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;;; -*- Log: code.log; Package: LISP -*-
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;;; **********************************************************************
;;; This code was written as part of the CMU Common Lisp project at
;;; Carnegie Mellon University, and has been placed in the public domain.
;;;
(ext:file-comment
  "$Header: /Volumes/share2/src/cmucl/cvs2git/cvsroot/src/code/fd-stream.lisp,v 1.82 2005/02/21 17:14:28 rtoy Exp $")
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;;; **********************************************************************
;;;
;;; Streams for UNIX file descriptors.
;;;
;;; Written by William Lott, July 1989 - January 1990.
;;; Some tuning by Rob MacLachlan.
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;;; 
;;; **********************************************************************


(in-package "SYSTEM")

(export '(fd-stream fd-stream-p fd-stream-fd make-fd-stream
          io-timeout beep *beep-function* output-raw-bytes
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	  *tty* *stdin* *stdout* *stderr*))


(in-package "EXTENSIONS")

(export '(*backup-extension*))


(in-package "LISP")

(export '(file-stream file-string-length))
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;;;; Buffer manipulation routines.

(defvar *available-buffers* ()
  "List of available buffers.  Each buffer is an sap pointing to
  bytes-per-buffer of memory.")
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(defconstant bytes-per-buffer (* 4 1024)
  "Number of bytes per buffer.")

;; This limit is rather arbitrary
(defconstant max-stream-element-size 1024
  "The maximum supported byte size for a stream element-type.")

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;;; NEXT-AVAILABLE-BUFFER -- Internal.
;;;
;;; Returns the next available buffer, creating one if necessary.
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;;;
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(declaim (inline next-available-buffer))
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;;;
(defun next-available-buffer ()
  (if *available-buffers*
      (pop *available-buffers*)
      (allocate-system-memory bytes-per-buffer)))
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;;;; The FD-STREAM structure.

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;;;; Superclass defined by the ANSI Spec
(defstruct (file-stream
	     (:include lisp-stream)
	     (:constructor nil)
	     (:copier nil)))

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(defstruct (fd-stream
	    (:print-function %print-fd-stream)
	    (:constructor %make-fd-stream)
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	    (:include file-stream
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		      (misc #'fd-stream-misc-routine)))

  (name nil)		      ; The name of this stream
  (file nil)		      ; The file this stream is for
  ;;
  ;; The backup file namestring for the old file, for :if-exists :rename or
  ;; :rename-and-delete.
  (original nil :type (or simple-string null))
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  (delete-original nil)	      ; for :if-exists :rename-and-delete
  ;;
  ;;; Number of bytes per element.
  (element-size 1 :type index)
  (element-type 'base-char)   ; The type of element being transfered.
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  (fd -1 :type fixnum)	      ; The file descriptor
  ;;
  ;; 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))
  ;;
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  ;; 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)
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  ;; The output buffer.
  (obuf-sap nil :type (or system-area-pointer null))
  (obuf-length nil :type (or index null))
  (obuf-tail 0 :type index)
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  ;; 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)))
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(defun %print-fd-stream (fd-stream stream depth)
  (declare (ignore depth) (stream stream))
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  (format stream "#<Stream for ~A>"
	  (fd-stream-name fd-stream)))


(define-condition io-timeout (stream-error)
  ((direction :reader io-timeout-direction :initarg :direction))
     (declare (stream stream))
     (format stream "Timeout ~(~A~)ing ~S."
	     (io-timeout-direction condition)
	     (stream-error-stream condition)))))

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;;;; Output routines and related noise.

(defvar *output-routines* ()
  "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.")

;;; DO-OUTPUT-LATER -- internal
;;;
;;;   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
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;;; 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))
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	 (length (- end start)))
    (declare (type index start end length))
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    (multiple-value-bind
	(count errno)
	(unix:unix-write (fd-stream-fd stream)
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			 base
			 start
			 length)
      (cond ((not count)
	     (if (= errno unix:ewouldblock)
		 (error "Write would have blocked, but SERVER told us to go.")
		 (error "While writing ~S: ~A"
			stream (unix:get-unix-error-msg errno))))
	    ((eql count length) ; Hot damn, it worked.
	     (when reuse-sap
	       (push base *available-buffers*)))
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	    ((not (null count)) ; Sorta worked.
	     (push (list base
			 (the index (+ start count))
		   (fd-stream-output-later stream))))))
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  (unless (fd-stream-output-later stream)
    (system:remove-fd-handler (fd-stream-handler stream))
    (setf (fd-stream-handler stream) nil)))

;;; OUTPUT-LATER -- internal
;;;
;;;   Arrange to output the string when we can write on the file descriptor.
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;;;
(defun output-later (stream base start end reuse-sap)
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  (cond ((null (fd-stream-output-later stream))
	 (setf (fd-stream-output-later stream)
	       (list (list base start end reuse-sap)))
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	 (setf (fd-stream-handler stream)
	       (system: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
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    (let ((new-buffer (next-available-buffer)))
      (setf (fd-stream-obuf-sap stream) new-buffer)
      (setf (fd-stream-obuf-length stream) bytes-per-buffer)))) 
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