[Q] string to int hash function for small range

I would like to have a function
given a user id varchar(64) to get a hash number between 0 and 255.

I first tried md5 but the number it returns is very big and cannot
be converted to an INT

there is likely a way to simply add ascii values of the userId together
to get a small integer, but wanted to know if there are any other
'built-in' ways

this is to get the database id based on user id.

thanks in advance,
Vlad
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  toreason@fastmail.fm

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