0.7.6.2:

[sbcl/lichteblau.git] / src / code / fd-stream.lisp

;;;; streams for UNIX file descriptors

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB!IMPL")

;;; FIXME: Wouldn't it be clearer to just have the structure
;;; definition be DEFSTRUCT FILE-STREAM (instead of DEFSTRUCT
;;; FD-STREAM)? That way we'd have TYPE-OF and PRINT-OBJECT refer to
;;; these objects as FILE-STREAMs (the ANSI name) instead of the
;;; internal implementation name FD-STREAM, and there might be other
;;; benefits as well.
(deftype file-stream () 'fd-stream)
\f
;;;; buffer manipulation routines

;;; FIXME: Is it really good to maintain this pool separate from the
;;; GC and the C malloc logic?
(defvar *available-buffers* ()
  #!+sb-doc
  "List of available buffers. Each buffer is an sap pointing to
  bytes-per-buffer of memory.")

(defconstant bytes-per-buffer (* 4 1024)
  #!+sb-doc
  "Number of bytes per buffer.")

;;; Return the next available buffer, creating one if necessary.
#!-sb-fluid (declaim (inline next-available-buffer))
(defun next-available-buffer ()
  (if *available-buffers*
      (pop *available-buffers*)
      (allocate-system-memory bytes-per-buffer)))
\f
;;;; the FD-STREAM structure

(defstruct (fd-stream
            (:constructor %make-fd-stream)
            (:include ansi-stream
                      (misc #'fd-stream-misc-routine))
            (:copier nil))

  ;; the name of this stream
  (name nil)
  ;; the file this stream is for
  (file nil)
  ;; the backup file namestring for the old file, for :IF-EXISTS
  ;; :RENAME or :RENAME-AND-DELETE.
  (original nil :type (or simple-string null))
  (delete-original nil)       ; for :if-exists :rename-and-delete
  ;;; the number of bytes per element
  (element-size 1 :type index)
  ;; the type of element being transfered
  (element-type 'base-char)   
  ;; the Unix file descriptor
  (fd -1 :type fixnum)        
  ;; controls when the output buffer is flushed
  (buffering :full :type (member :full :line :none))
  ;; character position (if known)
  (char-pos nil :type (or index null))
  ;; T if input is waiting on FD. :EOF if we hit EOF.
  (listen nil :type (member nil t :eof))

  ;; the input buffer
  (unread nil)
  (ibuf-sap nil :type (or system-area-pointer null))
  (ibuf-length nil :type (or index null))
  (ibuf-head 0 :type index)
  (ibuf-tail 0 :type index)

  ;; the output buffer
  (obuf-sap nil :type (or system-area-pointer null))
  (obuf-length nil :type (or index null))
  (obuf-tail 0 :type index)

  ;; output flushed, but not written due to non-blocking io?
  (output-later nil)
  (handler nil)
  ;; timeout specified for this stream, or NIL if none
  (timeout nil :type (or index null))
  ;; pathname of the file this stream is opened to (returned by PATHNAME)
  (pathname nil :type (or pathname null)))
(def!method print-object ((fd-stream fd-stream) stream)
  (declare (type stream stream))
  (print-unreadable-object (fd-stream stream :type t :identity t)
    (format stream "for ~S" (fd-stream-name fd-stream))))
\f
;;;; output routines and related noise

(defvar *output-routines* ()
  #!+sb-doc
  "List of all available output routines. Each element is a list of the
  element-type output, the kind of buffering, the function name, and the number
  of bytes per element.")

;;; common idioms for reporting low-level stream and file problems
(defun simple-stream-perror (note-format stream errno)
  (error 'simple-stream-error
         :stream stream
         :format-control "~@<~?: ~2I~_~A~:>"
         :format-arguments (list note-format (list stream) (strerror errno))))
(defun simple-file-perror (note-format pathname errno)
  (error 'simple-file-error
         :pathname pathname
         :format-control "~@<~?: ~2I~_~A~:>"
         :format-arguments
         (list note-format (list pathname) (strerror errno))))

;;; This is called by the server when we can write to the given file
;;; descriptor. Attempt to write the data again. If it worked, remove
;;; the data from the OUTPUT-LATER list. If it didn't work, something
;;; is wrong.
(defun frob-output-later (stream)
  (let* ((stuff (pop (fd-stream-output-later stream)))
         (base (car stuff))
         (start (cadr stuff))
         (end (caddr stuff))
         (reuse-sap (cadddr stuff))
         (length (- end start)))
    (declare (type index start end length))
    (multiple-value-bind (count errno)
        (sb!unix:unix-write (fd-stream-fd stream)
                            base
                            start
                            length)
      (cond ((not count)
             (if (= errno sb!unix:ewouldblock)
                 (error "Write would have blocked, but SERVER told us to go.")
                 (simple-stream-perror "couldn't write to ~S" stream errno)))
            ((eql count length) ; Hot damn, it worked.
             (when reuse-sap
               (push base *available-buffers*)))
            ((not (null count)) ; sorta worked..
             (push (list base
                         (the index (+ start count))
                         end)
                   (fd-stream-output-later stream))))))
  (unless (fd-stream-output-later stream)
    (sb!sys:remove-fd-handler (fd-stream-handler stream))
    (setf (fd-stream-handler stream) nil)))

;;; Arange to output the string when we can write on the file descriptor.
(defun output-later (stream base start end reuse-sap)
  (cond ((null (fd-stream-output-later stream))
         (setf (fd-stream-output-later stream)
               (list (list base start end reuse-sap)))
         (setf (fd-stream-handler stream)
               (sb!sys:add-fd-handler (fd-stream-fd stream)
                                      :output
                                      (lambda (fd)
                                        (declare (ignore fd))
                                        (frob-output-later stream)))))
        (t
         (nconc (fd-stream-output-later stream)
                (list (list base start end reuse-sap)))))
  (when reuse-sap
    (let ((new-buffer (next-available-buffer)))
      (setf (fd-stream-obuf-sap stream) new-buffer)
      (setf (fd-stream-obuf-length stream) bytes-per-buffer))))

