C# Constant.GetValue方法代碼示例

        public static CustomAttributeBuilder CreateDecimalConstantAttribute(Constant c)
        {
            PredefinedAttribute pa = PredefinedAttributes.Get.DecimalConstant;
            if (pa.Constructor == null &&
                !pa.ResolveConstructor (c.Location, TypeManager.byte_type, TypeManager.byte_type,
                    TypeManager.uint32_type, TypeManager.uint32_type, TypeManager.uint32_type))
                return null;

            Decimal d = (Decimal) c.GetValue ();
            int [] bits = Decimal.GetBits (d);
            object [] args = new object [] {
                (byte) (bits [3] >> 16),
                (byte) (bits [3] >> 31),
                (uint) bits [2], (uint) bits [1], (uint) bits [0]
            };

            return new CustomAttributeBuilder (pa.Constructor, args);
        }

			public override object Visit (Constant constant)
			{
				var result = new PrimitiveExpression (constant.GetValue (), Convert (constant.Location), constant.AsString ().Length);
				return result;
			}

			public override object Visit(Constant constant)
			{
				if (constant.GetValue() == null)
					return new NullReferenceExpression(Convert(constant.Location));
				string literalValue;
				var literalConstant = constant as ILiteralConstant;
				literalValue = literalConstant != null ? new string(literalConstant.ParsedValue) : constant.GetValueAsLiteral();
				object val = constant.GetValue();
				if (val is bool)
					literalValue = (bool)val ? "true" : "false";
				var result = new PrimitiveExpression(val, Convert(constant.Location), literalValue);
				return result;
			}

				public override object Visit (Constant constant)
				{
					return new CodePrimitiveExpression (constant.GetValue ());
				}

		/// <summary>
		///   Constant expression folder for binary operations.
		///
		///   Returns null if the expression can not be folded.
		/// </summary>
		static public Constant BinaryFold (ResolveContext ec, Binary.Operator oper,
						     Constant left, Constant right, Location loc)
		{
			Constant result = null;

			if (left is EmptyConstantCast)
				return BinaryFold (ec, oper, ((EmptyConstantCast)left).child, right, loc);

			if (left is SideEffectConstant) {
				result = BinaryFold (ec, oper, ((SideEffectConstant) left).value, right, loc);
				if (result == null)
					return null;
				return new SideEffectConstant (result, left, loc);
			}

			if (right is EmptyConstantCast)
				return BinaryFold (ec, oper, left, ((EmptyConstantCast)right).child, loc);

			if (right is SideEffectConstant) {
				result = BinaryFold (ec, oper, left, ((SideEffectConstant) right).value, loc);
				if (result == null)
					return null;
				return new SideEffectConstant (result, right, loc);
			}

			TypeSpec lt = left.Type;
			TypeSpec rt = right.Type;
			bool bool_res;

			if (lt.BuiltinType == BuiltinTypeSpec.Type.Bool && lt == rt) {
				bool lv = (bool) left.GetValue ();
				bool rv = (bool) right.GetValue ();			
				switch (oper) {
				case Binary.Operator.BitwiseAnd:
				case Binary.Operator.LogicalAnd:
					return new BoolConstant (ec.BuiltinTypes, lv && rv, left.Location);
				case Binary.Operator.BitwiseOr:
				case Binary.Operator.LogicalOr:
					return new BoolConstant (ec.BuiltinTypes, lv || rv, left.Location);
				case Binary.Operator.ExclusiveOr:
					return new BoolConstant (ec.BuiltinTypes, lv ^ rv, left.Location);
				case Binary.Operator.Equality:
					return new BoolConstant (ec.BuiltinTypes, lv == rv, left.Location);
				case Binary.Operator.Inequality:
					return new BoolConstant (ec.BuiltinTypes, lv != rv, left.Location);
				}
				return null;
			}

			//
			// During an enum evaluation, none of the rules are valid
			// Not sure whether it is bug in csc or in documentation
			//
			if (ec.HasSet (ResolveContext.Options.EnumScope)){
				if (left is EnumConstant)
					left = ((EnumConstant) left).Child;
				
				if (right is EnumConstant)
					right = ((EnumConstant) right).Child;
			} else if (left is EnumConstant && rt == lt) {
				switch (oper){
					///
					/// E operator |(E x, E y);
					/// E operator &(E x, E y);
					/// E operator ^(E x, E y);
					/// 
					case Binary.Operator.BitwiseOr:
					case Binary.Operator.BitwiseAnd:
					case Binary.Operator.ExclusiveOr:
						result = BinaryFold (ec, oper, ((EnumConstant)left).Child, ((EnumConstant)right).Child, loc);
						if (result != null)
							result = result.TryReduce (ec, lt);
						return result;

