com.netflix.spectator.gc.CircularBuffer Maven / Gradle / Ivy
/*
* Copyright 2014-2019 Netflix, 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
*
* 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.netflix.spectator.gc;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReferenceArray;
/**
* Fixed size buffer that overwrites previous entries after filling up all slots.
*/
class CircularBuffer {
private final AtomicInteger nextIndex;
private final AtomicReferenceArray data;
/** Create a new instance. */
CircularBuffer(int length) {
nextIndex = new AtomicInteger(0);
data = new AtomicReferenceArray<>(length);
}
/** Add a new item to the buffer. If the buffer is full a previous entry will get overwritten. */
void add(T item) {
int i = nextIndex.getAndIncrement() % data.length();
data.set(i, item);
}
/** Get the item in the buffer at position {@code i} or return null if it isn't set. */
T get(int i) {
return data.get(i);
}
/** Return the capacity of the buffer. */
int size() {
return data.length();
}
/** Return a list with a copy of the data in the buffer. */
List toList() {
List items = new ArrayList<>(data.length());
for (int i = 0; i < data.length(); ++i) {
T item = data.get(i);
if (item != null) {
items.add(item);
}
}
return items;
}
}