;;; Output the given noise. Check to see whether there are any pending
;;; writes. If so, just queue this one. Otherwise, try to write it. If
;;; this would block, queue it.
(defun frob-output (stream base start end reuse-sap)
  (declare (type fd-stream stream)
           (type (or system-area-pointer (simple-array * (*))) base)
           (type index start end))
  (if (not (null (fd-stream-output-later stream))) ; something buffered.
      (progn
        (output-later stream base start end reuse-sap)
        ;; ### check to see whether any of this noise can be output
        )
      (let ((length (- end start)))
        (multiple-value-bind (count errno)
            (sb!unix:unix-write (fd-stream-fd stream) base start length)
          (cond ((not count)
                 (if (= errno sb!unix:ewouldblock)
                     (output-later stream base start end reuse-sap)
                     (simple-stream-perror "couldn't write to ~S"
                                           stream
                                           errno)))
                ((not (eql count length))
                 (output-later stream base (the index (+ start count))
                               end reuse-sap)))))))

;;; Flush any data in the output buffer.
(defun flush-output-buffer (stream)
  (let ((length (fd-stream-obuf-tail stream)))
    (unless (= length 0)
      (frob-output stream (fd-stream-obuf-sap stream) 0 length t)
      (setf (fd-stream-obuf-tail stream) 0))))

;;; Define output routines that output numbers SIZE bytes long for the
;;; given bufferings. Use BODY to do the actual output.
(defmacro def-output-routines ((name-fmt size &rest bufferings) &body body)
  (declare (optimize (speed 1)))
  (cons 'progn
        (mapcar
            (lambda (buffering)
              (let ((function
                     (intern (let ((*print-case* :upcase))
                               (format nil name-fmt (car buffering))))))
                `(progn
                   (defun ,function (stream byte)
                     ,(unless (eq (car buffering) :none)
                        `(when (< (fd-stream-obuf-length stream)
                                  (+ (fd-stream-obuf-tail stream)
                                     ,size))
                           (flush-output-buffer stream)))
                     ,@body
                     (incf (fd-stream-obuf-tail stream) ,size)
                     ,(ecase (car buffering)
                        (:none
                         `(flush-output-buffer stream))
                        (:line
                         `(when (eq (char-code byte) (char-code #\Newline))
                            (flush-output-buffer stream)))
                        (:full
                         ))
                     (values))
                   (setf *output-routines*
                         (nconc *output-routines*
                                ',(mapcar
                                   (lambda (type)
                                     (list type
                                           (car buffering)
                                           function
                                           size))
                                   (cdr buffering)))))))
            bufferings)))

(def-output-routines ("OUTPUT-CHAR-~A-BUFFERED"
                      1
                      (:none character)
                      (:line character)
                      (:full character))
  (if (and (base-char-p byte) (char= byte #\Newline))
      (setf (fd-stream-char-pos stream) 0)
      (incf (fd-stream-char-pos stream)))
  (setf (sap-ref-8 (fd-stream-obuf-sap stream) (fd-stream-obuf-tail stream))
        (char-code byte)))

(def-output-routines ("OUTPUT-UNSIGNED-BYTE-~A-BUFFERED"
                      1
                      (:none (unsigned-byte 8))
                      (:full (unsigned-byte 8)))
  (setf (sap-ref-8 (fd-stream-obuf-sap stream) (fd-stream-obuf-tail stream))
        byte))

(def-output-routines ("OUTPUT-SIGNED-BYTE-~A-BUFFERED"
                      1
                      (:none (signed-byte 8))
                      (:full (signed-byte 8)))
  (setf (signed-sap-ref-8 (fd-stream-obuf-sap stream)
                          (fd-stream-obuf-tail stream))
        byte))

(def-output-routines ("OUTPUT-UNSIGNED-SHORT-~A-BUFFERED"
                      2
                      (:none (unsigned-byte 16))
                      (:full (unsigned-byte 16)))
  (setf (sap-ref-16 (fd-stream-obuf-sap stream) (fd-stream-obuf-tail stream))
        byte))

(def-output-routines ("OUTPUT-SIGNED-SHORT-~A-BUFFERED"
                      2
                      (:none (signed-byte 16))
                      (:full (signed-byte 16)))
  (setf (signed-sap-ref-16 (fd-stream-obuf-sap stream)
                           (fd-stream-obuf-tail stream))
        byte))

(def-output-routines ("OUTPUT-UNSIGNED-LONG-~A-BUFFERED"
                      4
                      (:none (unsigned-byte 32))
                      (:full (unsigned-byte 32)))
  (setf (sap-ref-32 (fd-stream-obuf-sap stream) (fd-stream-obuf-tail stream))
        byte))

(def-output-routines ("OUTPUT-SIGNED-LONG-~A-BUFFERED"
                      4
                      (:none (signed-byte 32))
                      (:full (signed-byte 32)))
  (setf (signed-sap-ref-32 (fd-stream-obuf-sap stream)
                           (fd-stream-obuf-tail stream))
        byte))

;;; Do the actual output. If there is space to buffer the string,
;;; buffer it. If the string would normally fit in the buffer, but
;;; doesn't because of other stuff in the buffer, flush the old noise
;;; out of the buffer and put the string in it. Otherwise we have a
;;; very long string, so just send it directly (after flushing the
;;; buffer, of course).
(defun output-raw-bytes (fd-stream thing &optional start end)
  #!+sb-doc
  "Output THING to FD-STREAM. THING can be any kind of vector or a SAP. If
  THING is a SAP, END must be supplied (as length won't work)."
  (let ((start (or start 0))
        (end (or end (length (the (simple-array * (*)) thing)))))
    (declare (type index start end))
    (let* ((len (fd-stream-obuf-length fd-stream))
           (tail (fd-stream-obuf-tail fd-stream))
           (space (- len tail))
           (bytes (- end start))
           (newtail (+ tail bytes)))
      (cond ((minusp bytes) ; error case
             (error ":END before :START!"))
            ((zerop bytes)) ; easy case
            ((<= bytes space)
             (if (system-area-pointer-p thing)
                 (system-area-copy thing
                                   (* start sb!vm:n-byte-bits)
                                   (fd-stream-obuf-sap fd-stream)
                                   (* tail sb!vm:n-byte-bits)
                                   (* bytes sb!vm:n-byte-bits))
                 ;; FIXME: There should be some type checking somewhere to
                 ;; verify that THING here is a vector, not just <not a SAP>.
                 (copy-to-system-area thing
                                      (+ (* start sb!vm:n-byte-bits)
                                         (* sb!vm:vector-data-offset
                                            sb!vm:n-word-bits))
                                      (fd-stream-obuf-sap fd-stream)
                                      (* tail sb!vm:n-byte-bits)
                                      (* bytes sb!vm:n-byte-bits)))
             (setf (fd-stream-obuf-tail fd-stream) newtail))
            ((<= bytes len)
             (flush-output-buffer fd-stream)
             (if (system-area-pointer-p thing)
                 (system-area-copy thing
                                   (* start sb!vm:n-byte-bits)
                                   (fd-stream-obuf-sap fd-stream)
                                   0
                                   (* bytes sb!vm:n-byte-bits))
                 ;; FIXME: There should be some type checking somewhere to
                 ;; verify that THING here is a vector, not just <not a SAP>.
                 (copy-to-system-area thing
                                      (+ (* start sb!vm:n-byte-bits)
                                         (* sb!vm:vector-data-offset
                                            sb!vm:n-word-bits))
                                      (fd-stream-obuf-sap fd-stream)
                                      0
                                      (* bytes sb!vm:n-byte-bits)))
             (setf (fd-stream-obuf-tail fd-stream) bytes))
            (t
             (flush-output-buffer fd-stream)
             (frob-output fd-stream thing start end nil))))))

