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         internal class MonoCustomAttrs {
  18
  19                 static Hashtable handle_to_attrs = new Hashtable ();
  20
  21                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
  22                 internal static extern object[] GetCustomAttributes (ICustomAttributeProvider obj);
  23
  24                 private static object[] from_cache (ICustomAttributeProvider obj)
  25                 {
  26                         object[] res = (object []) handle_to_attrs [obj];
  27                         if (res != null)
  28                                 return res;
  29                         res = GetCustomAttributes (obj);
  30                         handle_to_attrs.Add (obj, res);
  31                         return res;
  32                 }
  33
  34                 internal static Attribute GetCustomAttribute (ICustomAttributeProvider obj,
  35                                                               Type attributeType,
  36                                                               bool inherit)
  37                 {
  38                         if (obj == null)
  39                                 throw new ArgumentNullException ("attribute_type"); // argument name in the caller
  40
  41                         object[] res = from_cache (obj);
  42                         ICustomAttributeProvider btype = obj;
  43                         Attribute result = null;
  44
  45                         do {
  46                                 foreach (object attr in res) {
  47                                         if (!attributeType.IsAssignableFrom (attr.GetType ()))
  48                                                 continue;
  49
  50                                         if (result != null) {
  51                                                 string msg = "'{0}' has more than one attribute of type '{1}";
  52                                                 msg = String.Format (msg, obj, attributeType);
  53                                                 throw new AmbiguousMatchException (msg);
  54                                         }
  55                                         result = (Attribute) attr;
  56                                 }
  57
  58                                 if (inherit && (btype = GetBase (btype)) != null)
  59                                         res = from_cache (btype);
  60
  61                         // Stop when encounters the first one for a given provider.
  62                         } while (inherit && result == null && btype != null);
  63
  64                         return result;
  65                 }
  66
  67                 internal static object[] GetCustomAttributes (ICustomAttributeProvider obj, Type attributeType, bool inherit)
  68                 {
  69                         if (obj == null)
  70                                 return (object []) Array.CreateInstance (attributeType, 0);
  71
  72                         object[] r;
  73                         object[] res = from_cache (obj);
  74                         // shortcut
  75                         if (!inherit && res.Length == 1) {
  76                                 if (attributeType.IsAssignableFrom (res[0].GetType ())) {
  77                                         r = (object []) Array.CreateInstance (attributeType, 1);
  78                                         r [0] = res [0];
  79                                 } else {
  80                                         r = (object []) Array.CreateInstance (attributeType, 0);
  81                                 }
  82                                 return r;
  83                         }
  84
  85                         ArrayList a = new ArrayList ();
  86                         ICustomAttributeProvider btype = obj;
  87                         do {
  88                                 foreach (object attr in res)
  89                                         if (attributeType.IsAssignableFrom (attr.GetType ()))
  90                                                 a.Add (attr);
  91
  92                                 if ((btype = GetBase (btype)) != null)
  93                                         res = from_cache (btype);
  94                         } while (inherit && btype != null);
  95
  96                         return (object []) a.ToArray (attributeType);
  97                 }
  98
  99                 internal static object [] GetCustomAttributes (ICustomAttributeProvider obj, bool inherit)
 100                 {
 101                         if (obj == null)
 102                                 return new object [0]; //FIXME: Should i throw an exception here?
 103
 104                         if (!inherit)
 105                                 return (object []) from_cache (obj).Clone ();
 106
 107                         ArrayList a = new ArrayList ();
 108                         ICustomAttributeProvider btype = obj;
 109                         a.AddRange (from_cache (btype));
 110                         while ((btype = GetBase (btype)) != null)
 111                                 a.AddRange (from_cache (btype));
 112
 113                         return (object []) a.ToArray (typeof (Attribute));
 114                 }
 115
 116                 internal static bool IsDefined (ICustomAttributeProvider obj, Type attributeType, bool inherit)
 117                 {
 118                         object[] res = from_cache (obj);
 119                         foreach (object attr in res) {
 120                                 if (attributeType.Equals (attr.GetType ()))
 121                                         return true;
 122                         }
 123
 124                         ICustomAttributeProvider btype = GetBase (obj);
 125                         if (inherit && (btype != null))
 126                                 return IsDefined (btype, attributeType, inherit);
 127
 128                         return false;
 129                 }
 130
 131                 // Handles Type, MonoProperty and MonoMethod.
 132                 // The runtime has also cases for MonoEvent, MonoField, Assembly and ParameterInfo,
 133                 // but for those we return null here.
 134                 static ICustomAttributeProvider GetBase (ICustomAttributeProvider obj)
 135                 {
 136                         if (obj == null)
 137                                 return null;
 138
 139                         if (obj is Type)
 140                                 return ((Type) obj).BaseType;
 141
 142                         MethodInfo method = null;
 143                         if (obj is MonoProperty) {
 144                                 MonoProperty prop = (MonoProperty) obj;
 145                                 method = prop.GetGetMethod ();
 146                                 if (method == null)
 147                                         method = prop.GetSetMethod ();
 148                         } else if (obj is MonoMethod) {
 149                                 method = (MethodInfo) obj;
 150                         }
 151
 152                         /**
 153                          * ParameterInfo -> null
 154                          * Assembly -> null
 155                          * MonoEvent -> null
 156                          * MonoField -> null
 157                          */
 158                         if (method == null || !method.IsVirtual)
 159                                 return null;
 160
 161                         MethodInfo baseMethod = method.GetBaseDefinition ();
 162                         if (baseMethod == method)
 163                                 return null;
 164
 165                         return baseMethod;
 166                 }
 167         }
 168 }
 169