生成string类型的唯一ID代码,CSharp代码库,德仔网

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【CSharp】生成string类型的唯一ID
作者:dezai / 发布于2014/7/18/ 715

	using System;
	using System.Diagnostics;
	using System.Security.Cryptography;
	using System.Text;
	using System.Threading;

	namespace 命名空间
	{
	 /// <summary>
	 /// Represents an ObjectId (see also BsonObjectId).
	 /// </summary>
	 [Serializable]
	 public struct ObjectId : IComparable<ObjectId>, IEquatable<ObjectId>
	 {
	 #region private static fields
	 private static ObjectId emptyInstance = default(ObjectId);
	 private static int staticMachine;
	 private static short staticPid;
	 private static int staticIncrement; // high byte will be masked out when generating new ObjectId
	 #endregion

	 #region private fields
	 // we're using 14 bytes instead of 12 to hold the ObjectId in memory but unlike a byte[] there is no additional object on the heap
	 // the extra two bytes are not visible to anyone outside of this class and they buy us considerable simplification
	 // an additional advantage of this representation is that it will serialize to JSON without any 64 bit overflow problems
	 private int timestamp;
	 private int machine;
	 private short pid;
	 private int increment;
	 #endregion

	 #region static constructor
	 static ObjectId()
	 {
	 staticMachine = GetMachineHash();//获取机器名称
	 staticPid = (short)Process.GetCurrentProcess().Id; // use low order two bytes only
	 //取得新的 Process 元件，並將它與目前作用中的處理序相關聯。
	 staticIncrement = (new Random()).Next();//返回非负随机数
	 }
	 #endregion

	 #region constructors
	 /// <summary>
	 /// Initializes a new instance of the ObjectId class.
	 /// </summary>
	 /// <param name="bytes">The value.</param>
	 public ObjectId(
	 byte[] bytes
	 )
	 {
	 Unpack(bytes, out timestamp, out machine, out pid, out increment);
	 }

	 /// <summary>
	 /// Initializes a new instance of the ObjectId class.
	 /// </summary>
	 /// <param name="timestamp">The timestamp.</param>
	 /// <param name="machine">The machine hash.</param>
	 /// <param name="pid">The PID.</param>
	 /// <param name="increment">The increment.</param>
	 public ObjectId(
	 int timestamp,
	 int machine,
	 short pid,
	 int increment
	 )
	 {
	 this.timestamp = timestamp;
	 this.machine = machine;
	 this.pid = pid;
	 this.increment = increment;
	 }

	 /// <summary>
	 /// Initializes a new instance of the ObjectId class.
	 /// </summary>
	 /// <param name="value">The value.</param>
	 public ObjectId(
	 string value
	 )
	 {
	 Unpack(Utils.ParseHexString(value), out timestamp, out machine, out pid, out increment);
	 }
	 #endregion

	 #region public static properties
	 /// <summary>
	 /// Gets an instance of ObjectId where the value is empty.
	 /// </summary>
	 public static ObjectId Empty
	 {
	 get { return emptyInstance; }
	 }
	 #endregion

	 #region public properties
	 /// <summary>
	 /// Gets the timestamp.
	 /// </summary>
	 public int Timestamp
	 {
	 get { return timestamp; }
	 }

	 /// <summary>
	 /// Gets the machine.
	 /// </summary>
	 public int Machine
	 {
	 get { return machine; }
	 }

	 /// <summary>
	 /// Gets the PID.
	 /// </summary>
	 public short Pid
	 {
	 get { return pid; }
	 }

	 /// <summary>
	 /// Gets the increment.
	 /// </summary>
	 public int Increment
	 {
	 get { return increment; }
	 }

	 /// <summary>
	 /// Gets the creation time (derived from the timestamp).
	 /// </summary>
	 public DateTime CreationTime
	 {
	 get { return Constants.UnixEpoch.AddSeconds(timestamp); }
	 }
	 #endregion

	 #region public operators
	 /// <summary>
	 /// Compares two ObjectIds.
	 /// </summary>
	 /// <param name="lhs">The first ObjectId.</param>
	 /// <param name="rhs">The other ObjectId</param>
	 /// <returns>True if the first ObjectId is less than the second ObjectId.</returns>
	 public static bool operator <(
	 ObjectId lhs,
	 ObjectId rhs
	 )
	 {
	 return lhs.CompareTo(rhs) < 0;
	 }

