* Fix bug in INPUT-BUFFER/DISCARD-CHAR: was not doing anything if the

  input buffer was empty.

* Change INPUT-BUFFER/READ-SUBSTRING to read a whole buffer from the
  input channel if the required number of characters is less than the
  size of the buffer.

* Change INPUT-BUFFER/READ-SUBSTRING to continue reading from the
  input channel until the substring is filled or the channel has no
  more characters available.  This is a correct fix for the change
  made in revision 14.47; this fix does a probe of the channel to
  determine if there are any characters immediately available.
  Previous to 14.47 the procedure might have blocked waiting for input
  that was not ready, even if it had already partly filled the
  substring.  Now it will immediately return any characters that are
  available, and block only when nothing is available.

diff --git a/v7/src/runtime/io.scm b/v7/src/runtime/io.scm
index bc5760444b37d03a63673d3950950441d80f2d24..78f894b22df24890c7e47f612ecbacccf87163ed 100644 (file)
--- a/v7/src/runtime/io.scm
+++ b/v7/src/runtime/io.scm
@@ -1,8 +1,8 @@
 #| -*-Scheme-*-
 
-$Id: io.scm,v 14.48 1996/05/18 06:15:16 cph Exp $
+$Id: io.scm,v 14.49 1997/01/22 20:44:39 cph Exp $
 
-Copyright (c) 1988-96 Massachusetts Institute of Technology
+Copyright (c) 1988-97 Massachusetts Institute of Technology
 
 This material was developed by the Scheme project at the Massachusetts
 Institute of Technology, Department of Electrical Engineering and
@@ -1016,8 +1016,13 @@ MIT in each case. |#
   (without-interrupts
    (lambda ()
      (let ((start-index (input-buffer/start-index buffer)))
-       (if (fix:< start-index (input-buffer/end-index buffer))
-          (set-input-buffer/start-index! buffer (fix:+ start-index 1)))))))
+       (cond ((fix:< start-index (input-buffer/end-index buffer))
+             (set-input-buffer/start-index! buffer (fix:+ start-index 1)))
+            ((not (fix:= (input-buffer/real-end buffer) 0))
+             (if (let ((n (input-buffer/fill buffer)))
+                   (and n
+                        (not (fix:= n 0))))
+                 (set-input-buffer/start-index! buffer 1))))))))
 \f
 (define (input-buffer/read-substring buffer string start end)
   (define (transfer-input-buffer index)
@@ -1036,7 +1041,9 @@ MIT in each case. |#
                   (begin
                     (substring-move-left! bstring bstart bend string index)
                     (set-input-buffer/start-index! buffer bend)
-                    (fix:+ index available)))))
+                    (if (input-buffer/char-ready? buffer 0)
+                        (transfer-input-buffer (fix:+ index available))
+                        (fix:+ index available))))))
            ((or (fix:= (input-buffer/real-end buffer) 0)
                 (channel-closed? (input-buffer/channel buffer)))
             index)
@@ -1044,7 +1051,8 @@ MIT in each case. |#
             (read-directly index)))))
 
   (define (read-directly index)
-    (if (not (input-buffer/line-translation buffer))
+    (if (and (not (input-buffer/line-translation buffer))
+            (fix:>= (fix:- end index) (input-buffer/size buffer)))
        (let ((n
               (channel-read (input-buffer/channel buffer) string index end)))
          (if n