;;; the routine to use to output a string. If the stream is
;;; unbuffered, slam the string down the file descriptor, otherwise
;;; use OUTPUT-RAW-BYTES to buffer the string. Update charpos by
;;; checking to see where the last newline was.
;;;
;;; Note: some bozos (the FASL dumper) call write-string with things
;;; other than strings. Therefore, we must make sure we have a string
;;; before calling POSITION on it.
;;; KLUDGE: It would be better to fix the bozos instead of trying to
;;; cover for them here. -- WHN 20000203
(defun fd-sout (stream thing start end)
  (let ((start (or start 0))
        (end (or end (length (the vector thing)))))
    (declare (fixnum start end))
    (if (stringp thing)
        (let ((last-newline (and (find #\newline (the simple-string thing)
                                       :start start :end end)
                                 ;; FIXME why do we need both calls?
                                 ;; Is find faster forwards than
                                 ;; position is backwards?
                                 (position #\newline (the simple-string thing)
                                           :from-end t
                                           :start start
                                           :end end))))
          (ecase (fd-stream-buffering stream)
            (:full
             (output-raw-bytes stream thing start end))
            (:line
             (output-raw-bytes stream thing start end)
             (when last-newline
               (flush-output-buffer stream)))
            (:none
             (frob-output stream thing start end nil)))
          (if last-newline
              (setf (fd-stream-char-pos stream)
                    (- end last-newline 1))
              (incf (fd-stream-char-pos stream)
                    (- end start))))
        (ecase (fd-stream-buffering stream)
          ((:line :full)
           (output-raw-bytes stream thing start end))
          (:none
           (frob-output stream thing start end nil))))))

;;; Find an output routine to use given the type and buffering. Return
;;; as multiple values the routine, the real type transfered, and the
;;; number of bytes per element.
(defun pick-output-routine (type buffering)
  (dolist (entry *output-routines*)
    (when (and (subtypep type (car entry))
               (eq buffering (cadr entry)))
      (return (values (symbol-function (caddr entry))
                      (car entry)
                      (cadddr entry))))))
\f
;;;; input routines and related noise

;;; a list of all available input routines. Each element is a list of
;;; the element-type input, the function name, and the number of bytes
;;; per element.
(defvar *input-routines* ())

;;; Fill the input buffer, and return the first character. Throw to
;;; EOF-INPUT-CATCHER if the eof was reached. Drop into SYSTEM:SERVER
;;; if necessary.
(defun frob-input (stream)
  (let ((fd (fd-stream-fd stream))
        (ibuf-sap (fd-stream-ibuf-sap stream))
        (buflen (fd-stream-ibuf-length stream))
        (head (fd-stream-ibuf-head stream))
        (tail (fd-stream-ibuf-tail stream)))
    (declare (type index head tail))
    (unless (zerop head)
      (cond ((eql head tail)
             (setf head 0)
             (setf tail 0)
             (setf (fd-stream-ibuf-head stream) 0)
             (setf (fd-stream-ibuf-tail stream) 0))
            (t
             (decf tail head)
             (system-area-copy ibuf-sap (* head sb!vm:n-byte-bits)
                               ibuf-sap 0 (* tail sb!vm:n-byte-bits))
             (setf head 0)
             (setf (fd-stream-ibuf-head stream) 0)
             (setf (fd-stream-ibuf-tail stream) tail))))
    (setf (fd-stream-listen stream) nil)
    (multiple-value-bind (count errno)
        ;; FIXME: Judging from compiler warnings, this WITH-ALIEN form expands
        ;; into something which uses the not-yet-defined type
        ;;   (SB!ALIEN-INTERNALS:ALIEN (* (SB!ALIEN:STRUCT SB!UNIX:FD-SET))).
        ;; This is probably inefficient and unsafe and generally bad, so
        ;; try to find some way to make that type known before
        ;; this is compiled.
        (sb!alien:with-alien ((read-fds (sb!alien:struct sb!unix:fd-set)))
          (sb!unix:fd-zero read-fds)
          (sb!unix:fd-set fd read-fds)
          (sb!unix:unix-fast-select (1+ fd)
                                    (sb!alien:addr read-fds)
                                    nil
                                    nil
                                    0
                                    0))
      (case count
        (1)
        (0
         (unless #!-mp (sb!sys:wait-until-fd-usable
                       fd :input (fd-stream-timeout stream))
                 #!+mp (sb!mp:process-wait-until-fd-usable
                       fd :input (fd-stream-timeout stream))
           (error 'io-timeout :stream stream :direction :read)))
        (t
         (simple-stream-perror "couldn't check whether ~S is readable"
                               stream
                               errno))))
    (multiple-value-bind (count errno)
        (sb!unix:unix-read fd
                           (sb!sys:int-sap (+ (sb!sys:sap-int ibuf-sap) tail))
                           (- buflen tail))
      (cond ((null count)
             (if (eql errno sb!unix:ewouldblock)
                 (progn
                   (unless #!-mp (sb!sys:wait-until-fd-usable
                                 fd :input (fd-stream-timeout stream))
                           #!+mp (sb!mp:process-wait-until-fd-usable
                                 fd :input (fd-stream-timeout stream))
                     (error 'io-timeout :stream stream :direction :read))
                   (frob-input stream))
                 (simple-stream-perror "couldn't read from ~S" stream errno)))
            ((zerop count)
             (setf (fd-stream-listen stream) :eof)
             (/show0 "THROWing EOF-INPUT-CATCHER")
             (throw 'eof-input-catcher nil))
            (t
             (incf (fd-stream-ibuf-tail stream) count))))))
                        
