83 lines
2.4 KiB
C#
83 lines
2.4 KiB
C#
using System;
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using System.Buffers;
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using System.Security.Cryptography;
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namespace SharpChat {
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public static class RNG {
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public const string CHARS = "AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz0123456789";
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private static Random NormalRandom { get; } = new();
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private static RandomNumberGenerator SecureRandom { get; } = RandomNumberGenerator.Create();
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public static int Next() {
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return NormalRandom.Next();
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}
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public static int Next(int max) {
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return NormalRandom.Next(max);
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}
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public static int Next(int min, int max) {
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return NormalRandom.Next(min, max);
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}
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public static void NextBytes(byte[] buffer) {
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SecureRandom.GetBytes(buffer);
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}
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public static int SecureNext() {
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return SecureNext(int.MaxValue);
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}
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public static int SecureNext(int max) {
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return SecureNext(0, max);
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}
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public static int SecureNext(int min, int max) {
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--max;
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if(min == max)
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return min;
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uint umax = (uint)max - (uint)min;
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uint num;
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byte[] buffer = ArrayPool<byte>.Shared.Rent(4);
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try {
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SecureRandom.GetBytes(buffer);
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num = BitConverter.ToUInt32(buffer);
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if(umax != uint.MaxValue) {
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++umax;
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if((umax & (umax - 1)) != 0) {
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uint limit = uint.MaxValue - (uint.MaxValue & umax) - 1;
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while(num > limit) {
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SecureRandom.GetBytes(buffer);
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num = BitConverter.ToUInt32(buffer);
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}
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}
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}
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} finally {
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ArrayPool<byte>.Shared.Return(buffer);
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}
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return (int)((num % umax) + min);
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}
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private static string RandomStringInternal(Func<int, int> next, int length) {
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char[] str = new char[length];
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for(int i = 0; i < length; ++i)
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str[i] = CHARS[next(CHARS.Length)];
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return new string(str);
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}
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public static string RandomString(int length) {
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return RandomStringInternal(Next, length);
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}
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public static string SecureRandomString(int length) {
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return RandomStringInternal(SecureNext, length);
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}
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}
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}
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