hello? https://metacpan.org/pod/Hash::Util#hash_value

Nice find! But, it doesn't help :(

I can use the PERL_HASH macro to obtain the hash value; but even if I set up an SV with the key for hv_exists_ent() to ignore; it complains: Use of uninitialized value in subroutine entry; for every iteration; and apparently does nothing? 

HV* countColors( SV *img ) {
    STRLEN l;
    U32 *rgba = (U32*)SvPVx( img, l ), i;
    HV* counts = newHV();
    SV *dummy = newSV( 4 );

    l /= 4;
    for( i = 0; i < l; ++i ) {
        U32 hash;
        PERL_HASH( (U32)hash, (char*)&rgba[ i ], 4 );
        SvPV_set( dummy, (char*)&rgba[ i ] );

        if( hv_exists_ent( counts, dummy, hash  ) ) {
            SV **val = hv_fetch( counts, (char*)&rgba[ i ], 4, hash );
            SvIV_set( *val, SvIV( *val ) + 1 );
        }
        else {
            SV *val = newSViv( 1 );
            hv_store( counts, (char*)&rgba[ i ], 4, val, hash );
        }
    }
    return counts;
}

[download]

Even if I could work out (why do I have to guess? Why isn't this stuff documented?) how to persuade hv_exists_ent() to use the pre-calculated hash value and ignore the SV it requires, setting that SV up costs more than recalculating the hash does -- which is what I was trying to avoid.

What a dumb api.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". I knew I was on the right track :)
In the absence of evidence, opinion is indistinguishable from prejudice.
I'm with torvalds on this Agile (and TDD) debunked I told'em LLVM was the way to go. But did they listen!

In reply to Re^4: PerlApi: hashes by BrowserUk
in thread PerlApi: hashes by BrowserUk

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