1  /* Copyright (C) 1991-2023 Free Software Foundation, Inc.
       2     This file is part of the GNU C Library.
       3  
       4     The GNU C Library is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU Lesser General Public
       6     License as published by the Free Software Foundation; either
       7     version 2.1 of the License, or (at your option) any later version.
       8  
       9     The GNU C Library is distributed in the hope that it will be useful,
      10     but WITHOUT ANY WARRANTY; without even the implied warranty of
      11     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      12     Lesser General Public License for more details.
      13  
      14     You should have received a copy of the GNU Lesser General Public
      15     License along with the GNU C Library; if not, see
      16     <https://www.gnu.org/licenses/>.  */
      17  
      18  #include <errno.h>
      19  #include <stddef.h>
      20  #include <termios.h>
      21  #include <unistd.h>
      22  
      23  #include "bsdtty.h"
      24  
      25  /* Suspend or restart transmission on FD.  */
      26  int
      27  tcflow (int fd, int action)
      28  {
      29    switch (action)
      30      {
      31      case TCOOFF:
      32        return __ioctl (fd, TIOCSTOP, (void *) NULL);
      33      case TCOON:
      34        return __ioctl (fd, TIOCSTART, (void *) NULL);
      35  
      36      case TCIOFF:
      37      case TCION:
      38        {
      39  	/* This just writes the START or STOP character with
      40  	   `write'.  Is there another way to do this?  */
      41  	struct termios attr;
      42  	unsigned char c;
      43  	if (__tcgetattr (fd, &attr) < 0)
      44  	  return -1;
      45  	c = attr.c_cc[action == TCIOFF ? VSTOP : VSTART];
      46  	if (c != _POSIX_VDISABLE && write (fd, &c, 1) < 1)
      47  	  return -1;
      48  	return 0;
      49        }
      50  
      51      default:
      52        __set_errno (EINVAL);
      53        return -1;
      54      }
      55  }