【算法】CIDR集合的算法

    CIDR（Classless Inter-Domain Routing）是“无类别域间路由”的缩写。是当前用来表示路由的一种方式。由于在做某产品的时候需要用到CIDR集合的一些算法，例如集合的交集、并集、补集运算。下面给出相应的实现代码。

 

    首先是CIDR的结构：

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
public sealed class CIDR : IXmlSerializable, IComparable<CIDR>
{
    private byte[] bytes = null;
 
    public IPAddress IPAddress { get; private set; }
    public int Subnet { get; private set; }
 
    public override bool Equals(object obj)
    {
        CIDR cidr = obj as CIDR;
        if (cidr == null)
            return false;
        return this.Subnet == cidr.Subnet && this.IPAddress.Equals(cidr.IPAddress);
    }
    public override int GetHashCode()
    {
        return this.IPAddress.GetHashCode() ^ this.Subnet.GetHashCode();
    }
    public override string ToString()
    {
        return string.Format("{0}/{1}", IPAddress, Subnet);
    }
 
    public static CIDR Parse(string str)
    {
        CIDR cidr = new CIDR();
        cidr.SetFromString(str);
        return cidr;
    }
    private void SetFromString(string str)
    {
        int i = str.IndexOf('/');
        this.IPAddress = IPAddress.Parse(str.Substring(0, i));
        this.Subnet = int.Parse(str.Substring(i + 1));
        this.bytes = this.IPAddress.GetAddressBytes();
 
        int length = this.bytes.Length << 3;
        if (this.Subnet < 0 || this.Subnet > length)
            throw new ArgumentException("", "str");
        // can optimize
        for (i = this.Subnet + 1; i <= length; i++)
        {
            int bit = (bytes[(i - 1) >> 3] >> ((8 - i) & 7)) & 1;
            if (bit != 0)
                throw new ArgumentException("", "str");
        }
    }
 
    public bool IsIPv6
    {
        get { return this.IPAddress.AddressFamily == AddressFamily.InterNetworkV6; }
    }
 
    #region IXmlSerializable
    XmlSchema IXmlSerializable.GetSchema()
    {
        return null;
    }
 
    void IXmlSerializable.ReadXml(XmlReader reader)
    {
        this.SetFromString(reader.ReadElementContentAsString());
    }
 
    void IXmlSerializable.WriteXml(XmlWriter writer)
    {
        writer.WriteString(this.ToString());
    }
    #endregion
 
    #region CIDR Algorithm
    public CIDR GetPaired()
    {
        if (this.Subnet == 0)
            throw new NotSupportedException("Subnet=0");
        CIDR cidr = new CIDR();
        cidr.Subnet = this.Subnet;
        cidr.bytes = new byte[this.bytes.Length];
        this.bytes.CopyTo(cidr.bytes, 0);
 
        int k = this.Subnet - 1;
        int i = k >> 3;
        int j = (7 - k) & 7;
        cidr.bytes[i] = (byte)(cidr.bytes[i] ^ (1 << j));
        cidr.IPAddress = new IPAddress(cidr.bytes);
 
        return cidr;
    }
 
    public CIDR GetBiggerSubnet()
    {
        if (this.Subnet == 0)
            throw new NotSupportedException("Subnet=0");
        CIDR cidr = new CIDR();
        cidr.Subnet = this.Subnet - 1;
        cidr.bytes = new byte[this.bytes.Length];
        this.bytes.CopyTo(cidr.bytes, 0);
 
        int k = this.Subnet - 1;
        int i = k >> 3;
        int j = (7 - k) & 7;
        cidr.bytes[i] = (byte)(cidr.bytes[i] & ~(1 << j));
        cidr.IPAddress = new IPAddress(cidr.bytes);
 
        return cidr;
    }
 
    public CIDR GetSmallerSubnet()
    {
        if (this.Subnet == this.bytes.Length << 3)
            throw new NotSupportedException("Subnet=max");
        CIDR cidr = new CIDR();
        cidr.Subnet = this.Subnet + 1;
        cidr.bytes = this.bytes;
        cidr.IPAddress = this.IPAddress;
        return cidr;
    }
 
    public bool ExistsIntersection(CIDR other)
    {
        if (other == null)
            throw new ArgumentNullException("other");
 
        if (this.IsIPv6 != other.IsIPv6)
            throw new NotSupportedException("Different address family");
 
        if (this.Subnet == 0 || other.Subnet == 0)
            return true;
 
        int min = Math.Min(this.Subnet, other.Subnet) - 1;
        int length = min >> 3;
 
        int k;
        for (k = 0; k < length; k++)
            if (this.bytes[k] != other.bytes[k])
                return false;
 
