CodeDweller/mishmash.cpp

// mishmash.cpp (c) 20190407 _M
// non-cryptographic has for short strings

#include "mishmash.hpp"

namespace codedweller {

    uint32_t primes[256] {
        1019,   1021,   1031,   1033,   1039,   1049,   1051,   1061,
        1063,   1069,   1087,   1091,   1093,   1097,   1103,   1109,
        1117,   1123,   1129,   1151,   1153,   1163,   1171,   1181,
        1187,   1193,   1201,   1213,   1217,   1223,   1229,   1231,
        1237,   1249,   1259,   1277,   1279,   1283,   1289,   1291,
        1297,   1301,   1303,   1307,   1319,   1321,   1327,   1361,
        1367,   1373,   1381,   1399,   1409,   1423,   1427,   1429,
        1433,   1439,   1447,   1451,   1453,   1459,   1471,   1481,

        1483,   1487,   1489,   1493,   1499,   1511,   1523,   1531,
        1543,   1549,   1553,   1559,   1567,   1571,   1579,   1583,
        1597,   1601,   1607,   1609,   1613,   1619,   1621,   1627,
        1637,   1657,   1663,   1667,   1669,   1693,   1697,   1699,
        1709,   1721,   1723,   1733,   1741,   1747,   1753,   1759,
        1777,   1783,   1787,   1789,   1801,   1811,   1823,   1831,
        1847,   1861,   1867,   1871,   1873,   1877,   1879,   1889,
        1901,   1907,   1913,   1931,   1933,   1949,   1951,   1973,

        1979,   1987,   1993,   1997,   1999,   2003,   2011,   2017,
        2027,   2029,   2039,   2053,   2063,   2069,   2081,   2083,
        2087,   2089,   2099,   2111,   2113,   2129,   2131,   2137,
        2141,   2143,   2153,   2161,   2179,   2203,   2207,   2213,
        2221,   2237,   2239,   2243,   2251,   2267,   2269,   2273,
        2281,   2287,   2293,   2297,   2309,   2311,   2333,   2339,
        2341,   2347,   2351,   2357,   2371,   2377,   2381,   2383,
        2389,   2393,   2399,   2411,   2417,   2423,   2437,   2441,
        
        2447,   2459,   2467,   2473,   2477,   2503,   2521,   2531,
        2539,   2543,   2549,   2551,   2557,   2579,   2591,   2593,
        2609,   2617,   2621,   2633,   2647,   2657,   2659,   2663,
        2671,   2677,   2683,   2687,   2689,   2693,   2699,   2707,
        2711,   2713,   2719,   2729,   2731,   2741,   2749,   2753,
        2767,   2777,   2789,   2791,   2797,   2801,   2803,   2819,
        2833,   2837,   2843,   2851,   2857,   2861,   2879,   2887,
        2897,   2903,   2909,   2917,   2927,   2939,   2953,   2957
    };


    inline size_t mod256(size_t n) noexcept { return (n & 0xff); }
    
    inline uint32_t selectedPrime(size_t n) noexcept { return primes[mod256(n)]; }

    uint32_t hash(const unsigned char* buffer, size_t length) noexcept {
        uint64_t accumulator = selectedPrime(length);
        for(size_t index = 0; index < length; index++) {
            unsigned char byte = buffer[index];
            accumulator += selectedPrime(index + accumulator);
            accumulator *= selectedPrime(byte + accumulator);
            accumulator += accumulator >> 32;
            accumulator &= 0x00000fffffffffff;
        }
        return accumulator & 0x00000000ffffffff;
    }

    uint32_t hash(const std::string& s) noexcept { 
        return hash((const unsigned char*) s.c_str(), s.length()); 
    }

    uint32_t hash(const std::vector<unsigned char>& v) noexcept { 
        return hash(v.data(), v.size()); 
    }

}