Tools/DynamicProxy/Castle.DynamicProxy/Builder/CodeBuilder/SimpleAST/ConvertExpression.cs

   1 // Copyright 2004-2007 Castle Project - http://www.castleproject.org/
   2 //
   3 // Licensed under the Apache License, Version 2.0 (the "License");
   4 // you may not use this file except in compliance with the License.
   5 // You may obtain a copy of the License at
   6 //
   7 //     http://www.apache.org/licenses/LICENSE-2.0
   8 //
   9 // Unless required by applicable law or agreed to in writing, software
  10 // distributed under the License is distributed on an "AS IS" BASIS,
  11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 // See the License for the specific language governing permissions and
  13 // limitations under the License.
  14
  15 namespace Castle.DynamicProxy.Builder.CodeBuilder.SimpleAST
  16 {
  17         using System;
  18         using System.Reflection.Emit;
  19
  20         using Castle.DynamicProxy.Builder.CodeBuilder.Utils;
  21
  22         /// <summary>
  23         /// Summary description for ConvertExpression.
  24         /// </summary>
  25         [CLSCompliant(false)]
  26         public class ConvertExpression : Expression
  27         {
  28                 private Type _target;
  29                 private Type _fromType;
  30                 private Expression _right;
  31
  32                 public ConvertExpression( Type targetType, Expression right ) : this(targetType, typeof(object), right)
  33                 {
  34                 }
  35
  36                 public ConvertExpression( Type targetType, Type fromType, Expression right )
  37                 {
  38                         _target = targetType;
  39                         _fromType = fromType;
  40                         _right = right;
  41                 }
  42
  43                 public override void Emit(IEasyMember member, ILGenerator gen)
  44                 {
  45                         _right.Emit(member, gen);
  46
  47                         if (_fromType == _target)
  48                         {
  49                                 return;
  50                         }
  51
  52                         if (_fromType.IsByRef)
  53                         {
  54                                 throw new NotSupportedException("Cannot convert from ByRef types");
  55                         }
  56
  57                         if (_target.IsByRef)
  58                         {
  59                                 throw new NotSupportedException("Cannot convert to ByRef types");
  60                         }
  61
  62                         if (_target.IsValueType)
  63                         {
  64                                 if (_fromType.IsValueType)
  65                                 {
  66                                         throw new NotImplementedException("Cannot convert between distinct value types at the moment");
  67                                 }
  68                                 else
  69                                 {
  70                                         // Unbox conversion
  71                                         // Assumes fromType is a boxed value
  72                                         gen.Emit(OpCodes.Unbox, _target);
  73                                         OpCodeUtil.EmitLoadIndirectOpCodeForType(gen, _target);
  74                                 }
  75                         }
  76                         else
  77                         {
  78                                 if (_fromType.IsValueType)
  79                                 {
  80                                         // Box conversion
  81                                         gen.Emit(OpCodes.Box, _fromType);
  82                                         EmitCastIfNeeded(typeof(object), _target, gen);
  83                                 }
  84                                 else
  85                                 {
  86                                         // Possible down-cast
  87                                         EmitCastIfNeeded(_fromType, _target, gen);
  88                                 }
  89                         }
  90                 }
  91
  92                 private void EmitCastIfNeeded(Type from, Type target, ILGenerator gen)
  93                 {
  94                         if (target.IsSubclassOf(from))
  95                         {
  96                                 gen.Emit(OpCodes.Castclass, target);
  97                         }
  98                 }
  99         }
 100 }