        //int m = (0xff << (7 - min & 7)) & 0xff;
        int m = (0xff80 >> (min & 7));
        if (k < this.bytes.Length && (this.bytes[k] & m) != (other.bytes[k] & m))
            return false;
 
        return true;
    }
 
    public CIDR Intersect(CIDR other)
    {
        if (other == null)
            throw new ArgumentNullException("other");
 
        if (this.IsIPv6 != other.IsIPv6)
            throw new NotSupportedException("Different address family");
 
        if (this.ExistsIntersection(other))
            if (this.Subnet > other.Subnet)
                return this;
            else
                return other;
        else
            return null;
    }
 
    public CIDR[] Union(CIDR other)
    {
        if (other == null)
            throw new ArgumentNullException("other");
 
        if (this.IsIPv6 != other.IsIPv6)
            throw new NotSupportedException("Different address family");
 
        if (this.ExistsIntersection(other))
            if (this.Subnet < other.Subnet)
                return new[] { this };
            else
                return new[] { other };
        else
            if (this.Subnet == other.Subnet && this.Equals(other.GetPaired()))
                return new[] { this.GetBiggerSubnet() };
            else
                return new[] { this, other };
    }
    #endregion
 
    public int CompareTo(CIDR other)
    {
        if (other == null)
            throw new ArgumentNullException("other");
 
        if (this.IsIPv6 != other.IsIPv6)
            if (this.IsIPv6)
                return 1;
            else
                return -1;
        else if (this.Subnet > other.Subnet)
            return 1;
        else if (this.Subnet < other.Subnet)
            return -1;
        else
            for (int i = 0; i < this.bytes.Length; i++)
                if (this.bytes[i] > other.bytes[i])
                    return 1;
                else if (this.bytes[i] < other.bytes[i])
                    return -1;
        return 0;
    }
}

    这个类实现了序列化接口（IXmlSerializable）和可比较接口（IComparable<T>）。方便进行存储等操作。

    接下来是对CIDR集合的操作。由于在产品中叫做RouteGroup，所以在这里也就没改名字了：

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
public class RouteGroup
{
    public RouteGroup()
    {
        this.CIDRs = new HashSet<CIDR>();
    }
 
    [XmlAttribute]
    public string GroupName { get; set; }
    [XmlAttribute]
    public Guid GroupID { get; set; }
    public HashSet<CIDR> CIDRs { get; set; }
 
    public static RouteGroup Create(string groupName)
    {
        return new RouteGroup { GroupName = groupName, GroupID = Guid.NewGuid() };
    }
 
    public void Union(CIDR cidr)
    {
        if (cidr == null)
            throw new ArgumentNullException("cidr");
 
        var list = this.CIDRs
            .Where(s => s.IsIPv6 == cidr.IsIPv6 && s.ExistsIntersection(cidr))
            .ToList();
        if (list.Count == 0)
        {
            if (cidr.Subnet > 0 && this.CIDRs.Remove(cidr.GetPaired()))
                this.Union(cidr.GetBiggerSubnet());
            else
                this.CIDRs.Add(cidr);
        }
        else
        {
            foreach (var item in list)
                this.CIDRs.Remove(item);
 
            var max = list.Max();
            if (max.Subnet < cidr.Subnet)
                this.CIDRs.Add(max);
            else if (max.Subnet > cidr.Subnet)
                this.CIDRs.Add(cidr);
        }
    }
 
    public void Subtract(CIDR cidr)
    {
        if (cidr == null)
            throw new ArgumentNullException("cidr");
 
        var list = this.CIDRs
           .Where(s => s.IsIPv6 == cidr.IsIPv6 && s.ExistsIntersection(cidr))
           .ToList();
        if (list.Count > 0)
        {
            foreach (var item in list)
                this.CIDRs.Remove(item);
 
            var min = list.Min();
            CIDR other = cidr;
            for (int i = cidr.Subnet; i > min.Subnet; i--)
            {
                this.CIDRs.Add(other.GetPaired());
                other = other.GetBiggerSubnet();
            }
        }
    }
 
    public void Union(string cidr)
    {
        this.Union(CIDR.Parse(cidr));
    }
 
    public void Subtract(string cidr)
    {
        this.Subtract(CIDR.Parse(cidr));
    }
 
    public void Reverse()
    {
        var list = this.CIDRs.ToList();
        this.CIDRs.Clear();
        this.Union("0.0.0.0/0");
        foreach (var item in list)
            this.Subtract(item);
    }
 
    public void Sort()
    {
        var list = this.CIDRs.OrderBy(s => s).ToList();
        this.CIDRs.Clear();
        foreach (var item in list)
        {
            this.CIDRs.Add(item);
        }
    }
 
    public void Rebuild()
    {
        var list = this.CIDRs.OrderBy(s => s).ToList();
        this.CIDRs.Clear();
        foreach (var item in list)
        {
            this.Union(item);
        }
    }
}

