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https://github.com/qpdf/qpdf.git
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Improve stream length recovery
Eliminate PCRE and find endobj not preceded by endstream. Be more lax about placement of endstream and endobj.
This commit is contained in:
Jay Berkenbilt
parent
3082e4e606
commit
ca5b1d267a
@ -11,6 +11,12 @@
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the (bool, T*) version of the constructor instead. If not, just
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remove the second parameter.
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2017-08-09 Jay Berkenbilt <ejb@ql.org>
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* When recovering stream length, find endobj without endstream as
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well as just looking for endstream. Be a little more lax about
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where we allow it to be found.
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2017-08-05 Jay Berkenbilt <ejb@ql.org>
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* Add --single-pages option to cause output to be written to a
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@ -1030,6 +1030,7 @@ class QPDF
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// Methods to support pattern finding
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bool findHeader();
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bool findStartxref();
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bool findEndstream();
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// methods to support linearization checking -- implemented in
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// QPDF_linearization.cc
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@ -1231,76 +1231,43 @@ QPDF::readObject(PointerHolder<InputSource> input,
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return object;
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}
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bool
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QPDF::findEndstream()
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{
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// Find endstream or endobj. Position the input at that token.
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QPDFTokenizer::Token t = readToken(this->file, true);
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if ((t.getType() == QPDFTokenizer::tt_word) &&
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((t.getValue() == "endobj") ||
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(t.getValue() == "endstream")));
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{
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this->file->seek(this->file->getLastOffset(), SEEK_SET);
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return true;
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}
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return false;
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}
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size_t
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QPDF::recoverStreamLength(PointerHolder<InputSource> input,
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int objid, int generation,
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qpdf_offset_t stream_offset)
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{
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PCRE endobj_re("^\\s*endobj\\b");
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// Try to reconstruct stream length by looking for
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// endstream(\r\n?|\n)endobj
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// endstream or endobj
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warn(QPDFExc(qpdf_e_damaged_pdf, input->getName(),
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this->last_object_description, stream_offset,
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"attempting to recover stream length"));
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input->seek(0, SEEK_END);
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qpdf_offset_t eof = input->tell();
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input->seek(stream_offset, SEEK_SET);
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qpdf_offset_t last_line_offset = 0;
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PatternFinder ef(*this, &QPDF::findEndstream);
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size_t length = 0;
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static int const line_end_length = 12; // room for endstream\r\n\0
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char last_line_end[line_end_length];
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while (input->tell() < eof)
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if (this->file->findFirst("end", stream_offset, 0, ef))
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{
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std::string line = input->readLine(50);
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qpdf_offset_t line_offset = input->getLastOffset();
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if (endobj_re.match(line.c_str()))
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length = this->file->tell() - stream_offset;
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// Reread endstream but, if it was endobj, don't skip that.
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QPDFTokenizer::Token t = readToken(this->file);
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if (t.getValue() == "endobj")
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{
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qpdf_offset_t endstream_offset = 0;
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if (last_line_offset >= line_end_length)
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{
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qpdf_offset_t cur_offset = input->tell();
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// Read from the end of the last line, guaranteeing
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// null termination
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qpdf_offset_t search_offset =
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line_offset - (line_end_length - 1);
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input->seek(search_offset, SEEK_SET);
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memset(last_line_end, '\0', line_end_length);
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input->read(last_line_end, line_end_length - 1);
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input->seek(cur_offset, SEEK_SET);
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// if endstream[\r\n] will fit in last_line_end, the
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// 'e' has to be in one of the first three spots.
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// Check explicitly rather than using strstr directly
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// in case there are nulls right before endstream.
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char* p = ((last_line_end[0] == 'e') ? last_line_end :
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(last_line_end[1] == 'e') ? last_line_end + 1 :
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(last_line_end[2] == 'e') ? last_line_end + 2 :
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0);
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char* endstream_p = 0;
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if (p)
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{
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char* p1 = strstr(p, "endstream\n");
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char* p2 = strstr(p, "endstream\r");
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endstream_p = (p1 ? p1 : p2);
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}
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if (endstream_p)
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{
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endstream_offset =
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search_offset + (endstream_p - last_line_end);
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}
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}
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if (endstream_offset > 0)
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{
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// Stream probably ends right before "endstream"
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length = endstream_offset - stream_offset;
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// Go back to where we would have been if we had just
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// read the endstream.
