process

    pub fn process(
        self: *Decode,
        reader: *Reader,
        allocating: *Writer.Allocating,
        /// `CircularBuffer` or `std.compress.lzma2.AccumBuffer`.
        buffer: anytype,
        decoder: *RangeDecoder,
        n_read: *u64,
    ) !ProcessingStatus {
        const gpa = allocating.allocator;
        const writer = &allocating.writer;
        const pos_state = buffer.len & ((@as(usize, 1) << self.properties.pb) - 1);

        if (!try decoder.decodeBit(reader, &self.is_match[(self.state << 4) + pos_state], n_read)) {
            const byte: u8 = try self.decodeLiteral(reader, buffer, decoder, n_read);

            try buffer.appendLiteral(gpa, byte, writer);

            self.state = if (self.state < 4)
                0
            else if (self.state < 10)
                self.state - 3
            else
                self.state - 6;
            return .more;
        }

        var len: usize = undefined;
        if (try decoder.decodeBit(reader, &self.is_rep[self.state], n_read)) {
            if (!try decoder.decodeBit(reader, &self.is_rep_g0[self.state], n_read)) {
                if (!try decoder.decodeBit(reader, &self.is_rep_0long[(self.state << 4) + pos_state], n_read)) {
                    self.state = if (self.state < 7) 9 else 11;
                    const dist = self.rep[0] + 1;
                    try buffer.appendLz(gpa, 1, dist, writer);
                    return .more;
                }
            } else {
                const idx: usize = if (!try decoder.decodeBit(reader, &self.is_rep_g1[self.state], n_read))
                    1
                else if (!try decoder.decodeBit(reader, &self.is_rep_g2[self.state], n_read))
                    2
                else
                    3;
                const dist = self.rep[idx];
                var i = idx;
                while (i > 0) : (i -= 1) {
                    self.rep[i] = self.rep[i - 1];
                }
                self.rep[0] = dist;
            }

            len = try self.rep_len_decoder.decode(reader, decoder, pos_state, n_read);

            self.state = if (self.state < 7) 8 else 11;
        } else {
            self.rep[3] = self.rep[2];
            self.rep[2] = self.rep[1];
            self.rep[1] = self.rep[0];

            len = try self.len_decoder.decode(reader, decoder, pos_state, n_read);

            self.state = if (self.state < 7) 7 else 10;

            const rep_0 = try self.decodeDistance(reader, decoder, len, n_read);

            self.rep[0] = rep_0;
            if (self.rep[0] == 0xFFFF_FFFF) {
                if (decoder.isFinished()) {
                    return .finished;
                }
                return error.CorruptInput;
            }
        }

        len += 2;

        const dist = self.rep[0] + 1;
        try buffer.appendLz(gpa, len, dist, writer);

        return .more;
    }