80 lines
2.6 KiB
Scheme
80 lines
2.6 KiB
Scheme
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(library (ikarus io input-strings)
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(export open-input-string)
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(import
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(ikarus system $strings)
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(ikarus system $bytevectors)
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(ikarus system $fx)
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(ikarus system $pairs)
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(ikarus system $ports)
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(ikarus system $io)
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(except (ikarus) open-input-string))
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(define-syntax message-case
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(syntax-rules (else)
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[(_ msg args
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[(msg-name msg-arg* ...) b b* ...] ...
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[else else1 else2 ...])
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(let ([tmsg msg] [targs args])
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(define-syntax match-and-bind
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(syntax-rules ()
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[(__ y () body)
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(if (null? y)
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body
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(error 'message-case "unmatched ~s" (cons tmsg targs)))]
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[(__ y (a a* (... ...)) body)
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(if (pair? y)
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(let ([a (car y)] [d (cdr y)])
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(match-and-bind d (a* (... ...)) body))
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(error 'message-case "unmatched ~s" (cons tmsg targs)))]))
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(case tmsg
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[(msg-name)
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(match-and-bind targs (msg-arg* ...) (begin b b* ...))] ...
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[else else1 else2 ...]))]))
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(define make-input-string-handler
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(lambda (str)
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(let ((open? #t) (idx 0) (n (string-length str)))
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(lambda (msg . args)
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(message-case msg args
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[(read-char p)
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(if ($fx< idx n)
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(let ([c ($string-ref str idx)])
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(set! idx ($fxadd1 idx))
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c)
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(if open?
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(eof-object)
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(error 'read-char "port ~s is closed" p)))]
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[(peek-char p)
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(if ($fx< idx n)
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($string-ref str idx)
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(if open?
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(eof-object)
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(error 'peek-char "port ~s is closed" p)))]
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[(unread-char c p)
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(let ([i ($fxsub1 idx)])
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(if (and ($fx>= i 0)
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($fx< i n))
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(set! idx i)
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(if open?
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(error 'unread-char "port ~s is closed" p)
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(error 'unread-char "too many unread-chars"))))]
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[(port-name p) '*string-port*]
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[(close-port p)
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(when open?
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(set! open? #f))]
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[else
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(error 'input-string-handler
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"message not handled ~s" (cons msg args))])))))
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(define open-input-string
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(lambda (str)
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(unless (string? str)
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(error 'open-input-string "~s is not a string" str))
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(let ([port (make-input-port
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(make-input-string-handler str)
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'#vu8())])
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port)))
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)
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