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NonBindingMethodHolder.java
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NonBindingMethodHolder.java
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//
// ========================================================================
// Copyright (c) 1995-2022 Mort Bay Consulting Pty Ltd and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
// which is available at https://www.apache.org/licenses/LICENSE-2.0.
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
// ========================================================================
//
package org.eclipse.jetty.websocket.core.internal.util;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.WrongMethodTypeException;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Objects;
/**
* This implementation of {@link MethodHolder} is not thread safe.
* Mutual exclusion should be used when calling {@link #invoke(Object...)}, or this should only
* be invoked from a single thread.
*/
class NonBindingMethodHolder implements MethodHolder
{
private final MethodHandle _methodHandle;
private final Object[] _parameters;
private final List<Integer> _unboundParamIndexes = new LinkedList<>();
private final List<MethodHandle> _returnFilters = new ArrayList<>();
public NonBindingMethodHolder(MethodHandle methodHandle)
{
_methodHandle = Objects.requireNonNull(methodHandle);
int numParams = methodHandle.type().parameterCount();
_parameters = new Object[numParams];
for (int i = 0; i < numParams; i++)
{
_unboundParamIndexes.add(i);
}
}
@Override
public Object invoke(Object... args) throws Throwable
{
try
{
insertArguments(args);
Object o = _methodHandle.invokeWithArguments(_parameters);
for (MethodHandle filter : _returnFilters)
{
o = filter.invoke(o);
}
return o;
}
finally
{
clearArguments();
}
}
@Override
public MethodHolder bindTo(Object arg, int idx)
{
_parameters[_unboundParamIndexes.get(idx)] = arg;
_unboundParamIndexes.remove(idx);
return this;
}
@Override
public MethodHolder bindTo(Object arg)
{
return bindTo(arg, 0);
}
private void insertArguments(Object... args)
{
if (_unboundParamIndexes.size() != args.length)
throw new WrongMethodTypeException(String.format("Expected %s params but had %s", _unboundParamIndexes.size(), args.length));
int argsIndex = 0;
for (int index : _unboundParamIndexes)
{
_parameters[index] = args[argsIndex++];
}
}
private void clearArguments()
{
for (int i : _unboundParamIndexes)
{
_parameters[i] = null;
}
}
@Override
public MethodHolder filterReturnValue(MethodHandle filter)
{
_returnFilters.add(filter);
return this;
}
@Override
public Class<?> parameterType(int idx)
{
return _methodHandle.type().parameterType(_unboundParamIndexes.get(idx));
}
@Override
public Class<?> returnType()
{
return (_returnFilters.isEmpty() ? _methodHandle : _returnFilters.get(_returnFilters.size() - 1)).type().returnType();
}
}