;;; Make sure there are at least BYTES number of bytes in the input
;;; buffer. Keep calling FROB-INPUT until that condition is met.
(defmacro input-at-least (stream bytes)
  (let ((stream-var (gensym))
        (bytes-var (gensym)))
    `(let ((,stream-var ,stream)
           (,bytes-var ,bytes))
       (loop
         (when (>= (- (fd-stream-ibuf-tail ,stream-var)
                      (fd-stream-ibuf-head ,stream-var))
                   ,bytes-var)
           (return))
         (frob-input ,stream-var)))))

;;; a macro to wrap around all input routines to handle EOF-ERROR noise
(defmacro input-wrapper ((stream bytes eof-error eof-value) &body read-forms)
  (let ((stream-var (gensym))
        (element-var (gensym)))
    `(let ((,stream-var ,stream))
       (if (fd-stream-unread ,stream-var)
           (prog1
               (fd-stream-unread ,stream-var)
             (setf (fd-stream-unread ,stream-var) nil)
             (setf (fd-stream-listen ,stream-var) nil))
           (let ((,element-var
                  (catch 'eof-input-catcher
                    (input-at-least ,stream-var ,bytes)
                    ,@read-forms)))
             (cond (,element-var
                    (incf (fd-stream-ibuf-head ,stream-var) ,bytes)
                    ,element-var)
                   (t
                    (eof-or-lose ,stream-var ,eof-error ,eof-value))))))))

(defmacro def-input-routine (name
                             (type size sap head)
                             &rest body)
  `(progn
     (defun ,name (stream eof-error eof-value)
       (input-wrapper (stream ,size eof-error eof-value)
         (let ((,sap (fd-stream-ibuf-sap stream))
               (,head (fd-stream-ibuf-head stream)))
           ,@body)))
     (setf *input-routines*
           (nconc *input-routines*
                  (list (list ',type ',name ',size))))))

;;; STREAM-IN routine for reading a string char
(def-input-routine input-character
                   (character 1 sap head)
  (code-char (sap-ref-8 sap head)))

;;; STREAM-IN routine for reading an unsigned 8 bit number
(def-input-routine input-unsigned-8bit-byte
                   ((unsigned-byte 8) 1 sap head)
  (sap-ref-8 sap head))

;;; STREAM-IN routine for reading a signed 8 bit number
(def-input-routine input-signed-8bit-number
                   ((signed-byte 8) 1 sap head)
  (signed-sap-ref-8 sap head))

;;; STREAM-IN routine for reading an unsigned 16 bit number
(def-input-routine input-unsigned-16bit-byte
                   ((unsigned-byte 16) 2 sap head)
  (sap-ref-16 sap head))

;;; STREAM-IN routine for reading a signed 16 bit number
(def-input-routine input-signed-16bit-byte
                   ((signed-byte 16) 2 sap head)
  (signed-sap-ref-16 sap head))

;;; STREAM-IN routine for reading a unsigned 32 bit number
(def-input-routine input-unsigned-32bit-byte
                   ((unsigned-byte 32) 4 sap head)
  (sap-ref-32 sap head))

;;; STREAM-IN routine for reading a signed 32 bit number
(def-input-routine input-signed-32bit-byte
                   ((signed-byte 32) 4 sap head)
  (signed-sap-ref-32 sap head))

;;; Find an input routine to use given the type. Return as multiple
;;; values the routine, the real type transfered, and the number of
;;; bytes per element.
(defun pick-input-routine (type)
  (dolist (entry *input-routines*)
    (when (subtypep type (car entry))
      (return (values (symbol-function (cadr entry))
                      (car entry)
                      (caddr entry))))))

;;; Return a string constructed from SAP, START, and END.
(defun string-from-sap (sap start end)
  (declare (type index start end))
  (let* ((length (- end start))
         (string (make-string length)))
    (copy-from-system-area sap (* start sb!vm:n-byte-bits)
                           string (* sb!vm:vector-data-offset
                                     sb!vm:n-word-bits)
                           (* length sb!vm:n-byte-bits))
    string))

;;; the N-BIN method for FD-STREAMs
;;;
;;; Note that this blocks in UNIX-READ. It is generally used where
;;; there is a definite amount of reading to be done, so blocking
;;; isn't too problematical.
(defun fd-stream-read-n-bytes (stream buffer start requested eof-error-p)
  (declare (type fd-stream stream))
  (declare (type index start requested))
  (do ((total-copied 0))
      (nil)
    (declare (type index total-copied))
    (let* ((remaining-request (- requested total-copied))
           (head (fd-stream-ibuf-head stream))
           (tail (fd-stream-ibuf-tail stream))
           (available (- tail head))
           (n-this-copy (min remaining-request available))
           (this-start (+ start total-copied))
           (this-end (+ this-start n-this-copy))
           (sap (fd-stream-ibuf-sap stream)))
      (declare (type index remaining-request head tail available))
      (declare (type index n-this-copy))
      ;; Copy data from stream buffer into user's buffer. 
      (%byte-blt sap head buffer this-start this-end)
      (incf (fd-stream-ibuf-head stream) n-this-copy)
      (incf total-copied n-this-copy)
      ;; Maybe we need to refill the stream buffer.
      (cond (;; If there were enough data in the stream buffer, we're done.
             (= total-copied requested)
             (return total-copied))
            (;; If EOF, we're done in another way.
             (zerop (refill-fd-stream-buffer stream))
             (if eof-error-p
                 (error 'end-of-file :stream stream)
                 (return total-copied)))
            ;; Otherwise we refilled the stream buffer, so fall
            ;; through into another pass of the loop.
            ))))

;;; Try to refill the stream buffer. Return the number of bytes read.
;;; (For EOF, the return value will be zero, otherwise positive.)
(defun refill-fd-stream-buffer (stream)
  ;; We don't have any logic to preserve leftover bytes in the buffer,
  ;; so we should only be called when the buffer is empty.
  (aver (= (fd-stream-ibuf-head stream) (fd-stream-ibuf-tail stream)))
  (multiple-value-bind (count err)
      (sb!unix:unix-read (fd-stream-fd stream)
                         (fd-stream-ibuf-sap stream)
                         (fd-stream-ibuf-length stream))
    (declare (type (or index null) count))
    (when (null count)
      (simple-stream-perror "couldn't read from ~S" stream err))
    (setf (fd-stream-listen stream) nil
          (fd-stream-ibuf-head stream) 0
          (fd-stream-ibuf-tail stream) count)
    count))
\f
;;;; utility functions (misc routines, etc)

