From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 9 Dec 2015 17:05:53 +0000 (+0100)
Subject: resolved: grow DnsAnswer exponentially
X-Git-Tag: v229~217^2~7
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=2f763887b8696f2fd2d577bfbd011f3b2e889c1a;p=thirdparty%2Fsystemd.git

resolved: grow DnsAnswer exponentially

When increasing the DnsAnswer array, don't operate piecemeal, grow the
array exponentially.

This way, the default logic for DnsAnswer allocations matches the
behaviour for GREEDY_REALLOC and suchlike, and we can reduce the number
of necessary allocations.
---

diff --git a/src/resolve/resolved-dns-answer.c b/src/resolve/resolved-dns-answer.c
index f1f4d909ccf..92b9871dbb8 100644
--- a/src/resolve/resolved-dns-answer.c
+++ b/src/resolve/resolved-dns-answer.c
@@ -271,6 +271,8 @@ void dns_answer_order_by_scope(DnsAnswer *a, bool prefer_link_local) {
 int dns_answer_reserve(DnsAnswer **a, unsigned n_free) {
         DnsAnswer *n;
 
+        assert(a);
+
         if (n_free <= 0)
                 return 0;
 
@@ -285,6 +287,9 @@ int dns_answer_reserve(DnsAnswer **a, unsigned n_free) {
                 if ((*a)->n_allocated >= ns)
                         return 0;
 
+                /* Allocate more than we need */
+                ns *= 2;
+
                 n = realloc(*a, offsetof(DnsAnswer, items) + sizeof(DnsAnswerItem) * ns);
                 if (!n)
                         return -ENOMEM;