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ladybird/Userland/Libraries/LibPDF/DocumentParser.cpp
Julian Offenhäuser 34350ee9e7 LibPDF: Allow reading documents with incremental updates 
The PDF spec allows incremental changes of a document by appending a
new XRef table and file trailer to it. These will only contain the
changed objects and will point back to the previous change, forming an
arbitrarily long chain of XRef sections and file trailers.

Every one of those XRef sections may be encoded as an XRef stream as
well, in which case the trailer is part of the stream dictionary as
usual. To make this easier, I made it so every XRef table may "own" a
trailer. This means that the main file trailer is now part of the main
XRef table.
2023-02-12 10:55:37 +00:00

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/*
* Copyright (c) 2021-2022, Matthew Olsson <mattco@serenityos.org>
* Copyright (c) 2022, Julian Offenhäuser <offenhaeuser@protonmail.com>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/BitStream.h>
#include <AK/Endian.h>
#include <AK/MemoryStream.h>
#include <AK/Tuple.h>
#include <LibPDF/CommonNames.h>
#include <LibPDF/Document.h>
#include <LibPDF/DocumentParser.h>
#include <LibPDF/ObjectDerivatives.h>
namespace PDF {
DocumentParser::DocumentParser(Document* document, ReadonlyBytes bytes)
: Parser(document, bytes)
{
}
PDFErrorOr<void> DocumentParser::initialize()
{
TRY(parse_header());
auto const linearization_result = TRY(initialize_linearization_dict());
if (linearization_result == LinearizationResult::NotLinearized)
return initialize_non_linearized_xref_table();
bool is_linearized = m_linearization_dictionary.has_value();
if (is_linearized) {
// The file may have been linearized at one point, but could have been updated afterwards,
// which means it is no longer a linearized PDF file.
is_linearized = m_linearization_dictionary.value().length_of_file == m_reader.bytes().size();
if (!is_linearized) {
// FIXME: The file shouldn't be treated as linearized, yet the xref tables are still
// split. This might take some tweaking to ensure correct behavior, which can be
// implemented later.
TODO();
}
}
if (is_linearized)
return initialize_linearized_xref_table();
return initialize_non_linearized_xref_table();
}
PDFErrorOr<Value> DocumentParser::parse_object_with_index(u32 index)
{
VERIFY(m_xref_table->has_object(index));
if (m_xref_table->is_object_compressed(index))
// The object can be found in a object stream
return parse_compressed_object_with_index(index);
auto byte_offset = m_xref_table->byte_offset_for_object(index);
m_reader.move_to(byte_offset);
auto indirect_value = TRY(parse_indirect_value());
VERIFY(indirect_value->index() == index);
return indirect_value->value();
}
PDFErrorOr<void> DocumentParser::parse_header()
{
// FIXME: Do something with the version?
m_reader.set_reading_forwards();
if (m_reader.remaining() == 0)
return error("Empty PDF document");
m_reader.move_to(0);
if (m_reader.remaining() < 8 || !m_reader.matches("%PDF-"))
return error("Not a PDF document");
m_reader.move_by(5);
char major_ver = m_reader.read();
if (major_ver != '1' && major_ver != '2')
return error(DeprecatedString::formatted("Unknown major version \"{}\"", major_ver));
if (m_reader.read() != '.')
return error("Malformed PDF version");
char minor_ver = m_reader.read();
if (minor_ver < '0' || minor_ver > '7')
return error(DeprecatedString::formatted("Unknown minor version \"{}\"", minor_ver));
m_reader.consume_eol();
// Parse optional high-byte comment, which signifies a binary file
// FIXME: Do something with this?