;;; Fill in the various routine slots for the given type. INPUT-P and
;;; OUTPUT-P indicate what slots to fill. The buffering slot must be
;;; set prior to calling this routine.
(defun set-fd-stream-routines (fd-stream type input-p output-p buffer-p)
  (let ((target-type (case type
                       ((:default unsigned-byte)
                        '(unsigned-byte 8))
                       (signed-byte
                        '(signed-byte 8))
                       (t
                        type)))
        (input-type nil)
        (output-type nil)
        (input-size nil)
        (output-size nil))

    (when (fd-stream-obuf-sap fd-stream)
      (push (fd-stream-obuf-sap fd-stream) *available-buffers*)
      (setf (fd-stream-obuf-sap fd-stream) nil))
    (when (fd-stream-ibuf-sap fd-stream)
      (push (fd-stream-ibuf-sap fd-stream) *available-buffers*)
      (setf (fd-stream-ibuf-sap fd-stream) nil))

    (when input-p
      (multiple-value-bind (routine type size)
          (pick-input-routine target-type)
        (unless routine
          (error "could not find any input routine for ~S" target-type))
        (setf (fd-stream-ibuf-sap fd-stream) (next-available-buffer))
        (setf (fd-stream-ibuf-length fd-stream) bytes-per-buffer)
        (setf (fd-stream-ibuf-tail fd-stream) 0)
        (if (subtypep type 'character)
            (setf (fd-stream-in fd-stream) routine
                  (fd-stream-bin fd-stream) #'ill-bin)
            (setf (fd-stream-in fd-stream) #'ill-in
                  (fd-stream-bin fd-stream) routine))
        (when (eql size 1)
          (setf (fd-stream-n-bin fd-stream) #'fd-stream-read-n-bytes)
          (when buffer-p
            (setf (ansi-stream-in-buffer fd-stream)
                  (make-array +ansi-stream-in-buffer-length+
                              :element-type '(unsigned-byte 8)))))
        (setf input-size size)
        (setf input-type type)))

    (when output-p
      (multiple-value-bind (routine type size)
          (pick-output-routine target-type (fd-stream-buffering fd-stream))
        (unless routine
          (error "could not find any output routine for ~S buffered ~S"
                 (fd-stream-buffering fd-stream)
                 target-type))
        (setf (fd-stream-obuf-sap fd-stream) (next-available-buffer))
        (setf (fd-stream-obuf-length fd-stream) bytes-per-buffer)
        (setf (fd-stream-obuf-tail fd-stream) 0)
        (if (subtypep type 'character)
          (setf (fd-stream-out fd-stream) routine
                (fd-stream-bout fd-stream) #'ill-bout)
          (setf (fd-stream-out fd-stream)
                (or (if (eql size 1)
                      (pick-output-routine 'base-char
                                           (fd-stream-buffering fd-stream)))
                    #'ill-out)
                (fd-stream-bout fd-stream) routine))
        (setf (fd-stream-sout fd-stream)
              (if (eql size 1) #'fd-sout #'ill-out))
        (setf (fd-stream-char-pos fd-stream) 0)
        (setf output-size size)
        (setf output-type type)))

    (when (and input-size output-size
               (not (eq input-size output-size)))
      (error "Element sizes for input (~S:~S) and output (~S:~S) differ?"
             input-type input-size
             output-type output-size))
    (setf (fd-stream-element-size fd-stream)
          (or input-size output-size))

    (setf (fd-stream-element-type fd-stream)
          (cond ((equal input-type output-type)
                 input-type)
                ((null output-type)
                 input-type)
                ((null input-type)
                 output-type)
                ((subtypep input-type output-type)
                 input-type)
                ((subtypep output-type input-type)
                 output-type)
                (t
                 (error "Input type (~S) and output type (~S) are unrelated?"
                        input-type
                        output-type))))))