					///
					/// U operator -(E x, E y);
					/// 
					case Binary.Operator.Subtraction:
						result = BinaryFold (ec, oper, ((EnumConstant)left).Child, ((EnumConstant)right).Child, loc);
						if (result != null)
							result = result.TryReduce (ec, EnumSpec.GetUnderlyingType (lt));
						return result;

					///
					/// bool operator ==(E x, E y);
					/// bool operator !=(E x, E y);
					/// bool operator <(E x, E y);
					/// bool operator >(E x, E y);
					/// bool operator <=(E x, E y);
					/// bool operator >=(E x, E y);
					/// 
					case Binary.Operator.Equality:				
					case Binary.Operator.Inequality:
					case Binary.Operator.LessThan:				
					case Binary.Operator.GreaterThan:
//.........這裏部分代碼省略.........

			public override object Visit (Constant constant)
			{
				if (constant.GetValue () == null) 
					return new NullReferenceExpression (Convert (constant.Location));
				string literalValue;
				if (constant is ILiteralConstant) {
					literalValue = new string (((ILiteralConstant)constant).ParsedValue);
				} else {
					literalValue = constant.GetValueAsLiteral ();
				}
				var result = new PrimitiveExpression (constant.GetValue (), Convert (constant.Location), literalValue);
				return result;
			}

			public override object Visit (Constant constant)
			{
				if (constant.GetValue () == null) 
					return new NullReferenceExpression (Convert (constant.Location));
				var result = new PrimitiveExpression (constant.GetValue (), Convert (constant.Location), constant.GetValueAsLiteral ().Length);
				return result;
			}

//.........這裏部分代碼省略.........
					int value = ((IntConstant)e).Value;
					if (value == int.MinValue) {
						if (ec.ConstantCheckState) {
							ConstantFold.Error_CompileTimeOverflow (ec, loc);
							return null;
						}
						return e;
					}
					return new IntConstant (-value, e.Location);
				}
				if (expr_type == TypeManager.int64_type) {
					long value = ((LongConstant)e).Value;
					if (value == long.MinValue) {
						if (ec.ConstantCheckState) {
							ConstantFold.Error_CompileTimeOverflow (ec, loc);
							return null;
						}
						return e;
					}
					return new LongConstant (-value, e.Location);
				}
				
				if (expr_type == TypeManager.uint32_type) {
					UIntLiteral uil = e as UIntLiteral;
					if (uil != null) {
						if (uil.Value == 2147483648)
							return new IntLiteral (int.MinValue, e.Location);
						return new LongLiteral (-uil.Value, e.Location);
					}
					return new LongConstant (-((UIntConstant)e).Value, e.Location);
				}
				
				if (expr_type == TypeManager.uint64_type) {
					ULongLiteral ull = e as ULongLiteral;
					if (ull != null && ull.Value == 9223372036854775808)
						return new LongLiteral (long.MinValue, e.Location);
					return null;
				}
				
				if (expr_type == TypeManager.float_type) {
					FloatLiteral fl = e as FloatLiteral;
					// For better error reporting
					if (fl != null)
						return new FloatLiteral (-fl.Value, e.Location);

					return new FloatConstant (-((FloatConstant)e).Value, e.Location);
				}
				if (expr_type == TypeManager.double_type) {
					DoubleLiteral dl = e as DoubleLiteral;
					// For better error reporting
					if (dl != null)
						return new DoubleLiteral (-dl.Value, e.Location);

					return new DoubleConstant (-((DoubleConstant)e).Value, e.Location);
				}
				if (expr_type == TypeManager.decimal_type)
					return new DecimalConstant (-((DecimalConstant)e).Value, e.Location);
				
				return null;
				
			case Operator.LogicalNot:
				if (expr_type != TypeManager.bool_type)
					return null;
				
				bool b = (bool)e.GetValue ();
				return new BoolConstant (!b, e.Location);
				
			case Operator.OnesComplement:
				// Unary numeric promotions
				if (expr_type == TypeManager.byte_type)
					return new IntConstant (~((ByteConstant)e).Value, e.Location);
				if (expr_type == TypeManager.sbyte_type)
					return new IntConstant (~((SByteConstant)e).Value, e.Location);
				if (expr_type == TypeManager.short_type)
					return new IntConstant (~((ShortConstant)e).Value, e.Location);
				if (expr_type == TypeManager.ushort_type)
					return new IntConstant (~((UShortConstant)e).Value, e.Location);
				if (expr_type == TypeManager.char_type)
					return new IntConstant (~((CharConstant)e).Value, e.Location);
				
