src/code/target-stream.lisp

   1 ;;;; os-independent stream functions requiring reader machinery
   2
   3 ;;;; This software is part of the SBCL system. See the README file for
   4 ;;;; more information.
   5 ;;;;
   6 ;;;; This software is derived from the CMU CL system, which was
   7 ;;;; written at Carnegie Mellon University and released into the
   8 ;;;; public domain. The software is in the public domain and is
   9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
  10 ;;;; files for more information.
  11
  12 (in-package "SB!IMPL")
  13
  14 ;;; In the interest of ``once and only once'' this macro contains the
  15 ;;; framework necessary to implement a peek-char function, which has
  16 ;;; two special-cases (one for gray streams and one for echo streams)
  17 ;;; in addition to the normal case.
  18 ;;;
  19 ;;; All arguments are forms which will be used for a specific purpose
  20 ;;; PEEK-TYPE - the current peek-type as defined by ANSI CL
  21 ;;; EOF-RESULT - the eof-value argument to peek-char
  22 ;;; CHAR-VAR - the variable which will be used to store the current character
  23 ;;; READ-FORM - the form which will be used to read a character
  24 ;;; EOF-VALUE - the result returned from READ-FORM when hitting eof
  25 ;;; UNREAD-FORM - ditto for unread-char
  26 ;;; SKIPPED-CHAR-FORM - the form to execute when skipping a character
  27 ;;; EOF-DETECTED-FORM - the form to execute when EOF has been detected
  28 ;;;                     (this will default to EOF-RESULT)
  29 (sb!xc:defmacro generalized-peeking-mechanism
  30     (peek-type eof-value char-var read-form read-eof unread-form
  31      &optional (skipped-char-form nil) (eof-detected-form nil))
  32   `(let ((,char-var ,read-form))
  33     (cond ((eql ,char-var ,read-eof)
  34            ,(if eof-detected-form
  35                 eof-detected-form
  36                 eof-value))
  37           ((characterp ,peek-type)
  38            (do ((,char-var ,char-var ,read-form))
  39                ((or (eql ,char-var ,read-eof)
  40                     (char= ,char-var ,peek-type))
  41                 (cond ((eql ,char-var ,read-eof)
  42                        ,(if eof-detected-form
  43                             eof-detected-form
  44                             eof-value))
  45                       (t ,unread-form
  46                          ,char-var)))
  47              ,skipped-char-form))
  48           ((eql ,peek-type t)
  49            (do ((,char-var ,char-var ,read-form))
  50                ((or (eql ,char-var ,read-eof)
  51                     (not (whitespace[2]p ,char-var)))
  52                 (cond ((eql ,char-var ,read-eof)
  53                        ,(if eof-detected-form
  54                             eof-detected-form
  55                             eof-value))
  56                       (t ,unread-form
  57                          ,char-var)))
  58              ,skipped-char-form))
  59           ((null ,peek-type)
  60            ,unread-form
  61            ,char-var)
  62           (t
  63            (bug "Impossible case reached in PEEK-CHAR")))))
  64
  65 ;;; rudi (2004-08-09): There was an inline declaration for read-char,
  66 ;;; unread-char, read-byte, listen here that was removed because these
  67 ;;; functions are redefined when simple-streams are loaded.
