mirror of
https://github.com/RGBCube/serenity
synced 2025-07-25 04:07:44 +00:00
LibPDF: Harden the document/parser against errors
This commit is contained in:
Matthew Olsson
Ali Mohammad Pur
parent
d654fe0e41
commit
1ef5071d1b
6 changed files with 217 additions and 108 deletions
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@ -24,8 +24,8 @@ static NonnullRefPtr<T> make_object(Args... args) requires(IsBaseOf<Object, T>)
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Vector<Command> Parser::parse_graphics_commands(const ReadonlyBytes& bytes)
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{
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Parser parser(bytes);
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return parser.parse_graphics_commands();
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auto parser = adopt_ref(*new Parser(bytes));
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return parser->parse_graphics_commands();
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}
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Parser::Parser(Badge<Document>, const ReadonlyBytes& bytes)
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@ -43,26 +43,34 @@ bool Parser::perform_validation()
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return !sloppy_is_linearized() && parse_header();
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}
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Parser::XRefTableAndTrailer Parser::parse_last_xref_table_and_trailer()
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Optional<Parser::XRefTableAndTrailer> Parser::parse_last_xref_table_and_trailer()
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{
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m_reader.move_to(m_reader.bytes().size() - 1);
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VERIFY(navigate_to_before_eof_marker());
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navigate_to_after_startxref();
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VERIFY(!m_reader.done());
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if (!navigate_to_before_eof_marker())
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return {};
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if (!navigate_to_after_startxref())
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return {};
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if (m_reader.done())
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return {};
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m_reader.set_reading_forwards();
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auto xref_offset_value = parse_number();
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VERIFY(xref_offset_value.is_int());
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if (!xref_offset_value.is_int())
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return {};
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auto xref_offset = xref_offset_value.as_int();
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m_reader.move_to(xref_offset);
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auto xref_table = parse_xref_table();
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if (!xref_table.has_value())
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return {};
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auto trailer = parse_file_trailer();
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if (!trailer)
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return {};
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return { xref_table, trailer };
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return XRefTableAndTrailer { xref_table.value(), trailer.release_nonnull() };
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}
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NonnullRefPtr<IndirectValue> Parser::parse_indirect_value_at_offset(size_t offset)
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RefPtr<IndirectValue> Parser::parse_indirect_value_at_offset(size_t offset)
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{
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m_reader.set_reading_forwards();
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m_reader.move_to(offset);
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@ -103,11 +111,13 @@ bool Parser::parse_header()
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return true;
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}
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XRefTable Parser::parse_xref_table()
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Optional<XRefTable> Parser::parse_xref_table()
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{
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VERIFY(m_reader.matches("xref"));
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if (!m_reader.matches("xref"))
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return {};
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m_reader.move_by(4);
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consume_eol();
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if (!consume_eol())
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return {};
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XRefTable table;
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@ -125,23 +135,28 @@ XRefTable Parser::parse_xref_table()
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for (int i = 0; i < object_count; i++) {
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auto offset_string = String(m_reader.bytes().slice(m_reader.offset(), 10));
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m_reader.move_by(10);
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consume(' ');
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if (!consume(' '))
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return {};
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auto generation_string = String(m_reader.bytes().slice(m_reader.offset(), 5));
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m_reader.move_by(5);
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consume(' ');
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if (!consume(' '))
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return {};
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auto letter = m_reader.read();
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VERIFY(letter == 'n' || letter == 'f');
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if (letter != 'n' && letter != 'f')
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return {};
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// The line ending sequence can be one of the following:
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// SP CR, SP LF, or CR LF
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if (m_reader.matches(' ')) {
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consume();
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auto ch = consume();
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VERIFY(ch == '\r' || ch == '\n');
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if (ch != '\r' && ch != '\n')
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return {};
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} else {
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VERIFY(m_reader.matches("\r\n"));
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if (!m_reader.matches("\r\n"))
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return {};
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m_reader.move_by(2);
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}
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@ -157,23 +172,27 @@ XRefTable Parser::parse_xref_table()
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return table;
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}
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NonnullRefPtr<DictObject> Parser::parse_file_trailer()
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RefPtr<DictObject> Parser::parse_file_trailer()
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{
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VERIFY(m_reader.matches("trailer"));
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if (!m_reader.matches("trailer"))
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return {};
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m_reader.move_by(7);
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consume_whitespace();
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auto dict = parse_dict();
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if (!dict)
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return {};
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VERIFY(m_reader.matches("startxref"));
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if (!m_reader.matches("startxref"))
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return {};
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m_reader.move_by(9);
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consume_whitespace();
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m_reader.move_until([&](auto) { return matches_eol(); });
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consume_eol();
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VERIFY(m_reader.matches("%%EOF"));
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VERIFY(consume_eol());
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if (!m_reader.matches("%%EOF"))
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return {};
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m_reader.move_by(5);
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consume_whitespace();
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VERIFY(m_reader.done());
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return dict;
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}
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@ -291,8 +310,10 @@ Value Parser::parse_value()
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if (m_reader.matches("<<")) {
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auto dict = parse_dict();
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if (!dict)
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return {};
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if (m_reader.matches("stream\n"))
