source: branches/eraser6/DefaultPlugins/ISAAC.cs @ 217

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

using Eraser.Manager;

namespace Eraser.DefaultPlugins
{
    /// <summary>
    /// ISAAC CSPRNG.
    /// </summary>
    public class ISAAC : PRNG
    {
        public override string Name
        {
            get { return "ISAAC CSPRNG"; }
        }

        public override Guid GUID
        {
            get { return new Guid("{CB7DE02E-8067-4270-B115-70AB49F23BB7}"); }
        }

        public unsafe override void NextBytes(byte[] buffer)
        {
            lock (isaac)
            {
                for (int bytesGenerated = 0;
                    bytesGenerated < buffer.Length * sizeof(byte);
                    bytesGenerated += Rand.ISAAC.SIZE * sizeof(int))
                {
                    //Generate 256 ints.
                    if (isaac.count == 0)
                        isaac.Isaac();

                    //Copy the data.
                    fixed (int* src = isaac.rsl)
                    fixed (byte* dest = &buffer[bytesGenerated])
                    {
                        //Advance to the end of the array of unused randomness.
                        //byte* bSrc = (byte*)src;
                        byte* pSrc = (byte*)(src + isaac.count);
                        byte* pDest = dest;

                        //Copy four bytes at a time, moving the source pointer backwards,
                        //and the destination pointer forwards.
                        int bytesToCopy = Math.Min(isaac.count * sizeof(int),
                            buffer.Length - bytesGenerated);
                        while (bytesToCopy >= 4)
                        {
                            pSrc -= sizeof(int);
                            *(int*)pDest = *(int*)pSrc;
                            pDest += sizeof(int);

                            bytesToCopy -= sizeof(int);
                            --isaac.count;
                        }

                        //Copy the remaining bytes over.
                        if (bytesToCopy != 0)
                        {
                            while (bytesToCopy-- != 0)
                                *pDest++ = *pSrc--;
                            --isaac.count;
                        }
                    }
                }
            }
        }

        private Rand.ISAAC isaac = new Rand.ISAAC();
    }
}