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