auto comment = parse_comment();
if (!comment.is_empty()) {
auto binary = comment.length() >= 4;
if (binary) {
for (size_t i = 0; i < comment.length() && binary; i++)
binary = static_cast<u8>(comment[i]) > 128;
}
}
return {};
}
PDFErrorOr<DocumentParser::LinearizationResult> DocumentParser::initialize_linearization_dict()
{
// parse_header() is called immediately before this, so we are at the right location
auto indirect_value = Value(*TRY(parse_indirect_value()));
auto dict_value = TRY(m_document->resolve(indirect_value));
if (!dict_value.has<NonnullRefPtr<Object>>())
return error("Expected linearization object to be a dictionary");
auto dict_object = dict_value.get<NonnullRefPtr<Object>>();
if (!dict_object->is<DictObject>())
return LinearizationResult::NotLinearized;
auto dict = dict_object->cast<DictObject>();
if (!dict->contains(CommonNames::Linearized))
return LinearizationResult::NotLinearized;
if (!dict->contains(CommonNames::L, CommonNames::H, CommonNames::O, CommonNames::E, CommonNames::N, CommonNames::T))
return error("Malformed linearization dictionary");
auto length_of_file = dict->get_value(CommonNames::L);
auto hint_table = dict->get_value(CommonNames::H);
auto first_page_object_number = dict->get_value(CommonNames::O);
auto offset_of_first_page_end = dict->get_value(CommonNames::E);
auto number_of_pages = dict->get_value(CommonNames::N);
auto offset_of_main_xref_table = dict->get_value(CommonNames::T);
auto first_page = dict->get(CommonNames::P).value_or({});
// Validation
if (!length_of_file.has_u32()
|| !hint_table.has<NonnullRefPtr<Object>>()
|| !first_page_object_number.has_u32()
|| !number_of_pages.has_u16()
|| !offset_of_main_xref_table.has_u32()
|| (!first_page.has<Empty>() && !first_page.has_u32())) {
return error("Malformed linearization dictionary parameters");
}
auto hint_table_array = hint_table.get<NonnullRefPtr<Object>>()->cast<ArrayObject>();
auto hint_table_size = hint_table_array->size();
if (hint_table_size != 2 && hint_table_size != 4)
return error("Expected hint table to be of length 2 or 4");
auto primary_hint_stream_offset = hint_table_array->at(0);
auto primary_hint_stream_length = hint_table_array->at(1);
Value overflow_hint_stream_offset;
Value overflow_hint_stream_length;
if (hint_table_size == 4) {
overflow_hint_stream_offset = hint_table_array->at(2);
overflow_hint_stream_length = hint_table_array->at(3);
}
if (!primary_hint_stream_offset.has_u32()
|| !primary_hint_stream_length.has_u32()
|| (!overflow_hint_stream_offset.has<Empty>() && !overflow_hint_stream_offset.has_u32())
|| (!overflow_hint_stream_length.has<Empty>() && !overflow_hint_stream_length.has_u32())) {
return error("Malformed hint stream");
}
m_linearization_dictionary = LinearizationDictionary {
length_of_file.get_u32(),
primary_hint_stream_offset.get_u32(),
primary_hint_stream_length.get_u32(),
overflow_hint_stream_offset.has<Empty>() ? NumericLimits<u32>::max() : overflow_hint_stream_offset.get_u32(),
overflow_hint_stream_length.has<Empty>() ? NumericLimits<u32>::max() : overflow_hint_stream_length.get_u32(),
first_page_object_number.get_u32(),
offset_of_first_page_end.get_u32(),
number_of_pages.get_u16(),
offset_of_main_xref_table.get_u32(),
first_page.has<Empty>() ? NumericLimits<u32>::max() : first_page.get_u32(),
};
return LinearizationResult::Linearized;
}
PDFErrorOr<void> DocumentParser::initialize_linearized_xref_table()
{
// The linearization parameter dictionary has just been parsed, and the xref table
// comes immediately after it. We are in the correct spot.
m_xref_table = TRY(parse_xref_table());
// Also parse the main xref table and merge into the first-page xref table. Note
// that we don't use the main xref table offset from the linearization dict because
// for some reason, it specified the offset of the whitespace after the object
// index start and length? So it's much easier to do it this way.
