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http://www.cnblogs.com/heyuquan/archive/2013/08/16/global-guid-identity-maxId.html 最全文章 http://www.cnblogs.com/haoxinyue/p/5208136.html 比较好的 http://www.ogeek.net/article/43823.htm 可以看看 using System; using System.Collections.Generic; using System.ComponentModel; using System.Data.SqlTypes; using System.Linq; using System.Text; using System.Threading; using System.Threading.Tasks; using System.Xml; using System.Xml.Schema; using System.Xml.Serialization; namespace 唯一码 { /// <summary>COMB 类型 GUID,要存储在数据库中或要从数据库中检索的 GUID。</summary> /// <remarks>COMB 类型 GUID 是由Jimmy Nilsson在他的“The Cost of GUIDs as Primary Keys”一文中设计出来的。 /// <para>基本设计思路是这样的:既然GUID数据因毫无规律可言造成索引效率低下,影响了系统的性能,那么能不能通过组合的方式, /// 保留GUID的前10个字节,用后6个字节表示GUID生成的时间(DateTime),这样我们将时间信息与GUID组合起来, /// 在保留GUID的唯一性的同时增加了有序性,以此来提高索引效率。</para> /// <para>也许有人会担心GUID减少到10字节会造成数据出现重复,其实不用担心, /// 后6字节的时间精度可以达到 1/10000 秒,两个COMB类型数据完全相同的可能性是在这 1/10000 秒内生成的两个GUID前10个字节完全相同,这几乎是不可能的!</para> /// <para>理论上一天之内允许生成 864000000 个不重复的CombGuid;如果当天生成的个数大于 864000000 ,会一直累加 1 直到 2147483647 , /// 也就是说实际一天之内能生成 2147483647 个不重复的CombGuid。</para> /// </remarks> public struct CombGuid : INullable, IComparable, IComparable<CombGuid>, IEquatable<CombGuid>, IXmlSerializable { #region -- Fields -- private static readonly String _NullString = "nil"; private static readonly Int32 _SizeOfGuid = 16; // Comparison orders. private static readonly Int32[] _GuidComparisonOrders = new Int32[16] { 10, 11, 12, 13, 14, 15, 8, 9, 6, 7, 4, 5, 0, 1, 2, 3 }; // Parse orders. private static readonly Int32[] _GuidParseOrders32 = new Int32[32] { 30, 31, 28, 29, 26, 27, 24, 25, 22, 23, 20, 21, 18, 19, 16, 17, 12, 13, 14, 15, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 }; private static readonly Int32[] _GuidParseOrders36 = new Int32[36] { 34, 35, 32, 33, 30, 31, 28, 29, 27, 25, 26, 23, 24, 22, 20, 21, 18, 19, 17, 13, 14, 15, 16, 12, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 }; // the CombGuid is null if m_value is null private Byte[] m_value; #endregion #region -- 属性 -- /// <summary>CombGuid 结构的只读实例,其值空。</summary> public static readonly CombGuid Null = new CombGuid(true); /// <summary>获取 CombGuid 结构的值。 此属性为只读。</summary> public Guid Value { get { if (IsNull) { throw new SqlNullValueException(); } else { return new Guid(m_value); } } } /// <summary>获取 CombGuid 结构的日期时间属性。 /// <para>如果同一时间批量生成了大量的 CombGuid 时,返回的日期时间是不准确的!</para> /// </summary> public DateTime DateTime { get { if (IsNull) { throw new SqlNullValueException(); } else { var daysArray = new Byte[4]; var msecsArray = new Byte[4]; // Copy the date parts of the guid to the respective Byte arrays. Array.Copy(m_value, m_value.Length - 6, daysArray, 2, 2); Array.Copy(m_value, m_value.Length - 4, msecsArray, 0, 4); // Reverse the arrays to put them into the appropriate order Array.Reverse(daysArray); Array.Reverse(msecsArray); // Convert the bytes to ints var days = BitConverter.ToInt32(daysArray, 0); var msecs = BitConverter.ToInt32(msecsArray, 0); var date = _CombBaseDate.AddDays(days); if (msecs > _MaxTenthMilliseconds) { msecs = _MaxTenthMilliseconds; } msecs /= 10; return date.AddMilliseconds(msecs); } } } #endregion #region -- 构造 -- /// <summary>实例化一个空 CombGuid 结构</summary> private CombGuid(Boolean isNull) { m_value = null; } /// <summary>使用指定的字节数组初始化 CombGuid 结构的新实例。