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Refactor xref reconstruction

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Avoid unnecessary rescanning of lines and repositioning of input file.
Limit max size of tokens.
This commit is contained in:
m-holger 2024-07-28 18:03:30 +01:00
parent bbe732c015
commit aa4f288291
1 changed files with 8 additions and 11 deletions
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19
libqpdf/QPDF.cc
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@ -572,18 +572,13 @@ QPDF::reconstruct_xref(QPDFExc& e)
m->file->seek(0, SEEK_END);
qpdf_offset_t eof = m->file->tell();
m->file->seek(0, SEEK_SET);
qpdf_offset_t line_start = 0;
// Don't allow very long tokens here during recovery.
static size_t const MAX_LEN = 100;
// Don't allow very long tokens here during recovery. All the interesting tokens are covered.
static size_t const MAX_LEN = 10;
while (m->file->tell() < eof) {
m->file->findAndSkipNextEOL();
qpdf_offset_t next_line_start = m->file->tell();
m->file->seek(line_start, SEEK_SET);
QPDFTokenizer::Token t1 = readToken(m->file, MAX_LEN);
qpdf_offset_t token_start = m->file->tell() - toO(t1.getValue().length());
if (token_start >= next_line_start) {
// don't process yet -- wait until we get to the line containing this token
} else if (t1.isInteger()) {
if (t1.isInteger()) {
auto pos = m->file->tell();
QPDFTokenizer::Token t2 = readToken(m->file, MAX_LEN);
if ((t2.isInteger()) && (readToken(m->file, MAX_LEN).isWord("obj"))) {
int obj = QUtil::string_to_int(t1.getValue().c_str());
@ -595,17 +590,19 @@ QPDF::reconstruct_xref(QPDFExc& e)
"", 0, "ignoring object with impossibly large id " + std::to_string(obj)));
}
}
m->file->seek(pos, SEEK_SET);
} else if (!m->trailer.isInitialized() && t1.isWord("trailer")) {
auto pos = m->file->tell();
QPDFObjectHandle t = readTrailer();
if (!t.isDictionary()) {
// Oh well. It was worth a try.
} else {
setTrailer(t);
}
m->file->seek(pos, SEEK_SET);
}
check_warnings();
m->file->seek(next_line_start, SEEK_SET);
line_start = next_line_start;
m->file->findAndSkipNextEOL();
}
m->deleted_objects.clear();