auto main_xref_table_offset = m_xref_table->trailer()->get_value(CommonNames::Prev).to_int();
m_reader.move_to(main_xref_table_offset);
auto main_xref_table = TRY(parse_xref_table());
TRY(m_xref_table->merge(move(*main_xref_table)));
return validate_xref_table_and_fix_if_necessary();
}
PDFErrorOr<void> DocumentParser::initialize_hint_tables()
{
auto linearization_dict = m_linearization_dictionary.value();
auto primary_offset = linearization_dict.primary_hint_stream_offset;
auto overflow_offset = linearization_dict.overflow_hint_stream_offset;
auto parse_hint_table = [&](size_t offset) -> RefPtr<StreamObject> {
m_reader.move_to(offset);
auto stream_indirect_value = parse_indirect_value();
if (stream_indirect_value.is_error())
return {};
auto stream_value = stream_indirect_value.value()->value();
if (!stream_value.has<NonnullRefPtr<Object>>())
return {};
auto stream_object = stream_value.get<NonnullRefPtr<Object>>();
if (!stream_object->is<StreamObject>())
return {};
return stream_object->cast<StreamObject>();
};
auto primary_hint_stream = parse_hint_table(primary_offset);
if (!primary_hint_stream)
return error("Invalid primary hint stream");
RefPtr<StreamObject> overflow_hint_stream;
if (overflow_offset != NumericLimits<u32>::max())
overflow_hint_stream = parse_hint_table(overflow_offset);
ByteBuffer possible_merged_stream_buffer;
ReadonlyBytes hint_stream_bytes;
if (overflow_hint_stream) {
auto primary_size = primary_hint_stream->bytes().size();
auto overflow_size = overflow_hint_stream->bytes().size();
auto total_size = primary_size + overflow_size;
auto buffer_result = ByteBuffer::create_uninitialized(total_size);
if (buffer_result.is_error())
return Error { Error::Type::Internal, "Failed to allocate hint stream buffer" };
possible_merged_stream_buffer = buffer_result.release_value();
MUST(possible_merged_stream_buffer.try_append(primary_hint_stream->bytes()));
MUST(possible_merged_stream_buffer.try_append(overflow_hint_stream->bytes()));
hint_stream_bytes = possible_merged_stream_buffer.bytes();
} else {
hint_stream_bytes = primary_hint_stream->bytes();
}
auto hint_table = TRY(parse_page_offset_hint_table(hint_stream_bytes));
auto hint_table_entries = TRY(parse_all_page_offset_hint_table_entries(hint_table, hint_stream_bytes));
// FIXME: Do something with the hint tables
return {};
}
PDFErrorOr<void> DocumentParser::initialize_non_linearized_xref_table()
{
m_reader.move_to(m_reader.bytes().size() - 1);
if (!navigate_to_before_eof_marker())
return error("No EOF marker");
if (!navigate_to_after_startxref())
return error("No xref");
m_reader.set_reading_forwards();
auto xref_offset_value = TRY(parse_number());
auto xref_offset = TRY(m_document->resolve_to<int>(xref_offset_value));
m_reader.move_to(xref_offset);
// As per 7.5.6 Incremental Updates:
// When a conforming reader reads the file, it shall build its cross-reference
// information in such a way that the most recent copy of each object shall be
// the one accessed from the file.
// NOTE: This means that we have to follow back the chain of XRef table sections
// and only add objects that were not already specified in a previous
// (and thus newer) XRef section.
while (1) {
auto xref_table = TRY(parse_xref_table());
if (!m_xref_table)
m_xref_table = xref_table;
else
TRY(m_xref_table->merge(move(*xref_table)));
if (!xref_table->trailer() || !xref_table->trailer()->contains(CommonNames::Prev))
break;
auto offset = TRY(m_document->resolve_to<int>(xref_table->trailer()->get_value(CommonNames::Prev)));
m_reader.move_to(offset);
}
return validate_xref_table_and_fix_if_necessary();
}
PDFErrorOr<void> DocumentParser::validate_xref_table_and_fix_if_necessary()
{
/* While an xref table may start with an object number other than zero, this is
very uncommon and likely a sign of a document with broken indices.
