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TrustPilotChallenge/dotnet/WhiteRabbit/PhraseSet.cs

71 lines
2.6 KiB

namespace WhiteRabbit
{
using System.Diagnostics;
// Anagram representation optimized for MD5
internal unsafe struct PhraseSet
{
public fixed long Buffer[4 * Constants.PhrasesPerSet];
public PhraseSet(Word[] words, int[][] permutations, int offset, int numberOfCharacters)
{
Debug.Assert(numberOfCharacters + words.Length - 1 < 27);
fixed (long* bufferPointer = this.Buffer)
{
long* longBuffer = (long*)bufferPointer;
int numberOfWords = words.Length;
for (var i = 0; i < Constants.PhrasesPerSet; i++)
{
var permutation = permutations[offset + i];
var cumulativeWordOffsetX4 = 0;
for (var j = 0; j < numberOfWords; j++)
{
var currentWord = words[permutation[j]];
longBuffer[0] |= currentWord.Buffers[cumulativeWordOffsetX4 + 0];
longBuffer[1] |= currentWord.Buffers[cumulativeWordOffsetX4 + 1];
longBuffer[2] ^= currentWord.Buffers[cumulativeWordOffsetX4 + 2];
longBuffer[3] ^= currentWord.Buffers[cumulativeWordOffsetX4 + 3];
cumulativeWordOffsetX4 += currentWord.LengthX4;
}
longBuffer += 4;
}
var length = numberOfCharacters + numberOfWords - 1;
byte* byteBuffer = ((byte*)bufferPointer) + length;
for (var i = 0; i < Constants.PhrasesPerSet; i++)
{
*byteBuffer = 128;
byteBuffer += 32;
}
var lengthInBits = (uint)(length << 3);
uint* uintBuffer = ((uint*)bufferPointer) + 7;
for (var i = 0; i < Constants.PhrasesPerSet; i++)
{
*uintBuffer = lengthInBits;
uintBuffer += 8;
}
}
}
public byte[] GetBytes(int number)
{
Debug.Assert(number < Constants.PhrasesPerSet);
fixed(long* bufferPointer = this.Buffer)
{
var phrasePointer = bufferPointer + 4 * number;
var length = ((uint*)phrasePointer)[7] >> 3;
var result = new byte[length];
for (var i = 0; i < length; i++)
{
result[i] = ((byte*)phrasePointer)[i];
}
return result;
}
}
}
}