io.perfmark.java7.SecretMethodHandleGenerator Maven / Gradle / Ivy
/*
* Copyright 2019 Google LLC
*
* 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 io.perfmark.java7;
import io.perfmark.impl.Generator;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MutableCallSite;
final class SecretMethodHandleGenerator {
// UsedReflectively
public static final class MethodHandleGenerator extends Generator {
private static final MutableCallSite currentGeneration =
new MutableCallSite(MethodHandles.constant(long.class, 0));
private static final MutableCallSite[] currentGenerations =
new MutableCallSite[] {currentGeneration};
private static final MethodHandle currentGenerationGetter = currentGeneration.dynamicInvoker();
public MethodHandleGenerator() {}
@Override
public long getGeneration() {
try {
return (long) currentGenerationGetter.invoke();
} catch (Throwable throwable) {
return FAILURE;
}
}
@Override
public void setGeneration(long generation) {
currentGeneration.setTarget(MethodHandles.constant(long.class, generation));
MutableCallSite.syncAll(currentGenerations);
}
@Override
public long costOfGetNanos() {
// Method handles compile to constants, so this is effectively free.
// JMH testing on a Skylake x86_64 processor shows the cost to be about 0.3ns.
return 0;
}
@Override
public long costOfSetNanos() {
// based on JMH testing on a Skylake x86_64 processor.
return 2_000_000;
}
}
private SecretMethodHandleGenerator() {
throw new AssertionError("nope");
}
}