[Algorithm] CIDR set algorithm

Classless Inter-Domain Routing is short for classless Inter-Domain Routing. Is currently used to represent a route. Because some algorithms of the CIDR set are required for a product, such as intersection, union, and supplement operations of the set. The following shows the implementation code.

 

The first is the structure of CIDR:

    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;        }    }

This class implements the serialization interface (ixmlserializable) and the comparable interface (icomparable <t> ). Convenient storage and other operations.

The next step is to operate the CIDR set. Because routegroup is called in the product, the name is not changed here:

    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);            }        }    }

Sample Code:

   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 . . .             */        }

Welcome to the discussion.