Generates a 32/64-bit hash for the given string - CSharp Security

CSharp examples for Security:Hash

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Description

Generates a 32/64-bit hash for the given string

Demo Code


using System;// w w w.  j  a v  a 2s.  c o m

namespace ShortUrl.Helpers
{
    //This is a partial C# implementation of hash algorithm by Fowler/Noll/Vo
    //http://www.isthe.com/chongo/tech/comp/fnv/index.html
    public static class FNVHash
    {
        private static ulong FNV_Prime = 1099511628211;
        private static ulong Offest_basis = 14695981039346656037;

        private static uint FNV_32_PRIME = 0x01000193; //Which is Integer 16777619
        private static uint FNV1_32_INIT = 0x811c9dc5; //Which is Integer 2166136261

        /// <summary>
        /// Generates a 32-bit hash for the given string
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static uint fnv_32a_str(String str)
        {
            uint hash = FNV1_32_INIT;
            foreach (char c in str)
            {
                /* xor the bottom with the current octet */
                hash ^= (uint)c;

                /* multiply by the 64 bit FNV magic prime mod 2^32 */
                hash += (hash << 1) + (hash << 4) + (hash << 7) + (hash << 8) + (hash << 24);
            }

            return hash;
        }


        /// <summary>
        /// Generates a 64-bit hash for the given string
        /// </summary>
        /// <param name="str"></param>
        /// <returns></returns>
        public static ulong fnv_64a_str(String str)
        {
            ulong hash = Offest_basis;
            foreach (char c in str)
            {
                hash ^= (ulong)c;

                /* multiply by the 64 bit FNV magic prime mod 2^64 */
                hash += (hash << 1) + (hash << 4) + (hash << 5) + (hash << 7) + (hash << 8) + (hash << 40);
            }

            return hash;
        }
    }
}

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