;;; Handle miscellaneous operations on FD-STREAM.
(defun fd-stream-misc-routine (fd-stream operation &optional arg1 arg2)
  (declare (ignore arg2))
  (case operation
    (:listen
     (or (not (eql (fd-stream-ibuf-head fd-stream)
                   (fd-stream-ibuf-tail fd-stream)))
         (fd-stream-listen fd-stream)
         (setf (fd-stream-listen fd-stream)
               (eql (sb!alien:with-alien ((read-fds (sb!alien:struct
                                                     sb!unix:fd-set)))
                      (sb!unix:fd-zero read-fds)
                      (sb!unix:fd-set (fd-stream-fd fd-stream) read-fds)
                      (sb!unix:unix-fast-select (1+ (fd-stream-fd fd-stream))
                                                (sb!alien:addr read-fds)
                                                nil nil 0 0))
                    1))))
    (:unread
     (setf (fd-stream-unread fd-stream) arg1)
     (setf (fd-stream-listen fd-stream) t))
    (:close
     (cond (arg1
            ;; We got us an abort on our hands.
            (when (fd-stream-handler fd-stream)
                  (sb!sys:remove-fd-handler (fd-stream-handler fd-stream))
                  (setf (fd-stream-handler fd-stream) nil))
            (when (and (fd-stream-file fd-stream)
                       (fd-stream-obuf-sap fd-stream))
              ;; We can't do anything unless we know what file were
              ;; dealing with, and we don't want to do anything
              ;; strange unless we were writing to the file.
              (if (fd-stream-original fd-stream)
                  ;; We have a handle on the original, just revert.
                  (multiple-value-bind (okay err)
                      (sb!unix:unix-rename (fd-stream-original fd-stream)
                                           (fd-stream-file fd-stream))
                    (unless okay
                      (simple-stream-perror
                       "couldn't restore ~S to its original contents"
                       fd-stream
                       err)))
                  ;; We can't restore the original, so nuke that puppy.
                  (multiple-value-bind (okay err)
                      (sb!unix:unix-unlink (fd-stream-file fd-stream))
                    (unless okay
                      (error 'simple-file-error
                             :pathname (fd-stream-file fd-stream)
                             :format-control
                             "~@<couldn't remove ~S: ~2I~_~A~:>"
                             :format-arguments (list (fd-stream-file fd-stream)
                                                     (strerror err))))))))
           (t
            (fd-stream-misc-routine fd-stream :finish-output)
            (when (and (fd-stream-original fd-stream)
                       (fd-stream-delete-original fd-stream))
              (multiple-value-bind (okay err)
                  (sb!unix:unix-unlink (fd-stream-original fd-stream))
                (unless okay
                  (error 'simple-file-error
                         :pathname (fd-stream-original fd-stream)
                         :format-control 
                         "~@<couldn't delete ~S during close of ~S: ~
                          ~2I~_~A~:>"
                         :format-arguments
                         (list (fd-stream-original fd-stream)
                               fd-stream
                               (strerror err))))))))
     (when (fboundp 'cancel-finalization)
       (cancel-finalization fd-stream))
     (sb!unix:unix-close (fd-stream-fd fd-stream))
     (when (fd-stream-obuf-sap fd-stream)
       (push (fd-stream-obuf-sap fd-stream) *available-buffers*)
       (setf (fd-stream-obuf-sap fd-stream) nil))
     (when (fd-stream-ibuf-sap fd-stream)
       (push (fd-stream-ibuf-sap fd-stream) *available-buffers*)
       (setf (fd-stream-ibuf-sap fd-stream) nil))
     (sb!impl::set-closed-flame fd-stream))
    (:clear-input
     (setf (fd-stream-unread fd-stream) nil)
     (setf (fd-stream-ibuf-head fd-stream) 0)
     (setf (fd-stream-ibuf-tail fd-stream) 0)
     (catch 'eof-input-catcher
       (loop
        (let ((count (sb!alien:with-alien ((read-fds (sb!alien:struct
                                                      sb!unix:fd-set)))
                       (sb!unix:fd-zero read-fds)
                       (sb!unix:fd-set (fd-stream-fd fd-stream) read-fds)
                       (sb!unix:unix-fast-select (1+ (fd-stream-fd fd-stream))
                                                 (sb!alien:addr read-fds)
                                                 nil
                                                 nil
                                                 0
                                                 0))))
          (cond ((eql count 1)
                 (frob-input fd-stream)
                 (setf (fd-stream-ibuf-head fd-stream) 0)
                 (setf (fd-stream-ibuf-tail fd-stream) 0))
                (t
                 (return t)))))))
    (:force-output
     (flush-output-buffer fd-stream))
    (:finish-output
     (flush-output-buffer fd-stream)
     (do ()
         ((null (fd-stream-output-later fd-stream)))
       (sb!sys:serve-all-events)))
    (:element-type
     (fd-stream-element-type fd-stream))
    (:interactive-p
      ;; FIXME: sb!unix:unix-isatty is undefined.
     (sb!unix:unix-isatty (fd-stream-fd fd-stream)))
    (:line-length
     80)
    (:charpos
     (fd-stream-char-pos fd-stream))
    (:file-length
     (unless (fd-stream-file fd-stream)
       ;; This is a TYPE-ERROR because ANSI's species FILE-LENGTH
       ;; "should signal an error of type TYPE-ERROR if stream is not
       ;; a stream associated with a file". Too bad there's no very
       ;; appropriate value for the EXPECTED-TYPE slot..
       (error 'simple-type-error
              :datum fd-stream
              :expected-type 'file-stream
              :format-control "~S is not a stream associated with a file."
              :format-arguments (list fd-stream)))
     (multiple-value-bind (okay dev ino mode nlink uid gid rdev size
                           atime mtime ctime blksize blocks)
         (sb!unix:unix-fstat (fd-stream-fd fd-stream))
       (declare (ignore ino nlink uid gid rdev
                        atime mtime ctime blksize blocks))
       (unless okay
         (simple-stream-perror "failed Unix fstat(2) on ~S" fd-stream dev))
       (if (zerop mode)
           nil
           (truncate size (fd-stream-element-size fd-stream)))))
    (:file-position
     (fd-stream-file-position fd-stream arg1))))

(defun fd-stream-file-position (stream &optional newpos)
  (declare (type fd-stream stream)
           (type (or index (member nil :start :end)) newpos))
  (if (null newpos)
      (sb!sys:without-interrupts
        ;; First, find the position of the UNIX file descriptor in the file.
        (multiple-value-bind (posn errno)
            (sb!unix:unix-lseek (fd-stream-fd stream) 0 sb!unix:l_incr)
          (declare (type (or index null) posn))
          (cond ((fixnump posn)
                 ;; Adjust for buffered output: If there is any output
                 ;; buffered, the *real* file position will be larger
                 ;; than reported by lseek() because lseek() obviously
                 ;; cannot take into account output we have not sent
                 ;; yet.
                 (dolist (later (fd-stream-output-later stream))
                   (incf posn (- (the index (caddr later))
                                 (the index (cadr later)))))
                 (incf posn (fd-stream-obuf-tail stream))
                 ;; Adjust for unread input: If there is any input
                 ;; read from UNIX but not supplied to the user of the
                 ;; stream, the *real* file position will smaller than
                 ;; reported, because we want to look like the unread
                 ;; stuff is still available.
                 (decf posn (- (fd-stream-ibuf-tail stream)
                               (fd-stream-ibuf-head stream)))
                 (when (fd-stream-unread stream)
                   (decf posn))
                 ;; Divide bytes by element size.
                 (truncate posn (fd-stream-element-size stream)))
                ((eq errno sb!unix:espipe)
                 nil)
                (t
                 (sb!sys:with-interrupts
                   (simple-stream-perror "failure in Unix lseek() on ~S"
                                         stream
                                         errno))))))
      (let ((offset 0) origin)
        (declare (type index offset))
        ;; Make sure we don't have any output pending, because if we
        ;; move the file pointer before writing this stuff, it will be
        ;; written in the wrong location.
        (flush-output-buffer stream)
        (do ()
            ((null (fd-stream-output-later stream)))
          (sb!sys:serve-all-events))
        ;; Clear out any pending input to force the next read to go to
        ;; the disk.
        (setf (fd-stream-unread stream) nil)
        (setf (fd-stream-ibuf-head stream) 0)
        (setf (fd-stream-ibuf-tail stream) 0)
        ;; Trash cached value for listen, so that we check next time.
        (setf (fd-stream-listen stream) nil)
        ;; Now move it.
        (cond ((eq newpos :start)
               (setf offset 0 origin sb!unix:l_set))
              ((eq newpos :end)
               (setf offset 0 origin sb!unix:l_xtnd))
              ((typep newpos 'index)
               (setf offset (* newpos (fd-stream-element-size stream))
                     origin sb!unix:l_set))
              (t
               (error "invalid position given to FILE-POSITION: ~S" newpos)))
        (multiple-value-bind (posn errno)
            (sb!unix:unix-lseek (fd-stream-fd stream) offset origin)
          (cond ((typep posn 'fixnum)
                 t)
                ((eq errno sb!unix:espipe)
                 nil)
                (t
                 (simple-stream-perror "error in Unix lseek() on ~S"
                                       stream
                                       errno)))))))
\f
;;;; creation routines (MAKE-FD-STREAM and OPEN)

