library/cpp/digest/sfh/sfh.h


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#pragma once

#include <util/system/defaults.h>
#include <util/system/unaligned_mem.h>

inline ui32 SuperFastHash(const void* d, size_t l) noexcept {
    ui32 hash = (ui32)l; 
    ui32 tmp; 

    if (!l || !d) 
        return 0;

    TUnalignedMemoryIterator<ui16, 4> iter(d, l); 

    while (!iter.AtEnd()) { 
        hash += (ui32)iter.Next(); 
        tmp = ((ui32)iter.Next() << 11) ^ hash; 
        hash = (hash << 16) ^ tmp; 
        hash += hash >> 11; 
    }

    switch (iter.Left()) { 
        case 3: 
            hash += (ui32)iter.Next(); 
            hash ^= hash << 16;
            hash ^= ((ui32)(i32) * (const i8*)iter.Last()) << 18; 
            hash += hash >> 11;
            break;
 
        case 2: 
            hash += (ui32)iter.Cur(); 
            hash ^= hash << 11;
            hash += hash >> 17;
            break;
 
        case 1: 
            hash += *((const i8*)iter.Last()); 
            hash ^= hash << 10;
            hash += hash >> 1;
    }

    /* Force "avalanching" of final 127 bits */
    hash ^= hash << 3;
    hash += hash >> 5;
    hash ^= hash << 4;
    hash += hash >> 17;
    hash ^= hash << 25;
    hash += hash >> 6;

    return hash;
}