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Re^2: 32bit/64bit hash function: Use perls internal hash function?

by sectokia (Pilgrim)
on Apr 10, 2022 at 10:59 UTC ( #11142887=note: print w/replies, xml ) Need Help??


in reply to Re: 32bit/64bit hash function: Use perls internal hash function?
in thread 32bit/64bit hash function: Use perls internal hash function?

Sadly, B from hash() is useless for high speed stuff, because it appears to use a printf function to make its output string, which cripples its speed. Seems to be used just for debugging hash values, and not as interface to get a 32bit hash.
  • Comment on Re^2: 32bit/64bit hash function: Use perls internal hash function?

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Re^3: 32bit/64bit hash function: Use perls internal hash function? (Updated!)
by haukex (Archbishop) on Apr 10, 2022 at 11:33 UTC
    it appears to use a printf function to make its output string

    That is true, but its implementation in XS is pretty simple and can be adapted to suit your needs. Given the performance constraints you've described, I think you're going to have to venture in the direction of C/XS anyway.

    Update: In fact, it turns out to be pretty easy!

    use warnings; use strict; use B 'hash'; use Inline C => <<'_C_'; U32 myhash(SV* sv) { STRLEN len; U32 hash = 0; const char *s = SvPVbyte(sv, len); PERL_HASH(hash, s, len); return hash; } _C_ print hash("foo"), "\n"; printf "%#x\n", myhash("foo"); __END__ 0x6611676e 0x6611676e

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