From 72ac4b3e49aeb49d4e7542ef27a3c5749a1516e7 Mon Sep 17 00:00:00 2001
From: Chris Hanson <org/chris-hanson/cph>
Date: Sat, 28 Jan 2017 22:00:21 -0800
Subject: [PATCH] Fix bug: would-block value only returned if nothing has been
 read.

---
 src/runtime/genio.scm | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/runtime/genio.scm b/src/runtime/genio.scm
index 8669b9b59..4f9e78fbc 100644
--- a/src/runtime/genio.scm
+++ b/src/runtime/genio.scm
@@ -236,8 +236,12 @@ USA.
   (let loop ((index start))
     (if (fix:< index end)
 	(let ((char (generic-io/read-char port)))
-	  (cond ((not char) #f)
-		((eof-object? char) (fix:- index start))
+	  (cond ((not char)
+		 (if (fix:< start index)
+		     (fix:- index start)
+		     #f))
+		((eof-object? char)
+		 (fix:- index start))
 		(else
 		 (ustring-set! string index char)
 		 (loop (fix:+ index 1)))))
-- 
2.25.1