stream: autodetect direction

Previously, we required the user to specify the expected read/write flags
for a pipe or tty. But we've already been asking the OS to tell us
what they actually are (fcntl F_GETFL), so we can hopefully just use that
information directly.

Fix libuv#1936

src/unix/pipe.c

@@ -132,11 +132,21 @@ void uv__pipe_close(uv_pipe_t* handle) {
 
 
 int uv_pipe_open(uv_pipe_t* handle, uv_file fd) {
+  int flags;
+  int mode;
   int err;
+  flags = 0;
 
   if (uv__fd_exists(handle->loop, fd))
     return UV_EEXIST;
 
+  do
+    mode = fcntl(fd, F_GETFL);
+  while (mode == -1 && errno == EINTR);
+
+  if (mode == -1)
+    return UV__ERR(errno); /* according to docs, must be EBADF */
+
   err = uv__nonblock(fd, 1);
   if (err)
     return err;
@@ -147,9 +157,13 @@ int uv_pipe_open(uv_pipe_t* handle, uv_file fd) {
     return err;
 #endif /* defined(__APPLE__) */
 
-  return uv__stream_open((uv_stream_t*)handle,
-                         fd,
-                         UV_HANDLE_READABLE | UV_HANDLE_WRITABLE);
+  mode &= O_ACCMODE;
+  if (mode != O_WRONLY)
+    flags |= UV_HANDLE_READABLE;
+  if (mode != O_RDONLY)
+    flags |= UV_HANDLE_WRITABLE;
+
+  return uv__stream_open((uv_stream_t*)handle, fd, flags);
 }
 
 

src/unix/tty.c

@@ -92,13 +92,15 @@ static int uv__tty_is_slave(const int fd) {
   return result;
 }
 
-int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int readable) {
+int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int unused) {
   uv_handle_type type;
   int flags;
   int newfd;
   int r;
   int saved_flags;
+  int mode;
   char path[256];
+  (void)unused; /* deprecated parameter is no longer needed */
 
   /* File descriptors that refer to files cannot be monitored with epoll.
    * That restriction also applies to character devices like /dev/random
@@ -111,6 +113,15 @@ int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int readable) {
   flags = 0;
   newfd = -1;
 
+  /* Save the fd flags in case we need to restore them due to an error. */
+  do
+    saved_flags = fcntl(fd, F_GETFL);
+  while (saved_flags == -1 && errno == EINTR);
+
+  if (saved_flags == -1)
+    return UV__ERR(errno);
+  mode = saved_flags & O_ACCMODE;
+
   /* 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.
@@ -128,13 +139,13 @@ int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int readable) {
      * slave device.
      */
     if (uv__tty_is_slave(fd) && ttyname_r(fd, path, sizeof(path)) == 0)
-      r = uv__open_cloexec(path, O_RDWR);
+      r = uv__open_cloexec(path, saved_flags & O_ACCMODE);
     else
       r = -1;
 
     if (r < 0) {
       /* fallback to using blocking writes */
-      if (!readable)
+      if (mode != O_RDONLY)
         flags |= UV_HANDLE_BLOCKING_WRITES;
       goto skip;
     }
@@ -154,22 +165,6 @@ int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int readable) {
     fd = newfd;
   }
 
-#if defined(__APPLE__)
-  /* Save the fd flags in case we need to restore them due to an error. */
-  do
-    saved_flags = fcntl(fd, F_GETFL);
-  while (saved_flags == -1 && errno == EINTR);
-
-  if (saved_flags == -1) {
-    if (newfd != -1)
-      uv__close(newfd);
-    return UV__ERR(errno);
-  }
-#endif
-
-  /* Pacify the compiler. */
-  (void) &saved_flags;
-
 skip:
   uv__stream_init(loop, (uv_stream_t*) tty, UV_TTY);
 
@@ -194,9 +189,9 @@ int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, int fd, int readable) {
   }
 #endif
 
-  if (readable)
+  if (mode != O_WRONLY)
     flags |= UV_HANDLE_READABLE;
-  else
+  if (mode != O_RDONLY)
     flags |= UV_HANDLE_WRITABLE;
 
   uv__stream_open((uv_stream_t*) tty, fd, flags);

src/win/tty.c

@@ -172,9 +172,12 @@ void uv_console_init(void) {
 }
 
 
-int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, uv_file fd, int readable) {
+int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, uv_file fd, int unused) {
+  BOOL readable;
+  DWORD NumberOfEvents;
   HANDLE handle;
   CONSOLE_SCREEN_BUFFER_INFO screen_buffer_info;
+  (void)unused;
 
   uv__once_init();
   handle = (HANDLE) uv__get_osfhandle(fd);
@@ -199,6 +202,7 @@ int uv_tty_init(uv_loop_t* loop, uv_tty_t* tty, uv_file fd, int readable) {
     fd = -1;
   }
 
+  readable = GetNumberOfConsoleInputEvents(handle, &NumberOfEvents);
   if (!readable) {
     /* Obtain the screen buffer info with the output handle. */
     if (!GetConsoleScreenBufferInfo(handle, &screen_buffer_info)) {
@@ -382,12 +386,6 @@ int uv_tty_set_mode(uv_tty_t* tty, uv_tty_mode_t mode) {
 }
 
 
-int uv_is_tty(uv_file file) {
-  DWORD result;
-  return GetConsoleMode((HANDLE) _get_osfhandle(file), &result) != 0;
-}
-
-
 int uv_tty_get_winsize(uv_tty_t* tty, int* width, int* height) {
   CONSOLE_SCREEN_BUFFER_INFO info;