using System;
using System.Runtime.InteropServices;
using Stream		= System.IO.Stream;
using BinaryReader	= System.IO.BinaryReader;
using IOException	= System.IO.IOException;

namespace antlr
{
	/*ANTLR Translator Generator
	* Project led by Terence Parr at http://www.jGuru.com
	* Software rights: http://www.antlr.org/license.html
	*
	* $Id:$
	*/

	//
	// ANTLR C# Code Generator by Micheal Jordan
	//                            Kunle Odutola       : kunle UNDERSCORE odutola AT hotmail DOT com
	//                            Anthony Oguntimehin
	//
	// With many thanks to Eric V. Smith from the ANTLR list.
	//

	/*A Stream of characters fed to the lexer from a InputStream that can
	* be rewound via mark()/rewind() methods.
	* <p>
	* A dynamic array is used to buffer up all the input characters.  Normally,
	* "k" characters are stored in the buffer.  More characters may be stored during
	* guess mode (testing syntactic predicate), or when LT(i>k) is referenced.
	* Consumption of characters is deferred.  In other words, reading the next
	* character is not done by conume(), but deferred until needed by LA or LT.
	* <p>
	*/

	// SAS: added this class to handle Binary input w/ FileInputStream
	
	public class ByteBuffer:InputBuffer
	{
		
		// char source
		[NonSerialized()]
		internal Stream input;
		
		private const int BUF_SIZE = 16;
		/// <summary>
		/// Small buffer used to avoid reading individual chars
		/// </summary>
		private byte[] buf = new byte[BUF_SIZE];

		
		/*Create a character buffer */
		public ByteBuffer(Stream input_) : base()
		{
			input = input_;
		}
		
		/*Ensure that the character buffer is sufficiently full */
		override public void  fill(int amount)
		{
//			try
//			{
			syncConsume();
			// Fill the buffer sufficiently to hold needed characters
			int bytesToRead = (amount + markerOffset) - queue.Count;
			int c;

			while (bytesToRead > 0)
			{
				// Read a few characters
				c = input.Read(buf, 0, BUF_SIZE);
				for (int i = 0; i < c; i++)
				{
					// Append the next character
					queue.Add(unchecked((char) buf[i]));
				}
				if (c < BUF_SIZE)
				{
					while ((bytesToRead-- > 0) && (queue.Count < BUF_SIZE))
					{
						queue.Add(CharScanner.EOF_CHAR);
					}
					break;
				}
				bytesToRead -= c;
			}
			//			}
//			catch (IOException io)
//			{
//				throw new CharStreamIOException(io);
//			}
		}
	}
}