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/*
* [The "BSD licence"]
* Copyright (c) 2005-2008 Terence Parr
* All rights reserved.
*
* Conversion to C#:
* Copyright (c) 2008-2009 Sam Harwell, Pixel Mine, Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
namespace Antlr.Runtime.Misc
{
using System.Collections.Generic;
using ArgumentException = System.ArgumentException;
using InvalidOperationException = System.InvalidOperationException;
/** A queue that can dequeue and get(i) in O(1) and grow arbitrarily large.
* A linked list is fast at dequeue but slow at get(i). An array is
* the reverse. This is O(1) for both operations.
*
* List grows until you dequeue last element at end of buffer. Then
* it resets to start filling at 0 again. If adds/removes are balanced, the
* buffer will not grow too large.
*
* No iterator stuff as that's not how we'll use it.
*/
public class FastQueue<T>
{
/** <summary>dynamically-sized buffer of elements</summary> */
internal List<T> _data = new List<T>();
/** <summary>index of next element to fill</summary> */
internal int _p = 0;
public virtual int Count
{
get
{
return _data.Count - _p;
}
}
/// <summary>
/// How deep have we gone?
/// </summary>
public virtual int Range
{
get;
protected set;
}
/** <summary>
* Return element {@code i} elements ahead of current element. {@code i==0}
* gets current element. This is not an absolute index into {@link #data}
* since {@code p} defines the start of the real list.
* </summary>
*/
public virtual T this[int i]
{
get
{
int absIndex = _p + i;
if (absIndex >= _data.Count)
throw new ArgumentException(string.Format("queue index {0} > last index {1}", absIndex, _data.Count - 1));
if (absIndex < 0)
throw new ArgumentException(string.Format("queue index {0} < 0", absIndex));
if (absIndex > Range)
Range = absIndex;
return _data[absIndex];
}
}
/** <summary>Get and remove first element in queue</summary> */
public virtual T Dequeue()
{
if (Count == 0)
throw new InvalidOperationException();
T o = this[0];
_p++;
// have we hit end of buffer?
if ( _p == _data.Count )
{
// if so, it's an opportunity to start filling at index 0 again
Clear(); // size goes to 0, but retains memory
}
return o;
}
public virtual void Enqueue( T o )
{
_data.Add( o );
}
public virtual T Peek()
{
return this[0];
}
public virtual void Clear()
{
_p = 0;
_data.Clear();
}
/** <summary>Return string of current buffer contents; non-destructive</summary> */
public override string ToString()
{
System.Text.StringBuilder buf = new System.Text.StringBuilder();
int n = Count;
for ( int i = 0; i < n; i++ )
{
buf.Append( this[i] );
if ( ( i + 1 ) < n )
buf.Append( " " );
}
return buf.ToString();
}
}
}
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