From d2e3f4e6b56d5826ec0ab976f1351b33b57f8f9f Mon Sep 17 00:00:00 2001
From: James Zern <jzern@google.com>
Date: Sat, 16 Nov 2013 10:57:09 -0800
Subject: [PATCH] demux: add a tail pointer for chunks

a large number of non-frame chunks could slow the parse

Change-Id: I181bc73626e92263c3c5b2a6dc2bf6e6a0481d52
---
 src/demux/demux.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/demux/demux.c b/src/demux/demux.c
index 08a7c8ed..5a34a1ce 100644
--- a/src/demux/demux.c
+++ b/src/demux/demux.c
@@ -75,6 +75,7 @@ struct WebPDemuxer {
   Frame* frames_;
   Frame** frames_tail_;
   Chunk* chunks_;  // non-image chunks
+  Chunk** chunks_tail_;
 };
 
 typedef enum {
@@ -179,10 +180,9 @@ static WEBP_INLINE uint32_t ReadLE32(MemBuffer* const mem) {
 // Secondary chunk parsing
 
 static void AddChunk(WebPDemuxer* const dmux, Chunk* const chunk) {
-  Chunk** c = &dmux->chunks_;
-  while (*c != NULL) c = &(*c)->next_;
-  *c = chunk;
+  *dmux->chunks_tail_ = chunk;
   chunk->next_ = NULL;
+  dmux->chunks_tail_ = &chunk->next_;
 }
 
 // Add a frame to the end of the list, ensuring the last frame is complete.
@@ -697,6 +697,7 @@ static void InitDemux(WebPDemuxer* const dmux, const MemBuffer* const mem) {
   dmux->canvas_width_ = -1;
   dmux->canvas_height_ = -1;
   dmux->frames_tail_ = &dmux->frames_;
+  dmux->chunks_tail_ = &dmux->chunks_;
   dmux->mem_ = *mem;
 }