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1 | ;;;; buffered-input.scm --- construct a port from a buffered input reader |
2 | ;;;; | |
3 | ;;;; Copyright (C) 2001 Free Software Foundation, Inc. | |
4 | ;;;; | |
5 | ;;;; This program is free software; you can redistribute it and/or modify | |
6 | ;;;; it under the terms of the GNU General Public License as published by | |
7 | ;;;; the Free Software Foundation; either version 2, or (at your option) | |
8 | ;;;; any later version. | |
9 | ;;;; | |
10 | ;;;; This program is distributed in the hope that it will be useful, | |
11 | ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | ;;;; GNU General Public License for more details. | |
14 | ;;;; | |
15 | ;;;; You should have received a copy of the GNU General Public License | |
16 | ;;;; along with this software; see the file COPYING. If not, write to | |
17 | ;;;; the Free Software Foundation, Inc., 59 Temple Place, Suite 330, | |
18 | ;;;; Boston, MA 02111-1307 USA | |
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19 | ;;;; |
20 | ;;;; As a special exception, the Free Software Foundation gives permission | |
21 | ;;;; for additional uses of the text contained in its release of GUILE. | |
22 | ;;;; | |
23 | ;;;; The exception is that, if you link the GUILE library with other files | |
24 | ;;;; to produce an executable, this does not by itself cause the | |
25 | ;;;; resulting executable to be covered by the GNU General Public License. | |
26 | ;;;; Your use of that executable is in no way restricted on account of | |
27 | ;;;; linking the GUILE library code into it. | |
28 | ;;;; | |
29 | ;;;; This exception does not however invalidate any other reasons why | |
30 | ;;;; the executable file might be covered by the GNU General Public License. | |
31 | ;;;; | |
32 | ;;;; This exception applies only to the code released by the | |
33 | ;;;; Free Software Foundation under the name GUILE. If you copy | |
34 | ;;;; code from other Free Software Foundation releases into a copy of | |
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40 | ;;;; If you write modifications of your own for GUILE, it is your choice | |
41 | ;;;; whether to permit this exception to apply to your modifications. | |
42 | ;;;; If you do not wish that, delete this exception notice. | |
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43 | |
44 | (define-module (ice-9 buffered-input) | |
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45 | #:export (make-buffered-input-port |
46 | make-line-buffered-input-port | |
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47 | set-buffered-input-continuation?!)) |
48 | ||
49 | ;; @code{buffered-input-continuation?} is a property of the ports | |
50 | ;; created by @code{make-line-buffered-input-port} that stores the | |
51 | ;; read continuation flag for each such port. | |
52 | (define buffered-input-continuation? (make-object-property)) | |
53 | ||
54 | (define (set-buffered-input-continuation?! port val) | |
55 | "Set the read continuation flag for @var{port} to @var{val}. | |
56 | ||
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57 | See @code{make-buffered-input-port} for the meaning and use of this |
58 | flag." | |
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59 | (set! (buffered-input-continuation? port) val)) |
60 | ||
451d273a | 61 | (define (make-buffered-input-port reader) |
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62 | "Construct a line-buffered input port from the specified @var{reader}. |
63 | @var{reader} should be a procedure of one argument that somehow reads | |
451d273a | 64 | a chunk of input and returns it as a string. |
9155e458 | 65 | |
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66 | The port created by @code{make-buffered-input-port} does @emph{not} |
67 | interpolate any additional characters between the strings returned by | |
68 | @var{reader}. | |
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69 | |
70 | @var{reader} should take a boolean @var{continuation?} argument. | |
71 | @var{continuation?} indicates whether @var{reader} is being called to | |
72 | start a logically new read operation (in which case | |
73 | @var{continuation?} is @code{#f}) or to continue a read operation for | |
74 | which some input has already been read (in which case | |
75 | @var{continuation?} is @code{#t}). Some @var{reader} implementations | |
76 | use the @var{continuation?} argument to determine what prompt to | |
77 | display to the user. | |
78 | ||
79 | The new/continuation distinction is largely an application-level | |
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80 | concept: @code{set-buffered-input-continuation?!} allows an |
81 | application to specify when a read operation is considered to be new. | |
82 | But note that if there is non-whitespace data already buffered in the | |
83 | port when a new read operation starts, this data will be read before | |
84 | the first call to @var{reader}, and so @var{reader} will be called | |
85 | with @var{continuation?} set to @code{#t}." | |
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86 | (let ((read-string "") |
87 | (string-index -1)) | |
88 | (letrec ((get-character | |
89 | (lambda () | |
90 | (cond | |
91 | ((eof-object? read-string) | |
92 | read-string) | |
93 | ((>= string-index (string-length read-string)) | |
94 | (set! string-index -1) | |
451d273a | 95 | (get-character)) |
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96 | ((= string-index -1) |
97 | (set! read-string (reader (buffered-input-continuation? port))) | |
98 | (set! string-index 0) | |
99 | (if (not (eof-object? read-string)) | |
100 | (get-character) | |
101 | read-string)) | |
102 | (else | |
103 | (let ((res (string-ref read-string string-index))) | |
104 | (set! string-index (+ 1 string-index)) | |
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105 | (if (not (char-whitespace? res)) |
106 | (set! (buffered-input-continuation? port) #t)) | |
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107 | res))))) |
108 | (port #f)) | |
109 | (set! port (make-soft-port (vector #f #f #f get-character #f) "r")) | |
110 | (set! (buffered-input-continuation? port) #f) | |
111 | port))) | |
112 | ||
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113 | (define (make-line-buffered-input-port reader) |
114 | "Construct a line-buffered input port from the specified @var{reader}. | |
115 | @var{reader} should be a procedure of one argument that somehow reads | |
116 | a line of input and returns it as a string @emph{without} the | |
117 | terminating newline character. | |
118 | ||
119 | The port created by @code{make-line-buffered-input-port} automatically | |
120 | interpolates a newline character after each string returned by | |
121 | @var{reader}. | |
122 | ||
123 | @var{reader} should take a boolean @var{continuation?} argument. For | |
124 | the meaning and use of this argument, see | |
125 | @code{make-buffered-input-port}." | |
126 | (make-buffered-input-port (lambda (continuation?) | |
127 | (let ((str (reader continuation?))) | |
128 | (if (eof-object? str) | |
129 | str | |
130 | (string-append str "\n")))))) | |
131 | ||
9155e458 | 132 | ;;; buffered-input.scm ends here |