(精华)2020年6月27日 C#类库 一致性HASH帮助类
【摘要】
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Core....
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Core.Util
{
/// <summary>
/// 一致性HASH,解决传统HASH的扩容难的问题
/// 注:常用与分布式缓存与分表
/// </summary>
/// <typeparam name="T">泛型</typeparam>
public class ConsistentHash<T>
{
SortedDictionary<int, T> circle { get; set; } = new SortedDictionary<int, T>();//虚拟的圆环，对2的32方取模
int _replicate = 100; //虚拟节点数 count
int[] ayKeys = null; //缓存节点hash
/// <summary>
/// 初始化可迭代的节点数
/// </summary>
/// <param name="nodes">节点</param>
public void Init(IEnumerable<T> nodes)
{
Init(nodes, _replicate);
}
/// <summary>
/// 初始化可迭代的节点数，默认不缓存
/// </summary>
/// <param name="nodes">节点</param>
/// <param name="replicate"></param>
public void Init(IEnumerable<T> nodes, int replicate)
{
_replicate = replicate;
foreach (T node in nodes)
{
this.Add(node, false);
}
ayKeys = circle.Keys.ToArray();
}
/// <summary>
/// 添加节点，缓存
/// </summary>
/// <param name="node"></param>
public void Add(T node)
{
Add(node, true);
}
/// <summary>
/// 添加虚拟的圆环的节点
/// </summary>
/// <param name="node">节点</param>
/// <param name="updateKeyArray">是否缓存node的hash</param>
private void Add(T node, bool updateKeyArray)
{
for (int i = 0; i < _replicate; i++)
{
int hash = BetterHash(node.GetHashCode().ToString() + i);
circle[hash] = node;
}
if (updateKeyArray)
{
ayKeys = circle.Keys.ToArray();
}
}
/// <summary>
/// 删除真实机器节点，更新缓存
/// </summary>
/// <param name="node"></param>
public void Remove(T node)
{
for (int i = 0; i < _replicate; i++)
{
int hash = BetterHash(node.GetHashCode().ToString() + i);
if (!circle.Remove(hash))
{
throw new Exception("can not remove a node that not added");
}
}
ayKeys = circle.Keys.ToArray();
}
/// <summary>
/// 判断是否存在key对应的hash，有则返回没有返回最近一个节点
/// </summary>
/// <param name="key"></param>
/// <returns></returns>
private T GetNode_slow(String key)
{
int hash = BetterHash(key);
if (circle.ContainsKey(hash))
{
return circle[hash];
}
// 沿环的顺时针找到一个节点
int first = circle.Keys.FirstOrDefault(h => h >= hash);
if (first == new int())
{
first = ayKeys[0];
}
T node = circle[first];
return node;
}
int First_ge(int[] ay, int val)
{
int begin = 0;
int end = ay.Length - 1;
if (ay[end] < val || ay[0] > val)
{
return 0;
}
int mid = begin;
while (end - begin > 1)
{
mid = (end + begin) / 2;
if (ay[mid] >= val)
{
end = mid;
}
else
{
begin = mid;
}
}
if (ay[begin] > val || ay[end] < val)
{
throw new Exception("should not happen");
}
return end;
}
public T GetNode(String key)
{
int hash = BetterHash(key);
int first = First_ge(ayKeys, hash);
return circle[ayKeys[first]];
}
/// <summary>
/// MurMurHash2算法,性能高,碰撞率低
/// </summary>
/// <param name="key">计算hash的字符串</param>
/// <returns>hash值</returns>
public static int BetterHash(String key)
{
uint hash = MurmurHash2.Hash(Encoding.ASCII.GetBytes(key));
return (int)hash;
}
}
}
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MurMurHash2算法
using System;
using System.Runtime.InteropServices;
namespace Core.Util
{
public class MurmurHash2
{
public static UInt32 Hash(Byte[] data)
{
return Hash(data, 0xc58f1a7b);
}
const UInt32 m = 0x5bd1e995;
const Int32 r = 24;
[StructLayout(LayoutKind.Explicit)]
struct BytetoUInt32Converter
{
[FieldOffset(0)]
public Byte[] Bytes;
[FieldOffset(0)]
public UInt32[] UInts;
}
public static UInt32 Hash(Byte[] data, UInt32 seed)
{
Int32 length = data.Length;
if (length == 0)
return 0;
UInt32 h = seed ^ (UInt32)length;
Int32 currentIndex = 0;
// array will be length of Bytes but contains Uints
// therefore the currentIndex will jump with +1 while length will jump with +4
UInt32[] hackArray = new BytetoUInt32Converter { Bytes = data }.UInts;
while (length >= 4)
{
UInt32 k = hackArray[currentIndex++];
k *= m;
k ^= k >> r;
k *= m;
h *= m;
h ^= k;
length -= 4;
}
currentIndex *= 4; // fix the length
switch (length)
{
case 3:
h ^= (UInt16)(data[currentIndex++] | data[currentIndex++] << 8);
h ^= (UInt32)data[currentIndex] << 16;
h *= m;
break;
case 2:
h ^= (UInt16)(data[currentIndex++] | data[currentIndex] << 8);
h *= m;
break;
case 1:
h ^= data[currentIndex];
h *= m;
break;
default:
break;
}
// Do a few final mixes of the hash to ensure the last few
// bytes are well-incorporated.
h ^= h >> 13;
h *= m;
h ^= h >> 15;
return h;
}
}
}
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文章来源: codeboy.blog.csdn.net，作者：愚公搬代码，版权归原作者所有，如需转载，请联系作者。
原文链接：codeboy.blog.csdn.net/article/details/106982042
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