改进的“以非泛型方式调用泛型方法”之基于DynamicMethod的实现

本文针对双鱼座同志的以非泛型方式调用泛型方法一文，提出一种更通用的以非泛型方式调用泛型方法的实现——基于DynamicMethod的实现。
基于DynamicMethod的实现的优点是，执行性能和双鱼座的文中实现的第5种方案——动态生成的非泛型接口包装相当（因为都是基于Emit的），但是，避免了原文实现中必须额外定义接口、Delegate的需要，从而，非常通用，应该是目前所能想到最佳实现。

首先，贴出原文中的测试数据相对于DynamicMethod实现的比较和缺点：

方案	耗时	比对	其他优点
直接调用	18	1	不通用
泛型委托包装	43	2.39	不通用
反射	16538	918.78	通用，不需额外定义
非泛型接口包装	60	3.33	通用，需要额外定义并实现
动态生成的非泛型接口包装	72	4	通用，需要额外定义
DynamicMethod实现	72	4	通用，无需额外定义

实现代码如下：

  1    public abstract class DynamicMethodHelper
  2    {
  3        //该类不能实例化，只能静态调用
  4        private DynamicMethodHelper() {}
  5
  6        //通用的可变参数动态方法委托
  7        public delegate object DynamicMethodDelegate(params object[] paramObjs);
  8
  9        private static Dictionary<string, DynamicMethodDelegate> cache = new Dictionary<string, DynamicMethodDelegate>();
 10
 11        private static void LoadIndex(ILGenerator gen, int index)
 12        {
 13            switch (index)
 14            {
 15                case 0:
 16                    gen.Emit(OpCodes.Ldc_I4_0);
 17                    break;
 18                case 1:
 19                    gen.Emit(OpCodes.Ldc_I4_1);
 20                    break;
 21                case 2:
 22                    gen.Emit(OpCodes.Ldc_I4_2);
 23                    break;
 24                case 3:
 25                    gen.Emit(OpCodes.Ldc_I4_3);
 26                    break;
 27                case 4:
 28                    gen.Emit(OpCodes.Ldc_I4_4);
 29                    break;
 30                case 5:
 31                    gen.Emit(OpCodes.Ldc_I4_5);
 32                    break;
 33                case 6:
 34                    gen.Emit(OpCodes.Ldc_I4_6);
 35                    break;
 36                case 7:
 37                    gen.Emit(OpCodes.Ldc_I4_7);
 38                    break;
 39                case 8:
 40                    gen.Emit(OpCodes.Ldc_I4_8);
 41                    break;
 42                default:
 43                    if (index < 128)
 44                    {
 45                        gen.Emit(OpCodes.Ldc_I4_S, index);
 46                    }
 47                    else
 48                    {
 49                        gen.Emit(OpCodes.Ldc_I4, index);
 50                    }
 51                    break;
 52            }
 53        }
 54
 55        private static void StoreLocal(ILGenerator gen, int index)
 56        {
 57            switch (index)
 58            {
 59                case 0:
 60                    gen.Emit(OpCodes.Stloc_0);
 61                    break;
 62                case 1:
 63                    gen.Emit(OpCodes.Stloc_1);
 64                    break;
 65                case 2:
 66                    gen.Emit(OpCodes.Stloc_2);
 67                    break;
 68                case 3:
 69                    gen.Emit(OpCodes.Stloc_3);
 70                    break;
 71                default:
 72                    if (index < 128)
 73                    {
 74                        gen.Emit(OpCodes.Stloc_S, index);
 75                    }
 76                    else
 77                    {
 78                        gen.Emit(OpCodes.Stloc, index);
 79                    }
 80                    break;
 81            }
 82        }
 83
 84        private static void LoadLocal(ILGenerator gen, int index)
 85        {
 86            switch (index)
 87            {
 88                case 0:
 89                    gen.Emit(OpCodes.Ldloc_0);
 90                    break;
 91                case 1:
 92                    gen.Emit(OpCodes.Ldloc_1);
 93                    break;
 94                case 2:
 95                    gen.Emit(OpCodes.Ldloc_2);
 96                    break;
 97                case 3:
 98                    gen.Emit(OpCodes.Ldloc_3);
 99                    break;
100                default:
101                    if (index < 128)
102                    {
103                        gen.Emit(OpCodes.Ldloc_S, index);
104                    }
105                    else
106                    {
107                        gen.Emit(OpCodes.Ldloc, index);
108                    }
109                    break;
110            }
111        }
112
113        public static DynamicMethodDelegate GetDynamicMethodDelegate(MethodInfo genericMethodInfo, 
114            params Type[] genericParameterTypes)
115        {
116            检查参数的有效性#region 检查参数的有效性
117
118            if (genericMethodInfo == null)
119            {
120                throw new ArgumentNullException("需要被调用的方法的genericMethodInfo不能为空!");
121            }
122
123            if (genericParameterTypes != null)
124            {
125                if (genericParameterTypes.Length != genericMethodInfo.GetGenericArguments().Length)
126                {
127                    throw new ArgumentException("genericMethodInfo和泛型参数类型的数量不一致!");
128                }
129            }
130            else
131            {
132                if (genericMethodInfo.GetGenericArguments().Length > 0)
133                {
134                    throw new ArgumentException("没有为genericMethodInfo指定泛型参数类型!");
