1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
|
;;;; buffered-input.scm --- construct a port from a buffered input reader
;;;;
;;;; Copyright (C) 2001, 2006, 2010 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 3 of the License, or (at your option) any later version.
;;;;
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
(define-module (ice-9 buffered-input)
#:export (make-buffered-input-port
make-line-buffered-input-port
set-buffered-input-continuation?!))
;; @code{buffered-input-continuation?} is a property of the ports
;; created by @code{make-line-buffered-input-port} that stores the
;; read continuation flag for each such port.
(define buffered-input-continuation? (make-object-property))
(define (set-buffered-input-continuation?! port val)
"Set the read continuation flag for @var{port} to @var{val}.
See @code{make-buffered-input-port} for the meaning and use of this
flag."
(set! (buffered-input-continuation? port) val))
(define (make-buffered-input-port reader)
"Construct a line-buffered input port from the specified @var{reader}.
@var{reader} should be a procedure of one argument that somehow reads
a chunk of input and returns it as a string.
The port created by @code{make-buffered-input-port} does @emph{not}
interpolate any additional characters between the strings returned by
@var{reader}.
@var{reader} should take a boolean @var{continuation?} argument.
@var{continuation?} indicates whether @var{reader} is being called to
start a logically new read operation (in which case
@var{continuation?} is @code{#f}) or to continue a read operation for
which some input has already been read (in which case
@var{continuation?} is @code{#t}). Some @var{reader} implementations
use the @var{continuation?} argument to determine what prompt to
display to the user.
The new/continuation distinction is largely an application-level
concept: @code{set-buffered-input-continuation?!} allows an
application to specify when a read operation is considered to be new.
But note that if there is non-whitespace data already buffered in the
port when a new read operation starts, this data will be read before
the first call to @var{reader}, and so @var{reader} will be called
with @var{continuation?} set to @code{#t}."
(let ((read-string "")
(string-index 0))
(letrec ((get-character
(lambda ()
(if (< string-index (string-length read-string))
;; Read a char.
(let ((res (string-ref read-string string-index)))
(set! string-index (+ 1 string-index))
(if (not (char-whitespace? res))
(set! (buffered-input-continuation? port) #t))
res)
;; Fill the buffer.
(let ((x (reader (buffered-input-continuation? port))))
(cond
((eof-object? x)
;; Don't buffer the EOF object.
x)
(else
(set! read-string x)
(set! string-index 0)
(get-character)))))))
(input-waiting
(lambda ()
(- (string-length read-string) string-index)))
(port #f))
(set! port (make-soft-port (vector #f #f #f get-character #f input-waiting) "r"))
(set! (buffered-input-continuation? port) #f)
port)))
(define (make-line-buffered-input-port reader)
"Construct a line-buffered input port from the specified @var{reader}.
@var{reader} should be a procedure of one argument that somehow reads
a line of input and returns it as a string @emph{without} the
terminating newline character.
The port created by @code{make-line-buffered-input-port} automatically
interpolates a newline character after each string returned by
@var{reader}.
@var{reader} should take a boolean @var{continuation?} argument. For
the meaning and use of this argument, see
@code{make-buffered-input-port}."
(make-buffered-input-port (lambda (continuation?)
(let ((str (reader continuation?)))
(if (eof-object? str)
str
(string-append str "\n"))))))
;;; buffered-input.scm ends here
|
