using System.Runtime.CompilerServices; namespace System.Collections { internal static class HashHelpers { internal static ReadOnlySpan<int> Primes => RuntimeHelpers.CreateSpan<int>((RuntimeFieldHandle)); public static bool IsPrime(int candidate) { if ((candidate & 1) != 0) { int num = (int)Math.Sqrt((double)candidate); for (int i = 3; i <= num; i += 2) { if (candidate % i == 0) return false; } return true; } return candidate == 2; } public static int GetPrime(int min) { if (min < 0) throw new ArgumentException(System.SR.Arg_HTCapacityOverflow); ReadOnlySpan<int> primes = Primes; foreach (int num in primes) { if (num >= min) return num; } for (int j = min | 1; j < 2147483647; j += 2) { if (IsPrime(j) && (j - 1) % 101 != 0) return j; } return min; } public static int ExpandPrime(int oldSize) { int num = 2 * oldSize; if ((uint)num > 2147483587 && 2147483587 > oldSize) return 2147483587; return GetPrime(num); } public static ulong GetFastModMultiplier(uint divisor) { return ulong.MaxValue / (ulong)divisor + 1; } [MethodImpl(MethodImplOptions.AggressiveInlining)] public static uint FastMod(uint value, uint divisor, ulong multiplier) { return (uint)(((multiplier * value >> 32) + 1) * divisor >> 32); } } }