source: branches/eraser6/pluginsRewrite/Eraser.Plugins/ExtensionPoints/IPrng.cs @ 2439

/* 
 * $Id: PRNG.cs 1802 2010-02-10 09:08:32Z lowjoel $
 * Copyright 2008-2010 The Eraser Project
 * Original Author: Joel Low <lowjoel@users.sourceforge.net>
 * Modified By:
 * 
 * This file is part of Eraser.
 * 
 * Eraser 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 3 of the License, or (at your option) any later
 * version.
 * 
 * Eraser 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.
 * 
 * A copy of the GNU General Public License can be found at
 * <http://www.gnu.org/licenses/>.
 */

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Eraser.Plugins.ExtensionPoints
{
    /// <summary>
    /// An interface class for all pseudorandom number generators used for the
    /// random data erase passes.
    /// </summary>
    public abstract class IPrng : IRegisterable
    {
        public override string ToString()
        {
            return Name;
        }

        /// <summary>
        /// The name of this erase pass, used for display in the UI
        /// </summary>
        public abstract string Name
        {
            get;
        }

        /// <summary>
        /// The GUID for this PRNG.
        /// </summary>
        public abstract Guid Guid
        {
            get;
        }

        /// <summary>
        /// Reseeds the PRNG. This can be called by inherited classes, but its most
        /// important function is to provide new seeds regularly. The PRNGManager
        /// will call this function once in a whle to maintain the quality of
        /// generated numbers.
        /// </summary>
        /// <param name="seed">An arbitrary length of information that will be
        /// used to reseed the PRNG</param>
        protected internal abstract void Reseed(byte[] seed);

        #region Random members
        /// <summary>
        /// Returns a nonnegative random number less than the specified maximum.
        /// </summary>
        /// <param name="maxValue">The exclusive upper bound of the random number
        /// to be generated. maxValue must be greater than or equal to zero.</param>
        /// <returns>A 32-bit signed integer greater than or equal to zero, and
        /// less than maxValue; that is, the range of return values ordinarily
        /// includes zero but not maxValue. However, if maxValue equals zero,
        /// maxValue is returned.</returns>
        public int Next(int maxValue)
        {
            if (maxValue == 0)
                return 0;
            return Next() % maxValue;
        }

        /// <summary>
        /// Returns a random number within a specified range.
        /// </summary>
        /// <param name="minValue">The inclusive lower bound of the random number
        /// returned.</param>
        /// <param name="maxValue">The exclusive upper bound of the random number
        /// returned. maxValue must be greater than or equal to minValue.</param>
        /// <returns>A 32-bit signed integer greater than or equal to minValue and
        /// less than maxValue; that is, the range of return values includes minValue
        /// but not maxValue. If minValue equals maxValue, minValue is returned.</returns>
        public int Next(int minValue, int maxValue)
        {
            if (minValue > maxValue)
                throw new ArgumentOutOfRangeException("minValue", minValue,
                    "minValue is greater than maxValue");
            else if (minValue == maxValue)
                return minValue;
            return (Next() % (maxValue - minValue)) + minValue;
        }

        /// <summary>
        /// Returns a nonnegative random number.
        /// </summary>
        /// <returns>A 32-bit signed integer greater than or equal to zero and less
        /// than System.Int32.MaxValue.</returns>
        public int Next()
        {
            //Get the random-valued bytes to fill the int.
            byte[] rand = new byte[sizeof(int)];
            NextBytes(rand);

            //Then return the integral representation of the buffer.
            return Math.Abs(BitConverter.ToInt32(rand, 0));
        }

        /// <summary>
        /// Fills the elements of a specified array of bytes with random numbers.
        /// </summary>
        /// <param name="buffer">An array of bytes to contain random numbers.</param>
        public abstract void NextBytes(byte[] buffer);
        #endregion
    }

}