ikarus/src/ikarus.io.input-strings.ss

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2007-05-11 23:39:22 -04:00
(library (ikarus io input-strings)
(export open-input-string)
(import
(ikarus system $strings)
(ikarus system $fx)
(ikarus system $pairs)
(ikarus system $ports)
(ikarus system $io)
(except (ikarus) open-input-string))
(define-syntax message-case
(syntax-rules (else)
[(_ msg args
[(msg-name msg-arg* ...) b b* ...] ...
[else else1 else2 ...])
(let ([tmsg msg] [targs args])
(define-syntax match-and-bind
(syntax-rules ()
[(__ y () body)
(if (null? y)
body
(error 'message-case "unmatched ~s" (cons tmsg targs)))]
[(__ y (a a* (... ...)) body)
(if (pair? y)
(let ([a (car y)] [d (cdr y)])
(match-and-bind d (a* (... ...)) body))
(error 'message-case "unmatched ~s" (cons tmsg targs)))]))
(case tmsg
[(msg-name)
(match-and-bind targs (msg-arg* ...) (begin b b* ...))] ...
[else else1 else2 ...]))]))
(define make-input-string-handler
(lambda (str)
(let ((open? #t))
(lambda (msg . args)
(message-case msg args
[(read-char p)
(let ([idx ($port-input-index p)])
(if ($fx< idx ($port-input-size p))
(begin
($set-port-input-index! p ($fxadd1 idx))
($string-ref ($port-input-buffer p) idx))
(if open?
(eof-object)
(error 'read-char "port ~s is closed" p))))]
[(peek-char p)
(unless (input-port? p)
(error 'peek-char "~s is not an input port" p))
(let ([idx ($port-input-index p)])
(if ($fx< idx ($port-input-size p))
($string-ref ($port-input-buffer p) idx)
(if open?
(eof-object)
(error 'peek-char "port ~s is closed" p))))]
[(unread-char c p)
(unless (input-port? p)
(error 'unread-char "~s is not an input port" p))
(let ([idx ($fxsub1 ($port-input-index p))])
(if (and ($fx>= idx 0)
($fx< idx ($port-input-size p)))
(begin
($set-port-input-index! p idx)
($string-set! ($port-input-buffer p) idx c))
(if open?
(error 'unread-char "port ~s is closed" p)
(error 'unread-char "too many unread-chars"))))]
[(port-name p) '*string-port*]
[(close-port p)
(unless (input-port? p)
(error 'close-input-port "~s is not an input port" p))
(when open?
($set-port-input-size! p 0)
(set! open? #f))]
[else
(error 'input-string-handler
"message not handled ~s" (cons msg args))])))))
(define open-input-string
(lambda (str)
(unless (string? str)
(error 'open-input-string "~s is not a string" str))
(let ([port (make-input-port
(make-input-string-handler str)
str)])
port)))
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)