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;;; installed-scm-file
;;;; Copyright (C) 1996, 1998 Free Software Foundation, Inc.
;;;;
;;;; This program is free software; you can redistribute it and/or modify
;;;; it under the terms of the GNU General Public License as published by
;;;; the Free Software Foundation; either version 2, or (at your option)
;;;; any later version.
;;;;
;;;; This program is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;;;; GNU General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU General Public License
;;;; along with this software; see the file COPYING. If not, write to
;;;; the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
;;;; Boston, MA 02111-1307 USA
;;;;
(define-module (ice-9 lineio))
;;; {Line Buffering Input Ports}
;;;
;;; [This is a work-around to get past certain deficiencies in the capabilities
;;; of ports. Eventually, ports should be fixed and this module nuked.]
;;;
;;; A line buffering input port supports:
;;;
;;; read-string which returns the next line of input
;;; unread-string which pushes a line back onto the stream
;;;
;;; The implementation of unread-string is kind of limited; it doesn't
;;; interact properly with unread-char, or any of the other port
;;; reading functions. Only read-string will get you back the things that
;;; unread-string accepts.
;;;
;;; Normally a "line" is all characters up to and including a newline.
;;; If lines are put back using unread-string, they can be broken arbitrarily
;;; -- that is, read-string returns strings passed to unread-string (or
;;; shared substrings of them).
;;;
;; read-string port
;; unread-string port str
;; Read (or buffer) a line from PORT.
;;
;; Not all ports support these functions -- only those with
;; 'unread-string and 'read-string properties, bound to hooks
;; implementing these functions.
;;
(define-public (unread-string str line-buffering-input-port)
((object-property line-buffering-input-port 'unread-string) str))
;;
(define-public (read-string line-buffering-input-port)
((object-property line-buffering-input-port 'read-string)))
(define-public (lineio-port? port)
(not (not (object-property port 'read-string))))
;; make-line-buffering-input-port port
;; Return a wrapper for PORT. The wrapper handles read-string/unread-string.
;;
;; The port returned by this function reads newline terminated lines from PORT.
;; It buffers these characters internally, and parsels them out via calls
;; to read-char, read-string, and unread-string.
;;
(define-public (make-line-buffering-input-port underlying-port)
(let* (;; buffers - a list of strings put back by unread-string or cached
;; using read-line.
;;
(buffers '())
;; getc - return the next character from a buffer or from the underlying
;; port.
;;
(getc (lambda ()
(if (not buffers)
(read-char underlying-port)
(let ((c (string-ref (car buffers))))
(if (= 1 (string-length (car buffers)))
(set! buffers (cdr buffers))
(set-car! buffers (make-shared-substring (car buffers) 1)))
c))))
(propogate-close (lambda () (close-port underlying-port)))
(self (make-soft-port (vector #f #f #f getc propogate-close) "r"))
(unread-string (lambda (str)
(and (< 0 (string-length str))
(set! buffers (cons str buffers)))))
(read-string (lambda ()
(cond
((not (null? buffers))
(let ((answer (car buffers)))
(set! buffers (cdr buffers))
answer))
(else
(read-line underlying-port 'concat)))))) ;handle-newline->concat
(set-object-property! self 'unread-string unread-string)
(set-object-property! self 'read-string read-string)
self))
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