	 /// <summary>
	 /// Compares two ObjectIds.
	 /// </summary>
	 /// <param name="lhs">The first ObjectId.</param>
	 /// <param name="rhs">The other ObjectId</param>
	 /// <returns>True if the first ObjectId is less than or equal to the second ObjectId.</returns>
	 public static bool operator <=(
	 ObjectId lhs,
	 ObjectId rhs
	 )
	 {
	 return lhs.CompareTo(rhs) <= 0;
	 }

	 /// <summary>
	 /// Compares two ObjectIds.
	 /// </summary>
	 /// <param name="lhs">The first ObjectId.</param>
	 /// <param name="rhs">The other ObjectId.</param>
	 /// <returns>True if the two ObjectIds are equal.</returns>
	 public static bool operator ==(
	 ObjectId lhs,
	 ObjectId rhs
	 )
	 {
	 return lhs.Equals(rhs);
	 }

	 /// <summary>
	 /// Compares two ObjectIds.
	 /// </summary>
	 /// <param name="lhs">The first ObjectId.</param>
	 /// <param name="rhs">The other ObjectId.</param>
	 /// <returns>True if the two ObjectIds are not equal.</returns>
	 public static bool operator !=(
	 ObjectId lhs,
	 ObjectId rhs
	 )
	 {
	 return !lhs.Equals(rhs);
	 }

	 /// <summary>
	 /// Compares two ObjectIds.
	 /// </summary>
	 /// <param name="lhs">The first ObjectId.</param>
	 /// <param name="rhs">The other ObjectId</param>
	 /// <returns>True if the first ObjectId is greather than or equal to the second ObjectId.</returns>
	 public static bool operator >=(
	 ObjectId lhs,
	 ObjectId rhs
	 )
	 {
	 return lhs.CompareTo(rhs) >= 0;
	 }

	 /// <summary>
	 /// Compares two ObjectIds.
	 /// </summary>
	 /// <param name="lhs">The first ObjectId.</param>
	 /// <param name="rhs">The other ObjectId</param>
	 /// <returns>True if the first ObjectId is greather than the second ObjectId.</returns>
	 public static bool operator >(
	 ObjectId lhs,
	 ObjectId rhs
	 )
	 {
	 return lhs.CompareTo(rhs) > 0;
	 }
	 #endregion

	 #region public static methods
	 /// <summary>
	 /// Generates a new ObjectId with a unique value.
	 /// </summary>
	 /// <returns>A ObjectId.</returns>
	 public static ObjectId GenerateNewId()
	 {
	 int timestamp = GetCurrentTimestamp();//根据时间获取
	 int increment = Interlocked.Increment(ref ObjectId.staticIncrement) & 0x00ffffff; // only use low order 3 bytes
	 return new ObjectId(timestamp, staticMachine, staticPid, increment);
	 }

	 public static string NewId()
	 {
	 return GenerateNewId().ToString();
	 }

	 /// <summary>
	 /// Packs the components of an ObjectId into a byte array.
	 /// </summary>
	 /// <param name="timestamp">The timestamp.</param>
	 /// <param name="machine">The machine hash.</param>
	 /// <param name="pid">The PID.</param>
	 /// <param name="increment">The increment.</param>
	 /// <returns>A byte array.</returns>
	 public static byte[] Pack(
	 int timestamp,
	 int machine,
	 short pid,
	 int increment
	 )
	 {
	 byte[] bytes = new byte[12];
	 bytes[0] = (byte)(timestamp >> 24);
	 bytes[1] = (byte)(timestamp >> 16);
	 bytes[2] = (byte)(timestamp >> 8);
	 bytes[3] = (byte)(timestamp);
	 bytes[4] = (byte)(machine >> 16);
	 bytes[5] = (byte)(machine >> 8);
	 bytes[6] = (byte)(machine);
	 bytes[7] = (byte)(pid >> 8);
	 bytes[8] = (byte)(pid);
	 bytes[9] = (byte)(increment >> 16);
	 bytes[10] = (byte)(increment >> 8);
	 bytes[11] = (byte)(increment);
	 return bytes;
	 }

	 /// <summary>
	 /// Parses a string and creates a new ObjectId.
	 /// </summary>
	 /// <param name="s">The string value.</param>
	 /// <returns>A ObjectId.</returns>
	 public static ObjectId Parse(
	 string s
	 )
	 {
	 ObjectId objectId;
	 if (TryParse(s, out objectId))
	 {
	 return objectId;
	 }
	 else
	 {
	 var message = string.Format("'{0}' is not a valid 24 digit hex string.", s);
	 throw new FormatException(message);
	 }
	 }