  68
  69 #!-sb-fluid (declaim (inline ansi-stream-peek-char))
  70 (defun ansi-stream-peek-char (peek-type stream eof-error-p eof-value
  71                               recursive-p)
  72   (cond ((typep stream 'echo-stream)
  73          (echo-misc stream
  74                     :peek-char
  75                     peek-type
  76                     (list eof-error-p eof-value)))
  77         (t
  78          (generalized-peeking-mechanism
  79           peek-type eof-value char
  80           (ansi-stream-read-char stream eof-error-p :eof recursive-p)
  81           :eof
  82           (ansi-stream-unread-char char stream)))))
  83
  84 (defun peek-char (&optional (peek-type nil)
  85                             (stream *standard-input*)
  86                             (eof-error-p t)
  87                             eof-value
  88                             recursive-p)
  89   (the (or character boolean) peek-type)
  90   (let ((stream (in-synonym-of stream)))
  91     (if (ansi-stream-p stream)
  92         (ansi-stream-peek-char peek-type stream eof-error-p eof-value
  93                                recursive-p)
  94         ;; by elimination, must be Gray streams FUNDAMENTAL-STREAM
  95         (generalized-peeking-mechanism
  96          peek-type :eof char
  97          (if (null peek-type)
  98              (stream-peek-char stream)
  99              (stream-read-char stream))
 100          :eof
 101          (if (null peek-type)
 102              ()
 103              (stream-unread-char stream char))
 104          ()
 105          (eof-or-lose stream eof-error-p eof-value)))))
 106
 107 (defun echo-misc (stream operation &optional arg1 arg2)
 108   (let* ((in (two-way-stream-input-stream stream))
 109          (out (two-way-stream-output-stream stream)))
 110     (case operation
 111       (:listen
 112        (or (not (null (echo-stream-unread-stuff stream)))
 113            (if (ansi-stream-p in)
 114                (or (/= (the fixnum (ansi-stream-in-index in))
 115                        +ansi-stream-in-buffer-length+)
 116                    (funcall (ansi-stream-misc in) in :listen))
 117                (stream-misc-dispatch in :listen))))
 118       (:unread (push arg1 (echo-stream-unread-stuff stream)))
 119       (:element-type
 120        (let ((in-type (stream-element-type in))
 121              (out-type (stream-element-type out)))
 122          (if (equal in-type out-type)
 123              in-type `(and ,in-type ,out-type))))
 124       (:close
 125        (set-closed-flame stream))
 126       (:peek-char
 127        ;; For the special case of peeking into an echo-stream
 128        ;; arg1 is PEEK-TYPE, arg2 is (EOF-ERROR-P EOF-VALUE)
 129        ;; returns peeked-char, eof-value, or errors end-of-file
 130        ;;
 131        ;; Note: This code could be moved into PEEK-CHAR if desired.
 132        ;; I am unsure whether this belongs with echo-streams because it is
 133        ;; echo-stream specific, or PEEK-CHAR because it is peeking code.
 134        ;; -- mrd 2002-11-18
 135        ;;
 136        ;; UNREAD-CHAR-P indicates whether the current character was one
 137        ;; that was previously unread.  In that case, we need to ensure that
 138        ;; the semantics for UNREAD-CHAR are held; the character should
 139        ;; not be echoed again.
 140        (let ((unread-char-p nil))
 141          (flet ((outfn (c)
 142                   (unless unread-char-p
 143                     (if (ansi-stream-p out)
 144                         (funcall (ansi-stream-out out) out c)
 145                         ;; gray-stream
 146                         (stream-write-char out c))))
 147                 (infn ()
 148                   ;; Obtain input from unread buffer or input stream,
 149                   ;; and set the flag appropriately.
 150                   (cond ((not (null (echo-stream-unread-stuff stream)))
 151                          (setf unread-char-p t)
 152                          (pop (echo-stream-unread-stuff stream)))
 153                         (t
 154                          (setf unread-char-p nil)
 155                          (read-char in (first arg2) :eof)))))
 156            (generalized-peeking-mechanism
 157             arg1 (second arg2) char
 158             (infn)
 159             :eof
 160             (unread-char char in)
 161             (outfn char)))))
 162       (t
 163        (or (if (ansi-stream-p in)
 164                (funcall (ansi-stream-misc in) in operation arg1 arg2)
 165                (stream-misc-dispatch in operation arg1 arg2))
 166            (if (ansi-stream-p out)
 167                (funcall (ansi-stream-misc out) out operation arg1 arg2)
 168                (stream-misc-dispatch out operation arg1 arg2)))))))
 169