-/* From ntproc.c */
-extern Lisp_Object Vwin32_pipe_read_delay;
-
-/* Function to do blocking read of one byte, needed to implement
- select. It is only allowed on sockets and pipes. */
-int
-_sys_read_ahead (int fd)
-{
- child_process * cp;
- int rc;
-
- if (fd < 0 || fd >= MAXDESC)
- return STATUS_READ_ERROR;
-
- cp = fd_info[fd].cp;
-
- if (cp == NULL || cp->fd != fd || cp->status != STATUS_READ_READY)
- return STATUS_READ_ERROR;
-
- if ((fd_info[fd].flags & (FILE_PIPE | FILE_SOCKET)) == 0
- || (fd_info[fd].flags & FILE_READ) == 0)
- {
- /* fd is not a pipe or socket */
- abort ();
- }
-
- cp->status = STATUS_READ_IN_PROGRESS;
-
- if (fd_info[fd].flags & FILE_PIPE)
- {
- rc = _read (fd, &cp->chr, sizeof (char));
-
- /* Give subprocess time to buffer some more output for us before
- reporting that input is available; we need this because Win95
- connects DOS programs to pipes by making the pipe appear to be
- the normal console stdout - as a result most DOS programs will
- write to stdout without buffering, ie. one character at a
- time. Even some Win32 programs do this - "dir" in a command
- shell on NT is very slow if we don't do this. */
- if (rc > 0)
- {
- int wait = XINT (Vwin32_pipe_read_delay);
-
- if (wait > 0)
- Sleep (wait);
- else if (wait < 0)
- while (++wait <= 0)
- /* Yield remainder of our time slice, effectively giving a
- temporary priority boost to the child process. */
- Sleep (0);
- }
- }
-
- if (rc == sizeof (char))
- cp->status = STATUS_READ_SUCCEEDED;
- else
- cp->status = STATUS_READ_FAILED;
-
- return cp->status;
-}
-