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In Xref_table track (maximum possible) length of uncompressed objects
Use start of next object or xref table to put an upper bound on object length. Tests reuse existing incremental-1.pdf. incremental-1-bad.pdf is incremental-1.pdf with whitespace inserted after object 1 0.
This commit is contained in:
m-holger
parent
e8849ebe35
commit
413e8acd4f
@ -737,6 +737,7 @@ class QPDF
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// For testing only -- do not add to DLL
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static bool test_json_validators();
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void test_xref();
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private:
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// It has never been safe to copy QPDF objects as there is code in the library that assumes
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@ -1133,3 +1133,9 @@ QPDF::removeSecurityRestrictions()
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acroform.replaceKey("/SigFlags", QPDFObjectHandle::newInteger(0));
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}
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}
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void
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QPDF::test_xref()
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{
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objects().xref_table().test();
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}
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@ -2,6 +2,7 @@
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#include <qpdf/QPDF_private.hh>
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#include <algorithm>
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#include <array>
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#include <cstring>
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#include <limits>
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@ -89,6 +90,21 @@ namespace
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};
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} // namespace
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void
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Xref_table::test()
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{
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std::cout << "id, gen, offset, length, next\n";
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int i = 0;
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for (auto const& entry: table) {
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if (entry.type() == 1) {
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std::cout << i << ", " << entry.gen() << ", " << entry.type() << ", " << entry.offset()
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<< ", " << entry.length() << ", " << (entry.offset() + toO(entry.length()))
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<< '\n';
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}
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++i;
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}
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}
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bool
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QPDF::findStartxref()
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{
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@ -143,6 +159,7 @@ Xref_table::initialize()
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PatternFinder sf(qpdf, &QPDF::findStartxref);
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qpdf_offset_t xref_offset = 0;
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if (file->findLast("startxref", start_offset, 0, sf)) {
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offsets.emplace_back(file->tell(), 0);
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xref_offset = QUtil::string_to_ll(read_token().getValue().c_str());
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}
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@ -167,10 +184,30 @@ Xref_table::initialize()
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}
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}
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calc_lengths();
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prepare_obj_table();
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initialized_ = true;
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}
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void
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Xref_table::calc_lengths()
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{
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if (offsets.size() > 1) {
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std::sort(offsets.begin(), offsets.end());
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size_t id = 0;
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auto end = table.size();
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qpdf_offset_t offset = 0;
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for (auto const& item: offsets) {
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if (id && id < end) {
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table[id].length_ = toS(item.first - offset);
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}
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offset = item.first;
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id = item.second;
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}
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}
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offsets.clear();
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}
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// Remove any dangling reference picked up while parsing or reconstructing the xref table from the
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// object table.
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void
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@ -234,6 +271,7 @@ Xref_table::reconstruct(QPDFExc& e)
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file->seek(0, SEEK_END);
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qpdf_offset_t eof = file->tell();
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offsets.emplace_back(eof, 0);
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file->seek(0, SEEK_SET);
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// Don't allow very long tokens here during recovery. All the interesting tokens are covered.
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static size_t const MAX_LEN = 10;
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@ -256,8 +294,13 @@ Xref_table::reconstruct(QPDFExc& e)
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}
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}
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file->seek(pos, SEEK_SET);
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} else if (!trailer_ && t1.isWord("trailer")) {
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trailers.emplace_back(file->tell());
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} else if (t1.isWord("trailer")) {
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offsets.emplace_back(token_start, 0);
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if (!trailer_) {
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trailers.emplace_back(file->tell());
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}
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} else if (t1.isWord("xref")) {
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offsets.emplace_back(token_start, 0);
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}
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file->findAndSkipNextEOL();
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}
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@ -280,8 +323,9 @@ Xref_table::reconstruct(QPDFExc& e)
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for (auto it = found_objects.rbegin(); it != rend; it++) {
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auto [obj, gen, token_start] = *it;
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insert(obj, 1, token_start, gen);
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check_warnings();
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}
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calc_lengths();
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check_warnings();
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if (!trailer_) {
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qpdf_offset_t max_offset{0};
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@ -401,6 +445,7 @@ Xref_table::read(qpdf_offset_t xref_offset)
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while (QUtil::is_space(buf[skip])) {
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++skip;
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}
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offsets.emplace_back(xref_offset, 0);
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xref_offset = process_section(xref_offset + skip);
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} else {
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xref_offset = read_stream(xref_offset);
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@ -1037,6 +1082,11 @@ Xref_table::insert(int obj, int f0, qpdf_offset_t f1, int f2)
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// entry. This will need to be revisited when we want to support incremental updates or more
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// comprehensive checking.
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QTC::TC("qpdf", "QPDF xref replaced / deleted object", old_type == 0 ? 0 : 1);
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if (f0 == 1) {
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// Save offset of deleted/replaced object to allow us to calculate object length once we
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// are finished loading the xref table.
