finish

fn finish(d: *Decompress) !void {
    const input = d.input;
    const index_size = blk: {
        // Assume that we already peeked a zero in readBlock().
        assert(input.buffered()[0] == 0);
        var input_counter: u64 = 1;
        var checksum: Crc32 = .init();
        checksum.update(&.{0});
        input.toss(1);

        const record_count = try countLeb128(input, u64, &input_counter, &checksum);
        if (record_count != d.block_count)
            return error.CorruptInput;

        for (0..@intCast(record_count)) |_| {
            // TODO: validate records
            _ = try countLeb128(input, u64, &input_counter, &checksum);
            _ = try countLeb128(input, u64, &input_counter, &checksum);
        }

        const padding = try input.take(@intCast((4 - (input_counter % 4)) % 4));
        for (padding) |byte| {
            if (byte != 0) return error.CorruptInput;
        }
        checksum.update(padding);

        const declared_checksum = try input.takeInt(u32, .little);
        const computed_checksum = checksum.final();
        if (computed_checksum != declared_checksum) return error.WrongChecksum;

        break :blk input_counter + padding.len + 4;
    };

    const declared_checksum = try input.takeInt(u32, .little);
    const computed_checksum = Crc32.hash(try input.peek(4 + @sizeOf(StreamFlags)));
    if (declared_checksum != computed_checksum) return error.WrongChecksum;
    const backward_size = (@as(u64, try input.takeInt(u32, .little)) + 1) * 4;
    if (backward_size != index_size) return error.CorruptInput;
    input.toss(@sizeOf(StreamFlags));
    if (!std.mem.eql(u8, try input.takeArray(2), &.{ 'Y', 'Z' }))
        return error.CorruptInput;
}