mcs/class/corlib/System/Random.cs

   1 //
   2 // System.Random.cs
   3 //
   4 // Author:
   5 //   Bob Smith (bob@thestuff.net)
   6 //
   7 // (C) 2001 Bob Smith.  http://www.thestuff.net
   8 //
   9
  10 using System;
  11 using System.Globalization;
  12
  13 namespace System
  14 {
  15                 [Serializable]
  16         public class Random
  17         {
  18                 private int S = 1;
  19                 private const int A = 16807;
  20                 private const int M = 2147483647;
  21                 private const int Q = 127773;
  22                 private const int R = 2836;
  23
  24                 public Random()
  25                 {
  26                         S = (int)(DateTime.Now.Ticks);
  27                 }
  28
  29                 public Random(int Seed)
  30                 {
  31                         S = Seed;
  32                 }
  33
  34                 public virtual int Next()
  35                 {
  36                         return (int)(this.Sample()*Int32.MaxValue);
  37                 }
  38
  39                 public virtual int Next(int maxValue)
  40                 {
  41                         if (maxValue < 0)
  42                                 throw new ArgumentOutOfRangeException(Locale.GetText (
  43                                         "Max value is less then min value."));
  44                         else if (maxValue == 0)
  45                                 return 0;
  46                         return (int)(this.Sample()*maxValue);
  47                 }
  48
  49                 public virtual int Next(int minValue, int maxValue)
  50                 {
  51                         if (minValue > maxValue)
  52                                 throw new ArgumentOutOfRangeException(Locale.GetText (
  53                                         "Min value is greater then max value."));
  54                         else if (minValue == maxValue)
  55                                 return minValue;
  56                         return (int)(this.Sample()*(maxValue - minValue))+minValue;
  57                 }
  58                 public virtual void NextBytes(byte[] buffer)
  59                 {
  60                         int i, l;
  61                         if (buffer == null)
  62                                 throw new ArgumentNullException();
  63                         l = buffer.GetUpperBound(0);
  64                         for (i = buffer.GetLowerBound(0); i < l; i++)
  65                         {
  66                                 buffer[i] = (byte)(this.Sample()*Byte.MaxValue);
  67                         }
  68                 }
  69
  70                 public virtual double NextDouble ()
  71                 {
  72                         return this.Sample();
  73                 }
  74
  75                 protected virtual double Sample ()
  76                 {
  77                         S = A*(S%Q)-R*(S/Q);
  78                         if (S < 0)
  79                                 S+=M;
  80                         return S/(double)Int32.MaxValue;
  81                 }
  82         }
  83 }