trying to decompress xref stream from pdf - getting "ERROR incorrect header check"

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I am trying to parse the xref stream from PDF in JavaScript. I managed to succesfully isolate the stream itself (I checked that it's ok by comparing it in debugging mode with the value between steram. and endstream tags in PDF.

However, when I try to inflate it using pako lib, I get an error saying: ERROR incorrect header check.

The compression method is FlateDecode, which can be seen from the dictionary.

Here is the code in question:

const dict = pdfStr.slice(pdf.startXRef);
            const xrefStreamStart = this.getSubstringIndex(dict, 'stream', 1) + 'stream'.length + 2;
            const xrefStreamEnd = this.getSubstringIndex(dict, 'endstream', 1) + 1;
            const xrefStream = dict.slice(xrefStreamStart, xrefStreamEnd);
            const inflatedXrefStream = pako.inflate(this.str2ab(xrefStream), { to: 'string' });


pdfStr is the whole PDF read as a string, while *pdf.startXRef* holds the value of the position of the xref stream object.

Here's the whole PDF if someone wants to have a look: https://easyupload.io/lzf9he

EDIT: As mcernak has suggested I had a problem that I included /r and /n in the stream. However, now that I corrected the code I got a different error: invalid distance too far back

pdf javascript
1 Answers

The stream content is located between stream\r\n and \r\nendstream.

You need to take into account those two additional characters (\r\n) at the beginning and at the end to read the correct data:

const dict = pdfStr.slice(pdf.startXRef);
const xrefStreamStart = this.getSubstringIndex(dict, 'stream', 1) + 'stream'.length + 2;
const xrefStreamEnd = this.getSubstringIndex(dict, 'endstream', 1) - 2;
const xrefStream = dict.slice(xrefStreamStart, xrefStreamEnd);
const inflatedXrefStream = pako.inflate(this.str2ab(xrefStream), { to: 'string' });
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