diff --git a/src/IFoxCAD.Cad.Shared/Runtime/AcadVersion.cs b/src/IFoxCAD.Cad.Shared/Runtime/AcadVersion.cs
index 61aa6200e658d7356d96926f7880a42c57383135..d00cabab230534374bad500fb231a850eb2aef5e 100644
--- a/src/IFoxCAD.Cad.Shared/Runtime/AcadVersion.cs
+++ b/src/IFoxCAD.Cad.Shared/Runtime/AcadVersion.cs
@@ -1,4 +1,4 @@
-namespace IFoxCAD.Cad;
+namespace IFoxCAD.Cad;
 
 /// <summary>
 /// cad版本号类
@@ -67,4 +67,124 @@ public static List<CadVersion> Versions
                 return Versions[i];
         return null;
     }
+}
+
+public static class VersionTool
+{
+    // 年号.
+    // 1,不用存年号数组,索引+2000就是年号了,
+    // 2,官方是Acad2000i,用2001年顶替
+    // 3,官方没有Acad2003,但要满足1的规则,全部数组用上年数据补齐03年.
+    // static readonly int[] _years =>[
+    // 2000, 2001, 2002, 2003/*虚拟03年*/,
+    // 2004, 2005, 2006,
+    // 2007, 2008, 2009,
+    // 2010, 2011, 2012,
+    // 2013, 2014, 2015, 2016, 2017,
+    // 2018, 2019, 2020, 2021, 2022,
+    // 2023, 2024, 2025];
+    // 字段:public static readonly int[] Years;
+    // 构造:Years = _years;
+    // 异或判断数值是否一致
+    // if ((_years.Length ^ DwgVers.Length ^ AcadVers.Length) != AcadVers.Length)
+    //    throw new Exception(nameof(VersionTool)
+    //                  + "怎么长度不一样了捏?");
+    // [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static int IndexToYear(int index)
+    {
+        var year = index + 2000;
+        if (year < 2000) return -1;
+        if (year > 2000 + _acadVers.Length) return -1;
+        return year;
+    }
+
+    // 和二分法一样,
+    // 没有命中时将第一个大于搜索值的索引作为返回值并取反,
+    // 以提供没有命中的信息(负数)和最近值取反后再插入.
+    // [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static int YearToIndex(int year)
+    {
+        var index = year - 2000;
+        if (index < 0) return ~0;
+        if (index > _acadVers.Length - 1)
+            return ~(_acadVers.Length - 1);
+        return index;
+    }
+
+    // https://www.autodesk.com.cn/support/technical/article/caas/sfdcarticles/sfdcarticles/CHS/drawing-version-codes-for-autocad.html
+    // DWG签名的AC号.
+    private static readonly int[] _dwgVers = [
+        1015, 1015, 1015, 1015 /*补齐03年*/,
+        1018, 1018, 1018,
+        1021, 1021, 1021,
+        1024, 1024, 1024,
+        1027, 1027, 1027, 1027, 1027,
+        1032, 1032, 1032, 1032, 1032,
+        1032, 1032, 1032
+    ];
+
+    // CAD版本号,它与注册表和COM相关.
+    private static readonly string[] _acadVers = [
+        "R15.0", "R15.1", "R15.2", "R15.2" /*补齐03年*/,
+        "R16.0", "R16.1", "R16.2",
+        "R17.0", "R17.1", "R17.2",
+        "R18.0", "R18.1", "R18.2",
+        "R19.0", "R19.1", "R20.0", "R20.1", "R21.0",
+        "R22.0", "R23.0", "R23.1", "R24.0", "R24.1",
+        "R24.2", "R24.3", "R25.0"
+    ];
+
+    // 运行中的CAD版本号,位移+位或.
+    public static readonly int AcadVerOR;
+
+    // 这几个只读数组,有序等长,通过二分法共同索引.
+    public static readonly int[] AcadVers;
+    public static readonly int[] DwgVers;
+
+    // 静态构造函数
+    static VersionTool()
+    {
+        var major = Acap.Version.Major;
+        var minor = Acap.Version.Minor;
+        AcadVerOR = (major << 16) | minor;
+
+        // 消除字符串从而不需要构造hashmap.
+        // 位移+位或,使得它们从小数映射到整数,
+        // 并且保持大小关系,仍然有序可以能够二分.
+        // 编译时:C#没有循环消除,反编译源码还能看见,
+        // 运行时:避免求一次循环,可以把结果再重新粘贴回代码.
+        // --就像快速平方根倒数,浮点数转16进制,然后粘贴到代码上,成为魔法数
+        var v = new int[_acadVers.Length];
+        for (var i = 0; i < _acadVers.Length; i++)
+        {
+            var s = _acadVers[i];
+            var m = (s[1] - '0') * 10 + (s[2] - '0');
+            var n = (s[4] - '0'); //0是R,3是小数点,所以跳到4
+            v[i] = (m << 16) | n;
+        }
+
+        AcadVers = v;
+        _acadVers = null!; // 积极释放
+        DwgVers = _dwgVers;
+
+#if DEBUG
+
+        // 防止开发者忘记更新数组,提供一个报错来进行维护
+        var index = Array.BinarySearch(AcadVers, AcadVerOR);
+        if (index < 0)
+        {
+            throw new Exception(nameof(VersionTool)
+                                + "运行中的CAD版本未记录,请维护DWG版本号/CAD版本号");
+        }
+
+        if (DwgVers.Length != AcadVers.Length)
+            throw new Exception(nameof(VersionTool)
+                                + "怎么长度不一样了捏?");
+
+        // 解码版本号
+        var major2 = AcadVerOR >> 16;
+        var minor2 = AcadVerOR & 0xFFFF; //位与掩码,获取低16bit
+
+#endif
+    }
 }
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