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//
// System.Random.cs
//
// Authors:
// Bob Smith (bob@thestuff.net)
// Ben Maurer (bmaurer@users.sourceforge.net)
//
// (C) 2001 Bob Smith. http://www.thestuff.net
// (C) 2003 Ben Maurer
//
//
// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//
using System.Runtime.InteropServices;
namespace System
{
[Serializable]
#if NET_2_0
[ComVisible (true)]
#endif
public class Random
{
const int MBIG = int.MaxValue;
const int MSEED = 161803398;
const int MZ = 0;
int inext, inextp;
int [] SeedArray = new int [56];
public Random ()
: this (Environment.TickCount)
{
}
public Random (int Seed)
{
int ii;
int mj, mk;
// Numerical Recipes in C online @ http://www.library.cornell.edu/nr/bookcpdf/c7-1.pdf
// Math.Abs throws on Int32.MinValue, so we need to work around that case.
// Fixes: 605797
if (Seed == Int32.MinValue)
mj = MSEED - Math.Abs (Int32.MinValue + 1);
else
mj = MSEED - Math.Abs (Seed);
SeedArray [55] = mj;
mk = 1;
for (int i = 1; i < 55; i++) { // [1, 55] is special (Knuth)
ii = (21 * i) % 55;
SeedArray [ii] = mk;
mk = mj - mk;
if (mk < 0)
mk += MBIG;
mj = SeedArray [ii];
}
for (int k = 1; k < 5; k++) {
for (int i = 1; i < 56; i++) {
SeedArray [i] -= SeedArray [1 + (i + 30) % 55];
if (SeedArray [i] < 0)
SeedArray [i] += MBIG;
}
}
inext = 0;
inextp = 31;
}
protected virtual double Sample ()
{
int retVal;
if (++inext >= 56) inext = 1;
if (++inextp >= 56) inextp = 1;
retVal = SeedArray [inext] - SeedArray [inextp];
if (retVal < 0)
retVal += MBIG;
SeedArray [inext] = retVal;
return retVal * (1.0 / MBIG);
}
public virtual int Next ()
{
return (int)(Sample () * int.MaxValue);
}
public virtual int Next (int maxValue)
{
if (maxValue < 0)
throw new ArgumentOutOfRangeException(Locale.GetText (
"Max value is less than min value."));
return (int)(Sample () * maxValue);
}
public virtual int Next (int minValue, int maxValue)
{
if (minValue > maxValue)
throw new ArgumentOutOfRangeException (Locale.GetText (
"Min value is greater than max value."));
// special case: a difference of one (or less) will always return the minimum
// e.g. -1,-1 or -1,0 will always return -1
uint diff = (uint) (maxValue - minValue);
if (diff <= 1)
return minValue;
return (int)((uint)(Sample () * diff) + minValue);
}
public virtual void NextBytes (byte [] buffer)
{
if (buffer == null)
throw new ArgumentNullException ("buffer");
for (int i = 0; i < buffer.Length; i++) {
buffer [i] = (byte)(Sample () * (byte.MaxValue + 1));
}
}
public virtual double NextDouble ()
{
return this.Sample ();
}
}
}
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