unicodetools/com/ibm/text/utility/IntStack.java

/**
*******************************************************************************
* Copyright (C) 1996-2001, International Business Machines Corporation and    *
* others. All Rights Reserved.                                                *
*******************************************************************************
*
* $Source: /xsrl/Nsvn/icu/unicodetools/com/ibm/text/utility/IntStack.java,v $
* $Date: 2002/06/15 02:47:14 $
* $Revision: 1.4 $
*
*******************************************************************************
*/

package com.ibm.text.utility;

// =============================================================
// Simple stack mechanism, with push, pop and access
// =============================================================

public final class IntStack implements Comparable, Cloneable {
    private int[] values;
    private int top = 0;
    private int first = 0;

    public IntStack(int initialSize) {
        values = new int[initialSize];
    }
    
    public IntStack append(IntStack other) {
        // TODO speed up by copying arrays
        for (int i = 0; i < other.getTop(); ++i) {
            push(other.get(i));
        }
        return this;
    }

    public IntStack append(int value) {
        return push(value);
    }

    public int length() {
        return top - first;
    }

    public IntStack push(int value) {
        if (top >= values.length) { // must grow?
            int[] temp = new int[values.length*2];
            System.arraycopy(values,0,temp,0,values.length);
            values = temp;
        }
        values[top++] = value;
        return this;
    }

    public int pop() {
        if (top > first) {
            int result = values[--top];
            if (top == first && first > 0) {
                top = first = 0;
            }
            return result;
        }
        throw new IllegalArgumentException("Stack underflow");
    }

    public int popFront() {
        if (top > first) {
            int result = values[first++];
            if (top == first) {
                top = first = 0;
            }
            return result;
        }
        throw new IllegalArgumentException("Stack underflow");
    }

    public int get(int index) {
        if (first <= index && index < top) return values[index];
        throw new IllegalArgumentException("Stack index out of bounds");
    }

    public int getTop() {
        return top;
    }

    public boolean isEmpty() {
        return top - first == 0;
    }
    
    public void clear() {
        top = first = 0;
    }
    
    public int compareTo(Object other) {
        IntStack that = (IntStack) other;
        int myLen = top - first;
        int thatLen = that.top - that.first;
        int limit = first + ((myLen < thatLen) ? myLen : thatLen);
        int delta = that.first - first;
        for (int i = first; i < limit; ++i) {
            int result = values[i] - that.values[i + delta];
            if (result != 0) return result;
        }
        return myLen - thatLen;
    }

    public boolean equals(Object other) {
        return compareTo(other) == 0;
    }

    public int hashCode() {
        int result = top;
        for (int i = first; i < top; ++i) {
            result = result * 37 + values[i];
        }
        return result;
    }
    
    public Object clone() {
        try {
            IntStack result = (IntStack) (super.clone());
            result.values = (int[]) result.values.clone();
            return result;
        } catch (CloneNotSupportedException e) {
            throw new IllegalArgumentException("Will never happen");
        }
    }
}