135                }
136            }
137
138            #endregion
139
140            构造用于缓存的key#region  构造用于缓存的key
141
142            string key = genericMethodInfo.DeclaringType.ToString() + "|" + genericMethodInfo.ToString();
143            if (genericParameterTypes != null)
144            {
145                for (int i = 0; i < genericParameterTypes.Length; ++i)
146                {
147                    key += "|" + genericParameterTypes[i].ToString();
148                }
149            }
150
151            #endregion
152
153            DynamicMethodDelegate dmd;
154
155            lock (cache)
156            {
157                if (cache.ContainsKey(key))
158                {
159                    dmd = cache[key];
160                }
161                else
162                {
163                    //动态创建一个封装了泛型方法调用的非泛型方法，并返回绑定到他的DynamicMethodDelegate的实例
164                    //返回的动态方法的实现在编译期就是以显式方法调用泛型方法的，因此，最大程度上避免了反射的性能损失
165                    DynamicMethod dm = new DynamicMethod(Guid.NewGuid().ToString("N"), 
166                        typeof(object), 
167                        new Type[] { typeof(object[]) }, 
168                        typeof(string).Module);
169
170                    ILGenerator il = dm.GetILGenerator();
171
172                    创建所有方法的参数的本地变量#region 创建所有方法的参数的本地变量
173
174                    //首先获得目标方法的MethodInfo
175                    MethodInfo makeGenericMethodInfo;
176                    if (genericParameterTypes != null && genericParameterTypes.Length > 0)
177                    {
178                        makeGenericMethodInfo = genericMethodInfo.MakeGenericMethod(genericParameterTypes);
179                    }
180                    else
181                    {
182                        makeGenericMethodInfo = genericMethodInfo;
183                    }
184
185                    //声明本地变量
186                    ParameterInfo[] pis = makeGenericMethodInfo.GetParameters();
187                    for (int i = 0; i < pis.Length; ++i)
188                    {
189                        il.DeclareLocal(pis[i].ParameterType);
190                    }
191
192                    #endregion
193
194                    从paramObjs参数中解析所有参数值到本地变量中#region 从paramObjs参数中解析所有参数值到本地变量中
195
196                    for (int i = 0; i < pis.Length; ++i)
197                    {
198                        il.Emit(OpCodes.Ldarg_0);
199                        LoadIndex(il, i);
200                        il.Emit(OpCodes.Ldelem_Ref);
201                        if (pis[i].ParameterType.IsValueType)
202                        {
203                            il.Emit(OpCodes.Unbox_Any, pis[i].ParameterType);
204                        }
205                        else if (pis[i].ParameterType != typeof(object))
206                        {
207                            il.Emit(OpCodes.Castclass, pis[i].ParameterType);
208                        }
209                        StoreLocal(il, i);
210                    }
211
212                    #endregion
213
214                    执行目标方法#region 执行目标方法
215
216                    for (int i = 0; i < pis.Length; ++i)
217                    {
218                        LoadLocal(il, i);
219                    }
220                    if (makeGenericMethodInfo.IsStatic)
221                    {
222                        il.Emit(OpCodes.Call, makeGenericMethodInfo);
223                    }
224                    else
225                    {
226                        throw new NotImplementedException("暂时还没有实现该功能!");
227                    }
228
229                    if (makeGenericMethodInfo.ReturnType == typeof(void))
230                    {
231                        il.Emit(OpCodes.Ldnull);
232                    }
233
234                    #endregion
235
236                    il.Emit(OpCodes.Ret);
237
238                    dmd = (DynamicMethodDelegate)dm.CreateDelegate(typeof(DynamicMethodDelegate));
239                    cache.Add(key, dmd);
240                }
241            }
242
243            return dmd;
244        }
245    }

测试代码如下（基于在双鱼座原文的代码格式）：

 1            List<int> list = new List<int>();
 2            System.Diagnostics.Stopwatch watch = new System.Diagnostics.Stopwatch();
 3            watch.Reset();
 4            watch.Start();
 5            for (int i = 0; i < REPEAT_TIME; i++)
 6            {
 7                Program.Add<int>(i, list);
 8            }
 9            watch.Stop();
10            long l1 = watch.ElapsedMilliseconds;
11            watch.Reset();
12            MethodInfo mi = typeof(Program).GetMethod("Add");
13            DynamicMethodHelper.DynamicMethodDelegate dmd = DynamicMethodHelper.GetDynamicMethodDelegate(mi, typeof(int));
14            watch.Start();
15            for (int i = 0; i < REPEAT_TIME; i++)
16            {
17                dmd(i, list);
18            }
19            watch.Stop();
20            long l2 = watch.ElapsedMilliseconds;
21            Console.WriteLine("{0}\n{1} vs {2}", list.Count, l1, l2);
22            Console.ReadLine();

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