    样例代码：

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
static void Main(string[] args)
     {
         var rg = RouteGroup.Create("test");
         rg.Union("1.2.0.0/16");
         rg.Union("1.3.0.0/16");
         rg.Union("2.2.0.0/16");
         rg.Union("3.2.0.0/16");
         rg.Union("4.2.5.0/24");
         rg.Union("5.2.8.0/21");
         rg.Union("4.2.12.0/22");
         rg.Sort();
         foreach (var item in rg.CIDRs)
             Console.WriteLine(item);
         Console.WriteLine();
 
         rg.Reverse();
         rg.Sort();
         foreach (var item in rg.CIDRs)
             Console.WriteLine(item);
         Console.WriteLine();
 
         rg.Subtract("0.0.0.0/2");
         rg.Sort();
         foreach (var item in rg.CIDRs)
             Console.WriteLine(item);
 
         /*
          * 1.2.0.0/15
          * 2.2.0.0/16
          * 3.2.0.0/16
          * 5.2.8.0/21
          * 4.2.12.0/22
          * 4.2.5.0/24
          *
          * 128.0.0.0/1
          * 64.0.0.0/2
          * 32.0.0.0/3
          * 16.0.0.0/4
          * 8.0.0.0/5
          * 6.0.0.0/7
          * 0.0.0.0/8
          * 1.128.0.0/9
          * 2.128.0.0/9
          * 3.128.0.0/9
          * 4.128.0.0/9
          * 5.128.0.0/9
          * 1.64.0.0/10
          * 2.64.0.0/10
          * 3.64.0.0/10
          * 4.64.0.0/10
          * 5.64.0.0/10
          * 1.32.0.0/11
          * 2.32.0.0/11
          * 3.32.0.0/11
          * 4.32.0.0/11
          * 5.32.0.0/11
          * 1.16.0.0/12
          * 2.16.0.0/12
          * 3.16.0.0/12
          * 4.16.0.0/12
          * 5.16.0.0/12
          * 1.8.0.0/13
          * 2.8.0.0/13
          * 3.8.0.0/13
          * 4.8.0.0/13
          * 5.8.0.0/13
          * 1.4.0.0/14
          * 2.4.0.0/14
          * 3.4.0.0/14
          * 4.4.0.0/14
          * 5.4.0.0/14
          * 1.0.0.0/15
          * 2.0.0.0/15
          * 3.0.0.0/15
          * 4.0.0.0/15
          * 5.0.0.0/15
          * 2.3.0.0/16
          * 3.3.0.0/16
          * 4.3.0.0/16
          * 5.3.0.0/16
          * 4.2.128.0/17
          * 5.2.128.0/17
          * 4.2.64.0/18
          * 5.2.64.0/18
          * 4.2.32.0/19
          * 5.2.32.0/19
          * 4.2.16.0/20
          * 5.2.16.0/20
          * 5.2.0.0/21
          * 4.2.0.0/22
          * 4.2.8.0/22
          * 4.2.6.0/23
          * 4.2.4.0/24
          *
          * 128.0.0.0/1
          * 64.0.0.0/2
          * Press any key to continue . . .
          */
     }

    欢迎拍砖讨论。

posted @   Aimeast  阅读(2526)  评论(2)  编辑  收藏  举报
编辑推荐：
· 从 HTTP 原因短语缺失研究 HTTP/2 和 HTTP/3 的设计差异
· AI与.NET技术实操系列：向量存储与相似性搜索在 .NET 中的实现
· 基于Microsoft.Extensions.AI核心库实现RAG应用
· Linux系列：如何用heaptrack跟踪.NET程序的非托管内存泄露
· 开发者必知的日志记录最佳实践
阅读排行：
· TypeScript + Deepseek 打造卜卦网站：技术与玄学的结合
· Manus的开源复刻OpenManus初探
· AI 智能体引爆开源社区「GitHub 热点速览」
· C#/.NET/.NET Core技术前沿周刊 | 第 29 期（2025年3.1-3.9）
· 从HTTP原因短语缺失研究HTTP/2和HTTP/3的设计差异
点击右上角即可分享
微信分享提示
SQL AI 助手