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Don't get bytes eagerly when creating {Jpeg,Jpx,Jbig2}Stream objects.

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This avoids lots of unnecessary work when such streams are referred to via
fetch(), and so their bytes aren't subsequently read. This is a large
performance win on some files.
This commit is contained in:
Nicholas Nethercote 2014-03-06 17:07:02 -08:00
parent f12d588258
commit d0253c8291
2 changed files with 35 additions and 14 deletions
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9
src/core/parser.js
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@ -300,12 +300,10 @@ var Parser = (function ParserClosure() {
return new LZWStream(stream, earlyChange);
}
if (name == 'DCTDecode' || name == 'DCT') {
var bytes = stream.getBytes(length);
return new JpegStream(bytes, stream.dict, this.xref);
return new JpegStream(stream, length, stream.dict, this.xref);
}
if (name == 'JPXDecode' || name == 'JPX') {
var bytes = stream.getBytes(length);
return new JpxStream(bytes, stream.dict);
return new JpxStream(stream, length, stream.dict);
}
if (name == 'ASCII85Decode' || name == 'A85') {
return new Ascii85Stream(stream);
@ -320,8 +318,7 @@ var Parser = (function ParserClosure() {
return new RunLengthStream(stream);
}
if (name == 'JBIG2Decode') {
var bytes = stream.getBytes(length);
return new Jbig2Stream(bytes, stream.dict);
return new Jbig2Stream(stream, length, stream.dict);
}
warn('filter "' + name + '" not supported yet');
return stream;

40
src/core/stream.js
View File

@ -14,8 +14,8 @@
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/* globals bytesToString, ColorSpace, Dict, EOF, error, info, Jbig2Image,
JpegImage, JpxImage, Lexer, Util, PDFJS, isArray, warn */
/* globals bytesToString, ColorSpace, Dict, EOF, error, info, isArray,
Jbig2Image, JpegImage, JpxImage, Lexer, PDFJS, shadow, Util, warn */
'use strict';
@ -777,17 +777,25 @@ var PredictorStream = (function PredictorStreamClosure() {
* DecodeStreams.
*/
var JpegStream = (function JpegStreamClosure() {
function JpegStream(bytes, dict, xref) {
function JpegStream(stream, length, dict, xref) {
// TODO: per poppler, some images may have 'junk' before that
// need to be removed
this.stream = stream;
this.length = length;
this.dict = dict;
this.bytes = bytes;
DecodeStream.call(this);
}
JpegStream.prototype = Object.create(DecodeStream.prototype);
Object.defineProperty(JpegStream.prototype, 'bytes', {
get: function JpegStream_bytes() {
return shadow(this, 'bytes', this.stream.getBytes(this.length));
},
configurable: true
});
JpegStream.prototype.ensureBuffer = function JpegStream_ensureBuffer(req) {
if (this.bufferLength)
return;
@ -836,15 +844,23 @@ var JpegStream = (function JpegStreamClosure() {
* the stream behaves like all the other DecodeStreams.
*/
var JpxStream = (function JpxStreamClosure() {
function JpxStream(bytes, dict) {
function JpxStream(stream, length, dict) {
this.stream = stream;
this.length = length;
this.dict = dict;
this.bytes = bytes;
DecodeStream.call(this);
}
JpxStream.prototype = Object.create(DecodeStream.prototype);
Object.defineProperty(JpxStream.prototype, 'bytes', {
get: function JpxStream_bytes() {
return shadow(this, 'bytes', this.stream.getBytes(this.length));
},
configurable: true
});
JpxStream.prototype.ensureBuffer = function JpxStream_ensureBuffer(req) {
if (this.bufferLength)
return;
@ -935,15 +951,23 @@ var JpxStream = (function JpxStreamClosure() {
* the stream behaves like all the other DecodeStreams.
*/
var Jbig2Stream = (function Jbig2StreamClosure() {
function Jbig2Stream(bytes, dict) {
function Jbig2Stream(stream, length, dict) {
this.stream = stream;
this.length = length;
this.dict = dict;
this.bytes = bytes;
DecodeStream.call(this);
}
Jbig2Stream.prototype = Object.create(DecodeStream.prototype);
Object.defineProperty(Jbig2Stream.prototype, 'bytes', {
get: function Jbig2Stream_bytes() {
return shadow(this, 'bytes', this.stream.getBytes(this.length));
},
configurable: true
});
Jbig2Stream.prototype.ensureBuffer = function Jbig2Stream_ensureBuffer(req) {
if (this.bufferLength)
return;