Like most other PDF parsers seem to do, we still try to salvage the situation.
NOTE: This is probably not spec-compliant behavior.*/
size_t first_valid_index = 0;
while (m_xref_table->byte_offset_for_object(first_valid_index) == invalid_byte_offset)
first_valid_index++;
if (first_valid_index) {
auto& entries = m_xref_table->entries();
bool need_to_rebuild_table = true;
for (size_t i = first_valid_index; i < entries.size(); ++i) {
if (!entries[i].in_use)
continue;
size_t actual_object_number = 0;
if (entries[i].compressed) {
auto object_stream_index = m_xref_table->object_stream_for_object(i);
auto stream_offset = m_xref_table->byte_offset_for_object(object_stream_index);
m_reader.move_to(stream_offset);
auto first_number = TRY(parse_number());
actual_object_number = first_number.get_u32();
} else {
auto byte_offset = m_xref_table->byte_offset_for_object(i);
m_reader.move_to(byte_offset);
auto indirect_value = TRY(parse_indirect_value());
actual_object_number = indirect_value->index();
}
if (actual_object_number != i - first_valid_index) {
/* Our suspicion was wrong, not all object numbers are shifted equally.
This could mean that the document is hopelessly broken, or it just
starts at a non-zero object index for some reason. */
need_to_rebuild_table = false;
break;
}
}
if (need_to_rebuild_table) {
warnln("Broken xref table detected, trying to fix it.");
entries.remove(0, first_valid_index);
}
}
return {};
}
PDFErrorOr<NonnullRefPtr<XRefTable>> DocumentParser::parse_xref_stream()
{
auto first_number = TRY(parse_number());
auto second_number = TRY(parse_number());
if (!m_reader.matches("obj"))
return error("Malformed xref object");
m_reader.move_by(3);
if (m_reader.matches_eol())
m_reader.consume_eol();
auto dict = TRY(parse_dict());
auto type = TRY(dict->get_name(m_document, CommonNames::Type))->name();
if (type != "XRef")
return error("Malformed xref dictionary");
auto field_sizes = TRY(dict->get_array(m_document, "W"));
if (field_sizes->size() != 3)
return error("Malformed xref dictionary");
auto highest_object_number = dict->get_value("Size").get<int>() - 1;
Vector<Tuple<int, int>> subsections;
if (dict->contains(CommonNames::Index)) {
auto index_array = TRY(dict->get_array(m_document, CommonNames::Index));
if (index_array->size() % 2 != 0)
return error("Malformed xref dictionary");
for (size_t i = 0; i < index_array->size(); i += 2)
subsections.append({ index_array->at(i).get<int>(), index_array->at(i + 1).get<int>() - 1 });
} else {
subsections.append({ 0, highest_object_number });
}
auto stream = TRY(parse_stream(dict));
auto table = adopt_ref(*new XRefTable());
auto field_to_long = [](ReadonlyBytes field) -> long {
long value = 0;
const u8 max = (field.size() - 1) * 8;
for (size_t i = 0; i < field.size(); ++i) {
value |= static_cast<long>(field[i]) << (max - (i * 8));
}
return value;
};
size_t byte_index = 0;
size_t subsection_index = 0;
Vector<XRefEntry> entries;
for (int entry_index = 0; subsection_index < subsections.size(); ++entry_index) {
Array<long, 3> fields;
for (size_t field_index = 0; field_index < 3; ++field_index) {
auto field_size = field_sizes->at(field_index).get_u32();
if (byte_index + field_size > stream->bytes().size())
return error("The xref stream data cut off early");
auto field = stream->bytes().slice(byte_index, field_size);
fields[field_index] = field_to_long(field);
byte_index += field_size;
}
u8 type = fields[0];
if (!field_sizes->at(0).get_u32())
type = 1;
entries.append({ fields[1], static_cast<u16>(fields[2]), type != 0, type == 2 });
auto subsection = subsections[subsection_index];
