/*
* Copyright 2012-2014 headius.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.headius.invokebinder.transform;
import com.headius.invokebinder.InvalidTransformException;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
/**
* An return-filtering transform.
*
* Equivalent call: MethodHandles.filterReturn(MethodHandle, MethodHandle).
*/
public class FilterReturn extends Transform {
private final MethodHandle function;
public FilterReturn(MethodHandle function) {
this.function = function;
}
public MethodHandle up(MethodHandle target) {
return MethodHandles.filterReturnValue(target, function);
}
public MethodType down(MethodType type) {
int count = function.type().parameterCount();
switch (count) {
case 0:
return type.changeReturnType(void.class);
case 1:
return type.changeReturnType(function.type().parameterType(0));
default:
throw new InvalidTransformException("return filter " + function + " does not accept zero or one argument");
}
}
public String toString() {
return "filter return with " + function;
}
}