ice-9/lineio.scm

   1 ;;; installed-scm-file
   2
   3 ;;;;    Copyright (C) 1996, 1998, 2001 Free Software Foundation, Inc.
   4 ;;;;
   5 ;;;; This program is free software; you can redistribute it and/or modify
   6 ;;;; it under the terms of the GNU General Public License as published by
   7 ;;;; the Free Software Foundation; either version 2, or (at your option)
   8 ;;;; any later version.
   9 ;;;;
  10 ;;;; This program is distributed in the hope that it will be useful,
  11 ;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 ;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 ;;;; GNU General Public License for more details.
  14 ;;;;
  15 ;;;; You should have received a copy of the GNU General Public License
  16 ;;;; along with this software; see the file COPYING.  If not, write to
  17 ;;;; the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  18 ;;;; Boston, MA 02111-1307 USA
  19 ;;;;
  20 ;;;; As a special exception, the Free Software Foundation gives permission
  21 ;;;; for additional uses of the text contained in its release of GUILE.
  22 ;;;;
  23 ;;;; The exception is that, if you link the GUILE library with other files
  24 ;;;; to produce an executable, this does not by itself cause the
  25 ;;;; resulting executable to be covered by the GNU General Public License.
  26 ;;;; Your use of that executable is in no way restricted on account of
  27 ;;;; linking the GUILE library code into it.
  28 ;;;;
  29 ;;;; This exception does not however invalidate any other reasons why
  30 ;;;; the executable file might be covered by the GNU General Public License.
  31 ;;;;
  32 ;;;; This exception applies only to the code released by the
  33 ;;;; Free Software Foundation under the name GUILE.  If you copy
  34 ;;;; code from other Free Software Foundation releases into a copy of
  35 ;;;; GUILE, as the General Public License permits, the exception does
  36 ;;;; not apply to the code that you add in this way.  To avoid misleading
  37 ;;;; anyone as to the status of such modified files, you must delete
  38 ;;;; this exception notice from them.
  39 ;;;;
  40 ;;;; If you write modifications of your own for GUILE, it is your choice
  41 ;;;; whether to permit this exception to apply to your modifications.
  42 ;;;; If you do not wish that, delete this exception notice.
  43 ;;;;
  44
  45 \f
  46
  47 (define-module (ice-9 lineio)
  48   :use-module (ice-9 readline))
  49
  50 \f
  51 ;;; {Line Buffering Input Ports}
  52 ;;;
  53 ;;; [This is a work-around to get past certain deficiencies in the capabilities
  54 ;;;  of ports.  Eventually, ports should be fixed and this module nuked.]
  55 ;;;
  56 ;;; A line buffering input port supports:
  57 ;;;
  58 ;;;     read-string     which returns the next line of input
  59 ;;;     unread-string   which pushes a line back onto the stream
  60 ;;;
  61 ;;; The implementation of unread-string is kind of limited; it doesn't
  62 ;;; interact properly with unread-char, or any of the other port
  63 ;;; reading functions.  Only read-string will get you back the things that
  64 ;;; unread-string accepts.
  65 ;;;
  66 ;;; Normally a "line" is all characters up to and including a newline.
  67 ;;; If lines are put back using unread-string, they can be broken arbitrarily
  68 ;;; -- that is, read-string returns strings passed to unread-string (or
  69 ;;; shared substrings of them).
  70 ;;;
  71
  72 ;; read-string port
  73 ;; unread-string port str
  74 ;;   Read (or buffer) a line from PORT.
  75 ;;
  76 ;; Not all ports support these functions -- only those with
  77 ;; 'unread-string and 'read-string properties, bound to hooks
  78 ;; implementing these functions.
  79 ;;
  80 (define-public (unread-string str line-buffering-input-port)
  81   ((object-property line-buffering-input-port 'unread-string) str))
  82
  83 ;;
  84 (define-public (read-string line-buffering-input-port)
  85   ((object-property line-buffering-input-port 'read-string)))
  86
  87
  88 (define-public (lineio-port? port)
  89   (not (not (object-property port 'read-string))))
  90
  91 ;; make-line-buffering-input-port port
  92 ;;   Return a wrapper for PORT.  The wrapper handles read-string/unread-string.
  93 ;;
  94 ;; The port returned by this function reads newline terminated lines from PORT.
  95 ;; It buffers these characters internally, and parsels them out via calls
  96 ;; to read-char, read-string, and unread-string.
  97 ;;
  98
  99 (define-public (make-line-buffering-input-port underlying-port)
 100   (let* (;; buffers - a list of strings put back by unread-string or cached
 101          ;; using read-line.
 102          ;;
 103          (buffers '())
 104
 105          ;; getc - return the next character from a buffer or from the underlying
 106          ;; port.
 107          ;;
 108          (getc (lambda ()
 109                  (if (not buffers)
 110                      (read-char underlying-port)
 111                      (let ((c (string-ref (car buffers))))
 112                        (if (= 1 (string-length (car buffers)))
 113                            (set! buffers (cdr buffers))
 114                            (set-car! buffers (substring (car buffers) 1)))
 115                        c))))
 116
 117          (propogate-close (lambda () (close-port underlying-port)))
 118
 119          (self (make-soft-port (vector #f #f #f getc propogate-close) "r"))
 120
 121          (unread-string (lambda (str)
 122                           (and (< 0 (string-length str))
 123                                    (set! buffers (cons str buffers)))))
 124
 125          (read-string (lambda ()
 126                        (cond
 127                         ((not (null? buffers))
 128                          (let ((answer (car buffers)))
 129                            (set! buffers (cdr buffers))
 130                            answer))
 131                         (else
 132                          (read-line underlying-port 'concat)))))) ;handle-newline->concat
 133
 134     (set-object-property! self 'unread-string unread-string)
 135     (set-object-property! self 'read-string read-string)
 136     self))
 137
 138