Method WriteBlockPrefix

include/util/indexed_data.hpp:214–234

    /// Write a fixed length block prefix.
    template <typename OffsetIterator, typename OutByteIter>
    OutByteIter WriteBlockPrefix(OffsetIterator first, OffsetIterator last, OutByteIter out) const
    {
        constexpr std::size_t MAX_LENGTH =
            std::numeric_limits<std::make_unsigned_t<ValueType>>::max();

        auto index = 0;
        std::array<ValueType, BLOCK_SIZE> prefix{};

        for (OffsetIterator curr = first, next = std::next(first); curr != last; ++curr, ++next)
        {
            const std::uint32_t data_length = *next - *curr;
            if (data_length > MAX_LENGTH)
                throw util::exception(
                    std::format("too large data length {} > {}", data_length, MAX_LENGTH));

            prefix[index++] = data_length;
        }

        out = std::copy_n((const char *)prefix.data(), sizeof(ValueType) * BLOCK_SIZE, out);
        return out;
    }

    /// Advances the range to an item stored in the referenced block.
    /// Input [first..last) is a range of the complete block data with prefix.