	 /// <summary>
	 /// Tries to parse a string and create a new ObjectId.
	 /// </summary>
	 /// <param name="s">The string value.</param>
	 /// <param name="objectId">The new ObjectId.</param>
	 /// <returns>True if the string was parsed successfully.</returns>
	 public static bool TryParse(
	 string s,
	 out ObjectId objectId
	 )
	 {
	 if (s != null && s.Length == 24)
	 {
	 byte[] bytes;
	 if (Utils.TryParseHexString(s, out bytes))
	 {
	 objectId = new ObjectId(bytes);
	 return true;
	 }
	 }

	 objectId = default(ObjectId);
	 return false;
	 }

	 /// <summary>
	 /// Unpacks a byte array into the components of an ObjectId.
	 /// </summary>
	 /// <param name="bytes">A byte array.</param>
	 /// <param name="timestamp">The timestamp.</param>
	 /// <param name="machine">The machine hash.</param>
	 /// <param name="pid">The PID.</param>
	 /// <param name="increment">The increment.</param>
	 public static void Unpack(
	 byte[] bytes,
	 out int timestamp,
	 out int machine,
	 out short pid,
	 out int increment
	 )
	 {
	 if (bytes.Length != 12)
	 {
	 throw new ArgumentOutOfRangeException("Byte array must be 12 bytes long.");
	 }
	 timestamp = (bytes[0] << 24) + (bytes[1] << 16) + (bytes[2] << 8) + bytes[3];
	 machine = (bytes[4] << 16) + (bytes[5] << 8) + bytes[6];
	 pid = (short)((bytes[7] << 8) + bytes[8]);
	 increment = (bytes[9] << 16) + (bytes[10] << 8) + bytes[11];
	 }
	 #endregion

	 #region private static methods
	 private static int GetMachineHash()
	 {
	 var hostName = Environment.MachineName; // use instead of Dns.HostName so it will work offline
	 var md5 = MD5.Create();//哈希算法的默认实现的实例
	 var hash = md5.ComputeHash(Encoding.UTF8.GetBytes(hostName));//在派生类中重写时，将指定的System.String中的所有字符编码
	 return (hash[0] << 16) + (hash[1] << 8) + hash[2]; // use first 3 bytes of hash
	 }

	 private static int GetCurrentTimestamp()
	 {
	 DateTime now = DateTime.UtcNow;
	 return (int)Math.Floor((now - Constants.UnixEpoch).TotalSeconds);
	 }
	 #endregion

	 #region public methods
	 /// <summary>
	 /// Compares this ObjectId to another ObjectId.
	 /// </summary>
	 /// <param name="other">The other ObjectId.</param>
	 /// <returns>A 32-bit signed integer that indicates whether this ObjectId is less than, equal to, or greather than the other.</returns>
	 public int CompareTo(
	 ObjectId other
	 )
	 {
	 int r = timestamp.CompareTo(other.timestamp);
	 if (r != 0) { return r; }
	 r = machine.CompareTo(other.machine);
	 if (r != 0) { return r; }
	 r = pid.CompareTo(other.pid);
	 if (r != 0) { return r; }
	 return increment.CompareTo(other.increment);
	 }

	 /// <summary>
	 /// Compares this ObjectId to another ObjectId.
	 /// </summary>
	 /// <param name="rhs">The other ObjectId.</param>
	 /// <returns>True if the two ObjectIds are equal.</returns>
	 public bool Equals(
	 ObjectId rhs
	 )
	 {
	 return
	 this.timestamp == rhs.timestamp &&
	 this.machine == rhs.machine &&
	 this.pid == rhs.pid &&
	 this.increment == rhs.increment;
	 }

	 /// <summary>
	 /// Compares this ObjectId to another object.
	 /// </summary>
	 /// <param name="obj">The other object.</param>
	 /// <returns>True if the other object is an ObjectId and equal to this one.</returns>
	 public override bool Equals(
	 object obj
	 )
	 {
	 if (obj is ObjectId)
	 {
	 return Equals((ObjectId)obj);
	 }
	 else
	 {
	 return false;
	 }
	 }

