With -Wsign-conversion -Werror options I'm getting compilation error on m_index assign:

 inline void wrapForDecode( char *buffer, std::uint64_t *pos, const std::uint64_t actingVersion, const std::uint64_t bufferLength) { [...] m_index = -1; [...] } 

It would be better to define m_index as std::int64_t. (but then hasNext() needs to be adjusted as well)