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offsets.emplace_back(f1, 0);
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}
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return;
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}
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@ -1051,12 +1101,13 @@ Xref_table::insert(int obj, int f0, qpdf_offset_t f1, int f2)
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// f2 is generation
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QTC::TC("qpdf", "QPDF xref gen > 0", (f2 > 0) ? 1 : 0);
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entry = {f2, Uncompressed(f1)};
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break;
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offsets.emplace_back(f1, static_cast<size_t>(obj));
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return;
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case 2:
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entry = {0, Compressed(toI(f1), f2)};
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object_streams_ = true;
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break;
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return;
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default:
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throw qpdf.damagedPDF(
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@ -228,6 +228,8 @@ class QPDF::Objects
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return first_item_offset_;
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}
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void test();
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private:
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// Object, count, offset of first entry
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typedef std::tuple<int, int, qpdf_offset_t> Subsection;
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@ -294,7 +296,14 @@ class QPDF::Objects
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return type() == 2 ? std::get<2>(entry).stream_index : 0;
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}
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size_t
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length() const noexcept
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{
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return length_;
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}
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int gen_{0};
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size_t length_{0}; // For uncompressed objects.
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Xref entry;
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qpdf_offset_t end_before_space_{0};
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qpdf_offset_t end_after_space_{0};
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@ -314,6 +323,7 @@ class QPDF::Objects
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}
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void read(qpdf_offset_t offset);
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void calc_lengths();
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void prepare_obj_table();
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// Methods to parse tables
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@ -376,6 +386,9 @@ class QPDF::Objects
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std::vector<Entry> table;
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QPDFObjectHandle trailer_;
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// Temporary offset table used to calculate uncompressed object length.
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std::vector<std::pair<qpdf_offset_t, size_t>> offsets;
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bool attempt_recovery_{true};
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bool initialized_{false};
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bool ignore_streams_{false};
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@ -34,7 +34,8 @@ set(TEST_PROGRAMS
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rc4
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runlength
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sha2
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sparse_array)
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sparse_array
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xref)
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set(TEST_C_PROGRAMS
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logger_c)
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34
libtests/qtest/xref.test
Normal file
34
libtests/qtest/xref.test
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@ -0,0 +1,34 @@
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#!/usr/bin/env perl
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require 5.008;
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use warnings;
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use strict;
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unshift(@INC, '.');
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chdir("xref") or die "chdir testdir failed: $!\n";
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require TestDriver;
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my $td = new TestDriver('xref');
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my @files = ("incremental-1",
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"incremental-1-bad",
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);
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foreach my $file (@files)
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{
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$td->runtest("xref $file",
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{$td->COMMAND => "xref $file.pdf"},
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{$td->FILE => "$file.out",
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$td->EXIT_STATUS => 0},
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$td->NORMALIZE_NEWLINES);
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}
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cleanup();
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$td->report(scalar(@files));
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sub cleanup
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{
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unlink "tmp";
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}
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12
libtests/qtest/xref/incremental-1-bad.out
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12
libtests/qtest/xref/incremental-1-bad.out
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@ -0,0 +1,12 @@
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WARNING: incremental-1-bad.pdf: file is damaged
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WARNING: incremental-1-bad.pdf (offset 1241): xref not found
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WARNING: incremental-1-bad.pdf: Attempting to reconstruct cross-reference table
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id, gen, offset, length, next
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1, 0, 1, 9, 93, 102
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2, 0, 1, 102, 72, 174
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3, 0, 1, 1108, 172, 1280
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4, 1, 1, 987, 26, 1013
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5, 0, 1, 442, 35, 477
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6, 0, 1, 477, 118, 595
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7, 0, 1, 1013, 95, 1108
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xref done
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145
libtests/qtest/xref/incremental-1-bad.pdf
Normal file
145
libtests/qtest/xref/incremental-1-bad.pdf
Normal file
@ -0,0 +1,145 @@
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%PDF-1.3
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1 0 obj
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<<
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/Type /Catalog
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/Pages 2 0 R
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>>
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endobj
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2 0 obj
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<<
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/Type /Pages
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/Kids [
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3 0 R
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]
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/Count 1
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>>
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endobj
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3 0 obj
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<<
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/Type /Page
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/Parent 2 0 R
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/MediaBox [0 0 612 792]
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/Contents 4 0 R
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/Resources <<
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/ProcSet 5 0 R
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/Font <<
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/F1 6 0 R
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>>
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>>
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>>
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endobj
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4 0 obj
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<<
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/Length 44
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>>
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stream
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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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endstream
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endobj
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5 0 obj
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[
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/PDF
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/Text
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]
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endobj
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6 0 obj
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<<
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/Type /Font
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/Subtype /Type1
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/Name /F1
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/BaseFont /Helvetica
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/Encoding /WinAnsiEncoding
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>>
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endobj
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xref
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0 7
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0000000000 65535 f
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0000000009 00000 n
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0000000063 00000 n
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0000000135 00000 n
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0000000307 00000 n
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0000000403 00000 n
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0000000438 00000 n
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trailer <<
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/Size 7
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/Root 1 0 R
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>>
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startxref
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556
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%%EOF
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% Delete object 4 and increment generation
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xref
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0 1
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0000000004 65535 f
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4 1
