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/**
* Copyright 2017 VMware, Inc.
*
* 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
*
* https://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.micrometer.core.instrument.cumulative;
import io.micrometer.core.instrument.AbstractMeter;
import io.micrometer.core.instrument.FunctionCounter;
import io.micrometer.core.instrument.Meter;
import java.lang.ref.WeakReference;
import java.util.function.ToDoubleFunction;
public class CumulativeFunctionCounter extends AbstractMeter implements FunctionCounter {
private final WeakReference ref;
private final ToDoubleFunction f;
private volatile double last;
public CumulativeFunctionCounter(Meter.Id id, T obj, ToDoubleFunction f) {
super(id);
this.ref = new WeakReference<>(obj);
this.f = f;
}
@Override
public double count() {
T obj2 = ref.get();
return obj2 != null ? (last = f.applyAsDouble(obj2)) : last;
}
}