[nginx] Core: slight optimization in ngx_chain_update_chains().

[Maxim Dounin]

details:   http://hg.nginx.org/nginx/rev/40c2f3e06d23
branches:  
changeset: 6797:40c2f3e06d23
user:      hucongcong <hucong.c at foxmail.com>
date:      Thu Nov 10 10:17:53 2016 +0800
description:
Core: slight optimization in ngx_chain_update_chains().

It is not necessary to traverse *busy and link the *out when *out is NULL.

diffstat:

 src/core/ngx_buf.c |  16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diffs (30 lines):

diff --git a/src/core/ngx_buf.c b/src/core/ngx_buf.c
--- a/src/core/ngx_buf.c
+++ b/src/core/ngx_buf.c
@@ -186,17 +186,19 @@ ngx_chain_update_chains(ngx_pool_t *p, n
 {
     ngx_chain_t  *cl;
 
-    if (*busy == NULL) {
-        *busy = *out;
+    if (*out) {
+        if (*busy == NULL) {
+            *busy = *out;
 
-    } else {
-        for (cl = *busy; cl->next; cl = cl->next) { /* void */ }
+        } else {
+            for (cl = *busy; cl->next; cl = cl->next) { /* void */ }
 
-        cl->next = *out;
+            cl->next = *out;
+        }
+
+        *out = NULL;
     }
 
-    *out = NULL;
-
     while (*busy) {
         cl = *busy;