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input->seek(line_offset, SEEK_SET);
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break;
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}
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}
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last_line_offset = line_offset;
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this->file->seek(this->file->getLastOffset(), SEEK_SET);
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}
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}
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if (length)
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@ -1,10 +1,25 @@
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WARNING: bad24.pdf (object 4 0, file position 385): expected endstream
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WARNING: bad24.pdf (object 4 0, file position 341): attempting to recover stream length
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WARNING: bad24.pdf (object 4 0, file position 341): unable to recover stream data; treating stream as empty
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WARNING: bad24.pdf (object 4 0, file position 778): EOF while reading token
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/QTest is implicit
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/QTest is indirect and has type null (2)
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/QTest is null
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WARNING: bad24.pdf (object 4 0, file position 341): recovered stream length: 54
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/QTest is indirect and has type stream (10)
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/QTest is a stream. Dictionary: << /Length 44 >>
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Raw stream data:
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BT
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/F1 24 Tf
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72 720 Td
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(Potato) Tj
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ET
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enxstream
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Uncompressed stream data:
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BT
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/F1 24 Tf
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72 720 Td
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(Potato) Tj
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ET
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enxstream
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End of stream data
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unparse: 4 0 R
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unparseResolved: null
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unparseResolved: 4 0 R
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test 1 done
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@ -5,10 +5,16 @@ WARNING: issue-101.pdf (file position 1242): expected dictionary key but found n
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WARNING: issue-101.pdf (file position 1242): dictionary ended prematurely; using null as value for last key
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WARNING: issue-101.pdf (object 5 0, file position 1438): /Length key in stream dictionary is not an integer
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WARNING: issue-101.pdf (object 5 0, file position 1509): attempting to recover stream length
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WARNING: issue-101.pdf (object 5 0, file position 1509): recovered stream length: 205
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WARNING: issue-101.pdf (object 5 0, file position 1509): recovered stream length: 8
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WARNING: issue-101.pdf (trailer, file position 1631): /Length key in stream dictionary is not an integer
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WARNING: issue-101.pdf (trailer, file position 1702): attempting to recover stream length
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WARNING: issue-101.pdf (trailer, file position 1702): recovered stream length: 12
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WARNING: issue-101.pdf (trailer, file position 2026): /Length key in stream dictionary is not an integer
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WARNING: issue-101.pdf (trailer, file position 2097): attempting to recover stream length
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WARNING: issue-101.pdf (trailer, file position 2097): recovered stream length: 709
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WARNING: issue-101.pdf (trailer, file position 2097): recovered stream length: 12
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WARNING: issue-101.pdf (trailer, file position 2613): /Length key in stream dictionary is not an integer
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WARNING: issue-101.pdf (trailer, file position 2684): attempting to recover stream length
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WARNING: issue-101.pdf (trailer, file position 2684): recovered stream length: 74
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WARNING: issue-101.pdf (trailer, file position 2928): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (trailer, file position 2929): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (trailer, file position 2928): expected dictionary key but found non-name object; inserting key /QPDFFake1
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@ -22,8 +28,32 @@ WARNING: issue-101.pdf (trailer, file position 3410): attempting to recover stre
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WARNING: issue-101.pdf (trailer, file position 3410): recovered stream length: 12
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WARNING: issue-101.pdf (trailer, file position 3560): /Length key in stream dictionary is not an integer
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WARNING: issue-101.pdf (trailer, file position 3631): attempting to recover stream length
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WARNING: issue-101.pdf (trailer, file position 3631): recovered stream length: 167
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WARNING: issue-101.pdf (trailer, file position 3631): recovered stream length: 8
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WARNING: issue-101.pdf (trailer, file position 4113): /Length key in stream dictionary is not an integer
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WARNING: issue-101.pdf (trailer, file position 4184): attempting to recover stream length
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WARNING: issue-101.pdf (trailer, file position 4184): unable to recover stream data; treating stream as empty
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issue-101.pdf: unable to find trailer dictionary while recovering damaged file
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WARNING: issue-101.pdf (trailer, file position 4184): recovered stream length: 8
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WARNING: issue-101.pdf (file position 591): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 625): treating unexpected brace token as null
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WARNING: issue-101.pdf (file position 626): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 637): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 639): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 644): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 647): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 687): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 691): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 696): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 698): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 701): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 711): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 742): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 745): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 747): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 777): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 790): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 800): treating unexpected brace token as null
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WARNING: issue-101.pdf (file position 801): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 811): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 819): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 832): unknown token while reading object; treating as string
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WARNING: issue-101.pdf (file position 856): unexpected >
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issue-101.pdf (file position 856): unable to find /Root dictionary
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