/// <summary>
/// 写入类型转换的 IL 指令。
/// </summary>
/// <param name="generator">IL 的指令生成器。</param>
/// <param name="inputType">要转换的对象的类型。</param>
/// <param name="outputType">要将输入对象转换到的类型。</param>
/// <param name="isChecked">是否执行溢出检查。</param>
public override void Emit(ILGenerator generator, Type inputType, Type outputType, bool isChecked)
{
Contract.Assume(inputType.IsNullable());
Type inputUnderlyingType = Nullable.GetUnderlyingType(inputType);
generator.EmitCall(inputType.GetMethod("get_Value"));
if (inputUnderlyingType != outputType)
{
Conversion conversion = ConversionFactory.GetConversion(inputUnderlyingType, outputType);
Contract.Assume(conversion != null);
conversion.Emit(generator, inputUnderlyingType, outputType, isChecked);
}
}
/// <summary>
/// 写入类型转换的 IL 指令。
/// </summary>
/// <param name="generator">IL 的指令生成器。</param>
/// <param name="inputType">要被转换的类型。</param>
/// <param name="outputType">要转换到的类型。</param>
/// <param name="isChecked">是否执行溢出检查。</param>
public override void Emit(ILGenerator generator, Type inputType, Type outputType, bool isChecked)
{
Contract.Assume(inputType.IsNullable());
Type inputUnderlyingType = Nullable.GetUnderlyingType(inputType);
Type outputUnderlyingType = Nullable.GetUnderlyingType(outputType);
// 定义变量和标签
LocalBuilder inputLocal = generator.GetLocal(inputType);
Label trueCase = generator.DefineLabel();
Label endConvert = generator.DefineLabel();
// inputLocal = value;
generator.Emit(OpCodes.Stloc, inputLocal);
// if (input.HasValue)
generator.Emit(OpCodes.Ldloca, inputLocal);
MethodInfo hasValue = inputType.GetMethod("get_HasValue");
generator.Emit(OpCodes.Call, hasValue);
generator.Emit(OpCodes.Brtrue, trueCase);
// return null
if (outputUnderlyingType != null)
{
// Nullable<T>。
generator.EmitDefault(outputType);
}
else
{
// 引用类型。
generator.Emit(OpCodes.Ldnull);
}
generator.Emit(OpCodes.Br, endConvert);
// else
generator.MarkLabel(trueCase);
// (outputType)input.GetValueOrDefault();
generator.Emit(OpCodes.Ldloca, inputLocal);
generator.FreeLocal(inputLocal);
MethodInfo getValueOrDefault = inputType.GetMethod("GetValueOrDefault", Type.EmptyTypes);
generator.Emit(OpCodes.Call, getValueOrDefault);
ConversionFactory.GetConversion(inputUnderlyingType, outputUnderlyingType ?? outputType)
.Emit(generator, inputUnderlyingType, outputUnderlyingType ?? outputType, isChecked);
if (outputUnderlyingType != null)
{
ConstructorInfo ctor = outputType.GetConstructor(new[] { outputUnderlyingType });
Contract.Assume(ctor != null);
generator.Emit(OpCodes.Newobj, ctor);
}
generator.MarkLabel(endConvert);
}
/// <summary>
/// 写入类型转换的 IL 指令。
/// </summary>
/// <param name="generator">IL 的指令生成器。</param>
/// <param name="inputType">要转换的对象的类型。</param>
/// <param name="outputType">要将输入对象转换到的类型。</param>
/// <param name="isChecked">是否执行溢出检查。</param>
public override void Emit(ILGenerator generator, Type inputType, Type outputType, bool isChecked)
{
Contract.Assume(outputType.IsNullable());
var outputUnderlyingType = Nullable.GetUnderlyingType(outputType);
if (inputType != outputUnderlyingType)
{
var conversion = ConversionFactory.GetConversion(inputType, outputUnderlyingType);
Contract.Assume(conversion != null);
conversion.Emit(generator, inputType, outputUnderlyingType, isChecked);
}
var ctor = outputType.GetConstructor(new[] { outputUnderlyingType });
Contract.Assume(ctor != null);
generator.Emit(OpCodes.Newobj, ctor);
}