	 /// <summary>
	 /// Gets the hash code.
	 /// </summary>
	 /// <returns>The hash code.</returns>
	 public override int GetHashCode()
	 {
	 int hash = 17;
	 hash = 37 * hash + timestamp.GetHashCode();
	 hash = 37 * hash + machine.GetHashCode();
	 hash = 37 * hash + pid.GetHashCode();
	 hash = 37 * hash + increment.GetHashCode();
	 return hash;
	 }

	 /// <summary>
	 /// Converts the ObjectId to a byte array.
	 /// </summary>
	 /// <returns>A byte array.</returns>
	 public byte[] ToByteArray()
	 {
	 return Pack(timestamp, machine, pid, increment);
	 }

	 /// <summary>
	 /// Returns a string representation of the value.
	 /// </summary>
	 /// <returns>A string representation of the value.</returns>
	 public override string ToString()
	 {
	 return Utils.ToHexString(Pack(timestamp, machine, pid, increment));
	 }
	 #endregion

	
	 internal static class Utils
	 {
	 /// <summary>
	 /// Tries to parse a hex string to a byte array.
	 /// </summary>
	 /// <param name="s">The hex string.</param>
	 /// <param name="bytes">A byte array.</param>
	 /// <returns>True if the hex string was successfully parsed.</returns>
	 public static bool TryParseHexString(
	 string s,
	 out byte[] bytes
	 )
	 {
	 if (s != null)
	 {
	 if ((s.Length & 1) != 0) { s = "0" + s; } // make length of s even
	 bytes = new byte[s.Length / 2];
	 for (int i = 0; i < bytes.Length; i++)
	 {
	 string hex = s.Substring(2 * i, 2);
	 try
	 {
	 byte b = Convert.ToByte(hex, 16);
	 bytes[i] = b;
	 }
	 catch (FormatException)
	 {
	 bytes = null;
	 return false;
	 }
	 }
	 return true;
	 }

	 bytes = null;
	 return false;
	 }

	 /// <summary>
	 /// Tries to parse a hex string to a byte array.
	 /// </summary>
	 /// <param name="s">The hex string.</param>
	 /// <param name="bytes">A byte array.</param>
	 /// <returns>True if the hex string was successfully parsed.</returns>
	 public static byte[] ParseHexString(string s)
	 {
	 byte[] bytes;
	 if (!TryParseHexString(s, out bytes))
	 {
	 var message = string.Format("'{0}' is not a valid hex string.", s);
	 throw new FormatException(message);
	 }
	 return bytes;
	 }

	 /// <summary>
	 /// Converts a byte array to a hex string.
	 /// </summary>
	 /// <param name="bytes">The byte array.</param>
	 /// <returns>A hex string.</returns>
	 public static string ToHexString(
	 byte[] bytes
	 )
	 {
	 var sb = new StringBuilder(bytes.Length * 2);
	 foreach (var b in bytes)
	 {
	 sb.AppendFormat("{0:x2}", b);
	 }
	 return sb.ToString();
	 }
	 }

	 internal static class Constants
	 {
	 #region private static fields
	 private static readonly long dateTimeMaxValueMillisecondsSinceEpoch;
	 private static readonly long dateTimeMinValueMillisecondsSinceEpoch;
	 private static readonly DateTime unixEpoch;
	 #endregion

	 #region static constructor
	 static Constants()
	 {
	 // unixEpoch has to be initialized first
	 unixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
	 dateTimeMaxValueMillisecondsSinceEpoch = (DateTime.MaxValue - unixEpoch).Ticks / 10000;
	 dateTimeMinValueMillisecondsSinceEpoch = (DateTime.MinValue - unixEpoch).Ticks / 10000;
	 }
	 #endregion

	 #region public static properties
	 /// <summary>
	 /// Gets the number of milliseconds since the Unix epoch for DateTime.MaxValue.
	 /// </summary>
	 public static long DateTimeMaxValueMillisecondsSinceEpoch
	 {
	 get { return dateTimeMaxValueMillisecondsSinceEpoch; }
	 }

	 /// <summary>
	 /// Gets the number of milliseconds since the Unix epoch for DateTime.MinValue.
	 /// </summary>
	 public static long DateTimeMinValueMillisecondsSinceEpoch
	 {
	 get { return dateTimeMinValueMillisecondsSinceEpoch; }
	 }

	 /// <summary>
	 /// Gets the Unix Epoch for BSON DateTimes (1970-01-01).
	 /// </summary>
	 public static DateTime UnixEpoch { get { return unixEpoch; } }
	 #endregion
	 }

	 }
	}
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