// ==++== // // // Copyright (c) 2002 Microsoft Corporation. All rights reserved. // // The use and distribution terms for this software are contained in the file // named license.txt, which can be found in the root of this distribution. // By using this software in any fashion, you are agreeing to be bound by the // terms of this license. // // You must not remove this notice, or any other, from this software. // // // ==--== /**//*============================================================ ** ** Class: Random.cs ** ** ** ** Purpose: A random number generator. ** ** Date: July 8, 1998 ** ===========================================================*/ namespace System { using System; using System.Runtime.CompilerServices; /**////<include file='doc\Random.uex' path='docs/doc[@for="Random"]/*' /> [Serializable()] publicclass Random { // // Private Constants // privateconstint MBIG = Int32.MaxValue; privateconstint MSEED =161803398; privateconstint MZ =0; // // Member Variables // privateint inext, inextp; privateint[] SeedArray =newint[56]; // // Public Constants // // // Native Declarations // // // Constructors // /**////<include file='doc\Random.uex' path='docs/doc[@for="Random.Random"]/*' /> public Random() : this(Environment.TickCount) { } /**////<include file='doc\Random.uex' path='docs/doc[@for="Random.Random1"]/*' /> public Random(int Seed) { int ii; int mj, mk; //Initialize our Seed array. //This algorithm comes from Numerical Recipes in C (2nd Ed.) mj = MSEED - Math.Abs(Seed); SeedArray[55]=mj; mk=1; for (int i=1; i<55; i++) { //Apparently the range [1..55] is special (Knuth) and so we're wasting the 0'th position. 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 =21; Seed =1; } // // Package Private Methods // /**//*====================================Sample==================================== **Action: Return a new random number [0..1) and reSeed the Seed array. **Returns: A double [0..1) **Arguments: None **Exceptions: None ==============================================================================*/ /**////<include file='doc\Random.uex' path='docs/doc[@for="Random.Sample"]/*' /> protectedvirtualdouble Sample() { int retVal; int locINext = inext; int locINextp = inextp; if (++locINext >=56) locINext=1; if (++locINextp>=56) locINextp =1; retVal = SeedArray[locINext]-SeedArray[locINextp]; if (retVal<0) retVal+=MBIG; SeedArray[locINext]=retVal; inext = locINext; inextp = locINextp; //Including this division at the end gives us significantly improved //random number distribution. return (retVal*(1.0/MBIG)); } // // Public Instance Methods // /**//*=====================================Next===================================== **Returns: An int [0.._int4.MaxValue) **Arguments: None **Exceptions: None. ==============================================================================*/ /**////<include file='doc\Random.uex' path='docs/doc[@for="Random.Next"]/*' /> publicvirtualint Next() { return (int)(Sample()*Int32.MaxValue); } /**//*=====================================Next===================================== **Returns: An int [minvalue..maxvalue) **Arguments: minValue -- the least legal value for the Random number. ** maxValue -- the greatest legal return value. **Exceptions: None. ==============================================================================*/ /**////<include file='doc\Random.uex' path='docs/doc[@for="Random.Next1"]/*' /> publicvirtualint Next(int minValue, int maxValue) { if (minValue>maxValue) { thrownew ArgumentOutOfRangeException("minValue",String.Format(Environment.GetResourceString("Argument_MinMaxValue"), "minValue", "maxValue")); } int range = (maxValue-minValue); //This is the case where we flipped around (e.g. MaxValue-MinValue); if (range<0) { long longRange = (long)maxValue-(long)minValue; return (int)(((long)(Sample()*((double)longRange)))+minValue); } return ((int)(Sample()*(range)))+minValue; } /**//*=====================================Next===================================== **Returns: An int [0..maxValue) **Arguments: maxValue -- the greatest legal return value. **Exceptions: None. ==============================================================================*/ /**////<include file='doc\Random.uex' path='docs/doc[@for="Random.Next2"]/*' /> publicvirtualint Next(int maxValue) { if (maxValue<0) { thrownew ArgumentOutOfRangeException("maxValue", String.Format(Environment.GetResourceString("ArgumentOutOfRange_MustBePositive"), "maxValue")); } return (int)(Sample()*maxValue); } /**//*=====================================Next===================================== **Returns: A double [0..1) **Arguments: None **Exceptions: None ==============================================================================*/ /**////<include file='doc\Random.uex' path='docs/doc[@for="Random.NextDouble"]/*' /> publicvirtualdouble NextDouble() { return Sample(); } /**//*==================================NextBytes=================================== **Action: Fills the byte array with random bytes [0..0x7f]. The entire array is filled. **Returns:Void **Arugments: buffer -- the array to be filled. **Exceptions: None ==============================================================================*/ /**////<include file='doc\Random.uex' path='docs/doc[@for="Random.NextBytes"]/*' /> publicvirtualvoid NextBytes(byte [] buffer){ if (buffer==null) thrownew ArgumentNullException("buffer"); for (int i=0; i<buffer.Length; i++) { buffer[i]=(byte)(Sample()*(Byte.MaxValue+1)); } } } }
posted on
2005-08-04 01:35wanna
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