</summary> /// <param name="value">包含初始化 CombGuid 的值的 16 元素字节数组。</param> public CombGuid(Byte[] value) : this(value, false) { } /// <summary>使用指定的字节数组初始化 CombGuid 结构的新实例。</summary> /// <param name="value">包含初始化 CombGuid 的值的 16 元素字节数组。</param> /// <param name="isOwner">是否 CombGuid 结构直接使用</param> private CombGuid(Byte[] value, Boolean isOwner) { if (value == null || value.Length != _SizeOfGuid) { throw new ArgumentException("value 的长度不是 16 个字节。"); } if (isOwner) { m_value = value; } else { m_value = new Byte[_SizeOfGuid]; value.CopyTo(m_value, 0); } } /// <summary>使用指定字符串所表示的值初始化 CombGuid 结构的新实例。</summary> /// <param name="comb">包含下面任一格式的 CombGuid 的字符串(“d”表示忽略大小写的十六进制数字): /// <para>32 个连续的数字 dddddddddddddddddddddddddddddddd </para> /// <para>- 或 - </para> /// <para>12 和 4、4、4、8 位数字的分组,各组之间有连线符,dddddddddddd-dddd-dddd-dddd-dddddddd</para> /// </param> public CombGuid(String comb) { if (string.IsNullOrEmpty(comb)) throw new ArgumentNullException(nameof(comb)); Int32 a; Int16 b, c; Byte[] d; if (new GuidParser(comb).TryParse(out a, out b, out c, out d)) { m_value = new Byte[_SizeOfGuid]; Init(a, b, c, d); } else { throw CreateFormatException(comb); } } private static Exception CreateFormatException(String s) { return new FormatException(String.Format("Invalid CombGuid format: {0}", s)); } /// <summary>使用指定的 Guid 参数初始化 CombGuid 结构的新实例。</summary> /// <param name="g">一个 Guid</param> public CombGuid(Guid g) { m_value = g.ToByteArray(); } /// <summary>使用指定的整数和字节数组初始化 CombGuid 类的新实例。</summary> /// <param name="a">CombGuid 的开头四个字节。</param> /// <param name="b">CombGuid 的下两个字节。</param> /// <param name="c">CombGuid 的下两个字节。</param> /// <param name="d">CombGuid 的其余 8 个字节</param> public CombGuid(Int32 a, Int16 b, Int16 c, Byte[] d) { if (d == null || d.Length != 8) throw new ArgumentException(nameof(d) + "必须是8个字节的Bute数据"); // Check that array is not too big if (d.Length != 8) { throw new ArgumentException("d 的长度不是 8 个字节。"); } m_value = new Byte[_SizeOfGuid]; Init(a, b, c, d); } private void Init(Int32 a, Int16 b, Int16 c, Byte[] d) { m_value[0] = (Byte)(a); m_value[1] = (Byte)(a >> 8); m_value[2] = (Byte)(a >> 16); m_value[3] = (Byte)(a >> 24); m_value[4] = (Byte)(b); m_value[5] = (Byte)(b >> 8); m_value[6] = (Byte)(c); m_value[7] = (Byte)(c >> 8); m_value[8] = d[0]; m_value[9] = d[1]; m_value[10] = d[2]; m_value[11] = d[3]; m_value[12] = d[4]; m_value[13] = d[5]; m_value[14] = d[6]; m_value[15] = d[7]; } /// <summary>使用指定的值初始化 CombGuid 结构的新实例。</summary> /// <param name="a">CombGuid 的开头四个字节。</param> /// <param name="b">CombGuid 的下两个字节。</param> /// <param name="c">CombGuid 的下两个字节。</param> /// <param name="d">CombGuid 的下一个字节。</param> /// <param name="e">CombGuid 的下一个字节。</param> /// <param name="f">CombGuid 的下一个字节。</param> /// <param name="g">CombGuid 的下一个字节。</param> /// <param name="h">CombGuid 的下一个字节。</param> /// <param name="i">CombGuid 的下一个字节。</param> /// <param name="j">CombGuid 的下一个字节。</param> /// <param name="k">CombGuid 的下一个字节。