if (entry_index >= subsection.get<1>()) {
table->add_section({ subsection.get<0>(), subsection.get<1>(), entries });
entries.clear();
subsection_index++;
}
}
table->set_trailer(dict);
return table;
}
PDFErrorOr<NonnullRefPtr<XRefTable>> DocumentParser::parse_xref_table()
{
if (!m_reader.matches("xref")) {
// Since version 1.5, there may be a cross-reference stream instead
return parse_xref_stream();
}
m_reader.move_by(4);
if (!m_reader.consume_eol())
return error("Expected newline after \"xref\"");
auto table = adopt_ref(*new XRefTable());
while (m_reader.matches_number()) {
Vector<XRefEntry> entries;
auto starting_index_value = TRY(parse_number());
auto starting_index = starting_index_value.get<int>();
auto object_count_value = TRY(parse_number());
auto object_count = object_count_value.get<int>();
for (int i = 0; i < object_count; i++) {
auto offset_string = DeprecatedString(m_reader.bytes().slice(m_reader.offset(), 10));
m_reader.move_by(10);
if (!m_reader.consume(' '))
return error("Malformed xref entry");
auto generation_string = DeprecatedString(m_reader.bytes().slice(m_reader.offset(), 5));
m_reader.move_by(5);
if (!m_reader.consume(' '))
return error("Malformed xref entry");
auto letter = m_reader.read();
if (letter != 'n' && letter != 'f')
return error("Malformed xref entry");
// The line ending sequence can be one of the following:
// SP CR, SP LF, or CR LF
if (m_reader.matches(' ')) {
m_reader.consume();
auto ch = m_reader.consume();
if (ch != '\r' && ch != '\n')
return error("Malformed xref entry");
} else {
if (!m_reader.matches("\r\n"))
return error("Malformed xref entry");
m_reader.move_by(2);
}
auto offset = strtol(offset_string.characters(), nullptr, 10);
auto generation = strtol(generation_string.characters(), nullptr, 10);
entries.append({ offset, static_cast<u16>(generation), letter == 'n' });
}
table->add_section({ starting_index, object_count, entries });
}
m_reader.consume_whitespace();
if (m_reader.matches("trailer"))
table->set_trailer(TRY(parse_file_trailer()));
return table;
}
PDFErrorOr<NonnullRefPtr<DictObject>> DocumentParser::parse_file_trailer()
{
while (m_reader.matches_eol())
m_reader.consume_eol();
if (!m_reader.matches("trailer"))
return error("Expected \"trailer\" keyword");
m_reader.move_by(7);
m_reader.consume_whitespace();
auto dict = TRY(parse_dict());
if (!m_reader.matches("startxref"))
return error("Expected \"startxref\"");
m_reader.move_by(9);
m_reader.consume_whitespace();
m_reader.move_until([&](auto) { return m_reader.matches_eol(); });
VERIFY(m_reader.consume_eol());
if (!m_reader.matches("%%EOF"))
return error("Expected \"%%EOF\"");
m_reader.move_by(5);
m_reader.consume_whitespace();
return dict;
}
PDFErrorOr<Value> DocumentParser::parse_compressed_object_with_index(u32 index)
{
auto object_stream_index = m_xref_table->object_stream_for_object(index);
auto stream_offset = m_xref_table->byte_offset_for_object(object_stream_index);
m_reader.move_to(stream_offset);
auto first_number = TRY(parse_number());
auto second_number = TRY(parse_number());
if (first_number.get<int>() != object_stream_index)
return error("Mismatching object stream index");
if (second_number.get<int>() != 0)
return error("Non-zero object stream generation number");
if (!m_reader.matches("obj"))
return error("Malformed object stream");
m_reader.move_by(3);
if (m_reader.matches_eol())
m_reader.consume_eol();
auto dict = TRY(parse_dict());
auto type = TRY(dict->get_name(m_document, CommonNames::Type))->name();
if (type != "ObjStm")
return error("Invalid object stream type");
