[Pkg-javascript-commits] [pdf.js] 43/246: Optimize CMap.prototype.forEach().

[David Prévot]

This is an automated email from the git hooks/post-receive script.

taffit pushed a commit to branch master
in repository pdf.js.

commit 28687bca75d1e2a09458ddbb3b61cb6bcf67284a
Author: Nicholas Nethercote <nnethercote at mozilla.com>
Date:   Tue Jul 29 20:33:43 2014 -0700

    Optimize CMap.prototype.forEach().
    
    This change avoids the element stringification caused by for..in for the
    vast majority of CMaps.
    
    When loading the PDF from issue #4580, this change reduces peak RSS from ~650
    to ~600 MiB, and improves overall speed by ~20%, from 902 ms to 713 ms.  Other
    CMap-heavy documents will also see improvements.
---
 src/core/cmap.js | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/core/cmap.js b/src/core/cmap.js
index 771f3ff..446b11e 100644
--- a/src/core/cmap.js
+++ b/src/core/cmap.js
@@ -242,9 +242,24 @@ var CMap = (function CMapClosure() {
     },
 
     forEach: function(callback) {
+      // Most maps have fewer than 65536 entries, and for those we use normal
+      // array iteration. But really sparse tables are possible -- e.g. with
+      // indices in the *billions*. For such tables we use for..in, which isn't
+      // ideal because it stringifies the indices for all present elements, but
+      // it does avoid iterating over every undefined entry.
       var map = this._map;
-      for (var key in this._map) {
-        callback(key, map[key]);
+      var length = map.length;
+      var i;
+      if (length <= 0x10000) {
+        for (i = 0; i < length; i++) {
+          if (map[i] !== undefined) {
+            callback(i, map[i]);
+          }
+        }
+      } else {
+        for (i in this._map) {
+          callback(i, map[i]);
+        }
       }
     },
 

-- 
Alioth's /usr/local/bin/git-commit-notice on /srv/git.debian.org/git/pkg-javascript/pdf.js.git