/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/internal.h"
#include "libc/calls/struct/termios.h"
#include "libc/calls/termios.h"
#include "libc/sysv/consts/termios.h"
#include "libc/sysv/errfuns.h"

/**
 * Changes flow of teletypewriter data.
 *
 * - `TCOOFF` suspends output
 * - `TCOON` resumes output
 * - `TCIOFF` transmits a STOP character
 * - `TCION` transmits a START character
 */
int tcflow(int fd, int action) {
  uint8_t c;
  struct termios t;
  if (!IsBsd()) return sys_ioctl(fd, TCXONC, action);
  if (action == TCOOFF) return sys_ioctl(fd, TIOCSTOP, 0);
  if (action == TCOON) return sys_ioctl(fd, TIOCSTART, 0);
  if (action != TCIOFF && action != TCION) return einval();
  if (tcgetattr(fd, &t) == -1) return -1;
  if ((c = t.c_cc[action == TCIOFF ? VSTOP : VSTART]) != 255) {
    if (sys_write(fd, &c, 1) == -1) return -1;
  }
  return 0;
}