From 4a57326d371e5927229e1c8c67fb65ec7e9e20fa Mon Sep 17 00:00:00 2001
From: Stelian Ionescu <sionescu@common-lisp.net>
Date: Wed, 7 Jan 2009 01:30:16 +0100
Subject: [PATCH] %BUFFER-POSITION: guard against null return values of
 DEVICE-POSITION.

---
 io.streams/zeta/buffer.lisp | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/io.streams/zeta/buffer.lisp b/io.streams/zeta/buffer.lisp
index 903b9c8..e7f1b9b 100644
--- a/io.streams/zeta/buffer.lisp
+++ b/io.streams/zeta/buffer.lisp
@@ -220,6 +220,8 @@
 
 (defun %buffer-position (buffer)
   (let ((position (device-position (device-of buffer))))
+    (assert (not (null position)) (position)
+            "A single-channel-buffer's device must not return a NULL device-position.")
     (ecase (last-io-op-of buffer)
       (:read
        (- position (iobuf-available-octets (input-iobuf-of buffer))))
-- 
2.11.4.GIT