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/* Copyright (C) 1997-2007,2014  Egon Willighagen 
 *
 * Contact: [email protected]
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1
 * of the License, or (at your option) any later version.
 * All we ask is that proper credit is given for our work, which includes
 * - but is not limited to - adding the above copyright notice to the beginning
 * of your source code files, and to any copyright notice that you may distribute
 * with programs based on this work.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 */
package org.openscience.cdk.io.cml;


/**
 * Low weight alternative to Sun's Stack class.
 *
 * @cdk.module io
 * @cdk.githash
 *
 * @cdk.keyword stack
 */
public class CMLModuleStack {

    ICMLModule[] stack = new ICMLModule[64];
    int          sp    = 0;

    /**
     * Adds an entry to the stack.
     */
    public void push(ICMLModule item) {
        if (sp == stack.length) {
            ICMLModule[] temp = new ICMLModule[2 * sp];
            System.arraycopy(stack, 0, temp, 0, sp);
            stack = temp;
        }
        stack[sp++] = item;
    }

    public int length() {
        return sp;
    }

    /**
     * Retrieves and deletes to last added entry.
     *
     * @see #current()
     */
    public ICMLModule pop() {
        return stack[--sp];
    }

    /**
     * Returns the last added entry.
     *
     * @see #pop()
     */
    public ICMLModule current() {
        if (sp > 0) {
            return stack[sp - 1];
        } else {
            return null;
        }
    }

    /**
     * Returns a String representation of the stack.
     */
    @Override
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append('/');
        for (int i = 0; i < sp; ++i) {
            sb.append(stack[i].getClass().getSimpleName());
            sb.append('/');
        }
        return sb.toString();
    }

    /**
     * Convenience method to check the last added elements.
     */
    public boolean endsWith(ICMLModule lastElement) {
        return stack[sp - 1].equals(lastElement);
    }

    /**
     * Convenience method to check the last two added elements.
     */
    public boolean endsWith(ICMLModule oneButLast, ICMLModule lastElement) {
        return endsWith(lastElement) && stack[sp - 2].equals(oneButLast);
    }

    /**
     * Convenience method to check the last three added elements.
     */
    public boolean endsWith(ICMLModule twoButLast, ICMLModule oneButLast, ICMLModule lastElement) {
        return endsWith(oneButLast, lastElement) && stack[sp - 3].equals(twoButLast);
    }
}