Crc64

Crc64.cs

using System.Text;

namespace Std.Utility.Hashing
{
    public static class Crc64
    {
        public const ulong DefaultSeed = 0x0;

        private static readonly ulong[] _defaultTable = new ulong[]
        {
            0x0000000000000000L, 0x01b0000000000000L, 0x0360000000000000L,
            0x02d0000000000000L, 0x06c0000000000000L, 0x0770000000000000L,
            0x05a0000000000000L, 0x0410000000000000L, 0x0d80000000000000L,
            0x0c30000000000000L, 0x0ee0000000000000L, 0x0f50000000000000L,
            0x0b40000000000000L, 0x0af0000000000000L, 0x0820000000000000L,
            0x0990000000000000L, 0x1b00000000000000L, 0x1ab0000000000000L,
            0x1860000000000000L, 0x19d0000000000000L, 0x1dc0000000000000L,
            0x1c70000000000000L, 0x1ea0000000000000L, 0x1f10000000000000L,
            0x1680000000000000L, 0x1730000000000000L, 0x15e0000000000000L,
            0x1450000000000000L, 0x1040000000000000L, 0x11f0000000000000L,
            0x1320000000000000L, 0x1290000000000000L, 0x3600000000000000L,
            0x37b0000000000000L, 0x3560000000000000L, 0x34d0000000000000L,
            0x30c0000000000000L, 0x3170000000000000L, 0x33a0000000000000L,
            0x3210000000000000L, 0x3b80000000000000L, 0x3a30000000000000L,
            0x38e0000000000000L, 0x3950000000000000L, 0x3d40000000000000L,
            0x3cf0000000000000L, 0x3e20000000000000L, 0x3f90000000000000L,
            0x2d00000000000000L, 0x2cb0000000000000L, 0x2e60000000000000L,
            0x2fd0000000000000L, 0x2bc0000000000000L, 0x2a70000000000000L,
            0x28a0000000000000L, 0x2910000000000000L, 0x2080000000000000L,
            0x2130000000000000L, 0x23e0000000000000L, 0x2250000000000000L,
            0x2640000000000000L, 0x27f0000000000000L, 0x2520000000000000L,
            0x2490000000000000L, 0x6c00000000000000L, 0x6db0000000000000L,
            0x6f60000000000000L, 0x6ed0000000000000L, 0x6ac0000000000000L,
            0x6b70000000000000L, 0x69a0000000000000L, 0x6810000000000000L,
            0x6180000000000000L, 0x6030000000000000L, 0x62e0000000000000L,
            0x6350000000000000L, 0x6740000000000000L, 0x66f0000000000000L,
            0x6420000000000000L, 0x6590000000000000L, 0x7700000000000000L,
            0x76b0000000000000L, 0x7460000000000000L, 0x75d0000000000000L,
            0x71c0000000000000L, 0x7070000000000000L, 0x72a0000000000000L,
            0x7310000000000000L, 0x7a80000000000000L, 0x7b30000000000000L,
            0x79e0000000000000L, 0x7850000000000000L, 0x7c40000000000000L,
            0x7df0000000000000L, 0x7f20000000000000L, 0x7e90000000000000L,
            0x5a00000000000000L, 0x5bb0000000000000L, 0x5960000000000000L,
            0x58d0000000000000L, 0x5cc0000000000000L, 0x5d70000000000000L,
            0x5fa0000000000000L, 0x5e10000000000000L, 0x5780000000000000L,
            0x5630000000000000L, 0x54e0000000000000L, 0x5550000000000000L,
            0x5140000000000000L, 0x50f0000000000000L, 0x5220000000000000L,
            0x5390000000000000L, 0x4100000000000000L, 0x40b0000000000000L,
            0x4260000000000000L, 0x43d0000000000000L, 0x47c0000000000000L,
            0x4670000000000000L, 0x44a0000000000000L, 0x4510000000000000L,
            0x4c80000000000000L, 0x4d30000000000000L, 0x4fe0000000000000L,
            0x4e50000000000000L, 0x4a40000000000000L, 0x4bf0000000000000L,
            0x4920000000000000L, 0x4890000000000000L, 0xd800000000000000L,
            0xd9b0000000000000L, 0xdb60000000000000L, 0xdad0000000000000L,
            0xdec0000000000000L, 0xdf70000000000000L, 0xdda0000000000000L,
            0xdc10000000000000L, 0xd580000000000000L, 0xd430000000000000L,
