146 lines
4.0 KiB
C#
146 lines
4.0 KiB
C#
//
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// System.Random.cs
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//
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// Authors:
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// Bob Smith (bob@thestuff.net)
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// Ben Maurer (bmaurer@users.sourceforge.net)
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// Sebastien Pouliot <sebastien@xamarin.com>
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//
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// (C) 2001 Bob Smith. http://www.thestuff.net
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// (C) 2003 Ben Maurer
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// Copyright (C) 2004 Novell, Inc (http://www.novell.com)
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// Copyright 2013 Xamarin Inc. (http://www.xamarin.com)
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//
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// Permission is hereby granted, free of charge, to any person obtaining
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// a copy of this software and associated documentation files (the
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// "Software"), to deal in the Software without restriction, including
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// without limitation the rights to use, copy, modify, merge, publish,
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// distribute, sublicense, and/or sell copies of the Software, and to
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// permit persons to whom the Software is furnished to do so, subject to
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// the following conditions:
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//
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// The above copyright notice and this permission notice shall be
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// included in all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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//
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using System.Runtime.InteropServices;
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namespace System
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{
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[Serializable]
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[ComVisible (true)]
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public class Random
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{
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uint x;
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uint y;
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uint z;
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uint c;
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public Random ()
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: this (Environment.TickCount)
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{
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}
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public Random (int Seed)
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{
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x = (uint) Seed;
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y = (uint) 987654321;
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z = (uint) 43219876;
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c = (uint) 6543217;
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}
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uint JKiss ()
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{
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x = 314527869 * x + 1234567;
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y ^= y << 5;
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y ^= y >> 7;
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y ^= y << 22;
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ulong t = ((ulong) 4294584393 * z + c);
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c = (uint) (t >> 32);
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z = (uint) t;
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return (x + y + z);
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}
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public virtual int Next (int minValue, int maxValue)
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{
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if (minValue > maxValue)
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throw new ArgumentOutOfRangeException ("Maximum value is less than minimal value.");
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// special case: a difference of one (or less) will always return the minimum
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// e.g. -1,-1 or -1,0 will always return -1
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uint diff = (uint) (maxValue - minValue);
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if (diff <= 1)
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return minValue;
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return minValue + ((int) (JKiss () % diff));
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}
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public virtual int Next (int maxValue)
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{
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if (maxValue < 0)
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throw new ArgumentOutOfRangeException ("Maximum value is less than minimal value.");
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return maxValue > 0 ? (int)(JKiss () % maxValue) : 0;
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}
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public virtual int Next ()
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{
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// returns a non-negative, [0 - Int32.MacValue], random number
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// but we want to avoid calls to Math.Abs (call cost and branching cost it requires)
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// and the fact it would throw for Int32.MinValue (so roughly 1 time out of 2^32)
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int random = (int) JKiss ();
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while (random == Int32.MinValue)
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random = (int) JKiss ();
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int mask = random >> 31;
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random ^= mask;
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return random + (mask & 1);
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}
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public virtual void NextBytes (byte [] buffer)
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{
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if (buffer == null)
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throw new ArgumentNullException ("buffer");
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// each random `int` can fill 4 bytes
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int p = 0;
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uint random;
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for (int i = 0; i < (buffer.Length >> 2); i++) {
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random = JKiss ();
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buffer [p++] = (byte) (random >> 24);
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buffer [p++] = (byte) (random >> 16);
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buffer [p++] = (byte) (random >> 8);
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buffer [p++] = (byte) random;
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}
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if (p == buffer.Length)
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return;
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// complete the array
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random = JKiss ();
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while (p < buffer.Length) {
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buffer [p++] = (byte) random;
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random >>= 8;
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}
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}
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public virtual double NextDouble ()
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{
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// return a double value between [0,1]
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return Sample ();
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}
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protected virtual double Sample ()
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{
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// a single 32 bits random value is not enough to create a random double value
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uint a = JKiss () >> 6; // Upper 26 bits
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uint b = JKiss () >> 5; // Upper 27 bits
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return (a * 134217728.0 + b) / 9007199254740992.0;
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}
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}
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} |