mcs/class/corlib/System/MonoCustomAttrs.cs

   1 // System.MonoCustomAttrs.cs
   2 // Hooks into the runtime to get custom attributes for reflection handles
   3 //
   4 // Authors:
   5 //      Paolo Molaro (lupus@ximian.com)
   6 //      Gonzalo Paniagua Javier (gonzalo@ximian.com)
   7 //
   8 // (c) 2002,2003 Ximian, Inc. (http://www.ximian.com)
   9 //
  10
  11 using System;
  12 using System.Reflection;
  13 using System.Collections;
  14 using System.Runtime.CompilerServices;
  15
  16 namespace System
  17 {
  18         internal class MonoCustomAttrs
  19         {
  20                 [MethodImplAttribute (MethodImplOptions.InternalCall)]
  21                 internal static extern object[] GetCustomAttributes (ICustomAttributeProvider obj);
  22
  23                 internal static Attribute GetCustomAttribute (ICustomAttributeProvider obj,
  24                                                                 Type attributeType,
  25                                                                 bool inherit)
  26                 {
  27                         object[] res = GetCustomAttributes (obj, attributeType, inherit);
  28                         if (res.Length == 0)
  29                         {
  30                                 return null;
  31                         }
  32                         else if (res.Length > 1)
  33                         {
  34                                 string msg = "'{0}' has more than one attribute of type '{1}";
  35                                 msg = String.Format (msg, obj, attributeType);
  36                                 throw new AmbiguousMatchException (msg);
  37                         }
  38
  39                         return (Attribute) res[0];
  40                 }
  41
  42                 internal static object[] GetCustomAttributes (ICustomAttributeProvider obj, Type attributeType, bool inherit)
  43                 {
  44                         if (obj == null)
  45                                 throw new ArgumentNullException ("obj");
  46
  47                         object[] r;
  48                         object[] res = GetCustomAttributes (obj);
  49                         // shortcut
  50                         if (!inherit && res.Length == 1)
  51                         {
  52                                 if (attributeType != null)
  53                                 {
  54                                         if (attributeType.IsAssignableFrom (res[0].GetType ()))
  55                                         {
  56                                                 r = (object[]) Array.CreateInstance (attributeType, 1);
  57                                                 r[0] = res[0];
  58                                         }
  59                                         else
  60                                         {
  61                                                 r = (object[]) Array.CreateInstance (attributeType, 0);
  62                                         }
  63                                 }
  64                                 else
  65                                 {
  66                                         r = (object[]) Array.CreateInstance (res[0].GetType (), 1);
  67                                         r[0] = res[0];
  68                                 }
  69                                 return r;
  70                         }
  71
  72                         // if AttributeType is sealed, and Inherited is set to false, then
  73                         // there's no use in scanning base types
  74                         if ((attributeType != null && attributeType.IsSealed) && !inherit)
  75                         {
  76                                 AttributeUsageAttribute usageAttribute = RetrieveAttributeUsage (
  77                                         attributeType);
  78                                 if (!usageAttribute.Inherited)
  79                                 {
  80                                         inherit = false;
  81                                 }
  82                         }
  83
  84                         int initialSize = res.Length < 16 ? res.Length : 16;
  85
  86                         Hashtable attributeInfos = new Hashtable (initialSize);
  87                         ArrayList a = new ArrayList (initialSize);
  88                         ICustomAttributeProvider btype = obj;
  89
  90                         int inheritanceLevel = 0;
  91
  92                         do
  93                         {
  94                                 foreach (object attr in res)
  95                                 {
  96                                         AttributeUsageAttribute usage;
  97
  98                                         Type attrType = attr.GetType ();
  99                                         if (attributeType != null)
 100                                         {
 101                                                 if (!attributeType.IsAssignableFrom (attrType))
 102                                                 {
 103                                                         continue;
 104                                                 }
 105                                         }
 106
 107                                         AttributeInfo firstAttribute = (AttributeInfo) attributeInfos[attrType];
 108                                         if (firstAttribute != null)
 109                                         {
 110                                                 usage = firstAttribute.Usage;
 111                                         }
 112                                         else
 113                                         {
 114                                                 usage = RetrieveAttributeUsage (attrType);
 115                                         }
 116
 117                                         // only add attribute to the list of attributes if
 118                                         // - we are on the first inheritance level, or the attribute can be inherited anyway
 119                                         // and (
 120                                         // - multiple attributes of the type are allowed
 121                                         // or (
 122                                         // - this is the first attribute we've discovered
 123                                         // or
 124                                         // - the attribute is on same inheritance level than the first
 125                                         //   attribute that was discovered for this attribute type ))
 126                                         if ((inheritanceLevel == 0 || usage.Inherited) && (usage.AllowMultiple ||
 127                                                 (firstAttribute == null || (firstAttribute != null
 128                                                         && firstAttribute.InheritanceLevel == inheritanceLevel))))
 129                                         {
 130                                                 a.Add (attr);
 131                                         }
 132
 133                                         if (firstAttribute == null)
 134                                         {
 135                                                 attributeInfos.Add (attrType, new AttributeInfo (usage, inheritanceLevel));
 136                                         }
 137                                 }
 138
 139                                 if ((btype = GetBase (btype)) != null)
 140                                 {
 141                                         inheritanceLevel++;
 142                                         res = GetCustomAttributes (btype);
 143                                 }
 144                         } while (inherit && btype != null);
 145
 146                         object[] array = null;
 147                         if (attributeType == null || attributeType.IsValueType)
 148                         {
 149                                 array = (object[]) Array.CreateInstance (typeof(Attribute), a.Count);
 150                         }
 151                         else
 152                         {
 153                                 array = Array.CreateInstance (attributeType, a.Count) as object[];
 154                         }
 155
 156                         // copy attributes to array
 157                         a.CopyTo (array, 0);
 158
 159                         return array;
 160                 }
 161
 162                 internal static object[] GetCustomAttributes (ICustomAttributeProvider obj, bool inherit)
 163                 {
 164                         if (obj == null)
 165                                 throw new ArgumentNullException ("obj");
 166
 167                         if (!inherit)
 168                                 return (object[]) GetCustomAttributes (obj).Clone ();
 169
 170                         return GetCustomAttributes (obj, null, inherit);
 171                 }
 172
 173                 internal static bool IsDefined (ICustomAttributeProvider obj, Type attributeType, bool inherit)
 174                 {
 175                         object[] res = GetCustomAttributes (obj);
 176                         foreach (object attr in res)
 177                         {
 178                                 if (attributeType.Equals (attr.GetType ()))
 179                                         return true;
 180                         }
 181
 182                         ICustomAttributeProvider btype = GetBase (obj);
 183                         if (inherit && (btype != null))
 184                                 return IsDefined (btype, attributeType, inherit);
 185
 186                         return false;
 187                 }
 188
 189                 // Handles Type, MonoProperty and MonoMethod.
