;;;; 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)

;;;; 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)))

;;;; 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))))

;;;; 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 do-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))
					  (do-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 do-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)
      (do-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)
	     (do-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)
				 (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
	     (do-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
	   (do-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))))))

;;;; 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 do-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))
		   (do-input stream))
		 (simple-stream-perror "couldn't read from ~S" stream errno)))
	    ((zerop count)
	     (setf (fd-stream-listen stream) :eof)
	     (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 DO-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))
	 (do-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))

;;;; 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)
		 (do-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)))))))

;;;; 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 ~D" 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 ~D **~%"
			  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 do-old-rename (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 (pathname 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
			 (do-old-rename 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)))))))))

;;;; 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))

;;;; 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)))))

;;;; 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)