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TrustPilotChallenge/dotnet/WhiteRabbit/Program.cs

149 lines
5.3 KiB

namespace WhiteRabbit
{
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Diagnostics;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
/// <summary>
/// Main class
/// </summary>
public static class Program
{
/// <summary>
/// Main entry point
/// </summary>
public static void Main()
{
var stopwatch = new Stopwatch();
stopwatch.Start();
var sourcePhrase = ConfigurationManager.AppSettings["SourcePhrase"];
var sourceChars = ToOrderedChars(sourcePhrase);
var maxWordsInPhrase = int.Parse(ConfigurationManager.AppSettings["MaxWordsInPhrase"]);
if (sourceChars.Length + maxWordsInPhrase > 28)
{
Console.WriteLine("Only anagrams of up to 27 characters (including whitespace) are allowed");
return;
}
if (maxWordsInPhrase > Constants.MaxNumberOfWords)
{
Console.WriteLine($"Only anagrams of up to {Constants.MaxNumberOfWords} words are allowed");
return;
}
if (!BitConverter.IsLittleEndian)
{
Console.WriteLine("Only little-endian systems are supported due to MD5Digest optimizations");
return;
}
if (IntPtr.Size != 8)
{
Console.WriteLine("Only 64-bit systems are supported due to MD5Digest optimizations");
}
var expectedHashesFirstComponents = ConfigurationManager.AppSettings["ExpectedHashes"]
.Split(',')
.Select(hash => HexadecimalStringToUnsignedIntArray(hash)[0])
.ToArray();
var processor = new StringsProcessor(
Encoding.ASCII.GetBytes(sourcePhrase),
maxWordsInPhrase,
ReadInput());
Console.WriteLine($"Initialization complete; time from start: {stopwatch.Elapsed}");
#if DEBUG
var fastPhrasesCount = processor.GetPhrasesCount();
Console.WriteLine($"Number of phrases: {fastPhrasesCount}; time from start: {stopwatch.Elapsed}");
#endif
stopwatch.Restart();
processor.GeneratePhrases()
.ForAll(phraseSet =>
{
var hashesFirstComponents = MD5Digest.Compute(phraseSet);
for (var i = 0; i < Constants.PhrasesPerSet; i++)
{
Debug.Assert(
sourceChars == ToOrderedChars(ToString(phraseSet, i)),
$"StringsProcessor produced incorrect anagram: {ToString(phraseSet, i)}");
if (Array.IndexOf(expectedHashesFirstComponents, hashesFirstComponents[i]) >= 0)
{
var phrase = ToString(phraseSet, i);
var hash = ComputeFullMD5(phrase);
Console.WriteLine($"Found phrase for {hash} ({hashesFirstComponents[i]:x8}): {phrase}; time from start is {stopwatch.Elapsed}");
}
}
});
Console.WriteLine($"Done; time from start: {stopwatch.Elapsed}");
}
// Code taken from http://stackoverflow.com/a/321404/831314
private static uint[] HexadecimalStringToUnsignedIntArray(string hex)
{
return Enumerable.Range(0, hex.Length)
.Where(x => x % 8 == 0)
.Select(x => ChangeEndianness(hex.Substring(x, 8)))
.Select(hexLe => Convert.ToUInt32(hexLe, 16))
.ToArray();
}
// We can afford to spend some time here; this code will only run for matched phrases (and for one in several billion non-matched)
private static string ComputeFullMD5(string phrase)
{
var phraseBytes = Encoding.ASCII.GetBytes(phrase);
using (var hashAlgorithm = new MD5CryptoServiceProvider())
{
var resultBytes = hashAlgorithm.ComputeHash(phraseBytes);
return string.Concat(resultBytes.Select(b => b.ToString("x2")));
}
}
private static string ChangeEndianness(string hex)
{
return hex.Substring(6, 2) + hex.Substring(4, 2) + hex.Substring(2, 2) + hex.Substring(0, 2);
}
private static string ToString(PhraseSet phrase, int offset)
{
return Encoding.ASCII.GetString(phrase.GetBytes(offset));
}
private static IEnumerable<byte[]> ReadInput()
{
string line;
while ((line = Console.ReadLine()) != null)
{
yield return Encoding.ASCII.GetBytes(line);
}
}
private static string ToOrderedChars(string source)
{
return new string(source.Where(ch => ch != ' ').OrderBy(ch => ch).ToArray());
}
#if SINGLE_THREADED
private static void ForAll<T>(this IEnumerable<T> source, Action<T> action)
{
foreach (var entry in source)
{
action(entry);
}
}
#endif
}
}