46 lines
1.3 KiB
C#
46 lines
1.3 KiB
C#
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using System;
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using System.Security.Cryptography;
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namespace Geekbot.net.Lib.RandomNumberGenerator
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{
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public class RandomNumberGenerator : IRandomNumberGenerator
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{
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readonly RNGCryptoServiceProvider csp;
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public RandomNumberGenerator()
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{
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csp = new RNGCryptoServiceProvider();
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}
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public int Next(int minValue, int maxExclusiveValue)
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{
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if (minValue >= maxExclusiveValue)
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{
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throw new ArgumentOutOfRangeException("minValue must be lower than maxExclusiveValue");
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}
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var diff = (long)maxExclusiveValue - minValue;
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var upperBound = uint.MaxValue / diff * diff;
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uint ui;
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do
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{
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ui = GetRandomUInt();
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} while (ui >= upperBound);
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return (int)(minValue + (ui % diff));
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}
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private uint GetRandomUInt()
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{
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var randomBytes = GenerateRandomBytes(sizeof(uint));
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return BitConverter.ToUInt32(randomBytes, 0);
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}
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private byte[] GenerateRandomBytes(int bytesNumber)
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{
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var buffer = new byte[bytesNumber];
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csp.GetBytes(buffer);
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return buffer;
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}
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}
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}
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