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0000000000 00001 f
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trailer <<
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/Size 7
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/Root 1 0 R
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/Prev 556
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>>
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startxref
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807
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%%EOF
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% Reuse object 4
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4 1 obj
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[ 7 0 R ]
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endobj
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7 0 obj
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<<
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/Length 43
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>>
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stream
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BT
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/F1 24 Tf
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72 720 Td
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(Salad) Tj
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ET
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endstream
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endobj
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3 0 obj
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<<
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/Type /Page
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/Parent 2 0 R
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/MediaBox [0 0 612 792]
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/Contents 4 1 R
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/Resources <<
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/ProcSet 5 0 R
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/Font <<
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/F1 6 0 R
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>>
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>>
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>>
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endobj
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xref
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0 1
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0000000000 65535 f
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3 2
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0000001069 00000 n
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0000000948 00001 n
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7 1
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0000000974 00000 n
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trailer <<
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/Size 8
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/Root 1 0 R
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/Prev 807
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/Gone 4 0 R
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>>
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startxref
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1241
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%%EOF
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9
libtests/qtest/xref/incremental-1.out
Normal file
9
libtests/qtest/xref/incremental-1.out
Normal file
@ -0,0 +1,9 @@
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id, gen, offset, length, next
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1, 0, 1, 9, 54, 63
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2, 0, 1, 63, 72, 135
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3, 0, 1, 1069, 172, 1241
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4, 1, 1, 948, 26, 974
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5, 0, 1, 403, 35, 438
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6, 0, 1, 438, 118, 556
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7, 0, 1, 974, 95, 1069
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xref done
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145
libtests/qtest/xref/incremental-1.pdf
Normal file
145
libtests/qtest/xref/incremental-1.pdf
Normal file
@ -0,0 +1,145 @@
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%PDF-1.3
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1 0 obj
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<<
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/Type /Catalog
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/Pages 2 0 R
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>>
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endobj
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2 0 obj
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<<
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/Type /Pages
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/Kids [
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3 0 R
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]
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/Count 1
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>>
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endobj
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3 0 obj
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<<
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/Type /Page
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/Parent 2 0 R
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/MediaBox [0 0 612 792]
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/Contents 4 0 R
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/Resources <<
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/ProcSet 5 0 R
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/Font <<
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/F1 6 0 R
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>>
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>>
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>>
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endobj
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4 0 obj
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<<
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/Length 44
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>>
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stream
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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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endstream
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endobj
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5 0 obj
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[
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/PDF
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/Text
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]
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endobj
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6 0 obj
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<<
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/Type /Font
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/Subtype /Type1
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/Name /F1
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/BaseFont /Helvetica
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/Encoding /WinAnsiEncoding
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>>
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endobj
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xref
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0 7
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0000000000 65535 f
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0000000009 00000 n
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0000000063 00000 n
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0000000135 00000 n
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0000000307 00000 n
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0000000403 00000 n
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0000000438 00000 n
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trailer <<
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/Size 7
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/Root 1 0 R
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>>
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startxref
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556
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%%EOF
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% Delete object 4 and increment generation
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xref
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0 1
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0000000004 65535 f
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4 1
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0000000000 00001 f
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trailer <<
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/Size 7
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/Root 1 0 R
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/Prev 556
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>>
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startxref
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807
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%%EOF
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% Reuse object 4
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4 1 obj
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[ 7 0 R ]
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endobj
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7 0 obj
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<<
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/Length 43
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>>
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stream
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BT
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/F1 24 Tf
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72 720 Td
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(Salad) Tj
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ET
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endstream
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endobj
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3 0 obj
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<<
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/Type /Page
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/Parent 2 0 R
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/MediaBox [0 0 612 792]
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/Contents 4 1 R
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/Resources <<
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/ProcSet 5 0 R
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/Font <<
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/F1 6 0 R
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>>
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>>
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>>
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endobj
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xref
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0 1
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0000000000 65535 f
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3 2
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0000001069 00000 n
|
||||
0000000948 00001 n
|
||||
7 1
|
||||
0000000974 00000 n
|
||||
trailer <<
|
||||
/Size 8
|
||||
/Root 1 0 R
|
||||
/Prev 807
|
||||
/Gone 4 0 R
|
||||
>>
|
||||
startxref
|
||||
1241
|
||||
%%EOF
|
||||
25
libtests/xref.cc
Normal file
25
libtests/xref.cc
Normal file
@ -0,0 +1,25 @@
|
||||
#include <qpdf/QPDF.hh>
|
||||
|
||||
#include <cstdlib>
|
||||
#include <iostream>
|
||||
#include <map>
|
||||
|
||||
int
|
||||
main(int argc, char* argv[])
|
||||
{
|
||||
if (argc != 2) {
|
||||
std::cerr << "usage: xref INFILE\n";
|
||||
std::exit(2);
|
||||
}
|
||||
|
||||
try {
|
||||
QPDF qpdf;
|
||||
qpdf.processFile(argv[1]);
|
||||
qpdf.test_xref();
|
||||
} catch (std::exception& e) {
|
||||
std::cerr << e.what() << '\n';
|
||||
std::exit(2);
|
||||
}
|
||||
std::cout << "xref done\n";
|
||||
return 0;
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user