auto object_count = dict->get_value("N").get_u32();
auto first_object_offset = dict->get_value("First").get_u32();
auto stream = TRY(parse_stream(dict));
Parser stream_parser(m_document, stream->bytes());
for (u32 i = 0; i < object_count; ++i) {
auto object_number = TRY(stream_parser.parse_number());
auto object_offset = TRY(stream_parser.parse_number());
if (object_number.get_u32() == index) {
stream_parser.move_to(first_object_offset + object_offset.get_u32());
break;
}
}
return TRY(stream_parser.parse_value());
}
PDFErrorOr<DocumentParser::PageOffsetHintTable> DocumentParser::parse_page_offset_hint_table(ReadonlyBytes hint_stream_bytes)
{
if (hint_stream_bytes.size() < sizeof(PageOffsetHintTable))
return error("Hint stream is too small");
size_t offset = 0;
auto read_u32 = [&] {
u32 data = reinterpret_cast<const u32*>(hint_stream_bytes.data() + offset)[0];
offset += 4;
return AK::convert_between_host_and_big_endian(data);
};
auto read_u16 = [&] {
u16 data = reinterpret_cast<const u16*>(hint_stream_bytes.data() + offset)[0];
offset += 2;
return AK::convert_between_host_and_big_endian(data);
};
PageOffsetHintTable hint_table {
read_u32(),
read_u32(),
read_u16(),
read_u32(),
read_u16(),
read_u32(),
read_u16(),
read_u32(),
read_u16(),
read_u16(),
read_u16(),
read_u16(),
read_u16(),
};
// Verify that all of the bits_required_for_xyz fields are <= 32, since all of the numeric
// fields in PageOffsetHintTableEntry are u32
VERIFY(hint_table.bits_required_for_object_number <= 32);
VERIFY(hint_table.bits_required_for_page_length <= 32);
VERIFY(hint_table.bits_required_for_content_stream_offsets <= 32);
VERIFY(hint_table.bits_required_for_content_stream_length <= 32);
VERIFY(hint_table.bits_required_for_number_of_shared_obj_refs <= 32);
VERIFY(hint_table.bits_required_for_greatest_shared_obj_identifier <= 32);
VERIFY(hint_table.bits_required_for_fraction_numerator <= 32);
return hint_table;
}
PDFErrorOr<Vector<DocumentParser::PageOffsetHintTableEntry>> DocumentParser::parse_all_page_offset_hint_table_entries(PageOffsetHintTable const& hint_table, ReadonlyBytes hint_stream_bytes)
{
auto input_stream = TRY(try_make<FixedMemoryStream>(hint_stream_bytes));
TRY(input_stream->seek(sizeof(PageOffsetHintTable)));
LittleEndianInputBitStream bit_stream { move(input_stream) };
auto number_of_pages = m_linearization_dictionary.value().number_of_pages;
Vector<PageOffsetHintTableEntry> entries;
for (size_t i = 0; i < number_of_pages; i++)
entries.append(PageOffsetHintTableEntry {});
auto bits_required_for_object_number = hint_table.bits_required_for_object_number;
auto bits_required_for_page_length = hint_table.bits_required_for_page_length;
auto bits_required_for_content_stream_offsets = hint_table.bits_required_for_content_stream_offsets;
auto bits_required_for_content_stream_length = hint_table.bits_required_for_content_stream_length;
auto bits_required_for_number_of_shared_obj_refs = hint_table.bits_required_for_number_of_shared_obj_refs;
auto bits_required_for_greatest_shared_obj_identifier = hint_table.bits_required_for_greatest_shared_obj_identifier;
auto bits_required_for_fraction_numerator = hint_table.bits_required_for_fraction_numerator;
auto parse_int_entry = [&](u32 PageOffsetHintTableEntry::*field, u32 bit_size) -> ErrorOr<void> {
if (bit_size <= 0)
return {};
for (int i = 0; i < number_of_pages; i++) {
auto& entry = entries[i];
entry.*field = TRY(bit_stream.read_bits(bit_size));
}
return {};
};
auto parse_vector_entry = [&](Vector<u32> PageOffsetHintTableEntry::*field, u32 bit_size) -> ErrorOr<void> {
