/usr/share/guile/3.0/ice-9
Edit: /usr/share/guile/3.0/ice-9/lineio.scm (3941B)
;;; installed-scm-file
;;;; Copyright (C) 1996, 1998, 2001, 2003, 2006 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 3 of the License, or (at your option) any later version.
;;;;
;;;; This library 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
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;;;
(define-module (ice-9 lineio)
:use-module (ice-9 rdelim)
:export (unread-string read-string lineio-port?
make-line-buffering-input-port))
;;; {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 (unread-string str line-buffering-input-port)
((object-property line-buffering-input-port 'unread-string) str))
;;
(define (read-string line-buffering-input-port)
((object-property line-buffering-input-port 'read-string)))
(define (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 (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) 0)))
(if (= 1 (string-length (car buffers)))
(set! buffers (cdr buffers))
(set-car! buffers (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))