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Only skip parsing a stream in Parser_makeFilter when we know for sure that it is empty (PR 6372 follow-up)

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For PDF files with multiple `/Filter`s, where the `/Length` entry is zero, we fail to render the file correctly. The reason is that `maybeLength` is `null` for the every filter except the first, and `!maybeLength` is thus truthy.
Hence it seems that we should completely ignore the `/Length` entry and also explicitly check `maybeLength === 0`.

Note that I've not (yet) come across a PDF file with this issue in the wild, but given all the stupid things PDF generators do I wouldn't be surprised if such a file actually exists. In order to prevent a possible future bug, I'm submitting this patch which includes a hand-edited PDF file that we currently cannot render correctly (but e.g. Adobe Reader can).
This commit is contained in:
Jonas Jenwald 2016-09-25 12:19:22 +02:00
parent 6c263c1994
commit a22f0ae820
4 changed files with 12 additions and 1 deletions
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5
src/core/parser.js
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@ -564,7 +564,10 @@ var Parser = (function ParserClosure() {
return stream;
},
makeFilter: function Parser_makeFilter(stream, name, maybeLength, params) {
if (stream.dict.get('Length') === 0 && !maybeLength) {
// Since the 'Length' entry in the stream dictionary can be completely
// wrong, e.g. zero for non-empty streams, only skip parsing the stream
// when we can be absolutely certain that it actually is empty.
if (maybeLength === 0) {
warn('Empty "' + name + '" stream.');
return new NullStream(stream);
}