summaryrefslogtreecommitdiffstats
path: root/comparse.scm
blob: 5dc1a5026f6a1a612ed4b85ea80a1a7d3e7a1c55 (plain)
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
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
;;; "comparse.scm" Break command line into arguments.
;Copyright (C) 1995, 1997, 2003 Aubrey Jaffer
;
;Permission to copy this software, to modify it, to redistribute it,
;to distribute modified versions, and to use it for any purpose is
;granted, subject to the following restrictions and understandings.
;
;1.  Any copy made of this software must include this copyright notice
;in full.
;
;2.  I have made no warranty or representation that the operation of
;this software will be error-free, and I am under no obligation to
;provide any services, by way of maintenance, update, or otherwise.
;
;3.  In conjunction with products arising from the use of this
;material, there shall be no use of my name in any advertising,
;promotional, or sales literature without prior written consent in
;each case.

;;;; This is a simple command-line reader.  It could be made fancier
;;; to handle lots of `shell' syntaxes.

;;; Albert L. Ting points out that a similar process can be used for
;;; reading files of options -- therefore READ-OPTIONS-FILE.

(require 'string-port)

;;@code{(require 'read-command)}
;;@ftindex read-command

(define (read-command-from-port port nl-term?)
  (define argv '())
  (define obj "")
  (define chars '())
  (define readc (lambda () (read-char port)))
  (define peekc (lambda () (peek-char port)))
  (define s-expression
    (lambda ()
      (splice-arg (call-with-output-string
		   (lambda (p) (display (slib:eval (read port)) p))))))
  (define backslash
    (lambda (goto)
      (readc)
      (let ((c (readc)))
	(cond ((eqv? #\newline c) (goto (peekc)))
	      ((and (char-whitespace? c) (eqv? #\newline (peekc))
		    (eqv? 13 (char->integer c)))
	       (readc) (goto (peekc)))
	      (else (set! chars (cons c chars)) (build-token (peekc)))))))
  (define loop
    (lambda (c)
      (case c
	((#\\) (backslash loop))
	((#\") (splice-arg (read port)))
	((#\( #\') (s-expression))
	((#\#) (do ((c (readc) (readc)))
		   ((or (eof-object? c) (eqv? #\newline c))
		    (if nl-term? c (loop (peekc))))))
	((#\;) (readc))
	((#\newline) (readc) (and (not nl-term?) (loop (peekc))))
	(else (cond ((eof-object? c) c)
		    ((char-whitespace? c) (readc) (loop (peekc)))
		    (else (build-token c)))))))
  (define splice-arg
    (lambda (arg)
      (set! obj (string-append obj (list->string (reverse chars)) arg))
      (set! chars '())
      (build-token (peekc))))
  (define buildit
    (lambda ()
      (readc)
      (set! argv (cons (string-append obj (list->string (reverse chars)))
		       argv))))
  (define build-token
    (lambda (c)
      (case c
	((#\") (splice-arg (read port)))
	((#\() (s-expression))
	((#\\) (backslash build-token))
	((#\;) (buildit))
	(else (cond ((or (eof-object? c) (char-whitespace? c))
		     (buildit)
		     (cond ((not (and nl-term? (eqv? c #\newline)))
			    (set! obj "")
			    (set! chars '())
			    (loop (peekc)))))
		    (else (set! chars (cons (readc) chars))
			  (build-token (peekc))))))))
  (let ((c (loop (peekc))))
    (cond ((and (null? argv) (eof-object? c)) c)
	  (else (reverse argv)))))

;;@args port
;;@args
;;@code{read-command} converts a @dfn{command line} into a list of strings
;;@cindex command line
;;suitable for parsing by @code{getopt}.  The syntax of command lines
;;supported resembles that of popular @dfn{shell}s.  @code{read-command}
;;updates @var{port} to point to the first character past the command
;;delimiter.
;;
;;If an end of file is encountered in the input before any characters are
;;found that can begin an object or comment, then an end of file object is
;;returned.
;;
;;The @var{port} argument may be omitted, in which case it defaults to the
;;value returned by @code{current-input-port}.
;;
;;The fields into which the command line is split are delimited by
;;whitespace as defined by @code{char-whitespace?}.  The end of a command
;;is delimited by end-of-file or unescaped semicolon (@key{;}) or
;;@key{newline}.  Any character can be literally included in a field by
;;escaping it with a backslach (@key{\}).
;;
;;The initial character and types of fields recognized are:
;;@table @asis
;;@item @samp{\}
;;The next character has is taken literally and not interpreted as a field
;;delimiter.  If @key{\} is the last character before a @key{newline},
;;that @key{newline} is just ignored.  Processing continues from the
;;characters after the @key{newline} as though the backslash and
;;@key{newline} were not there.
;;@item @samp{"}
;;The characters up to the next unescaped @key{"} are taken literally,
;;according to [R4RS] rules for literal strings (@pxref{Strings, , ,r4rs,
;;Revised(4) Scheme}).
;;@item @samp{(}, @samp{%'}
;;One scheme expression is @code{read} starting with this character.  The
;;@code{read} expression is evaluated, converted to a string
;;(using @code{display}), and replaces the expression in the returned
;;field.
;;@item @samp{;}
;;Semicolon delimits a command.  Using semicolons more than one command
;;can appear on a line.  Escaped semicolons and semicolons inside strings
;;do not delimit commands.
;;@end table
;;
;;@noindent
;;The comment field differs from the previous fields in that it must be
;;the first character of a command or appear after whitespace in order to
;;be recognized.  @key{#} can be part of fields if these conditions are
;;not met.  For instance, @code{ab#c} is just the field ab#c.
;;
;;@table @samp
;;@item #
;;Introduces a comment.  The comment continues to the end of the line on
;;which the semicolon appears.  Comments are treated as whitespace by
;;@code{read-dommand-line} and backslashes before @key{newline}s in
;;comments are also ignored.
;;@end table
(define (read-command . port)
  (read-command-from-port (cond ((null? port) (current-input-port))
				((= 1 (length port)) (car port))
				(else
				 (slib:error 'read-command
					     "Wrong Number of ARGs:" port)))
			  #t))

;;@body
;;@code{read-options-file} converts an @dfn{options file} into a list of
;;@cindex options file
;;strings suitable for parsing by @code{getopt}.  The syntax of options
;;files is the same as the syntax for command
;;lines, except that @key{newline}s do not terminate reading (only @key{;}
;;or end of file).
;;
;;If an end of file is encountered before any characters are found that
;;can begin an object or comment, then an end of file object is returned.
(define (read-options-file filename)
  (call-with-input-file filename
    (lambda (port) (read-command-from-port port #f))))