# HG changeset patch
# User Maxim Dounin <mdounin@mdounin.ru>
# Date 1323621042 0
# Node ID 1003326eccc556efffd69e55a43a795db023ec5c
# Parent  f8881d301d62fa5da8b53355316db4be7e6daf87
Microoptimization of sendfile(2) usage under FreeBSD.

FreeBSD kernel checks headers/trailers pointer against NULL, not
corresponding count.  Passing NULL if there are no headers/trailers
helps to avoid unneeded work in kernel, as well as unexpected 0 bytes
GIO in traces.

diff -r f8881d301d62 -r 1003326eccc5 src/os/unix/ngx_freebsd_sendfile_chain.c
--- a/src/os/unix/ngx_freebsd_sendfile_chain.c	Fri Dec 09 16:17:12 2011 +0000
+++ b/src/os/unix/ngx_freebsd_sendfile_chain.c	Sun Dec 11 16:30:42 2011 +0000
@@ -246,9 +246,14 @@
                 }
             }
 
-            hdtr.headers = (struct iovec *) header.elts;
+            /*
+             * sendfile() does unneeded work if sf_hdtr's count is 0,
+             * but corresponding pointer is not NULL
+             */
+
+            hdtr.headers = header.nelts ? (struct iovec *) header.elts: NULL;
             hdtr.hdr_cnt = header.nelts;
-            hdtr.trailers = (struct iovec *) trailer.elts;
+            hdtr.trailers = trailer.nelts ? (struct iovec *) trailer.elts: NULL;
             hdtr.trl_cnt = trailer.nelts;
 
             /*