1 ;;;; os-independent stream functions requiring reader machinery
3 ;;;; This software is part of the SBCL system. See the README file for
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.
12 (in-package "SB!IMPL")
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.
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-VALUE - 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 ;;; UNREAD-FORM - ditto for unread-char
25 ;;; SKIPPED-CHAR-FORM - the form to execute when skipping a character
26 ;;; EOF-DETECTED-FORM - the form to execute when EOF has been detected
27 ;;; (this will default to CHAR-VAR)
28 (eval-when (:compile-toplevel :execute)
29 (sb!xc:defmacro generalized-peeking-mechanism
30 (peek-type eof-value char-var read-form unread-form
31 &optional (skipped-char-form nil) (eof-detected-form nil))
32 `(let ((,char-var ,read-form))
33 (cond ((eql ,char-var ,eof-value)
34 ,(if eof-detected-form
37 ((characterp ,peek-type)
38 (do ((,char-var ,char-var ,read-form))
39 ((or (eql ,char-var ,eof-value)
40 (char= ,char-var ,peek-type))
41 (cond ((eql ,char-var ,eof-value)
42 ,(if eof-detected-form
49 (do ((,char-var ,char-var ,read-form))
50 ((or (eql ,char-var ,eof-value)
51 (not (whitespacep ,char-var)))
52 (cond ((eql ,char-var ,eof-value)
53 ,(if eof-detected-form
63 (bug "Impossible case reached in PEEK-CHAR"))))))
65 ;;; We proclaim them INLINE here, then proclaim them MAYBE-INLINE at EOF,
66 ;;; so, except in this file, they are not inline by default, but they can be.
67 #!-sb-fluid (declaim (inline read-char unread-char read-byte listen))
69 (defun peek-char (&optional (peek-type nil)
70 (stream *standard-input*)
74 (declare (ignore recursive-p))
75 (the (or character boolean) peek-type)
76 (let ((stream (in-synonym-of stream)))
77 (cond ((typep stream 'echo-stream)
81 (list eof-error-p eof-value)))
82 ((ansi-stream-p stream)
83 (generalized-peeking-mechanism
84 peek-type eof-value char
85 (read-char stream eof-error-p eof-value)
86 (unread-char char stream)))
88 ;; by elimination, must be Gray streams FUNDAMENTAL-STREAM
89 (generalized-peeking-mechanism
92 (stream-peek-char stream)
93 (stream-read-char stream))
96 (stream-unread-char stream char))
98 (eof-or-lose stream eof-error-p eof-value))))))
100 (defun echo-misc (stream operation &optional arg1 arg2)
101 (let* ((in (two-way-stream-input-stream stream))
102 (out (two-way-stream-output-stream stream)))
105 (or (not (null (echo-stream-unread-stuff stream)))
106 (if (ansi-stream-p in)
107 (or (/= (the fixnum (ansi-stream-in-index in))
108 +ansi-stream-in-buffer-length+)
109 (funcall (ansi-stream-misc in) in :listen))
110 (stream-misc-dispatch in :listen))))
111 (:unread (push arg1 (echo-stream-unread-stuff stream)))
113 (let ((in-type (stream-element-type in))
114 (out-type (stream-element-type out)))
115 (if (equal in-type out-type)
116 in-type `(and ,in-type ,out-type))))
118 (set-closed-flame stream))
120 ;; For the special case of peeking into an echo-stream
121 ;; arg1 is PEEK-TYPE, arg2 is (EOF-ERROR-P EOF-VALUE)
122 ;; returns peeked-char, eof-value, or errors end-of-file
124 ;; Note: This code could be moved into PEEK-CHAR if desired.
125 ;; I am unsure whether this belongs with echo-streams because it is
126 ;; echo-stream specific, or PEEK-CHAR because it is peeking code.
129 ;; UNREAD-CHAR-P indicates whether the current character was one
130 ;; that was previously unread. In that case, we need to ensure that
131 ;; the semantics for UNREAD-CHAR are held; the character should
132 ;; not be echoed again.
133 (let ((unread-char-p nil))
135 (unless unread-char-p
136 (if (ansi-stream-p out)
137 (funcall (ansi-stream-out out) out c)
139 (stream-write-char out c))))
141 ;; Obtain input from unread buffer or input stream,
142 ;; and set the flag appropriately.
143 (cond ((not (null (echo-stream-unread-stuff stream)))
144 (setf unread-char-p t)
145 (pop (echo-stream-unread-stuff stream)))
147 (setf unread-char-p nil)
148 (read-char in (first arg2) (second arg2))))))
149 (generalized-peeking-mechanism
150 arg1 (second arg2) char
152 (unread-char char in)
155 (or (if (ansi-stream-p in)
156 (funcall (ansi-stream-misc in) in operation arg1 arg2)
157 (stream-misc-dispatch in operation arg1 arg2))
158 (if (ansi-stream-p out)
159 (funcall (ansi-stream-misc out) out operation arg1 arg2)
160 (stream-misc-dispatch out operation arg1 arg2)))))))
162 (declaim (maybe-inline read-char unread-char read-byte listen))