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return parse_stream(dict);
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return parse_stream(dict.release_nonnull());
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return dict;
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}
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@ -335,23 +356,28 @@ Value Parser::parse_possible_indirect_value_or_ref()
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return first_number;
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}
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NonnullRefPtr<IndirectValue> Parser::parse_indirect_value(int index, int generation)
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RefPtr<IndirectValue> Parser::parse_indirect_value(int index, int generation)
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{
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VERIFY(m_reader.matches("obj"));
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if (!m_reader.matches("obj"))
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return {};
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m_reader.move_by(3);
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if (matches_eol())
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consume_eol();
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auto value = parse_value();
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VERIFY(m_reader.matches("endobj"));
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if (!m_reader.matches("endobj"))
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return {};
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return make_object<IndirectValue>(index, generation, value);
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}
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NonnullRefPtr<IndirectValue> Parser::parse_indirect_value()
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RefPtr<IndirectValue> Parser::parse_indirect_value()
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{
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auto first_number = parse_number();
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if (!first_number.is_int())
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return {};
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auto second_number = parse_number();
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VERIFY(first_number.is_int() && second_number.is_int());
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if (!second_number.is_int())
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return {};
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return parse_indirect_value(first_number.as_int(), second_number.as_int());
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}
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@ -387,9 +413,10 @@ Value Parser::parse_number()
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return Value(static_cast<int>(f));
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}
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NonnullRefPtr<NameObject> Parser::parse_name()
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RefPtr<NameObject> Parser::parse_name()
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{
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consume('/');
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if (!consume('/'))
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return {};
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StringBuilder builder;
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while (true) {
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@ -400,7 +427,8 @@ NonnullRefPtr<NameObject> Parser::parse_name()
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int hex_value = 0;
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for (int i = 0; i < 2; i++) {
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auto ch = consume();
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VERIFY(isxdigit(ch));
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if (!isxdigit(ch))
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return {};
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hex_value *= 16;
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if (ch <= '9') {
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hex_value += ch - '0';
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@ -420,7 +448,7 @@ NonnullRefPtr<NameObject> Parser::parse_name()
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return make_object<NameObject>(builder.to_string());
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}
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NonnullRefPtr<StringObject> Parser::parse_string()
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RefPtr<StringObject> Parser::parse_string()
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{
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ScopeGuard guard([&] { consume_whitespace(); });
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@ -435,6 +463,9 @@ NonnullRefPtr<StringObject> Parser::parse_string()
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is_binary_string = true;
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}
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if (string.is_null())
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return {};
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if (string.bytes().starts_with(Array<u8, 2> { 0xfe, 0xff })) {
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// The string is encoded in UTF16-BE
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string = TextCodec::decoder_for("utf-16be")->to_utf8(string.substring(2));
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@ -449,7 +480,8 @@ NonnullRefPtr<StringObject> Parser::parse_string()
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String Parser::parse_literal_string()
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{
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consume('(');
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if (!consume('('))
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return {};
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StringBuilder builder;
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auto opened_parens = 0;
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@ -470,7 +502,9 @@ String Parser::parse_literal_string()
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continue;
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}
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VERIFY(!m_reader.done());
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if (m_reader.done())
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return {};
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auto ch = consume();
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switch (ch) {
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case 'n':
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@ -520,13 +554,16 @@ String Parser::parse_literal_string()
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}
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}
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VERIFY(opened_parens == 0);
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if (opened_parens != 0)
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return {};
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return builder.to_string();
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}
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String Parser::parse_hex_string()
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{
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consume('<');
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if (!consume('<'))
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return {};
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StringBuilder builder;
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while (true) {
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@ -546,7 +583,9 @@ String Parser::parse_hex_string()
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builder.append(static_cast<char>(hex_value));
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return builder.to_string();
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}
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VERIFY(isxdigit(ch));
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if (!isxdigit(ch))
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return {};
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hex_value *= 16;
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if (ch <= '9') {
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@ -561,25 +600,31 @@ String Parser::parse_hex_string()
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}
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}
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NonnullRefPtr<ArrayObject> Parser::parse_array()
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RefPtr<ArrayObject> Parser::parse_array()
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{
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consume('[');
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if (!consume('['))
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return {};
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consume_whitespace();
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Vector<Value> values;
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while (!m_reader.matches(']'))
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values.append(parse_value());
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while (!m_reader.matches(']')) {
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auto value = parse_value();
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if (!value)
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return {};
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values.append(value);
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}
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consume(']');
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if (!consume(']'))
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return {};
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consume_whitespace();
