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Avoid an allocation in readCharCode().

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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%.
This commit is contained in:
Nicholas Nethercote 2014-08-10 22:27:04 -07:00
parent 0e4d9061b2
commit 61e6b576d4
3 changed files with 21 additions and 16 deletions
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10
src/core/cmap.js
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@ -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;

7
src/core/fonts.js
View file

@ -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);