X-Git-Url: https://git.octo.it/?a=blobdiff_plain;f=src%2Frrd_open.c;h=4ee68a67f65e17ca0f1d5e2e975f69e186f7dee0;hb=7769bc2e3878d617cacab27d0839adc5995979ad;hp=c6a2d7d9d49f09a65eaa01f263e23975c97a4064;hpb=f972da18c85ebeb8591f585e7480fae9c1c5c380;p=rrdtool.git

diff --git a/src/rrd_open.c b/src/rrd_open.c
index c6a2d7d..4ee68a6 100644
--- a/src/rrd_open.c
+++ b/src/rrd_open.c
@@ -469,7 +469,7 @@ inline ssize_t rrd_read(
 
 /* write count bytes from buffer buf to the current position
  * rrd_file->pos of rrd_file->fd.
- * Returns the number of bytes written.  */
+ * Returns the number of bytes written or <0 on error.  */
 
 inline ssize_t rrd_write(
     rrd_file_t *rrd_file,
@@ -477,6 +477,10 @@ inline ssize_t rrd_write(
     size_t count)
 {
 #ifdef HAVE_MMAP
+    if (count == 0)
+       return 0;
+    if (buf == NULL)
+       return -1; /* EINVAL */
     memcpy(rrd_file->file_start + rrd_file->pos, buf, count);
     rrd_file->pos += count;
     return count;       /* mimmic write() semantics */