// IChecksum.cs - Interface to compute a data checksum
// Copyright (C) 2001 Mike Krueger
//
// This file was translated from java, it was part of the GNU Classpath
// Copyright (C) 1999, 2000, 2001 Free Software Foundation, Inc.
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License
// as published by the Free Software Foundation; either version 2
// of the License, or (at your option) any later version.
//
// 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
// combination.
// 
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent
// modules, and to copy and distribute the resulting executable under
// terms of your choice, provided that you also meet, for each linked
// independent module, the terms and conditions of the license of that
// module.  An independent module is a module which is not derived from
// or based on this library.  If you modify this library, you may extend
// this exception to your version of the library, but you are not
// obligated to do so.  If you do not wish to do so, delete this
// exception statement from your version.

namespace PdfSharp.SharpZipLib.Checksums 
{
	
	/// <summary>
	/// Interface to compute a data checksum used by checked input/output streams.
	/// A data checksum can be updated by one byte or with a byte array. After each
	/// update the value of the current checksum can be returned by calling
	/// <code>getValue</code>. The complete checksum object can also be reset
	/// so it can be used again with new data.
	/// </summary>
	internal interface IChecksum
	{
		/// <summary>
		/// Returns the data checksum computed so far.
		/// </summary>
		long Value 
		{
			get;
		}
		
		/// <summary>
		/// Resets the data checksum as if no update was ever called.
		/// </summary>
		void Reset();
		
		/// <summary>
		/// Adds one byte to the data checksum.
		/// </summary>
		/// <param name = "bval">
		/// the data value to add. The high byte of the int is ignored.
		/// </param>
		void Update(int bval);
		
		/// <summary>
		/// Updates the data checksum with the bytes taken from the array.
		/// </summary>
		/// <param name="buffer">
		/// buffer an array of bytes
		/// </param>
		void Update(byte[] buffer);
		
		/// <summary>
		/// Adds the byte array to the data checksum.
		/// </summary>
		/// <param name = "buf">
		/// the buffer which contains the data
		/// </param>
		/// <param name = "off">
		/// the offset in the buffer where the data starts
		/// </param>
		/// <param name = "len">
		/// the length of the data
		/// </param>
		void Update(byte[] buf, int off, int len);
	}
}
