/*
* Copyright 2004-2023 H2 Group. Multiple-Licensed under the MPL 2.0,
* and the EPL 1.0 (https://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.util;
import java.util.Arrays;
import java.util.NoSuchElementException;
/**
* The stack of byte values. This class is not synchronized and should not be
* used by multiple threads concurrently.
*/
public final class ByteStack {
private static final int MAX_ARRAY_SIZE = Integer.MAX_VALUE - 8;
private int size;
private byte[] array;
/**
* Creates a new empty instance.
*/
public ByteStack() {
array = Utils.EMPTY_BYTES;
}
/**
* Pushes an item onto the top of this stack.
*
* @param item
* the item to push
*/
public void push(byte item) {
int index = size;
int oldLength = array.length;
if (index >= oldLength) {
grow(oldLength);
}
array[index] = item;
size = index + 1;
}
/**
* Removes the item at the top of this stack and returns that item.
*
* @return the item at the top of this stack
* @throws NoSuchElementException
* if stack is empty
*/
public byte pop() {
int index = size - 1;
if (index < 0) {
throw new NoSuchElementException();
}
size = index;
return array[index];
}
/**
* Removes the item at the top of this stack and returns that item.
*
* @param defaultValue
* value to return if stack is empty
* @return the item at the top of this stack, or default value
*/
public int poll(int defaultValue) {
int index = size - 1;
if (index < 0) {
return defaultValue;
}
size = index;
return array[index];
}
/**
* Looks at the item at the top of this stack without removing it.
*
* @param defaultValue
* value to return if stack is empty
* @return the item at the top of this stack, or default value
*/
public int peek(int defaultValue) {
int index = size - 1;
if (index < 0) {
return defaultValue;
}
return array[index];
}
/**
* Returns {@code true} if this stack is empty.
*
* @return {@code true} if this stack is empty
*/
public boolean isEmpty() {
return size == 0;
}
/**
* Returns the number of items in this stack.
*
* @return the number of items in this stack
*/
public int size() {
return size;
}
private void grow(int length) {
if (length == 0) {
length = 0x10;
} else if (length >= MAX_ARRAY_SIZE) {
throw new OutOfMemoryError();
} else if ((length <<= 1) < 0) {
length = MAX_ARRAY_SIZE;
}
array = Arrays.copyOf(array, length);
}
}