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

#define kNtPurgeTxclear 4
#define kNtPurgeRxclear 8

static const char *DescribeFlush(char buf[12], int action) {
  if (action == TCIFLUSH) return "TCIFLUSH";
  if (action == TCOFLUSH) return "TCOFLUSH";
  if (action == TCIOFLUSH) return "TCIOFLUSH";
  FormatInt32(buf, action);
  return buf;
}

static dontinline textwindows int sys_tcflush_nt(int fd, int queue) {
  bool32 ok;
  int64_t h;
  if (!__isfdopen(fd)) return ebadf();
  ok = true;
  h = g_fds.p[fd].handle;
  if (queue == TCIFLUSH || queue == TCIOFLUSH) {
    ok &= !!PurgeComm(h, kNtPurgeRxclear);
  }
  if (queue == TCOFLUSH || queue == TCIOFLUSH) {
    ok &= !!PurgeComm(h, kNtPurgeTxclear);
  }
  return ok ? 0 : __winerr();
}

/**
 * Discards queued data on teletypewriter.
 *
 * @param queue may be one of:
 *     - `TCIFLUSH` flushes data received but not read
 *     - `TCOFLUSH` flushes data written but not transmitted
 *     - `TCIOFLUSH` does both `TCOFLUSH` and `TCIFLUSH`
 * @return 0 on success, or -1 w/ errno
 * @raise EINVAL if `action` is invalid
 * @raise EBADF if `fd` isn't an open file descriptor
 * @raise ENOTTY if `fd` is open but not a teletypewriter
 * @raise EIO if process group of writer is orphoned, calling thread is
 *     not blocking `SIGTTOU`, and process isn't ignoring `SIGTTOU`
 * @raise ENOSYS on bare metal
 * @asyncsignalsafe
 */
int tcflush(int fd, int queue) {
  int rc;
  if (IsMetal()) {
    rc = enosys();
  } else if (!IsWindows()) {
    rc = sys_ioctl(fd, TCFLSH, queue);
  } else {
    rc = sys_tcflush_nt(fd, queue);
  }
  STRACE("tcflush(%d, %s) â %d% m", fd, DescribeFlush(alloca(12), queue), rc);
  return rc;
}
