From f972da18c85ebeb8591f585e7480fae9c1c5c380 Mon Sep 17 00:00:00 2001
From: oetiker <oetiker@a5681a0c-68f1-0310-ab6d-d61299d08faa>
Date: Thu, 6 Sep 2007 08:40:36 +0000
Subject: [PATCH] rrd_open.c (rrd_read): Mimicing read() behaviour for EOF case
 and NULL buffer case. -- Bernhard Fischer

git-svn-id: svn://svn.oetiker.ch/rrdtool/trunk/program@1197 a5681a0c-68f1-0310-ab6d-d61299d08faa
---
 src/rrd_open.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/rrd_open.c b/src/rrd_open.c
index 0774bce..c6a2d7d 100644
--- a/src/rrd_open.c
+++ b/src/rrd_open.c
@@ -440,8 +440,13 @@ inline ssize_t rrd_read(
 {
 #ifdef HAVE_MMAP
     size_t    _cnt = count;
-    ssize_t   _surplus = rrd_file->pos + _cnt - rrd_file->file_len;
+    ssize_t   _surplus;
 
+    if (rrd_file->pos > rrd_file->file_len || _cnt == 0) /* EOF */
+       return 0;
+    if (buf == NULL)
+       return -1; /* EINVAL */
+    _surplus = rrd_file->pos + _cnt - rrd_file->file_len;
     if (_surplus > 0) { /* short read */
         _cnt -= _surplus;
     }
-- 
2.30.2