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Hashing (cont)

hash_any() gives hash value as 32-bit quantity (uint32).

Two ways to map raw hash value into a page address:

  • if b = 2k, bitwise AND with k low-order bits set to one 

    uint32 hashToPageNum(uint32 hval) {
    uint32 mask = 0xFFFFFFFF;
    return (hval & (mask >> (32-k)));
}

  • otherwise, use mod to produce value in range 0..b-1 

    uint32 hashToPageNum(uint32 hval) {
    return (hval % b);
}