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Caching inlined mask images

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This commit is contained in:
Yury Delendik 2014-02-24 09:59:02 -06:00
parent f48f57e30a
commit 257898b359
4 changed files with 173 additions and 36 deletions
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45
src/core/parser.js
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@ -32,6 +32,11 @@ var Parser = (function ParserClosure() {
this.lexer = lexer;
this.allowStreams = allowStreams;
this.xref = xref;
this.imageCache = {
length: 0,
adler32: 0,
stream: null
};
this.refill();
}
@ -169,10 +174,48 @@ var Parser = (function ParserClosure() {
var length = (stream.pos - 4) - startPos;
var imageStream = stream.makeSubStream(startPos, length, dict);
if (cipherTransform)
// trying to cache repeat images, first we are trying to "warm up" caching
// using length, then comparing adler32
var MAX_LENGTH_TO_CACHE = 1000;
var cacheImage = false, adler32;
if (length < MAX_LENGTH_TO_CACHE && this.imageCache.length === length) {
var imageBytes = imageStream.getBytes();
imageStream.reset();
var a = 1;
var b = 0;
for (var i = 0, ii = imageBytes.length; i < ii; ++i) {
a = (a + (imageBytes[i] & 0xff)) % 65521;
b = (b + a) % 65521;
}
adler32 = (b << 16) | a;
if (this.imageCache.stream && this.imageCache.adler32 === adler32) {
this.buf2 = Cmd.get('EI');
this.shift();
this.imageCache.stream.reset();
return this.imageCache.stream;
}
cacheImage = true;
}
if (!cacheImage && !this.imageCache.stream) {
this.imageCache.length = length;
this.imageCache.stream = null;
}
if (cipherTransform) {
imageStream = cipherTransform.createStream(imageStream, length);
}
imageStream = this.filter(imageStream, dict, length);
imageStream.dict = dict;
if (cacheImage) {
imageStream.cacheKey = 'inline_' + length + '_' + adler32;
this.imageCache.adler32 = adler32;
this.imageCache.stream = imageStream;
}
this.buf2 = Cmd.get('EI');
this.shift();