if (bit_size <= 0)
return {};
for (int page = 1; page < number_of_pages; page++) {
auto number_of_shared_objects = entries[page].number_of_shared_objects;
Vector<u32> items;
items.ensure_capacity(number_of_shared_objects);
for (size_t i = 0; i < number_of_shared_objects; i++)
items.unchecked_append(TRY(bit_stream.read_bits(bit_size)));
entries[page].*field = move(items);
}
return {};
};
TRY(parse_int_entry(&PageOffsetHintTableEntry::objects_in_page_number, bits_required_for_object_number));
TRY(parse_int_entry(&PageOffsetHintTableEntry::page_length_number, bits_required_for_page_length));
TRY(parse_int_entry(&PageOffsetHintTableEntry::number_of_shared_objects, bits_required_for_number_of_shared_obj_refs));
TRY(parse_vector_entry(&PageOffsetHintTableEntry::shared_object_identifiers, bits_required_for_greatest_shared_obj_identifier));
TRY(parse_vector_entry(&PageOffsetHintTableEntry::shared_object_location_numerators, bits_required_for_fraction_numerator));
TRY(parse_int_entry(&PageOffsetHintTableEntry::page_content_stream_offset_number, bits_required_for_content_stream_offsets));
TRY(parse_int_entry(&PageOffsetHintTableEntry::page_content_stream_length_number, bits_required_for_content_stream_length));
return entries;
}
bool DocumentParser::navigate_to_before_eof_marker()
{
m_reader.set_reading_backwards();
while (!m_reader.done()) {
m_reader.move_until([&](auto) { return m_reader.matches_eol(); });
if (m_reader.done())
return false;
m_reader.consume_eol();
if (!m_reader.matches("%%EOF"))
continue;
m_reader.move_by(5);
if (!m_reader.matches_eol())
continue;
m_reader.consume_eol();
return true;
}
return false;
}
bool DocumentParser::navigate_to_after_startxref()
{
m_reader.set_reading_backwards();
while (!m_reader.done()) {
m_reader.move_until([&](auto) { return m_reader.matches_eol(); });
auto offset = m_reader.offset() + 1;
m_reader.consume_eol();
if (!m_reader.matches("startxref"))
continue;
m_reader.move_by(9);
if (!m_reader.matches_eol())
continue;
m_reader.move_to(offset);
return true;
}
return false;
}
PDFErrorOr<RefPtr<DictObject>> DocumentParser::conditionally_parse_page_tree_node(u32 object_index)
{
auto dict_value = TRY(parse_object_with_index(object_index));
auto dict_object = dict_value.get<NonnullRefPtr<Object>>();
if (!dict_object->is<DictObject>())
return error(DeprecatedString::formatted("Invalid page tree with xref index {}", object_index));
auto dict = dict_object->cast<DictObject>();
if (!dict->contains_any_of(CommonNames::Type, CommonNames::Parent, CommonNames::Kids, CommonNames::Count))
// This is a page, not a page tree node
return RefPtr<DictObject> {};
if (!dict->contains(CommonNames::Type))
return RefPtr<DictObject> {};
auto type_object = TRY(dict->get_object(m_document, CommonNames::Type));
if (!type_object->is<NameObject>())
return RefPtr<DictObject> {};
auto type_name = type_object->cast<NameObject>();
if (type_name->name() != CommonNames::Pages)
return RefPtr<DictObject> {};
return dict;
}
}
namespace AK {
template<>
struct Formatter<PDF::DocumentParser::LinearizationDictionary> : Formatter<StringView> {
ErrorOr<void> format(FormatBuilder& format_builder, PDF::DocumentParser::LinearizationDictionary const& dict)
{
StringBuilder builder;
builder.append("{\n"sv);
builder.appendff(" length_of_file={}\n", dict.length_of_file);
builder.appendff(" primary_hint_stream_offset={}\n", dict.primary_hint_stream_offset);
builder.appendff(" primary_hint_stream_length={}\n", dict.primary_hint_stream_length);
builder.appendff(" overflow_hint_stream_offset={}\n", dict.overflow_hint_stream_offset);
