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-rw-r--r--src/mscorlib/src/System/Random.cs249
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diff --git a/src/mscorlib/src/System/Random.cs b/src/mscorlib/src/System/Random.cs
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-// Licensed to the .NET Foundation under one or more agreements.
-// The .NET Foundation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-/*============================================================
-**
-**
-**
-** Purpose: A random number generator.
-**
-**
-===========================================================*/
-namespace System {
-
- using System;
- using System.Runtime;
- using System.Runtime.CompilerServices;
- using System.Globalization;
- using System.Diagnostics.Contracts;
-
- [Serializable]
- public class Random {
- //
- // Private Constants
- //
- private const int MBIG = Int32.MaxValue;
- private const int MSEED = 161803398;
- private const int MZ = 0;
-
-
- //
- // Member Variables
- //
- private int inext;
- private int inextp;
- private int[] SeedArray = new int[56];
-
- //
- // Public Constants
- //
-
- //
- // Native Declarations
- //
-
- //
- // Constructors
- //
-
- /*=========================================================================================
- **Action: Initializes a new instance of the Random class, using a default seed value
- ===========================================================================================*/
- public Random()
- : this(GenerateSeed()) {
- }
-
- /*=========================================================================================
- **Action: Initializes a new instance of the Random class, using a specified seed value
- ===========================================================================================*/
- public Random(int Seed) {
- int ii = 0;
- int mj, mk;
-
- //Initialize our Seed array.
- int subtraction = (Seed == Int32.MinValue) ? Int32.MaxValue : Math.Abs(Seed);
- mj = MSEED - subtraction;
- 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.
- if ((ii += 21) >= 55) ii -= 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++) {
- int n = i + 30;
- if (n >= 55) n -= 55;
- SeedArray[i] -= SeedArray[1 + n];
- 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
- ==============================================================================*/
- protected virtual double Sample() {
- //Including this division at the end gives us significantly improved
- //random number distribution.
- return (InternalSample()*(1.0/MBIG));
- }
-
- private int InternalSample() {
- 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 == MBIG) retVal--;
- if (retVal<0) retVal+=MBIG;
-
- SeedArray[locINext]=retVal;
-
- inext = locINext;
- inextp = locINextp;
-
- return retVal;
- }
-
-
- [ThreadStatic]
- private static Random t_threadRandom;
- private static readonly Random s_globalRandom = new Random(GenerateGlobalSeed());
-
- /*=====================================GenerateSeed=====================================
- **Returns: An integer that can be used as seed values for consecutively
- creating lots of instances on the same thread within a short period of time.
- ========================================================================================*/
- private static int GenerateSeed() {
- Random rnd = t_threadRandom;
- if (rnd == null) {
- int seed;
- lock (s_globalRandom) {
- seed = s_globalRandom.Next();
- }
- rnd = new Random(seed);
- t_threadRandom = rnd;
- }
- return rnd.Next();
- }
-
- /*==================================GenerateGlobalSeed====================================
- **Action: Creates a number to use as global seed.
- **Returns: An integer that is safe to use as seed values for thread-local seed generators.
- ==========================================================================================*/
- private static int GenerateGlobalSeed() {
- return Guid.NewGuid().GetHashCode();
- }
-
- //
- // Public Instance Methods
- //
-
-
- /*=====================================Next=====================================
- **Returns: An int [0..Int32.MaxValue)
- **Arguments: None
- **Exceptions: None.
- ==============================================================================*/
- public virtual int Next() {
- return InternalSample();
- }
-
- private double GetSampleForLargeRange() {
- // The distribution of double value returned by Sample
- // is not distributed well enough for a large range.
- // If we use Sample for a range [Int32.MinValue..Int32.MaxValue)
- // We will end up getting even numbers only.
-
- int result = InternalSample();
- // Note we can't use addition here. The distribution will be bad if we do that.
- bool negative = (InternalSample()%2 == 0) ? true : false; // decide the sign based on second sample
- if( negative) {
- result = -result;
- }
- double d = result;
- d += (Int32.MaxValue - 1); // get a number in range [0 .. 2 * Int32MaxValue - 1)
- d /= 2*(uint)Int32.MaxValue - 1 ;
- return d;
- }
-
-
- /*=====================================Next=====================================
- **Returns: An int [minvalue..maxvalue)
- **Arguments: minValue -- the least legal value for the Random number.
- ** maxValue -- One greater than the greatest legal return value.
- **Exceptions: None.
- ==============================================================================*/
- public virtual int Next(int minValue, int maxValue) {
- if (minValue>maxValue) {
- throw new ArgumentOutOfRangeException(nameof(minValue),Environment.GetResourceString("Argument_MinMaxValue", nameof(minValue), nameof(maxValue)));
- }
- Contract.EndContractBlock();
-
- long range = (long)maxValue-minValue;
- if( range <= (long)Int32.MaxValue) {
- return ((int)(Sample() * range) + minValue);
- }
- else {
- return (int)((long)(GetSampleForLargeRange() * range) + minValue);
- }
- }
-
-
- /*=====================================Next=====================================
- **Returns: An int [0..maxValue)
- **Arguments: maxValue -- One more than the greatest legal return value.
- **Exceptions: None.
- ==============================================================================*/
- public virtual int Next(int maxValue) {
- if (maxValue<0) {
- throw new ArgumentOutOfRangeException(nameof(maxValue), Environment.GetResourceString("ArgumentOutOfRange_MustBePositive", nameof(maxValue)));
- }
- Contract.EndContractBlock();
- return (int)(Sample()*maxValue);
- }
-
-
- /*=====================================Next=====================================
- **Returns: A double [0..1)
- **Arguments: None
- **Exceptions: None
- ==============================================================================*/
- public virtual double 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
- ==============================================================================*/
- public virtual void NextBytes(byte [] buffer){
- if (buffer==null) throw new ArgumentNullException(nameof(buffer));
- Contract.EndContractBlock();
- for (int i=0; i<buffer.Length; i++) {
- buffer[i]=(byte)(InternalSample()%(Byte.MaxValue+1));
- }
- }
- }
-}