testuniques.cs

/*
EXAMPLE EXECUTION

testname: GetNeverPonyNumber
uniques: 50000000
collisions: 0
examples: 8702a199572565e1, 84a4a866d8222e3f, 7de9de6bc852e14d
elapsed: 00:03:47.0953452


testname: GetRealyNumber
uniques: 50000000
collisions: 0
examples: xfw2av1e1ao38, opxgipe2cjkwx, 3qcn8np84hgli
elapsed: 00:02:10.8699939


testname: GetCriptoNumber
uniques: 50000000
collisions: 0
examples: 5qfvcfsa0bppo, zskhfefz1vppa, 600rajsztqdnj
elapsed: 00:02:21.0801211
*/

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Security.Cryptography;

class Program
{
    const int batchSize = 50_000_000;
    static readonly Random _random = new Random();
    static readonly RNGCryptoServiceProvider _cryptoServiceProvider = new RNGCryptoServiceProvider();

    static void Main(string[] args)
    {
        Test("GetNeverPonyNumber", GetNeverPonyNumber); // generated lenght 16 characters, 16 possible values => combinations: 18446744073709551616 
        Test("GetRealyNumber", () => GetRelayNumber(13, "1234567890abcdefghijklmnopqrstuvwxyz")); // generated lenght 13 characters, 36 possible values => combinations: 170581728179578208256 (aprox 10x > 18446744073709551616)
        Test("GetCriptoNumber", () => GetCriptoNumber(13, "1234567890abcdefghijklmnopqrstuvwxyz")); // generated lenght 13 characters, 36 possible values => combinations: 170581728179578208256 (aprox 10x > 18446744073709551616)
        Console.WriteLine("Enter to continue . . .");
        Console.ReadLine();
    }

    private static void Test(string testname, Func<string> algorithm)
    {
        var stopWatch = Stopwatch.StartNew();
        var uniques = new HashSet<string>();
        var collisions = 0;

        for (var i = 0; i < batchSize; i++)
        {
            var generated = algorithm();
            if (!uniques.Add(generated))
            {
                collisions++;
            }
        }
        var elapsed = stopWatch.Elapsed;
        Console.WriteLine($@"
testname: {testname}
uniques: {uniques.Count()}
collisions: {collisions}
examples: {string.Join(", ", uniques.Take(3))}
elapsed: {elapsed}
");
    }

    static private string GetNeverPonyNumber()
    {
        long i = 1;
        foreach (byte b in Guid.NewGuid().ToByteArray())
        {
            i *= ((int)b + 1);
        }
        return string.Format("{0:x}", i - DateTime.Now.Ticks);
    }

    static string GetRelayNumber(int length, string charset) =>
      string.Join(string.Empty,
        Enumerable.Repeat(true, length).Select(
          x => charset[_random.Next(charset.Length)]));

    static string GetCriptoNumber(int length, string charset)
    {
        var data = new byte[length];
        _cryptoServiceProvider.GetNonZeroBytes(data);
        return string.Join(string.Empty,
          data.Select(x => charset[x % charset.Length]));
    }
}