io.netty.buffer.IntPriorityQueue Maven / Gradle / Ivy
/*
* Copyright 2020 The Netty Project
*
* The Netty Project licenses this file to you 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.netty.buffer;
import java.util.Arrays;
/**
* Internal primitive priority queue, used by {@link PoolChunk}.
* The implementation is based on the binary heap, as described in Algorithms by Sedgewick and Wayne.
*/
final class IntPriorityQueue {
public static final int NO_VALUE = -1;
private int[] array = new int[9];
private int size;
public void offer(int handle) {
if (handle == NO_VALUE) {
throw new IllegalArgumentException("The NO_VALUE (" + NO_VALUE + ") cannot be added to the queue.");
}
size++;
if (size == array.length) {
// Grow queue capacity.
array = Arrays.copyOf(array, 1 + (array.length - 1) * 2);
}
array[size] = handle;
lift(size);
}
public void remove(int value) {
for (int i = 1; i <= size; i++) {
if (array[i] == value) {
array[i] = array[size--];
lift(i);
sink(i);
return;
}
}
}
public int peek() {
if (size == 0) {
return NO_VALUE;
}
return array[1];
}
public int poll() {
if (size == 0) {
return NO_VALUE;
}
int val = array[1];
array[1] = array[size];
array[size] = 0;
size--;
sink(1);
return val;
}
public boolean isEmpty() {
return size == 0;
}
private void lift(int index) {
int parentIndex;
while (index > 1 && subord(parentIndex = index >> 1, index)) {
swap(index, parentIndex);
index = parentIndex;
}
}
private void sink(int index) {
int child;
while ((child = index << 1) <= size) {
if (child < size && subord(child, child + 1)) {
child++;
}
if (!subord(index, child)) {
break;
}
swap(index, child);
index = child;
}
}
private boolean subord(int a, int b) {
return array[a] > array[b];
}
private void swap(int a, int b) {
int value = array[a];
array[a] = array[b];
array[b] = value;
}
}