int nfds; /* Number of file descriptors */
	fd_set input; /* Input set for reading */
	time_t curtime = 0, /* Current time */
	snmp_update = 0;/* Last SNMP status update */
	struct timeval timeout; /* Timeout for select() */


	fprintf(stderr, "DEBUG: backendWaitLoop(snmp_fd=%d, addr=%p, side_cb=%p)\n",
	snmp_fd, addr, side_cb);

	/*
	* Now loop until we receive data from stdin...
	*/

	if (snmp_fd >= 0)
	snmp_update = time(NULL) + 5;

	for (;;)
	{
	/*
	* Use select() to determine whether we have data to copy around...
	*/

	FD_ZERO(&input);
	FD_SET(0, &input);
	if (side_cb)
	FD_SET(CUPS_SC_FD, &input);

	if (snmp_fd >= 0)
	{
	curtime = time(NULL);
	timeout.tv_sec = curtime >= snmp_update ? 0 : snmp_update - curtime;
	timeout.tv_usec = 0;

	nfds = select(CUPS_SC_FD + 1, &input, NULL, NULL, &timeout);
	}
	else
	nfds = select(CUPS_SC_FD + 1, &input, NULL, NULL, NULL);

	if (nfds < 0)
	{
	/*
	* Pause printing to clear any pending errors...
	*/

	if (errno == EINTR)
	{
	fputs("DEBUG: Received an interrupt before any bytes were "
	"written, aborting.\n", stderr);
	return (0);
	}

	sleep(1);
	continue;
	}

	/*
	* Check for input on stdin...
	*/

	if (FD_ISSET(0, &input))
	break;

	/*
	* Check if we have a side-channel request ready...
	*/

	if (side_cb && FD_ISSET(CUPS_SC_FD, &input))
	{
	/*
	* Do the side-channel request, then start back over in the select
	* loop since it may have read from print_fd...
	*/

	if ((*side_cb)(0, -1, snmp_fd, addr, use_bc))
	side_cb = NULL;
	continue;
	}

	/*
	* Do SNMP updates periodically...
	*/

	if (snmp_fd >= 0 && curtime >= snmp_update)
	{
	if (backendSNMPSupplies(snmp_fd, addr, NULL, NULL))
	snmp_fd = -1;
	else
	snmp_update = curtime + 5;
	}
	}

	/*
	* Return with success...
	*/

	return (1);
	}