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/*
* Copyright (C) 2024 The Android Open Source Project
*
* 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 android.utils;
import libcore.util.EmptyArray;
import java.util.NoSuchElementException;
/**
* Copied from frameworks/base/core/java/android/util/LongArrayQueue.java
*
* @hide
*/
public class LongArrayQueue {
private long[] mValues;
private int mSize;
private int mHead;
private int mTail;
private long[] newUnpaddedLongArray(int num) {
return new long[num];
}
/**
* Initializes a queue with the given starting capacity.
*
* @param initialCapacity the capacity.
*/
public LongArrayQueue(int initialCapacity) {
if (initialCapacity == 0) {
mValues = EmptyArray.LONG;
} else {
mValues = newUnpaddedLongArray(initialCapacity);
}
mSize = 0;
mHead = mTail = 0;
}
/**
* Initializes a queue with default starting capacity.
*/
public LongArrayQueue() {
this(16);
}
/** @hide */
public static int growSize(int currentSize) {
return currentSize <= 4 ? 8 : currentSize * 2;
}
private void grow() {
if (mSize < mValues.length) {
throw new IllegalStateException("Queue not full yet!");
}
final int newSize = growSize(mSize);
final long[] newArray = newUnpaddedLongArray(newSize);
final int r = mValues.length - mHead; // Number of elements on and to the right of head.
System.arraycopy(mValues, mHead, newArray, 0, r);
System.arraycopy(mValues, 0, newArray, r, mHead);
mValues = newArray;
mHead = 0;
mTail = mSize;
}
/**
* Returns the number of elements in the queue.
*/
public int size() {
return mSize;
}
/**
* Removes all elements from this queue.
*/
public void clear() {
mSize = 0;
mHead = mTail = 0;
}
/**
* Adds a value to the tail of the queue.
*
* @param value the value to be added.
*/
public void addLast(long value) {
if (mSize == mValues.length) {
grow();
}
mValues[mTail] = value;
mTail = (mTail + 1) % mValues.length;
mSize++;
}
/**
* Removes an element from the head of the queue.
*
* @return the element at the head of the queue.
* @throws NoSuchElementException if the queue is empty.
*/
public long removeFirst() {
if (mSize == 0) {
throw new NoSuchElementException("Queue is empty!");
}
final long ret = mValues[mHead];
mHead = (mHead + 1) % mValues.length;
mSize--;
return ret;
}
/**
* Returns the element at the given position from the head of the queue, where 0 represents the
* head of the queue.
*
* @param position the position from the head of the queue.
* @return the element found at the given position.
* @throws IndexOutOfBoundsException if {@code position} < {@code 0} or
* {@code position} >= {@link #size()}
*/
public long get(int position) {
if (position < 0 || position >= mSize) {
throw new IndexOutOfBoundsException("Index " + position
+ " not valid for a queue of size " + mSize);
}
final int index = (mHead + position) % mValues.length;
return mValues[index];
}
/**
* Returns the element at the head of the queue, without removing it.
*
* @return the element at the head of the queue.
* @throws NoSuchElementException if the queue is empty
*/
public long peekFirst() {
if (mSize == 0) {
throw new NoSuchElementException("Queue is empty!");
}
return mValues[mHead];
}
/**
* Returns the element at the tail of the queue.
*
* @return the element at the tail of the queue.
* @throws NoSuchElementException if the queue is empty.
*/
public long peekLast() {
if (mSize == 0) {
throw new NoSuchElementException("Queue is empty!");
}
final int index = (mTail == 0) ? mValues.length - 1 : mTail - 1;
return mValues[index];
}
/**
* {@inheritDoc}
*/
@Override
public String toString() {
if (mSize <= 0) {
return "{}";
}
final StringBuilder buffer = new StringBuilder(mSize * 64);
buffer.append('{');
buffer.append(get(0));
for (int i = 1; i < mSize; i++) {
buffer.append(", ");
buffer.append(get(i));
}
buffer.append('}');
return buffer.toString();
}
}
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