Guarantee that CHANNEL-READ not return #f if the argument channel is

set to blocking mode.

diff --git a/v7/src/runtime/io.scm b/v7/src/runtime/io.scm
index 4e482acdd752623009424bb489f45b4f1e21a301..5f2a0f543f14e05dc82c90fe7adafbe1891108a8 100644 (file)
--- a/v7/src/runtime/io.scm
+++ b/v7/src/runtime/io.scm
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: io.scm,v 14.35 1993/06/16 15:00:21 gjr Exp $
+$Id: io.scm,v 14.36 1993/08/18 22:52:46 cph Exp $
 
 Copyright (c) 1988-1993 Massachusetts Institute of Technology
 
@@ -235,17 +235,27 @@ MIT in each case. |#
        (ucode-primitive terminal-set-state 2)))
 \f
 (define (channel-read channel buffer start end)
-  (if (and have-select? (not (channel-type=file? channel)))
-      (let ((block-events? (block-thread-events)))
-       (let ((result
-              (and (eq? 'INPUT-AVAILABLE (test-for-input-on-channel channel))
-                   ((ucode-primitive channel-read 4)
-                    (channel-descriptor channel) buffer start end))))
-         (if (not block-events?)
-             (unblock-thread-events))
-         result))
-      ((ucode-primitive channel-read 4) (channel-descriptor channel)
-                                       buffer start end)))
+  (let ((do-read
+        (lambda ()
+          ((ucode-primitive channel-read 4) (channel-descriptor channel)
+                                            buffer start end)))
+       (do-test
+        (lambda ()
+          (eq? 'INPUT-AVAILABLE (test-for-input-on-channel channel)))))
+    (declare (integrate-operator do-read do-test))
+    (if (and have-select? (not (channel-type=file? channel)))
+       (let ((block-events? (block-thread-events)))
+         (let ((result
+                (if (channel-blocking? channel)
+                    (begin
+                      (do () ((do-test)))
+                      (do-read))
+                    (and (do-test)
+                         (do-read)))))
+           (if (not block-events?)
+               (unblock-thread-events))
+           result))
+       (do-read))))
 
 (define (channel-read-block channel buffer start end)
   (let loop ()