架构师训练营第 1 期第五周作业

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
namespace HashRing
{
    public class HashRingManager
    {
        private readonly SortedList<long, string> VNodes;
        private HashAlgorithm HashAlg;
        public HashRingManager(List<string> nodes, int vNodeNumebr)
        {
            VNodes = new SortedList<long, string>();
            foreach (string node in nodes)
            {
                for (int i = 0; i < vNodeNumebr / 4; i++)
                {
                    byte[] digest = HashAlgorithm.ComputeMd5(node + i);
                    for (int h = 0; h < 4; h++)
                    {
                        long m = HashAlgorithm.Hash(digest, h);
                        VNodes[m] = node;
                    }
                }
            }
        }
        public string GetPrimary(string key)
        {
            byte[] digest = HashAlgorithm.ComputeMd5(key);
            return GetNode(HashAlgorithm.Hash(digest, 0));
        }
        private string GetNode(long hash)
        {
            long key = hash;
            
            if (!VNodes.ContainsKey(key))
            {
                var tailMap = from node in VNodes
                              where node.Key > hash
                              select new { node.Key };
                if (tailMap == null || tailMap.Count() == 0)
                    key = VNodes.FirstOrDefault().Key;
                else
                    key = tailMap.FirstOrDefault().Key;
            }
            return VNodes[key];
        }
    }
    public class HashAlgorithm
    {
        public static long Hash(byte[] digest, int nTime)
        {
            long rv = ((long)(digest[3 + nTime * 4] & 0xFF) << 24)
                    | ((long)(digest[2 + nTime * 4] & 0xFF) << 16)
                    | ((long)(digest[1 + nTime * 4] & 0xFF) << 8)
                    | ((long)digest[0 + nTime * 4] & 0xFF);
            return rv & 0xffffffffL; /* Truncate to 32-bits */
        }
        
        public static byte[] ComputeMd5(string key)
        {
            MD5 md5 = new MD5CryptoServiceProvider();
            byte[] keyBytes = md5.ComputeHash(Encoding.UTF8.GetBytes(key));
            md5.Clear();
            return keyBytes;
        }
    }
}