;;; Create a stream for the given Unix file descriptor.
;;;
;;; If INPUT is non-NIL, allow input operations. If OUTPUT is non-nil,
;;; allow output operations. If neither INPUT nor OUTPUT is specified,
;;; default to allowing input.
;;;
;;; ELEMENT-TYPE indicates the element type to use (as for OPEN).
;;;
;;; BUFFERING indicates the kind of buffering to use.
;;;
;;; TIMEOUT (if true) is the number of seconds to wait for input. If
;;; NIL (the default), then wait forever. When we time out, we signal
;;; IO-TIMEOUT.
;;;
;;; FILE is the name of the file (will be returned by PATHNAME).
;;;
;;; NAME is used to identify the stream when printed.
(defun make-fd-stream (fd
                       &key
                       (input nil input-p)
                       (output nil output-p)
                       (element-type 'base-char)
                       (buffering :full)
                       timeout
                       file
                       original
                       delete-original
                       pathname
                       input-buffer-p
                       (name (if file
                                 (format nil "file ~S" file)
                                 (format nil "descriptor ~W" fd)))
                       auto-close)
  (declare (type index fd) (type (or index null) timeout)
           (type (member :none :line :full) buffering))
  (cond ((not (or input-p output-p))
         (setf input t))
        ((not (or input output))
         (error "File descriptor must be opened either for input or output.")))
  (let ((stream (%make-fd-stream :fd fd
                                 :name name
                                 :file file
                                 :original original
                                 :delete-original delete-original
                                 :pathname pathname
                                 :buffering buffering
                                 :timeout timeout)))
    (set-fd-stream-routines stream element-type input output input-buffer-p)
    (when (and auto-close (fboundp 'finalize))
      (finalize stream
                (lambda ()
                  (sb!unix:unix-close fd)
                  #!+sb-show
                  (format *terminal-io* "** closed file descriptor ~W **~%"
                          fd))))
    stream))

;;; Pick a name to use for the backup file for the :IF-EXISTS
;;; :RENAME-AND-DELETE and :RENAME options.
(defun pick-backup-name (name)
  (declare (type simple-string name))
  (concatenate 'simple-string name ".bak"))

;;; Ensure that the given arg is one of the given list of valid
;;; things. Allow the user to fix any problems.
(defun ensure-one-of (item list what)
  (unless (member item list)
    (error 'simple-type-error
           :datum item
           :expected-type `(member ,@list)
           :format-control "~@<~S is ~_invalid for ~S; ~_need one of~{ ~S~}~:>"
           :format-arguments (list item what list))))

;;; Rename NAMESTRING to ORIGINAL. First, check whether we have write
;;; access, since we don't want to trash unwritable files even if we
;;; technically can. We return true if we succeed in renaming.
(defun rename-the-old-one (namestring original)
  (unless (sb!unix:unix-access namestring sb!unix:w_ok)
    (error "~@<The file ~2I~_~S ~I~_is not writable.~:>" namestring))
  (multiple-value-bind (okay err) (sb!unix:unix-rename namestring original)
    (if okay
        t
        (error 'simple-file-error
               :pathname namestring
               :format-control 
               "~@<couldn't rename ~2I~_~S ~I~_to ~2I~_~S: ~4I~_~A~:>"
               :format-arguments (list namestring original (strerror err))))))

(defun open (filename
             &key
             (direction :input)
             (element-type 'base-char)
             (if-exists nil if-exists-given)
             (if-does-not-exist nil if-does-not-exist-given)
             (external-format :default)
             &aux ; Squelch assignment warning.
             (direction direction)
             (if-does-not-exist if-does-not-exist)
             (if-exists if-exists))
  #!+sb-doc
  "Return a stream which reads from or writes to FILENAME.
  Defined keywords:
   :DIRECTION - one of :INPUT, :OUTPUT, :IO, or :PROBE
   :ELEMENT-TYPE - the type of object to read or write, default BASE-CHAR
   :IF-EXISTS - one of :ERROR, :NEW-VERSION, :RENAME, :RENAME-AND-DELETE,
                       :OVERWRITE, :APPEND, :SUPERSEDE or NIL
   :IF-DOES-NOT-EXIST - one of :ERROR, :CREATE or nil
  See the manual for details."

  (unless (eq external-format :default)
    (error "Any external format other than :DEFAULT isn't recognized."))

  ;; First, make sure that DIRECTION is valid.
  (ensure-one-of direction
                 '(:input :output :io :probe)
                 :direction)

  ;; Calculate useful stuff.
  (multiple-value-bind (input output mask)
      (case direction
        (:input  (values   t nil sb!unix:o_rdonly))
        (:output (values nil   t sb!unix:o_wronly))
        (:io     (values   t   t sb!unix:o_rdwr))
        (:probe  (values   t nil sb!unix:o_rdonly)))
    (declare (type index mask))
    (let* ((pathname (merge-pathnames filename))
           (namestring
            (cond ((unix-namestring pathname input))
                  ((and input (eq if-does-not-exist :create))
                   (unix-namestring pathname nil)))))
      ;; Process if-exists argument if we are doing any output.
      (cond (output
             (unless if-exists-given
               (setf if-exists
                     (if (eq (pathname-version pathname) :newest)
                         :new-version
                         :error)))
             (ensure-one-of if-exists
                            '(:error :new-version :rename
                                     :rename-and-delete :overwrite
                                     :append :supersede nil)
                            :if-exists)
             (case if-exists
               ((:error nil)
                (setf mask (logior mask sb!unix:o_excl)))
               ((:rename :rename-and-delete)
                (setf mask (logior mask sb!unix:o_creat)))
               ((:new-version :supersede)
                (setf mask (logior mask sb!unix:o_trunc)))
               (:append
                (setf mask (logior mask sb!unix:o_append)))))
            (t
             (setf if-exists :ignore-this-arg)))

      (unless if-does-not-exist-given
        (setf if-does-not-exist
              (cond ((eq direction :input) :error)
                    ((and output
                          (member if-exists '(:overwrite :append)))
                     :error)
                    ((eq direction :probe)
                     nil)
                    (t
                     :create))))
      (ensure-one-of if-does-not-exist
                     '(:error :create nil)
                     :if-does-not-exist)
      (if (eq if-does-not-exist :create)
        (setf mask (logior mask sb!unix:o_creat)))

