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LibPDF: Fix treating not finding the linearized dict as a fatal error

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We now try to parse the first indirect value and see 
if it's the `Linearization Parameter Dictionary`. if it's not, we 
fallback to reading the xref table from the end of the document
This commit is contained in:
Wesley Moret 2021-07-14 21:48:09 -04:00 committed by Andreas Kling
parent 5d4d70355e
commit 1b8f73b6b3
Notes: sideshowbarker 2024-07-18 08:55:13 +09:00 
Author: https://github.com/InusualZ
Commit: https://github.com/SerenityOS/serenity/commit/1b8f73b6b3a
Pull-request: https://github.com/SerenityOS/serenity/pull/8763
Reviewed-by: https://github.com/mattco98 ✅
2 changed files with 26 additions and 13 deletions
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31
Userland/Libraries/LibPDF/Parser.cpp
View File

@ -45,14 +45,18 @@ bool Parser::initialize()
if (!parse_header())
return {};
if (!initialize_linearization_dict())
const auto result = initialize_linearization_dict();
if (result == LinearizationResult::Error)
return {};
if (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 = is_linearized && m_linearization_dictionary.value().length_of_file == m_reader.bytes().size();
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
@ -113,21 +117,24 @@ bool Parser::parse_header()
return true;
}
bool Parser::initialize_linearization_dict()
Parser::LinearizationResult Parser::initialize_linearization_dict()
{
// parse_header() is called immediately before this, so we are at the right location
auto dict_value = m_document->resolve(parse_indirect_value());
if (!dict_value || !dict_value.is_object())
return false;
return LinearizationResult::Error;
auto dict_object = dict_value.as_object();
if (!dict_object->is_dict())
return false;
return LinearizationResult::NotLinearized;
auto dict = object_cast<DictObject>(dict_object);
if (!dict->contains(CommonNames::Linearized))
return LinearizationResult::NotLinearized;
if (!dict->contains(CommonNames::L, CommonNames::H, CommonNames::O, CommonNames::E, CommonNames::N, CommonNames::T))
return true;
return LinearizationResult::Error;
auto length_of_file = dict->get_value(CommonNames::L);
auto hint_table = dict->get_value(CommonNames::H);
@ -144,17 +151,17 @@ bool Parser::initialize_linearization_dict()
|| !number_of_pages.is_int_type<u16>()
|| !offset_of_main_xref_table.is_int_type<u32>()
|| (first_page && !first_page.is_int_type<u32>())) {
return true;
return LinearizationResult::Error;
}
auto hint_table_object = hint_table.as_object();
if (!hint_table_object->is_array())
return true;
return LinearizationResult::Error;
auto hint_table_array = object_cast<ArrayObject>(hint_table_object);
auto hint_table_size = hint_table_array->size();
if (hint_table_size != 2 && hint_table_size != 4)
return true;
return LinearizationResult::Error;
auto primary_hint_stream_offset = hint_table_array->at(0);
auto primary_hint_stream_length = hint_table_array->at(1);
@ -170,7 +177,7 @@ bool Parser::initialize_linearization_dict()
|| !primary_hint_stream_length.is_int_type<u32>()
|| (overflow_hint_stream_offset && !overflow_hint_stream_offset.is_int_type<u32>())
|| (overflow_hint_stream_length && !overflow_hint_stream_length.is_int_type<u32>())) {
return true;
return LinearizationResult::Error;
}
m_linearization_dictionary = LinearizationDictionary {
@ -186,7 +193,7 @@ bool Parser::initialize_linearization_dict()
first_page ? first_page.as_int_type<u32>() : NumericLimits<u32>::max(),
};
return true;
return LinearizationResult::Linearized;
}
bool Parser::initialize_linearized_xref_table()
@ -1023,7 +1030,7 @@ RefPtr<StreamObject> Parser::parse_stream(NonnullRefPtr<DictObject> dict)
ReadonlyBytes bytes;
auto maybe_length = dict->get(CommonNames::Length);
if (maybe_length.has_value()) {
if (maybe_length.has_value() && (!maybe_length->is_ref() || m_xref_table)) {
// The PDF writer has kindly provided us with the direct length of the stream
m_reader.save();
auto length = m_document->resolve_to<int>(maybe_length.value());

8
Userland/Libraries/LibPDF/Parser.h
View File

@ -18,6 +18,12 @@ class Document;
class Parser final : public RefCounted<Parser> {
public:
enum class LinearizationResult {
Error,
NotLinearized,
Linearized,
};
static Vector<Command> parse_graphics_commands(ReadonlyBytes const&);
Parser(Badge<Document>, ReadonlyBytes const&);
@ -83,7 +89,7 @@ private:
explicit Parser(ReadonlyBytes const&);
bool parse_header();
bool initialize_linearization_dict();
LinearizationResult initialize_linearization_dict();
bool initialize_linearized_xref_table();
bool initialize_non_linearized_xref_table();
bool initialize_hint_tables();