Class ObjStack

core/src/main/java/io/questdb/std/ObjStack.java:29–182

import java.util.Arrays;

public class ObjStack<T> implements Mutable {
    public static final int DEFAULT_INITIAL_CAPACITY = 16;
    private final int initialCapacity;
    private int bottom;
    private T[] elements;
    private int head;
    private int mask;
    private int tail;

    public ObjStack() {
        this(DEFAULT_INITIAL_CAPACITY);
    }

    public ObjStack(int initialCapacity) {
        this.initialCapacity = initialCapacity;
        allocateElements(initialCapacity);
    }

    public void clear() {
        if (head != tail) {
            head = tail = 0;
            Arrays.fill(elements, null);
            bottom = 0;
        }
    }

    public int getBottom() {
        return bottom;
    }

    public int getCapacity() {
        return elements.length;
    }

    public boolean notEmpty() {
        return size() > 0;
    }

    public T peek() {
        return peek(0);
    }

    public T peek(int n) {
        return n < size() ? elements[(head + n) & mask] : null;
    }

    public T pop() {
        if (size() == 0) {
            return null;
        }
        final int h = head;
        final T result = elements[h];
        if (result == null) {
            return null;
        }
        elements[h] = null;
        head = (h + 1) & mask;
        return result;