				// Predefined operators
				if (expr_type == TypeManager.int32_type)
					return new IntConstant (~((IntConstant)e).Value, e.Location);
				if (expr_type == TypeManager.uint32_type)
					return new UIntConstant (~((UIntConstant)e).Value, e.Location);
				if (expr_type == TypeManager.int64_type)
					return new LongConstant (~((LongConstant)e).Value, e.Location);
				if (expr_type == TypeManager.uint64_type){
					return new ULongConstant (~((ULongConstant)e).Value, e.Location);
				}
				if (e is EnumConstant) {
					e = TryReduceConstant (ec, ((EnumConstant)e).Child);
					if (e != null)
						e = new EnumConstant (e, expr_type);
					return e;
				}
				return null;
			}
			throw new Exception ("Can not constant fold: " + Oper.ToString());
		}

		/// <summary>
		///   Constant expression folder for binary operations.
		///
		///   Returns null if the expression can not be folded.
		/// </summary>
		static public Constant BinaryFold (EmitContext ec, Binary.Operator oper,
						     Constant left, Constant right, Location loc)
		{
			Constant result = null;

			if (left is EmptyConstantCast)
				return BinaryFold (ec, oper, ((EmptyConstantCast)left).child, right, loc);

			if (left is SideEffectConstant) {
				result = BinaryFold (ec, oper, ((SideEffectConstant) left).value, right, loc);
				if (result == null)
					return null;
				return new SideEffectConstant (result, left, loc);
			}

			if (right is EmptyConstantCast)
				return BinaryFold (ec, oper, left, ((EmptyConstantCast)right).child, loc);

			if (right is SideEffectConstant) {
				result = BinaryFold (ec, oper, left, ((SideEffectConstant) right).value, loc);
				if (result == null)
					return null;
				return new SideEffectConstant (result, right, loc);
			}

			Type lt = left.Type;
			Type rt = right.Type;
			bool bool_res;

			if (lt == TypeManager.bool_type && lt == rt) {
				bool lv = (bool) left.GetValue ();
				bool rv = (bool) right.GetValue ();			
				switch (oper) {
				case Binary.Operator.BitwiseAnd:
				case Binary.Operator.LogicalAnd:
					return new BoolConstant (lv && rv, left.Location);
				case Binary.Operator.BitwiseOr:
				case Binary.Operator.LogicalOr:
					return new BoolConstant (lv || rv, left.Location);
				case Binary.Operator.ExclusiveOr:
					return new BoolConstant (lv ^ rv, left.Location);
				case Binary.Operator.Equality:
					return new BoolConstant (lv == rv, left.Location);
				case Binary.Operator.Inequality:
					return new BoolConstant (lv != rv, left.Location);
				}
				return null;
			}

			//
			// During an enum evaluation, none of the rules are valid
			// Not sure whether it is bug in csc or in documentation
			//
			if (ec.InEnumContext){
				if (left is EnumConstant)
					left = ((EnumConstant) left).Child;
				
				if (right is EnumConstant)
					right = ((EnumConstant) right).Child;
			} else if (left is EnumConstant && rt == lt) {
				switch (oper){
					///
					/// E operator |(E x, E y);
					/// E operator &(E x, E y);
					/// E operator ^(E x, E y);
					/// 
					case Binary.Operator.BitwiseOr:
					case Binary.Operator.BitwiseAnd:
					case Binary.Operator.ExclusiveOr:
						return BinaryFold (ec, oper, ((EnumConstant)left).Child,
								((EnumConstant)right).Child, loc).TryReduce (ec, lt, loc);

					///
					/// U operator -(E x, E y);
					/// 
					case Binary.Operator.Subtraction:
						result = BinaryFold (ec, oper, ((EnumConstant)left).Child, ((EnumConstant)right).Child, loc);
						return result.TryReduce (ec, ((EnumConstant)left).Child.Type, loc);

					///
					/// bool operator ==(E x, E y);
					/// bool operator !=(E x, E y);
					/// bool operator <(E x, E y);
					/// bool operator >(E x, E y);
					/// bool operator <=(E x, E y);
					/// bool operator >=(E x, E y);
					/// 
					case Binary.Operator.Equality:				
					case Binary.Operator.Inequality:
					case Binary.Operator.LessThan:				
					case Binary.Operator.GreaterThan:
					case Binary.Operator.LessThanOrEqual:				
					case Binary.Operator.GreaterThanOrEqual:
						return BinaryFold(ec, oper, ((EnumConstant)left).Child, ((EnumConstant)right).Child, loc);
				}
//.........這裏部分代碼省略.........