builder.appendff(" overflow_hint_stream_length={}\n", dict.overflow_hint_stream_length);
builder.appendff(" first_page_object_number={}\n", dict.first_page_object_number);
builder.appendff(" offset_of_first_page_end={}\n", dict.offset_of_first_page_end);
builder.appendff(" number_of_pages={}\n", dict.number_of_pages);
builder.appendff(" offset_of_main_xref_table={}\n", dict.offset_of_main_xref_table);
builder.appendff(" first_page={}\n", dict.first_page);
builder.append('}');
return Formatter<StringView>::format(format_builder, builder.to_deprecated_string());
}
};
template<>
struct Formatter<PDF::DocumentParser::PageOffsetHintTable> : Formatter<StringView> {
ErrorOr<void> format(FormatBuilder& format_builder, PDF::DocumentParser::PageOffsetHintTable const& table)
{
StringBuilder builder;
builder.append("{\n"sv);
builder.appendff(" least_number_of_objects_in_a_page={}\n", table.least_number_of_objects_in_a_page);
builder.appendff(" location_of_first_page_object={}\n", table.location_of_first_page_object);
builder.appendff(" bits_required_for_object_number={}\n", table.bits_required_for_object_number);
builder.appendff(" least_length_of_a_page={}\n", table.least_length_of_a_page);
builder.appendff(" bits_required_for_page_length={}\n", table.bits_required_for_page_length);
builder.appendff(" least_offset_of_any_content_stream={}\n", table.least_offset_of_any_content_stream);
builder.appendff(" bits_required_for_content_stream_offsets={}\n", table.bits_required_for_content_stream_offsets);
builder.appendff(" least_content_stream_length={}\n", table.least_content_stream_length);
builder.appendff(" bits_required_for_content_stream_length={}\n", table.bits_required_for_content_stream_length);
builder.appendff(" bits_required_for_number_of_shared_obj_refs={}\n", table.bits_required_for_number_of_shared_obj_refs);
builder.appendff(" bits_required_for_greatest_shared_obj_identifier={}\n", table.bits_required_for_greatest_shared_obj_identifier);
builder.appendff(" bits_required_for_fraction_numerator={}\n", table.bits_required_for_fraction_numerator);
builder.appendff(" shared_object_reference_fraction_denominator={}\n", table.shared_object_reference_fraction_denominator);
builder.append('}');
return Formatter<StringView>::format(format_builder, builder.to_deprecated_string());
}
};
template<>
struct Formatter<PDF::DocumentParser::PageOffsetHintTableEntry> : Formatter<StringView> {
ErrorOr<void> format(FormatBuilder& format_builder, PDF::DocumentParser::PageOffsetHintTableEntry const& entry)
{
StringBuilder builder;
builder.append("{\n"sv);
builder.appendff(" objects_in_page_number={}\n", entry.objects_in_page_number);
builder.appendff(" page_length_number={}\n", entry.page_length_number);
builder.appendff(" number_of_shared_objects={}\n", entry.number_of_shared_objects);
builder.append(" shared_object_identifiers=["sv);
for (auto& identifier : entry.shared_object_identifiers)
builder.appendff(" {}", identifier);
builder.append(" ]\n"sv);
builder.append(" shared_object_location_numerators=["sv);
for (auto& numerator : entry.shared_object_location_numerators)
builder.appendff(" {}", numerator);
builder.append(" ]\n"sv);
builder.appendff(" page_content_stream_offset_number={}\n", entry.page_content_stream_offset_number);
builder.appendff(" page_content_stream_length_number={}\n", entry.page_content_stream_length_number);
builder.append('}');
return Formatter<StringView>::format(format_builder, builder.to_deprecated_string());
}
};
}
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