Not an author, so these are just my best guesses

On Fri, Apr 11, 2025 at 8:13 PM Marek Küthe via Boost-users <boost-users@lists.boost.org> wrote:
Hello,

I have two questions about the Boost.Hash2 library:
1. Which xxHash algorithm is implemented exactly (I somehow couldn't see
this in the documentation). As far as I know there are four: XXH32,
XXH64, XXH3_64bits and XXH3_128bits [1]. Boost.Hash2 implements
xxhash_32 and xxhash_64, but is this the old xxHash version (XXH32,
XXH64) or the new xxHash version 3 (XXH3_64bits, XXH3_128bits)?
 
https://github.com/boostorg/hash2/blob/14a374ea904cf7a58cfef65e11d1de067fe0dd82/test/xxhash_2.cpp#L44C59-L44C80
matching 
https://github.com/Cyan4973/xxHash/blob/dd11140c2dc5d53a3c0a949d67af7f40f546878e/cli/xsum_sanity_check.c#L113
Seems to suggest that 64bit hash is XXH64.

 
2. Is there a specific reason why the old cstdio library and not
iostream/fstream from C++ is used in the examples [2]?

I think there is no reason.