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serenity/Userland/Libraries/LibPDF/DocumentParser.cpp

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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 <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<Version> DocumentParser::initialize()
{
m_reader.set_reading_forwards();
if (m_reader.remaining() == 0)
return error("Empty PDF document");
auto maybe_version = parse_header();
if (maybe_version.is_error()) {
warnln("{}", maybe_version.error().message());
warnln("No valid PDF header detected, continuing anyway.");
maybe_version = Version { 1, 6 }; // ¯\_(ツ)_/¯
}
auto const linearization_result = TRY(initialize_linearization_dict());
if (linearization_result == LinearizationResult::NotLinearized) {
TRY(initialize_non_linearized_xref_table());
return maybe_version.value();
}
bool is_linearized = m_linearization_dictionary.has_value();
if (is_linearized) {
// If the length given in the linearization dictionary is not equal to the length
// of the document, then this file has most likely been incrementally updated, and
// should no longer be treated as linearized.
// FIXME: This check requires knowing the full size of the file, while linearization
// is all about being able to render some of it without having to download all of it.
// PDF 2.0 Annex G.7 "Accessing an updated file" talks about this some,
// but mostly just throws its hand in the air.
is_linearized = m_linearization_dictionary.value().length_of_file == m_reader.bytes().size();
}
if (is_linearized)
TRY(initialize_linearized_xref_table());
else
TRY(initialize_non_linearized_xref_table());
return maybe_version.value();
}
PDFErrorOr<Value> DocumentParser::parse_object_with_index(u32 index)
{
VERIFY(m_xref_table->has_object(index));
// PDF spec 1.7, Indirect Objects:
// "An indirect reference to an undefined object is not an error; it is simply treated as a reference to the null object."
// FIXME: Should this apply to the !has_object() case right above too?
if (!m_xref_table->is_object_in_use(index))
return nullptr;
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<size_t> DocumentParser::scan_for_header_start(ReadonlyBytes bytes)
{
// PDF 1.7 spec, APPENDIX H, 3.4.1 "File Header":
// "13. Acrobat viewers require only that the header appear somewhere within the first 1024 bytes of the file."
// ...which of course means files depend on it.
// All offsets in the file are relative to the header start, not to the start of the file.
StringView first_bytes { bytes.data(), min(bytes.size(), 1024 - "1.4"sv.length()) };
Optional<size_t> start_offset = first_bytes.find("%PDF-"sv);
if (!start_offset.has_value())
return Error { Error::Type::Parse, "Failed to find PDF start" };
return start_offset.value();
}
PDFErrorOr<Version> DocumentParser::parse_header()
{
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') {
dbgln_if(PDF_DEBUG, "Unknown major version \"{}\"", major_ver);
return error("Unknown major version");
}
if (m_reader.read() != '.')
return error("Malformed PDF version");
char minor_ver = m_reader.read();
if (minor_ver < '0' || minor_ver > '7') {
dbgln_if(PDF_DEBUG, "Unknown minor version \"{}\"", minor_ver);
return error("Unknown minor version");
}
m_reader.consume_eol();
m_reader.consume_whitespace();
// 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 Version { major_ver - '0', minor_ver - '0' };
}
PDFErrorOr<DocumentParser::LinearizationResult> DocumentParser::initialize_linearization_dict()
{
// parse_header() is called immediately before this, so we are at the right location.
// There may not actually be a linearization dict, or even a valid PDF object here.
// If that is the case, this file may be completely valid but not linearized.
// If there is indeed a linearization dict, there should be an object number here.
if (!m_reader.matches_number())
return LinearizationResult::NotLinearized;
// At this point, we still don't know for sure if we are dealing with a valid object.
// The linearization dict is read before decryption state is initialized.
// A linearization dict only contains numbers, so the decryption dictionary is not been needed (only strings and streams get decrypted, and only streams get unfiltered).
// But we don't know if the first object is a linearization dictionary until after parsing it, so the object might be a stream.
// If that stream is encrypted and filtered, we'd try to unfilter it while it's still encrypted, handing encrypted data to the unfiltering algorithms.
// This makes them assert, since they can't make sense of the encrypted data.
// So read the first object without unfiltering.
// If it is a linearization dict, there's no stream data and this has no effect.
// If it is a stream, this isn't a linearized file and the object will be read on demand (and unfiltered) later, when the object is lazily read via an xref entry.
set_filters_enabled(false);
auto indirect_value_or_error = parse_indirect_value();
set_filters_enabled(true);
if (indirect_value_or_error.is_error())
return LinearizationResult::NotLinearized;
auto dict_value = indirect_value_or_error.value()->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 {};
}
static PDFErrorOr<NonnullRefPtr<StreamObject>> indirect_value_as_stream(NonnullRefPtr<IndirectValue> indirect_value)
{
auto value = indirect_value->value();
if (!value.has<NonnullRefPtr<Object>>())
return Error { Error::Type::Parse, "Expected indirect value to be a stream" };
auto value_object = value.get<NonnullRefPtr<Object>>();
if (!value_object->is<StreamObject>())
return Error { Error::Type::Parse, "Expected indirect value to be a stream" };
return value_object->cast<StreamObject>();
}
PDFErrorOr<NonnullRefPtr<XRefTable>> DocumentParser::parse_xref_stream()
{
auto xref_stream = TRY(parse_indirect_value());
auto stream = TRY(indirect_value_as_stream(xref_stream));
auto dict = stream->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");
if (field_sizes->at(1).get_u32() == 0)
return error("Malformed xref dictionary");
auto number_of_object_entries = dict->get_value("Size").get<int>();
struct Subsection {
int start;
int count;
};
Vector<Subsection> 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>() });
} else {
subsections.append({ 0, number_of_object_entries });
}
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;
for (auto [start, count] : subsections) {
Vector<XRefEntry> entries;
for (int i = 0; i < count; i++) {
Array<long, 3> fields;
for (size_t field_index = 0; field_index < 3; ++field_index) {
if (!field_sizes->at(field_index).has_u32())
return error("Malformed xref stream");
auto field_size = field_sizes->at(field_index).get_u32();
if (field_size > 8)
return error("Malformed xref stream");
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() == 0)
type = 1;
entries.append({ fields[1], static_cast<u16>(fields[2]), type != 0, type == 2 });
}
table->add_section({ start, count, move(entries) });
}
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);
m_reader.consume_non_eol_whitespace();
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 object_count_value = TRY(parse_number());
if (!(starting_index_value.has_u32() && object_count_value.has_u32()))
return error("Malformed xref entry");
auto object_count = object_count_value.get<int>();
auto starting_index = starting_index_value.get<int>();
for (int i = 0; i < object_count; i++) {
auto offset_string = ByteString(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 = ByteString(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();
return parse_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 obj_stream = TRY(parse_indirect_value());
auto stream = TRY(indirect_value_as_stream(obj_stream));
if (obj_stream->index() != object_stream_index)
return error("Mismatching object stream index");
auto dict = stream->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();
Parser stream_parser(m_document, stream->bytes());
// The data was already decrypted when reading the outer compressed ObjStm.
stream_parser.set_encryption_enabled(false);
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;
}
}
stream_parser.push_reference({ index, 0 });
auto value = TRY(stream_parser.parse_value());
stream_parser.pop_reference();
return 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.consume_eol();
m_reader.consume_whitespace();
if (m_reader.matches("%%EOF")) {
m_reader.move_by(5);
return true;
}
m_reader.move_until([&](auto) { return m_reader.matches_eol(); });
}
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();
m_reader.consume_whitespace();
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(ByteString::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_byte_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_byte_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_byte_string());
}
};
}
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