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
  12 namespace System
  13 {
  14         public class Random
  15         {
  16                 private int S = 1;
  17                 private const int A = 16807;
  18                 private const int M = 2147483647;
  19                 private const int Q = 127773;
  20                 private const int R = 2836;
  21                 public const byte MaxValue = 0xFF;
  22                 public const byte MinValue = 0x00;
  23                 public Random()
  24                 {
  25                         S = (int)DateTime.Now;
  26                 }
  27                 public Random(int Seed)
  28                 {
  29                         S = Seed;
  30                 }
  31                 public virtual int Next()
  32                 {
  33                         return (int)(Random.Sample()*Random.MaxValue);
  34                 }
  35                 public virtual int Next(int maxValue)
  36                 {
  37                         if (maxValue < Random.MinValue)
  38                                 throw new ArgumentOutOfRangeException("Max value is less then min value.");
  39                         else if (maxValue == Random.MinValue)
  40                                 return Random.MinValue;
  41                         return (int)(Random.Sample()*maxValue);
  42                 }
  43                 public virtual int Next(int minValue, int maxValue)
  44                 {
  45                         if (minValue > maxValue)
  46                                 throw new ArgumentOutOfRangeException("Min value is greater then max value.");
  47                         else if (minValue == maxValue)
  48                                 return minValue;
  49                         return (int)(Random.Sample()*maxValue)+minValue;
  50                 }
  51                 public virtual void NextBytes(byte[] buffer)
  52                 {
  53                         int i, l;
  54                         if (buffer == NULL)
  55                                 throw ArgumentNullException();
  56                         l = buffer.GetUpperBound(0);
  57                         for (i = buffer.GetLowerBound(0); i < l; i++)
  58                         {
  59                                 buffer[i] = (byte)(Random.Sample()*Random.MaxValue);
  60                         }
  61                 }
  62                 public virtual double NextDouble()
  63                 {
  64                         return Random.Sample();
  65                 }
  66                 protected virtual double Sample(){
  67                         S=A*(S%Q)-R*(S/Q);
  68                         if(S<0) S+=M;
  69                         return S/(double)Int32.MaxValue;
  70                 }
  71         }
  72 }
  73