serenity/Userland/Libraries/LibPDF/Fonts/CFF.cpp

/*
 * Copyright (c) 2023, Rodrigo Tobar <rtobarc@gmail.com>.
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#include <AK/Endian.h>
#include <AK/String.h>
#include <LibGfx/Forward.h>
#include <LibPDF/Encoding.h>
#include <LibPDF/Error.h>
#include <LibPDF/Fonts/CFF.h>
#include <LibPDF/Reader.h>

namespace PDF {

PDFErrorOr<NonnullRefPtr<CFF>> CFF::create(ReadonlyBytes const& cff_bytes, RefPtr<Encoding> encoding)
{
    Reader reader(cff_bytes);

    // Header
    // skip major, minor version
    reader.consume(2);
    auto header_size = TRY(reader.try_read<Card8>());
    // skip offset size
    reader.consume(1);
    reader.move_to(header_size);

    // Name INDEX
    Vector<String> font_names;
    TRY(parse_index(reader, [&](ReadonlyBytes const& data) -> PDFErrorOr<void> {
        auto string = TRY(String::from_utf8(data));
        return TRY(font_names.try_append(string));
    }));

    auto cff = adopt_ref(*new CFF());
    cff->set_font_matrix({ 0.001f, 0.0f, 0.0f, 0.001f, 0.0f, 0.0f });

    // Top DICT INDEX
    int charset_offset = 0;
    Vector<u8> encoding_codes;
    auto charstrings_offset = 0;
    Vector<ByteBuffer> subroutines;
    int defaultWidthX = 0;
    int nominalWidthX = 0;
    TRY(parse_index(reader, [&](ReadonlyBytes const& element_data) {
        Reader element_reader { element_data };
        return parse_dict<TopDictOperator>(element_reader, [&](TopDictOperator op, Vector<DictOperand> const& operands) -> PDFErrorOr<void> {
            switch (op) {
            case TopDictOperator::Encoding: {
                auto encoding_offset = 0;
                if (!operands.is_empty())
                    encoding_offset = operands[0].get<int>();
                encoding_codes = TRY(parse_encoding(Reader(cff_bytes.slice(encoding_offset))));
                break;
            }
            case TopDictOperator::Charset: {
                if (!operands.is_empty())
                    charset_offset = operands[0].get<int>();
                break;
            }
            case TopDictOperator::CharStrings: {
                if (!operands.is_empty())
                    charstrings_offset = operands[0].get<int>();
                break;
            }
            case TopDictOperator::Private: {
                auto private_dict_size = operands[0].get<int>();
                auto private_dict_offset = operands[1].get<int>();
                Reader priv_dict_reader { cff_bytes.slice(private_dict_offset, private_dict_size) };
                TRY(parse_dict<PrivDictOperator>(priv_dict_reader, [&](PrivDictOperator op, Vector<DictOperand> const& operands) -> PDFErrorOr<void> {
                    switch (op) {
                    case PrivDictOperator::Subrs: {
                        auto subrs_offset = operands[0].get<int>();
                        Reader subrs_reader { cff_bytes.slice(private_dict_offset + subrs_offset) };
                        dbgln("Parsing Subrs INDEX");
                        TRY(parse_index(subrs_reader, [&](ReadonlyBytes const& subroutine_bytes) -> PDFErrorOr<void> {
                            return TRY(subroutines.try_append(TRY(ByteBuffer::copy(subroutine_bytes))));
                        }));
                        break;
                    }
                    case PrivDictOperator::DefaultWidthX:
                        defaultWidthX = operands[0].get<int>();
                        break;
                    case PrivDictOperator::NominalWidthX:
                        nominalWidthX = operands[0].get<int>();
                        break;
                    }
                    return {};
                }));
                break;
            }
            default:;
            }
            return {};
        });
    }));