            0xd6e0000000000000L, 0xd750000000000000L, 0xd340000000000000L,
            0xd2f0000000000000L, 0xd020000000000000L, 0xd190000000000000L,
            0xc300000000000000L, 0xc2b0000000000000L, 0xc060000000000000L,
            0xc1d0000000000000L, 0xc5c0000000000000L, 0xc470000000000000L,
            0xc6a0000000000000L, 0xc710000000000000L, 0xce80000000000000L,
            0xcf30000000000000L, 0xcde0000000000000L, 0xcc50000000000000L,
            0xc840000000000000L, 0xc9f0000000000000L, 0xcb20000000000000L,
            0xca90000000000000L, 0xee00000000000000L, 0xefb0000000000000L,
            0xed60000000000000L, 0xecd0000000000000L, 0xe8c0000000000000L,
            0xe970000000000000L, 0xeba0000000000000L, 0xea10000000000000L,
            0xe380000000000000L, 0xe230000000000000L, 0xe0e0000000000000L,
            0xe150000000000000L, 0xe540000000000000L, 0xe4f0000000000000L,
            0xe620000000000000L, 0xe790000000000000L, 0xf500000000000000L,
            0xf4b0000000000000L, 0xf660000000000000L, 0xf7d0000000000000L,
            0xf3c0000000000000L, 0xf270000000000000L, 0xf0a0000000000000L,
            0xf110000000000000L, 0xf880000000000000L, 0xf930000000000000L,
            0xfbe0000000000000L, 0xfa50000000000000L, 0xfe40000000000000L,
            0xfff0000000000000L, 0xfd20000000000000L, 0xfc90000000000000L,
            0xb400000000000000L, 0xb5b0000000000000L, 0xb760000000000000L,
            0xb6d0000000000000L, 0xb2c0000000000000L, 0xb370000000000000L,
            0xb1a0000000000000L, 0xb010000000000000L, 0xb980000000000000L,
            0xb830000000000000L, 0xbae0000000000000L, 0xbb50000000000000L,
            0xbf40000000000000L, 0xbef0000000000000L, 0xbc20000000000000L,
            0xbd90000000000000L, 0xaf00000000000000L, 0xaeb0000000000000L,
            0xac60000000000000L, 0xadd0000000000000L, 0xa9c0000000000000L,
            0xa870000000000000L, 0xaaa0000000000000L, 0xab10000000000000L,
            0xa280000000000000L, 0xa330000000000000L, 0xa1e0000000000000L,
            0xa050000000000000L, 0xa440000000000000L, 0xa5f0000000000000L,
            0xa720000000000000L, 0xa690000000000000L, 0x8200000000000000L,
            0x83b0000000000000L, 0x8160000000000000L, 0x80d0000000000000L,
            0x84c0000000000000L, 0x8570000000000000L, 0x87a0000000000000L,
            0x8610000000000000L, 0x8f80000000000000L, 0x8e30000000000000L,
            0x8ce0000000000000L, 0x8d50000000000000L, 0x8940000000000000L,
            0x88f0000000000000L, 0x8a20000000000000L, 0x8b90000000000000L,
            0x9900000000000000L, 0x98b0000000000000L, 0x9a60000000000000L,
            0x9bd0000000000000L, 0x9fc0000000000000L, 0x9e70000000000000L,
            0x9ca0000000000000L, 0x9d10000000000000L, 0x9480000000000000L,
            0x9530000000000000L, 0x97e0000000000000L, 0x9650000000000000L,
            0x9240000000000000L, 0x93f0000000000000L, 0x9120000000000000L,
            0x9090000000000000L
        };

        public static ulong Compute(string data)
        {
            var buffer = Encoding.UTF8.GetBytes(data);
            return Compute(DefaultSeed, buffer);
        }

        public static ulong Compute(ulong seed, byte[] buffer)
        {
            return CalculateHash(seed, buffer, 0, buffer.Length);
        }

        private static ulong CalculateHash(ulong seed, byte[] buffer, int start, int size)
        {
            ulong crc = seed;

            for (int i = start; i < size; i++)
            {
                unchecked
                {
                    crc = (crc >> 8) ^ _defaultTable[(buffer[i] ^ crc) & 0xff];
                }
            }

            return crc;
        }
    }
}