From f12d5882580c780db052cc327c09f1165f67b4ff Mon Sep 17 00:00:00 2001
From: Nicholas Nethercote <nnethercote@mozilla.com>
Date: Thu, 6 Mar 2014 16:14:21 -0800
Subject: [PATCH] Add an ensureRange() call to ChunkedStream_makeSubStream().

By checking if the data is all present before making a substream, we avoid
cases where we parse part of a stream and then throw a MissingDataException
part-way through, which forces us to later re-read the stream -- possibly
multiple times. This is a sizeable performance win for some cases when file
loading is slow (e.g. over the web).
---
 src/core/chunked_stream.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/core/chunked_stream.js b/src/core/chunked_stream.js
index 040151815..98e8d7216 100644
--- a/src/core/chunked_stream.js
+++ b/src/core/chunked_stream.js
@@ -187,6 +187,8 @@ var ChunkedStream = (function ChunkedStreamClosure() {
     },
 
     makeSubStream: function ChunkedStream_makeSubStream(start, length, dict) {
+      this.ensureRange(start, start + length);
+
       function ChunkedStreamSubstream() {}
       ChunkedStreamSubstream.prototype = Object.create(this);
       ChunkedStreamSubstream.prototype.getMissingChunks = function() {