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✏️ Editing: tty.c

/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "uv.h"
#include "internal.h"
#include "spinlock.h"

#include <assert.h>
#include <unistd.h>
#include <termios.h>
#include <errno.h>
#include <sys/ioctl.h>

static int orig_termios_fd = -1;
static struct termios orig_termios;
static uv_spinlock_t termios_spinlock = UV_SPINLOCK_INITIALIZER;

int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int readable) {
  uv_handle_type type;
  int flags;
  int newfd;
  int r;

/* File descriptors that refer to files cannot be monitored with epoll.
   * That restriction also applies to character devices like /dev/random
   * (but obviously not /dev/tty.)
   */
  type = uv_guess_handle(fd);
  if (type == UV_FILE || type == UV_UNKNOWN_HANDLE)
    return -EINVAL;

flags = 0;
  newfd = -1;

/* Reopen the file descriptor when it refers to a tty. This lets us put the
   * tty in non-blocking mode without affecting other processes that share it
   * with us.
   *
   * Example: `node | cat` - if we put our fd 0 in non-blocking mode, it also
   * affects fd 1 of `cat` because both file descriptors refer to the same
   * struct file in the kernel. When we reopen our fd 0, it points to a
   * different struct file, hence changing its properties doesn't affect
   * other processes.
   */
  if (type == UV_TTY) {
    r = uv__open_cloexec("/dev/tty", O_RDWR);

if (r < 0) {
      /* fallback to using blocking writes */
      if (!readable)
        flags |= UV_STREAM_BLOCKING;
      goto skip;
    }

newfd = r;

r = uv__dup2_cloexec(newfd, fd);
    if (r < 0 && r != -EINVAL) {
      /* EINVAL means newfd == fd which could conceivably happen if another
       * thread called close(fd) between our calls to isatty() and open().
       * That's a rather unlikely event but let's handle it anyway.
       */
      uv__close(newfd);
      return r;
    }

fd = newfd;
  }

skip:
  uv__stream_init(loop, (uv_stream_t*) tty, UV_TTY);

/* If anything fails beyond this point we need to remove the handle from
   * the handle queue, since it was added by uv__handle_init in uv_stream_init.
   */

#if defined(__APPLE__)
  r = uv__stream_try_select((uv_stream_t*) tty, &fd);
  if (r) {
    if (newfd != -1)
      uv__close(newfd);
    QUEUE_REMOVE(&tty->handle_queue);
    return r;
  }
#endif

if (readable)
    flags |= UV_STREAM_READABLE;
  else
    flags |= UV_STREAM_WRITABLE;

if (!(flags & UV_STREAM_BLOCKING))
    uv__nonblock(fd, 1);

uv__stream_open((uv_stream_t*) tty, fd, flags);
  tty->mode = UV_TTY_MODE_NORMAL;

return 0;
}

static void uv__tty_make_raw(struct termios* tio) {
  assert(tio != NULL);

#ifdef __sun
  /*
   * This implementation of cfmakeraw for Solaris and derivatives is taken from
   * http://www.perkin.org.uk/posts/solaris-portability-cfmakeraw.html.
   */
  tio->c_iflag &= ~(IMAXBEL | IGNBRK | BRKINT | PARMRK | ISTRIP | INLCR |
                    IGNCR | ICRNL | IXON);
  tio->c_oflag &= ~OPOST;
  tio->c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
  tio->c_cflag &= ~(CSIZE | PARENB);
  tio->c_cflag |= CS8;
#else
  cfmakeraw(tio);
#endif /* #ifdef __sun */
}

int uv_tty_set_mode(uv_tty_t* tty, uv_tty_mode_t mode) {
  struct termios tmp;
  int fd;

if (tty->mode == (int) mode)
    return 0;

fd = uv__stream_fd(tty);
  if (tty->mode == UV_TTY_MODE_NORMAL && mode != UV_TTY_MODE_NORMAL) {
    if (tcgetattr(fd, &tty->orig_termios))
      return -errno;

/* This is used for uv_tty_reset_mode() */
    uv_spinlock_lock(&termios_spinlock);
    if (orig_termios_fd == -1) {
      orig_termios = tty->orig_termios;
      orig_termios_fd = fd;
    }
    uv_spinlock_unlock(&termios_spinlock);
  }

tmp = tty->orig_termios;
  switch (mode) {
    case UV_TTY_MODE_NORMAL:
      break;
    case UV_TTY_MODE_RAW:
      tmp.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
      tmp.c_oflag |= (ONLCR);
      tmp.c_cflag |= (CS8);
      tmp.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
      tmp.c_cc[VMIN] = 1;
      tmp.c_cc[VTIME] = 0;
      break;
    case UV_TTY_MODE_IO:
      uv__tty_make_raw(&tmp);
      break;
  }

/* Apply changes after draining */
  if (tcsetattr(fd, TCSADRAIN, &tmp))
    return -errno;

tty->mode = mode;
  return 0;
}

int uv_tty_get_winsize(uv_tty_t* tty, int* width, int* height) {
  struct winsize ws;

if (ioctl(uv__stream_fd(tty), TIOCGWINSZ, &ws))
    return -errno;

*width = ws.ws_col;
  *height = ws.ws_row;

return 0;
}

uv_handle_type uv_guess_handle(uv_file file) {
  struct sockaddr sa;
  struct stat s;
  socklen_t len;
  int type;

if (file < 0)
    return UV_UNKNOWN_HANDLE;

if (isatty(file))
    return UV_TTY;

if (fstat(file, &s))
    return UV_UNKNOWN_HANDLE;

if (S_ISREG(s.st_mode))
    return UV_FILE;

if (S_ISCHR(s.st_mode))
    return UV_FILE;  /* XXX UV_NAMED_PIPE? */

if (S_ISFIFO(s.st_mode))
    return UV_NAMED_PIPE;

if (!S_ISSOCK(s.st_mode))
    return UV_UNKNOWN_HANDLE;

len = sizeof(type);
  if (getsockopt(file, SOL_SOCKET, SO_TYPE, &type, &len))
    return UV_UNKNOWN_HANDLE;

len = sizeof(sa);
  if (getsockname(file, &sa, &len))
    return UV_UNKNOWN_HANDLE;

if (type == SOCK_DGRAM)
    if (sa.sa_family == AF_INET || sa.sa_family == AF_INET6)
      return UV_UDP;

if (type == SOCK_STREAM) {
#if defined(_AIX)
    /* on AIX the getsockname call returns an empty sa structure
     * for sockets of type AF_UNIX.  For all other types it will
     * return a properly filled in structure.
     */
    if (len == 0)
      return UV_NAMED_PIPE;
#endif /* defined(_AIX) */

if (sa.sa_family == AF_INET || sa.sa_family == AF_INET6)
      return UV_TCP;
    if (sa.sa_family == AF_UNIX)
      return UV_NAMED_PIPE;
  }

return UV_UNKNOWN_HANDLE;
}

/* This function is async signal-safe, meaning that it's safe to call from
 * inside a signal handler _unless_ execution was inside uv_tty_set_mode()'s
 * critical section when the signal was raised.
 */
int uv_tty_reset_mode(void) {
  int saved_errno;
  int err;

saved_errno = errno;
  if (!uv_spinlock_trylock(&termios_spinlock))
    return -EBUSY;  /* In uv_tty_set_mode(). */

err = 0;
  if (orig_termios_fd != -1)
    if (tcsetattr(orig_termios_fd, TCSANOW, &orig_termios))
      err = -errno;

uv_spinlock_unlock(&termios_spinlock);
  errno = saved_errno;

return err;
}

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