C# 生成有序Guid

public enum SequentialGuidType
{/// <summary>/// 用于 MySql 和 PostgreSql.///  当使用 <see cref="Guid.ToString()" /> 方法进行格式化时连续./// </summary>AsString,/// <summary>/// 用于 Oracle./// 当使用 <see cref="Guid.ToByteArray()" /> 方法进行格式化时连续./// </summary>AsBinary,/// <summary>/// 用以 SqlServer./// 连续性体现于 GUID 的第4块（Data4）./// </summary>AtEnd
}public static class GuidHelper
{private const byte version = (byte)4;private const byte variant = (byte)8;private const byte filterHighBit = 0b00001111;private const byte filterLowBit = 0b11110000;private static readonly RandomNumberGenerator _randomNumberGenerator = RandomNumberGenerator.Create();/// <summary>/// 连续 Guid 类型，默认：AsString./// </summary>public static SequentialGuidType SequentialGuidType { get; set; } = SequentialGuidType.AsString;/// <summary>/// 生成连续 Guid./// </summary>/// <returns></returns>public static Guid Next(){return Next(SequentialGuidType);}/// <summary>/// 生成连续 Guid（生成的 Guid 并不符合 RFC 4122 标准）./// 来源：Abp. from jhtodd/SequentialGuid https://github.com/jhtodd/SequentialGuid/blob/master/SequentialGuid/Classes/SequentialGuid.cs ./// </summary>/// <param name="guidType"></param>/// <returns></returns>public static Guid NextOld(SequentialGuidType guidType){var randomBytes = new byte[8];_randomNumberGenerator.GetBytes(randomBytes);long timestamp = DateTime.UtcNow.Ticks;byte[] timestampBytes = BitConverter.GetBytes(timestamp);if (BitConverter.IsLittleEndian){Array.Reverse(timestampBytes);}byte[] guidBytes = new byte[16];switch (guidType){case SequentialGuidType.AsString:case SequentialGuidType.AsBinary:// 16位数组：前8位为时间戳，后8位为随机数Buffer.BlockCopy(timestampBytes, 0, guidBytes, 0, 8);Buffer.BlockCopy(randomBytes, 0, guidBytes, 8, 8);// .NET中，Data1、Data2、Data3 块 分别视为 Int32、Int16、Int16，在小端系统，需要翻转这3个块。if (guidType == SequentialGuidType.AsString && BitConverter.IsLittleEndian){Array.Reverse(guidBytes, 0, 4);Array.Reverse(guidBytes, 4, 2);Array.Reverse(guidBytes, 6, 2);}break;case SequentialGuidType.AtEnd:// 16位数组：前8位为随机数，后8位为时间戳Buffer.BlockCopy(randomBytes, 0, guidBytes, 0, 8);Buffer.BlockCopy(timestampBytes, 6, guidBytes, 8, 2);Buffer.BlockCopy(timestampBytes, 0, guidBytes, 10, 6);break;}return new Guid(guidBytes);}/// <summary>/// 生成连续 Guid./// </summary>/// <param name="guidType"></param>/// <returns></returns>public static Guid Next(SequentialGuidType guidType){// see: What is a GUID? http://guid.one/guid// see: https://github.com/richardtallent/RT.Comb#gory-details-about-uuids-and-guids// According to RFC 4122:// dddddddd-dddd-Mddd-Ndrr-rrrrrrrrrrrr// - M = RFC 版本（version）, 版本4的话，值为4// - N = RFC 变体（variant），值为 8, 9, A, B 其中一个，这里固定为8// - d = 从公元1年1月1日0时至今的时钟周期数（DateTime.UtcNow.Ticks）// - r = 随机数（random bytes）var randomBytes = new byte[8];_randomNumberGenerator.GetBytes(randomBytes);long timestamp = DateTime.UtcNow.Ticks;byte[] timestampBytes = BitConverter.GetBytes(timestamp);if (BitConverter.IsLittleEndian){Array.Reverse(timestampBytes);}byte[] guidBytes = new byte[16];switch (guidType){case SequentialGuidType.AsString:case SequentialGuidType.AsBinary:// AsString: dddddddd-dddd-Mddd-Ndrr-rrrrrrrrrrrrBuffer.BlockCopy(timestampBytes, 0, guidBytes, 0, 6); // 时间戳前6个字节，共48位guidBytes[6] = (byte)((version << 4) | ((timestampBytes[6] & filterLowBit) >> 4)); // 高4位为版本 | 低4位取时间戳序号[6]的元素的高4位guidBytes[7] = (byte)(((timestampBytes[6] & filterHighBit) << 4) | ((timestampBytes[7] & filterLowBit) >> 4)); // 高4位取：[6]低4位 | 低4位取：[7]高4位guidBytes[8] = (byte)((variant << 4) | (timestampBytes[7] & filterHighBit)); // 高4位为：变体 | 低4位取：[7]低4位Buffer.BlockCopy(randomBytes, 0, guidBytes, 9, 7); // 余下7个字节由随机数组填充// .NET中，Data1、Data2、Data3 块 分别视为 Int32、Int16、Int16，在小端系统，需要翻转这3个块。if (guidType == SequentialGuidType.AsString && BitConverter.IsLittleEndian){Array.Reverse(guidBytes, 0, 4);Array.Reverse(guidBytes, 4, 2);Array.Reverse(guidBytes, 6, 2);}break;case SequentialGuidType.AtEnd:// AtEnd: rrrrrrrr-rrrr-Mxdr-Nddd-dddddddddddd// Block: 1        2    3    4    5// Data4 = Block4 + Block5// 排序顺序：Block5 > Block4 > Block3 > Block2 > Block1// Data3 = Block3 被认为是 uint16，排序并不是从左到右，为消除影响，x 位取固定值Buffer.BlockCopy(randomBytes, 0, guidBytes, 0, 6);guidBytes[6] = (byte)(version << 4); // Mx 高4位为版本 | 低4位取：全0guidBytes[7] = (byte)(((timestampBytes[7] & filterHighBit) << 4) | (randomBytes[7] & filterHighBit)); ; // dr 高4位为：时间戳[7]低4位 | 低4位取：随机数guidBytes[8] = (byte)((variant << 4) | ((timestampBytes[6] & filterLowBit) >> 4)); // Nd 高4位为：变体 | 低4位取：时间戳[6]高4位guidBytes[9] = (byte)(((timestampBytes[6] & filterHighBit) << 4) | ((timestampBytes[7] & filterLowBit) >> 4)); // dd 高4位为：时间戳[6]低4位 | 低4位取：时间戳[7]高4位Buffer.BlockCopy(timestampBytes, 0, guidBytes, 10, 6); // 时间戳前6个字节if (BitConverter.IsLittleEndian){Array.Reverse(guidBytes, 6, 2); // 包含版本号的 Data3 块需要翻转}break;}return new Guid(guidBytes);}
}