</param> public CombGuid(Int32 a, Int16 b, Int16 c, Byte d, Byte e, Byte f, Byte g, Byte h, Byte i, Byte j, Byte k) { m_value = new Byte[_SizeOfGuid]; m_value[0] = (Byte)(a); m_value[1] = (Byte)(a >> 8); m_value[2] = (Byte)(a >> 16); m_value[3] = (Byte)(a >> 24); m_value[4] = (Byte)(b); m_value[5] = (Byte)(b >> 8); m_value[6] = (Byte)(c); m_value[7] = (Byte)(c >> 8); m_value[8] = d; m_value[9] = e; m_value[10] = f; m_value[11] = g; m_value[12] = h; m_value[13] = i; m_value[14] = j; m_value[15] = k; } #endregion #region -- 方法 -- #region - ToByteArray - /// <summary>将此 CombGuid 结构转换为字节数组</summary> /// <returns>16 元素字节数组。</returns> public Byte[] ToByteArray() { var ret = new Byte[_SizeOfGuid]; m_value.CopyTo(ret, 0); return ret; } #endregion #region - GetByteArray - /// <summary>直接获取此 CombGuid 结构内部的字节数组,如果此 CombGuid 为空,返回空值。 /// <para>调用此方法后,不要对获取的字节数组做任何改变!!!</para> /// </summary> /// <returns>16 元素字节数组 或 null。</returns> [EditorBrowsable(EditorBrowsableState.Advanced)] public Byte[] GetByteArray() { return m_value; } #endregion #region - ToString - /// <summary>已重载,将此 CombGuid 结构转换为字符串。</summary> /// <returns>返回该 CombGuid 结构的字符串表示形式。</returns> public override String ToString() { return ToString(CombGuidFormatStringType.Comb); } /// <summary>根据所提供的格式方式,返回此 CombGuid 实例值的字符串表示形式。</summary> /// <param name="formatType">格式化方式,它指示如何格式化此 CombGuid 的值。</param> /// <returns>此 CombGuid 的值,用一系列指定格式的小写十六进制位表示</returns> public String ToString(CombGuidFormatStringType formatType) { if (IsNull) { return _NullString; } var offset = 0; var strLength = 36; var dash = true; if (formatType == CombGuidFormatStringType.Guid32Digits || formatType == CombGuidFormatStringType.Comb32Digits) { strLength = 32; dash = false; } var guidChars = new Char[strLength]; var isComb = formatType == CombGuidFormatStringType.Comb || formatType == CombGuidFormatStringType.Comb32Digits; #region MS GUID类内部代码 //g[0] = (Byte)(_a); //g[1] = (Byte)(_a >> 8); //g[2] = (Byte)(_a >> 16); //g[3] = (Byte)(_a >> 24); //g[4] = (Byte)(_b); //g[5] = (Byte)(_b >> 8); //g[6] = (Byte)(_c); //g[7] = (Byte)(_c >> 8); //g[8] = _d; //g[9] = _e; //g[10] = _f; //g[11] = _g; //g[12] = _h; //g[13] = _i; //g[14] = _j; //g[15] = _k; //// [{|(]dddddddd[-]dddd[-]dddd[-]dddd[-]dddddddddddd[}|)] //offset = HexsToChars(guidChars, offset, _a >> 24, _a >> 16); //offset = HexsToChars(guidChars, offset, _a >> 8, _a); //if (dash) guidChars[offset++] = '-'; //offset = HexsToChars(guidChars, offset, _b >> 8, _b); //if (dash) guidChars[offset++] = '-'; //offset = HexsToChars(guidChars, offset, _c >> 8, _c); //if (dash) guidChars[offset++] = '-'; //offset = HexsToChars(guidChars, offset, _d, _e); //if (dash) guidChars[offset++] = '-'; //offset = HexsToChars(guidChars, offset, _f, _g); //offset = HexsToChars(guidChars, offset, _h, _i); //offset = HexsToChars(guidChars, offset, _j, _k); #endregion if (isComb) { offset = HexsToChars(guidChars, offset, m_value[10], m_value[11]); offset = HexsToChars(guidChars, offset, m_value[12], m_value[13]); offset = HexsToChars(guidChars, offset, m_value[14], m_value[15]); if (dash) { guidChars[offset++] = '-'; } offset = HexsToChars(guidChars, offset, m_value[8], m_value[9]); if (dash) { guidChars[offset++] = '-'; } offset = HexsToChars(guidChars, offset, m_value[6], m_value[7]); if (dash) { guidChars[offset++] = '-'; } offset = HexsToChars(guidChars, offset, m_value[4], m_value[5]); if (dash) { guidChars[offset++] = '-'; } offset = HexsToChars(guidChars, offset, m_value[0], m_value[1]); offset = HexsToChars(guidChars, offset, m_value[2], m_value[3]); } else { offset = HexsToChars(guidChars, offset, m_value[3], m_value[2]); offset = HexsToChars(guidChars, offset, m_value[1], m_value[0]); if (dash) { guidChars[offset++] = '-'; } offset = HexsToChars(guidChars, offset, m_value[5], m_value[4]); if (dash) { guidChars[offset++] = '-'; } offset = HexsToChars(guidChars, offset, m_value[7], m_value[6]); if (dash) { guidChars[offset++] = '-'; } offset = HexsToChars(guidChars, offset, m_value[8], m_value[9]); if (dash) { guidChars[offset++] = '-'; } offset = HexsToChars(guidChars, offset, m_value[10], m_value[11]); offset = HexsToChars(guidChars, offset, m_value[12], m_value[13]); offset = HexsToChars(guidChars, offset, m_value[14], m_value[15]); } return new String(guidChars, 0, strLength); } private static Int32 HexsToChars(Char[] guidChars, Int32 offset, Int32 a, Int32 b) { guidChars[offset++] = HexToChar(a >> 4); guidChars[offset++] = HexToChar(a); guidChars[offset++] = HexToChar(b >> 4); guidChars[offset++] = HexToChar(b); return offset; } private static Char HexToChar(Int32 a) { a = a & 0xf; return (Char)((a > 9) ? a - 10 + 0x61 : a + 0x30); } #endregion #endregion #region -- 静态方法 -- private static readonly DateTime _CombBaseDate = new DateTime(1900, 1, 1); private static Int32 _LastDays; // 天数 private static Int32 _LastTenthMilliseconds; // 单位:1/10 毫秒 private static readonly Int32 _MaxTenthMilliseconds = 863999999; #region - NewComb - /// <summary>初始化 CombGuid 结构的新实例。</summary> /// <returns>一个新的 CombGuid 对象。</returns> public static CombGuid NewComb() { var guidArray = Guid.NewGuid().ToByteArray(); var now = DateTime.Now; // Get the days and milliseconds which will be used to build the Byte String var days = new TimeSpan(now.Ticks - _CombBaseDate.Ticks).Days; var tenthMilliseconds = (Int32)(now.TimeOfDay.TotalMilliseconds * 10D); var lastDays = _LastDays; var lastTenthMilliseconds = _LastTenthMilliseconds; if (days > lastDays) { Interlocked.CompareExchange(ref _LastDays, days, lastDays); Interlocked.CompareExchange(ref _LastTenthMilliseconds, tenthMilliseconds, lastTenthMilliseconds); } else { if (tenthMilliseconds > lastTenthMilliseconds) { Interlocked.CompareExchange(ref _LastTenthMilliseconds, tenthMilliseconds, lastTenthMilliseconds); } else { if (_LastTenthMilliseconds < Int32.MaxValue) { Interlocked.Increment(ref _LastTenthMilliseconds); } tenthMilliseconds = _LastTenthMilliseconds; } } // Convert to a Byte array var daysArray = BitConverter.GetBytes(days); var msecsArray = BitConverter.GetBytes(tenthMilliseconds); // Reverse the bytes to match SQL Servers ordering Array.Reverse(daysArray); Array.Reverse(msecsArray); // Copy the bytes into the guid Array.Copy(daysArray, daysArray.Length - 2, guidArray, guidArray.Length - 6, 2); //Array.Copy(msecsArray, msecsArray.Length - 4, guidArray, guidArray.Length - 4, 4); Array.Copy(msecsArray, 0, guidArray, guidArray.Length - 4, 4); return new CombGuid(guidArray, true); } #endregion #region - Parse - /// <summary>将 CombGuid 的字符串表示形式转换为等效的 CombGuid 结构。</summary> /// |
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