HWStack.cs

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namespace System.Xml;
 
internal sealed class HWStack : ICloneable
{
    private object[] _stack;
 
    private readonly int _growthRate;
 
    private int _used;
 
    private int _size;
 
    private readonly int _limit;
 
    internal object this[int index]
    {
        get
        {
            if (index >= 0 && index < _used)
            {
                return _stack[index];
            }
            throw new IndexOutOfRangeException();
        }
        set
        {
            if (index >= 0 && index < _used)
            {
                _stack[index] = value;
                return;
            }
            throw new IndexOutOfRangeException();
        }
    }
 
    internal int Length => _used;
 
    internal HWStack(int GrowthRate)
        : this(GrowthRate, int.MaxValue)
    {
    }
 
    internal HWStack(int GrowthRate, int limit)
    {
        _growthRate = GrowthRate;
        _used = 0;
        _stack = new object[GrowthRate];
        _size = GrowthRate;
        _limit = limit;
    }
 
    internal object Push()
    {
        if (_used == _size)
        {
            if (_limit <= _used)
            {
                throw new XmlException(System.SR.Xml_StackOverflow, string.Empty);
            }
            object[] array = new object[_size + _growthRate];
            if (_used > 0)
            {
                Array.Copy(_stack, array, _used);
            }
            _stack = array;
            _size += _growthRate;
        }
        return _stack[_used++];
    }
 
    internal object Pop()
    {
        if (0 < _used)
        {
            _used--;
            return _stack[_used];
        }
        return null;
    }
 
    internal object Peek()
    {
        if (_used <= 0)
        {
            return null;
        }
        return _stack[_used - 1];
    }
 
    internal void AddToTop(object o)
    {
        if (_used > 0)
        {
            _stack[_used - 1] = o;
        }
    }
 
    private HWStack(object[] stack, int growthRate, int used, int size)
    {
        _stack = stack;
        _growthRate = growthRate;
        _used = used;
        _size = size;
    }
 
    public object Clone()
    {
        return new HWStack((object[])_stack.Clone(), _growthRate, _used, _size);
    }
}