block_result block_database::get(const size_t height) const
{
    if (height >= index_.size())
        return block_result(nullptr);
    const position_type position = read_position(height);
    const slab_type slab = allocator_.get(position);
    return block_result(slab);
}
block_result block_database::get(const size_t height) const
{
    if (height >= index_.count())
        return block_result(nullptr);

    const auto position = read_position(height);
    const auto slab = allocator_.get(position);
    return block_result(slab);
}
block_result block_database::get(const hash_digest& hash) const
{
    const slab_type slab = map_.get(hash);
    return block_result(slab);
}