    // Create glpyhs (now that we have the subroutines) and associate missing information to store them and their encoding
    auto glyphs = TRY(parse_charstrings(Reader(cff_bytes.slice(charstrings_offset)), subroutines));
    auto charset = TRY(parse_charset(Reader { cff_bytes.slice(charset_offset) }, glyphs.size()));

    // Adjust glyphs' widths as they are deltas from nominalWidthX
    for (auto& glyph : glyphs) {
        if (!glyph.width_specified)
            glyph.width = float(defaultWidthX);
        else
            glyph.width += float(nominalWidthX);
    }

    // Encoding given or read
    if (encoding) {
        for (size_t i = 0; i < glyphs.size(); i++) {
            if (i == 0) {
                TRY(cff->add_glyph(0, move(glyphs[0])));
                continue;
            }
            auto const& name = charset[i - 1];
            u16 code = encoding->get_char_code(name);
            TRY(cff->add_glyph(code, move(glyphs[i])));
        }
        cff->set_encoding(move(encoding));
    } else {
        auto encoding = Encoding::create();
        for (size_t i = 0; i < glyphs.size(); i++) {
            if (i == 0) {
                TRY(cff->add_glyph(0, move(glyphs[0])));
                encoding->set(0, ".notdef");
                continue;
            }
            auto code = encoding_codes[i - 1];
            auto char_name = charset[i - 1];
            TRY(cff->add_glyph(code, move(glyphs[i])));
            encoding->set(code, char_name);
        }
        cff->set_encoding(move(encoding));
    }

    return cff;
}

HashMap<CFF::SID, DeprecatedFlyString> CFF::builtin_names {
    { 0, ".notdef" },
    { 1, "space" },
    { 9, "parenleft" },
    { 10, "parenright" },
    { 13, "comma" },
    { 14, "hyphen" },
    { 15, "period" },

    { 17, "zero" },
    { 18, "one" },
    { 19, "two" },
    { 20, "three" },
    { 21, "four" },
    { 22, "five" },
    { 23, "six" },
    { 24, "seven" },
    { 25, "eight" },
    { 26, "nine" },
    { 27, "colon" },
    { 28, "semicolon" },

    { 34, "A" },
    { 35, "B" },
    { 36, "C" },
    { 37, "D" },
    { 38, "E" },
    { 39, "F" },
    { 40, "G" },
    { 41, "H" },
    { 42, "I" },
    { 43, "J" },
    { 44, "K" },
    { 45, "L" },
    { 46, "M" },
    { 47, "N" },
    { 48, "O" },
    { 49, "P" },
    { 50, "Q" },
    { 51, "R" },
    { 52, "S" },
    { 53, "T" },
    { 54, "U" },
    { 55, "V" },
    { 56, "W" },
    { 57, "X" },
    { 58, "Y" },
    { 59, "Z" },
    { 66, "a" },
    { 67, "b" },
    { 68, "c" },
    { 69, "d" },
    { 70, "e" },
    { 71, "f" },
    { 72, "g" },
    { 73, "h" },
    { 74, "i" },
    { 75, "j" },
    { 76, "k" },
    { 77, "l" },
    { 78, "m" },
    { 79, "n" },
    { 80, "o" },
    { 81, "p" },
    { 82, "q" },
    { 83, "r" },
    { 84, "s" },
    { 85, "t" },
    { 86, "u" },
    { 87, "v" },
    { 88, "w" },
    { 89, "x" },
    { 90, "y" },
    { 91, "z" },

    { 104, "quotesingle" },
    { 105, "quotedblleft" },

    { 111, "endash" },

    { 116, "bullet" },

    { 119, "quotedblright" },

    { 137, "emdash" },

    { 170, "copyright" },
};

