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;;; "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))))
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