[Pkg-javascript-commits] [pdf.js] 182/246: Avoid an allocation in readCharCode().

[David Prévot]

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

commit 61e6b576d40134c2921a9c738e362fd507df32a3
Author: Nicholas Nethercote <nnethercote at mozilla.com>
Date:   Sun Aug 10 22:27:04 2014 -0700

    Avoid an allocation in readCharCode().
    
    readCharCode() returns two values, and currently allocates a length-2
    array on every call to do so. This change makes it instead us a
    passed-in object which can be reused.
    
    This tiny change reduces the total JS allocations done for the document
    in Mozilla bug 992125 by 4.2%.
---
 src/core/cmap.js       | 10 ++++++----
 src/core/fonts.js      |  7 ++++---
 test/unit/cmap_spec.js | 20 +++++++++++---------
 3 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/src/core/cmap.js b/src/core/cmap.js
index 604dc94..1cdaa03 100644
--- a/src/core/cmap.js
+++ b/src/core/cmap.js
@@ -281,7 +281,7 @@ var CMap = (function CMapClosure() {
       return this._map;
     },
 
-    readCharCode: function(str, offset) {
+    readCharCode: function(str, offset, out) {
       var c = 0;
       var codespaceRanges = this.codespaceRanges;
       var codespaceRangesLen = this.codespaceRanges.length;
@@ -295,12 +295,14 @@ var CMap = (function CMapClosure() {
           var low = codespaceRange[k++];
           var high = codespaceRange[k++];
           if (c >= low && c <= high) {
-            return [c, n + 1];
+            out.charcode = c;
+            out.length = n + 1;
+            return;
           }
         }
       }
-
-      return [0, 1];
+      out.charcode = 0;
+      out.length = 1;
     }
   };
   return CMap;
diff --git a/src/core/fonts.js b/src/core/fonts.js
index fce7f8d..741cbd0 100644
--- a/src/core/fonts.js
+++ b/src/core/fonts.js
@@ -4574,10 +4574,11 @@ var Font = (function FontClosure() {
       if (this.cMap) {
         // composite fonts have multi-byte strings convert the string from
         // single-byte to multi-byte
+        var c = {};
         while (i < chars.length) {
-          var c = this.cMap.readCharCode(chars, i);
-          charcode = c[0];
-          var length = c[1];
+          this.cMap.readCharCode(chars, i, c);
+          charcode = c.charcode;
+          var length = c.length;
           i += length;
           glyph = this.charToGlyph(charcode);
           glyphs.push(glyph);
diff --git a/test/unit/cmap_spec.js b/test/unit/cmap_spec.js
index 2a4fb9c..e3c2a0b 100644
--- a/test/unit/cmap_spec.js
+++ b/test/unit/cmap_spec.js
@@ -65,12 +65,13 @@ describe('cmap', function() {
               'endcodespacerange\n';
     var stream = new StringStream(str);
     var cmap = CMapFactory.create(stream);
-    var c = cmap.readCharCode(String.fromCharCode(1), 0);
-    expect(c[0]).toEqual(1);
-    expect(c[1]).toEqual(1);
-    c = cmap.readCharCode(String.fromCharCode(0, 0, 0, 3), 0);
-    expect(c[0]).toEqual(3);
-    expect(c[1]).toEqual(4);
+    var c = {};
+    cmap.readCharCode(String.fromCharCode(1), 0, c);
+    expect(c.charcode).toEqual(1);
+    expect(c.length).toEqual(1);
+    cmap.readCharCode(String.fromCharCode(0, 0, 0, 3), 0, c);
+    expect(c.charcode).toEqual(3);
+    expect(c.length).toEqual(4);
   });
   it('decodes 4 byte codespace ranges', function() {
     var str = '1 begincodespacerange\n' +
@@ -78,9 +79,10 @@ describe('cmap', function() {
               'endcodespacerange\n';
     var stream = new StringStream(str);
     var cmap = CMapFactory.create(stream);
-    var c = cmap.readCharCode(String.fromCharCode(0x8E, 0xA1, 0xA1, 0xA1), 0);
-    expect(c[0]).toEqual(0x8EA1A1A1);
-    expect(c[1]).toEqual(4);
+    var c = {};
+    cmap.readCharCode(String.fromCharCode(0x8E, 0xA1, 0xA1, 0xA1), 0, c);
+    expect(c.charcode).toEqual(0x8EA1A1A1);
+    expect(c.length).toEqual(4);
   });
   it('read usecmap', function() {
     var str = '/Adobe-Japan1-1 usecmap\n';

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