PDFErrorOr<Vector<DeprecatedFlyString>> CFF::parse_charset(Reader&& reader, size_t glyph_count)
{
    Vector<DeprecatedFlyString> names;
    auto resolve = [](SID sid) {
        auto x = builtin_names.find(sid);
        if (x == builtin_names.end()) {
            dbgln("Cound't find string for SID {}, going with space", sid);
            return DeprecatedFlyString("space");
        }
        return x->value;
    };

    auto format = TRY(reader.try_read<Card8>());
    if (format == 0) {
        for (u8 i = 0; i < glyph_count - 1; i++) {
            SID sid = TRY(reader.try_read<BigEndian<SID>>());
            TRY(names.try_append(resolve(sid)));
        }
    } else if (format == 1) {
        while (names.size() < glyph_count - 1) {
            auto first_sid = TRY(reader.try_read<BigEndian<SID>>());
            int left = TRY(reader.try_read<Card8>());
            for (u8 sid = first_sid; left >= 0; left--, sid++)
                TRY(names.try_append(resolve(sid)));
        }
    }
    return names;
}

PDFErrorOr<Vector<CFF::Glyph>> CFF::parse_charstrings(Reader&& reader, Vector<ByteBuffer> const& subroutines)
{
    Vector<Glyph> glyphs;
    TRY(parse_index(reader, [&](ReadonlyBytes const& charstring_data) -> PDFErrorOr<void> {
        GlyphParserState state;
        auto glyph = TRY(parse_glyph(charstring_data, subroutines, state, true));
        return TRY(glyphs.try_append(glyph));
    }));
    return glyphs;
}

PDFErrorOr<Vector<u8>> CFF::parse_encoding(Reader&& reader)
{
    Vector<u8> encoding_codes;
    auto format = TRY(reader.try_read<Card8>());
    if (format == 0) {
        auto n_codes = TRY(reader.try_read<Card8>());
        for (u8 i = 0; i < n_codes; i++) {
            TRY(encoding_codes.try_append(TRY(reader.try_read<Card8>())));
        }
    } else if (format == 1) {
        auto n_ranges = TRY(reader.try_read<Card8>());
        for (u8 i = 0; i < n_ranges; i++) {
            auto first_code = TRY(reader.try_read<Card8>());
            int left = TRY(reader.try_read<Card8>());
            for (u8 code = first_code; left >= 0; left--, code++)
                TRY(encoding_codes.try_append(code));
        }
    } else
        return error(DeprecatedString::formatted("Invalid encoding format: {}", format));
    return encoding_codes;
}

template<typename OperatorT>
PDFErrorOr<void> CFF::parse_dict(Reader& reader, DictEntryHandler<OperatorT>&& handler)
{
    Vector<DictOperand> operands;
    while (reader.remaining() > 0) {
        auto b0 = reader.read<u8>();
        // A command
        if (b0 <= 21) {
            auto op = TRY(parse_dict_operator<OperatorT>(b0, reader));
            TRY(handler(op, operands));
            operands.clear();
            continue;
        }
        // An operand
        TRY(operands.try_append(TRY(load_dict_operand(b0, reader))));
    }
    return {};
}

template PDFErrorOr<void> CFF::parse_dict<CFF::TopDictOperator>(Reader&, DictEntryHandler<TopDictOperator>&&);
template PDFErrorOr<void> CFF::parse_dict<CFF::PrivDictOperator>(Reader&, DictEntryHandler<PrivDictOperator>&&);

template<typename OperatorT>
PDFErrorOr<OperatorT> CFF::parse_dict_operator(u8 b0, Reader& reader)
{
    VERIFY(b0 <= 21);
    if (b0 != 12)
        return OperatorT { (int)b0 };
    auto b1 = TRY(reader.try_read<u8>());
    return OperatorT { b0 << 8 | b1 };
}

template PDFErrorOr<CFF::TopDictOperator> CFF::parse_dict_operator(u8, Reader&);