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return make_object<ArrayObject>(values);
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}
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NonnullRefPtr<DictObject> Parser::parse_dict()
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RefPtr<DictObject> Parser::parse_dict()
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{
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consume('<');
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consume('<');
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if (!consume('<') || !consume('<'))
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return {};
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consume_whitespace();
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HashMap<FlyString, Value> map;
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@ -587,28 +632,38 @@ NonnullRefPtr<DictObject> Parser::parse_dict()
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if (m_reader.matches(">>"))
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break;
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auto name = parse_name();
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if (!name)
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return {};
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auto value = parse_value();
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if (!value)
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return {};
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map.set(name->name(), value);
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}
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consume('>');
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consume('>');
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if (!consume('>') || !consume('>'))
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return {};
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consume_whitespace();
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return make_object<DictObject>(map);
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}
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RefPtr<DictObject> Parser::conditionally_parse_page_tree_node_at_offset(size_t offset)
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RefPtr<DictObject> Parser::conditionally_parse_page_tree_node_at_offset(size_t offset, bool& ok)
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{
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ok = true;
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m_reader.move_to(offset);
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parse_number();
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parse_number();
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VERIFY(m_reader.matches("obj"));
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if (!m_reader.matches("obj")) {
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ok = false;
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return {};
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}
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m_reader.move_by(3);
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consume_whitespace();
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consume('<');
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consume('<');
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if (!consume('<') || !consume('<'))
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return {};
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consume_whitespace();
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HashMap<FlyString, Value> map;
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@ -616,12 +671,21 @@ RefPtr<DictObject> Parser::conditionally_parse_page_tree_node_at_offset(size_t o
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if (m_reader.matches(">>"))
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break;
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auto name = parse_name();
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if (!name) {
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ok = false;
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return {};
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}
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auto name_string = name->name();
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if (!name_string.is_one_of(CommonNames::Type, CommonNames::Parent, CommonNames::Kids, CommonNames::Count)) {
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// This is a page, not a page tree node
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return {};
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}
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auto value = parse_value();
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if (!value) {
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ok = false;
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return {};
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}
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if (name_string == CommonNames::Type) {
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if (!value.is_object())
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return {};
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@ -635,18 +699,20 @@ RefPtr<DictObject> Parser::conditionally_parse_page_tree_node_at_offset(size_t o
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map.set(name->name(), value);
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}
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consume('>');
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consume('>');
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if (!consume('>') || !consume('>'))
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return {};
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consume_whitespace();
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return make_object<DictObject>(map);
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}
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NonnullRefPtr<StreamObject> Parser::parse_stream(NonnullRefPtr<DictObject> dict)
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RefPtr<StreamObject> Parser::parse_stream(NonnullRefPtr<DictObject> dict)
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{
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VERIFY(m_reader.matches("stream"));
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if (!m_reader.matches("stream"))
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return {};
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m_reader.move_by(6);
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consume_eol();
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if (!consume_eol())
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return {};
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ReadonlyBytes bytes;
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@ -681,8 +747,8 @@ NonnullRefPtr<StreamObject> Parser::parse_stream(NonnullRefPtr<DictObject> dict)
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if (dict->contains(CommonNames::Filter)) {
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auto filter_type = dict->get_name(m_document, CommonNames::Filter)->name();
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auto maybe_bytes = Filter::decode(bytes, filter_type);
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// FIXME: Handle error condition
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VERIFY(maybe_bytes.has_value());
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if (!maybe_bytes.has_value())
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return {};
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return make_object<EncodedStreamObject>(dict, move(maybe_bytes.value()));
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}
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@ -752,14 +818,15 @@ bool Parser::matches_regular_character() const
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return !matches_delimiter() && !matches_whitespace();
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}
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void Parser::consume_eol()
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bool Parser::consume_eol()
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{
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if (m_reader.matches("\r\n")) {
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consume(2);
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} else {
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auto consumed = consume();
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VERIFY(consumed == 0xd || consumed == 0xa);
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return true;
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}
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auto consumed = consume();
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return consumed == 0xd || consumed == 0xa;
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}
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bool Parser::consume_whitespace()
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@ -777,9 +844,15 @@ char Parser::consume()
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return m_reader.read();
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}
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void Parser::consume(char ch)
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void Parser::consume(int amount)
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{
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VERIFY(consume() == ch);
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for (size_t i = 0; i < static_cast<size_t>(amount); i++)
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consume();
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}
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bool Parser::consume(char ch)
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{
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return consume() == ch;
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}
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}
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