On 32-bit platforms `std::size_t` is just 4 bytes big which is not enough
to handle large data sizes. Using `std::streamsize` would likely be most
appropriate but switching signdness is likely not the best idea for
compatibility and it would mean a comparison with different signdness
because the buffer size is still `std::size_t`. So using `std::uint64_t`
now.
In a future version these overloads could use native APIs such
as POSIX sendfile() to improve the speed. Libraries such as
tagparser will benefit from this change automatically when in
places where NativeFileStream is already used anyways.
Martchus