PDFErrorOr<void> CFF::parse_index(Reader& reader, IndexDataHandler&& data_handler)
{
    Card16 count = TRY(reader.try_read<BigEndian<Card16>>());
    if (count == 0)
        return {};
    auto offset_size = TRY(reader.try_read<OffSize>());
    if (offset_size == 1)
        return parse_index_data<u8>(count, reader, data_handler);
    if (offset_size == 2)
        return parse_index_data<u16>(count, reader, data_handler);
    if (offset_size == 4)
        return parse_index_data<u32>(count, reader, data_handler);
    VERIFY_NOT_REACHED();
}

template<typename OffsetType>
PDFErrorOr<void> CFF::parse_index_data(Card16 count, Reader& reader, IndexDataHandler& handler)
{
    OffsetType last_data_end = 1;
    auto offset_refpoint = reader.offset() + sizeof(OffsetType) * (count + 1) - 1;
    for (u16 i = 0; i < count; i++) {
        reader.save();
        reader.move_by(sizeof(OffsetType) * i);
        OffsetType data_start = reader.read<BigEndian<OffsetType>>();
        last_data_end = reader.read<BigEndian<OffsetType>>();
        auto data_size = last_data_end - data_start;
        reader.move_to(offset_refpoint + data_start);
        TRY(handler(reader.bytes().slice(reader.offset(), data_size)));
        reader.load();
    }
    reader.move_to(offset_refpoint + last_data_end);
    return {};
}

template PDFErrorOr<void> CFF::parse_index_data<u8>(Card16, Reader&, IndexDataHandler&);
template PDFErrorOr<void> CFF::parse_index_data<u16>(Card16, Reader&, IndexDataHandler&);
template PDFErrorOr<void> CFF::parse_index_data<u32>(Card16, Reader&, IndexDataHandler&);

// 4 DICT DATA, Table 3 Operand Encoding
int CFF::load_int_dict_operand(u8 b0, Reader& reader)
{
    if (b0 >= 32 && b0 <= 246) {
        return b0 - 139;
    }
    if (b0 >= 247 && b0 <= 250) {
        auto b1 = reader.read<u8>();
        return (b0 - 247) * 256 + b1 + 108;
    }
    if (b0 >= 251 && b0 <= 254) {
        auto b1 = reader.read<u8>();
        return -(b0 - 251) * 256 - b1 - 108;
    }
    if (b0 == 28) {
        auto b1 = reader.read<u8>();
        auto b2 = reader.read<u8>();
        return b1 << 8 | b2;
    }
    if (b0 == 29) {
        auto b1 = reader.read<u8>();
        auto b2 = reader.read<u8>();
        auto b3 = reader.read<u8>();
        auto b4 = reader.read<u8>();
        return b1 << 24 | b2 << 16 | b3 << 8 | b4;
    }
    VERIFY_NOT_REACHED();
}

float CFF::load_float_dict_operand(Reader& reader)
{
    StringBuilder sb;
    auto add_nibble = [&](char nibble) {
        if (nibble < 0xa)
            sb.append('0' + nibble);
        else if (nibble == 0xa)
            sb.append('.');
        else if (nibble == 0xb)
            sb.append('E');
        else if (nibble == 0xc)
            sb.append("E-"sv);
        else if (nibble == 0xe)
            sb.append('-');
    };
    while (true) {
        auto byte = reader.read<u8>();
        char nibble1 = (byte & 0xf0) >> 4;
        char nibble2 = byte & 0x0f;
        if (nibble1 == 0xf)
            break;
        add_nibble(nibble1);
        if (nibble2 == 0xf)
            break;
        add_nibble(nibble2);
    }
    auto result = AK::StringUtils::convert_to_floating_point<float>(sb.string_view());
    return result.release_value();
}

PDFErrorOr<CFF::DictOperand> CFF::load_dict_operand(u8 b0, Reader& reader)
{
    if (b0 == 30)
        return load_float_dict_operand(reader);
    if (b0 >= 28)
        return load_int_dict_operand(b0, reader);
    return Error { Error::Type::MalformedPDF, DeprecatedString::formatted("Unknown CFF dict element prefix: {}", b0) };
}
}