54 lines
1.8 KiB
Scheme
54 lines
1.8 KiB
Scheme
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;;; Read cr/lf and lf terminated lines. -*- Scheme -*-
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;;; Copyright (c) 1995 by Olin Shivers. <shivers@lcs.mit.edu>
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;;; External dependencies and non-R4RS'isms
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; ascii->char (To create a carriage-return)
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;;; read-line write-string force-output (scsh I/O procs)
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;;; receive values (MV return)
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;;; let-optionals
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;;; "\r\n" in strings for cr/lf. (Not R4RS)
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;;; (read-crlf-line [fd/port retain-crlf?]) -> string or EOF object
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;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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;;; Read a line terminated by either line-feed or EOF. If RETAIN-CRLF? is #f
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;;; (the default), a terminating cr/lf or lf sequence is trimmed from the
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;;; returned string.
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;;;
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;;; This is simple and inefficient. It would be save one copy if we didn't
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;;; use READ-LINE, but replicated its implementation instead.
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(define (read-crlf-line . args)
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(let-optionals args ((fd/port (current-input-port))
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(retain-crlf? #f))
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(let ((ln (read-line fd/port retain-crlf?)))
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(if (or retain-crlf? (eof-object? ln))
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ln
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(let ((slen (string-length ln))) ; Trim a trailing cr, if any.
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(if (or (zero? slen)
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(not (char=? (string-ref ln (- slen 1)) cr)))
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ln
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(substring ln 0 (- slen 1))))))))
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(define cr (ascii->char 13))
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(define (write-crlf port)
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(write-string "\r\n" port)
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(force-output port))
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(define (read-crlf-line-timeout . args)
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(let-optionals args ((fd/port (current-input-port))
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(retain-crlf? #f)
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(timeout 8000)
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(max-interval 500))
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(let loop ((waited 0) (interval 100))
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(cond ((> waited timeout)
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'timeout)
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((char-ready? fd/port)
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(read-crlf-line fd/port retain-crlf?))
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(else (sleep interval)
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(loop (+ waited interval) (min (* interval 2)
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max-interval)))))))
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