 190                 // The runtime has also cases for MonoEvent, MonoField, Assembly and ParameterInfo,
 191                 // but for those we return null here.
 192                 static ICustomAttributeProvider GetBase (ICustomAttributeProvider obj)
 193                 {
 194                         if (obj == null)
 195                                 return null;
 196
 197                         if (obj is Type)
 198                                 return ((Type) obj).BaseType;
 199
 200                         MethodInfo method = null;
 201                         if (obj is MonoProperty)
 202                         {
 203                                 MonoProperty prop = (MonoProperty) obj;
 204                                 method = prop.GetGetMethod (true);
 205                                 if (method == null)
 206                                         method = prop.GetSetMethod (true);
 207                         }
 208                         else if (obj is MonoMethod)
 209                         {
 210                                 method = (MethodInfo) obj;
 211                         }
 212
 213                         /**
 214                          * ParameterInfo -> null
 215                          * Assembly -> null
 216                          * MonoEvent -> null
 217                          * MonoField -> null
 218                          */
 219                         if (method == null || !method.IsVirtual)
 220                                 return null;
 221
 222                         MethodInfo baseMethod = method.GetBaseDefinition ();
 223                         if (baseMethod == method)
 224                                 return null;
 225
 226                         return baseMethod;
 227                 }
 228
 229                 private static AttributeUsageAttribute RetrieveAttributeUsage (Type attributeType)
 230                 {
 231                         AttributeUsageAttribute usageAttribute = null;
 232                         object[] attribs = GetCustomAttributes (attributeType,
 233                                 MonoCustomAttrs.AttributeUsageType, false);
 234                         if (attribs.Length == 0)
 235                         {
 236                                 // if no AttributeUsage was defined on the attribute level, then
 237                                 // try to retrieve if from its base type
 238                                 if (attributeType.BaseType != null)
 239                                 {
 240                                         usageAttribute = RetrieveAttributeUsage (attributeType.BaseType);
 241
 242                                 }
 243                                 if (usageAttribute != null)
 244                                 {
 245                                         // return AttributeUsage of base class
 246                                         return usageAttribute;
 247
 248                                 }
 249                                 // return default AttributeUsageAttribute if no AttributeUsage
 250                                 // was defined on attribute, or its base class
 251                                 return DefaultAttributeUsage;
 252                         }
 253                         // check if more than one AttributeUsageAttribute has been specified
 254                         // on the type
 255                         // NOTE: compilers should prevent this, but that doesn't prevent
 256                         // anyone from using IL ofcourse
 257                         if (attribs.Length > 1)
 258                         {
 259                                 throw new FormatException ("Duplicate AttributeUsageAttribute cannot be specified on an attribute type.");
 260                         }
 261
 262                         return ((AttributeUsageAttribute) attribs[0]);
 263                 }
 264
 265                 private static readonly Type AttributeUsageType = typeof(AttributeUsageAttribute);
 266                 private static readonly AttributeUsageAttribute DefaultAttributeUsage =
 267                         new AttributeUsageAttribute (AttributeTargets.All);
 268
 269                 private class AttributeInfo
 270                 {
 271                         private AttributeUsageAttribute _usage;
 272                         private int _inheritanceLevel;
 273
 274                         public AttributeInfo (AttributeUsageAttribute usage, int inheritanceLevel)
 275                         {
 276                                 _usage = usage;
 277                                 _inheritanceLevel = inheritanceLevel;
 278                         }
 279
 280                         public AttributeUsageAttribute Usage
 281                         {
 282                                 get
 283                                 {
 284                                         return _usage;
 285                                 }
 286                         }
 287
 288                         public int InheritanceLevel
 289                         {
 290                                 get
 291                                 {
 292                                         return _inheritanceLevel;
 293                                 }
 294                         }
 295                 }
 296         }
 297 }
 298