C# 生成有序Guid
csharp
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-rrrrrrrrrrrr
Buffer.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0
guidBytes[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);
}
}