      (let ((original (if (member if-exists
                                  '(:rename :rename-and-delete))
                          (pick-backup-name namestring)))
            (delete-original (eq if-exists :rename-and-delete))
            (mode #o666))
        (when original
          ;; We are doing a :RENAME or :RENAME-AND-DELETE. Determine
          ;; whether the file already exists, make sure the original
          ;; file is not a directory, and keep the mode.
          (let ((exists
                 (and namestring
                      (multiple-value-bind (okay err/dev inode orig-mode)
                          (sb!unix:unix-stat namestring)
                        (declare (ignore inode)
                                 (type (or index null) orig-mode))
                        (cond
                         (okay
                          (when (and output (= (logand orig-mode #o170000)
                                               #o40000))
                            (error 'simple-file-error
                                   :pathname namestring
                                   :format-control
                                   "can't open ~S for output: is a directory"
                                   :format-arguments (list namestring)))
                          (setf mode (logand orig-mode #o777))
                          t)
                         ((eql err/dev sb!unix:enoent)
                          nil)
                         (t
                          (simple-file-perror "can't find ~S"
                                              namestring
                                              err/dev)))))))
            (unless (and exists
                         (rename-the-old-one namestring original))
              (setf original nil)
              (setf delete-original nil)
              ;; In order to use :SUPERSEDE instead, we have to make
              ;; sure SB!UNIX:O_CREAT corresponds to
              ;; IF-DOES-NOT-EXIST. SB!UNIX:O_CREAT was set before
              ;; because of IF-EXISTS being :RENAME.
              (unless (eq if-does-not-exist :create)
                (setf mask
                      (logior (logandc2 mask sb!unix:o_creat)
                              sb!unix:o_trunc)))
              (setf if-exists :supersede))))
        
        ;; Now we can try the actual Unix open(2).
        (multiple-value-bind (fd errno)
            (if namestring
                (sb!unix:unix-open namestring mask mode)
                (values nil sb!unix:enoent))
          (labels ((open-error (format-control &rest format-arguments)
                     (error 'simple-file-error
                            :pathname pathname
                            :format-control format-control
                            :format-arguments format-arguments))
                   (vanilla-open-error ()
                     (simple-file-perror "error opening ~S" pathname errno)))
            (cond ((numberp fd)
                   (case direction
                     ((:input :output :io)
                      (make-fd-stream fd
                                      :input input
                                      :output output
                                      :element-type element-type
                                      :file namestring
                                      :original original
                                      :delete-original delete-original
                                      :pathname pathname
                                      :input-buffer-p t
                                      :auto-close t))
                     (:probe
                      (let ((stream
                             (%make-fd-stream :name namestring
                                              :fd fd
                                              :pathname pathname
                                              :element-type element-type)))
                        (close stream)
                        stream))))
                  ((eql errno sb!unix:enoent)
                   (case if-does-not-exist
                     (:error (vanilla-open-error))
                     (:create
                      (open-error "~@<The path ~2I~_~S ~I~_does not exist.~:>"
                                  pathname))
                     (t nil)))
                  ((and (eql errno sb!unix:eexist) if-exists)
                   nil)
                  (t
                   (vanilla-open-error)))))))))
\f
;;;; initialization

;;; the stream connected to the controlling terminal, or NIL if there is none
(defvar *tty*)

;;; the stream connected to the standard input (file descriptor 0)
(defvar *stdin*)

;;; the stream connected to the standard output (file descriptor 1)
(defvar *stdout*)

;;; the stream connected to the standard error output (file descriptor 2)
(defvar *stderr*)

;;; This is called when the cold load is first started up, and may also
;;; be called in an attempt to recover from nested errors.
(defun stream-cold-init-or-reset ()
  (stream-reinit)
  (setf *terminal-io* (make-synonym-stream '*tty*))
  (setf *standard-output* (make-synonym-stream '*stdout*))
  (setf *standard-input*
        (#!-high-security
         ;; FIXME: Why is *STANDARD-INPUT* a TWO-WAY-STREAM? ANSI says
         ;; it's an input stream.
         make-two-way-stream
         #!+high-security
         %make-two-way-stream (make-synonym-stream '*stdin*)
                             *standard-output*))
  (setf *error-output* (make-synonym-stream '*stderr*))
  (setf *query-io* (make-synonym-stream '*terminal-io*))
  (setf *debug-io* *query-io*)
  (setf *trace-output* *standard-output*)
  (values))

;;; This is called whenever a saved core is restarted.
(defun stream-reinit ()
  (setf *available-buffers* nil)
  (setf *stdin*
        (make-fd-stream 0 :name "standard input" :input t :buffering :line))
  (setf *stdout*
        (make-fd-stream 1 :name "standard output" :output t :buffering :line))
  (setf *stderr*
        (make-fd-stream 2 :name "standard error" :output t :buffering :line))
  (let ((tty (sb!unix:unix-open "/dev/tty" sb!unix:o_rdwr #o666)))
    (if tty
        (setf *tty*
              (make-fd-stream tty
                              :name "the terminal"
                              :input t
                              :output t
                              :buffering :line
                              :auto-close t))
        (setf *tty* (make-two-way-stream *stdin* *stdout*))))
  (values))
\f
;;;; miscellany

;;; the Unix way to beep
(defun beep (stream)
  (write-char (code-char bell-char-code) stream)
  (finish-output stream))

;;; This is kind of like FILE-POSITION, but is an internal hack used
;;; by the filesys stuff to get and set the file name.
;;;
;;; FIXME: misleading name, screwy interface
(defun file-name (stream &optional new-name)
  (when (typep stream 'fd-stream)
      (cond (new-name
             (setf (fd-stream-pathname stream) new-name)
             (setf (fd-stream-file stream)
                   (unix-namestring new-name nil))
             t)
            (t
             (fd-stream-pathname stream)))))
\f
;;;; international character support (which is trivial for our simple
;;;; character sets)

;;;; (Those who do Lisp only in English might not remember that ANSI
;;;; requires these functions to be exported from package
;;;; COMMON-LISP.)

(defun file-string-length (stream object)
  (declare (type (or string character) object) (type file-stream stream))
  #!+sb-doc
  "Return the delta in STREAM's FILE-POSITION that would be caused by writing
   OBJECT to STREAM. Non-trivial only in implementations that support
   international character sets."
  (declare (ignore stream))
  (etypecase object
    (character 1)
    (string (length object))))

(defun stream-external-format (stream)
  (declare (type file-stream stream) (ignore stream))
  #!+sb-doc
  "Return :DEFAULT."
  :default)