/// <summary>
/// Method used for decompression of a compressed suffix array based on Delta encoding algorithm.
/// This method is also using method which generates suffix array from Psi function.
/// See <see cref="PsiFunction.PsiToSA(int[])"/>.
/// </summary>
/// <param name="delta">Dictionary of compressed values divided by characters from the original input.</param>
/// <param name="length">Length of the original input.</param>
/// <returns>Suffix array.</returns>
public static int[] DecompressDeltaEncoding(Dictionary <char, List <Int16> > delta, int length)
{
int[] psi = new int[length];
psi[0] = -1;
int j = 1;
foreach (var key in delta.Keys)
{
psi[j++] = Convert.ToInt32(delta[key][0]);
for (int i = 1; i < delta[key].Count; i++)
{
psi[j] = Convert.ToInt32(delta[key][i]) + psi[j - 1];
j++;
}
}
return(PsiFunction.PsiToSA(psi));
}
/// <summary>
/// Method used for decompression of list of byte arrays based on Elias-Fano algorithm.
/// </summary>
/// <param name="eliasFano">List of byte arrays. Result of Elias-Fano compression.</param>
/// <param name="bitLengthOfSeq">List of values that represent length of resulting bit sequences by increasing sequences.</param>
/// <param name="bitLengthOfOrigParts">List of integer arrays containing information about length of leading and lower bit sequences.</param>
/// <returns>Suffix array.</returns>
public static int[] DecompressEliasFano(List <byte[]> eliasFano, List <int> bitLengthOfSeq, List <int[]> bitLengthOfOrigParts)
{
int highLowBitsSeam = 0;
List <int> sequence;
List <int> psi = new List <int>();
psi.Insert(0, -1);
int k = 1;
for (int i = 0; i < eliasFano.Count; i++)
{
bool[] bitArray = ByteToBit(eliasFano[i], bitLengthOfSeq[i]);
highLowBitsSeam = GetHigherLowerBitsSeam(bitArray, bitLengthOfOrigParts[i][0]);
List <bool[]> leadingBits = GenerateLeadingBits(bitArray, highLowBitsSeam, bitLengthOfOrigParts[i][0]);
List <bool[]> lowerBits = GenerateLowerBits(bitArray, highLowBitsSeam, bitLengthOfOrigParts[i][1]);
if (bitLengthOfOrigParts[i][1] == 0)
{
sequence = new List <int>();
int index = 0;
foreach (var item in leadingBits)
{
sequence.Insert(index, GetNumberFromBits(item));
index++;
}
}
else
{
sequence = GenerateSequence(leadingBits, lowerBits);
}
foreach (var el in sequence)
{
psi.Insert(k, el);
k++;
}
}
return(PsiFunction.PsiToSA(psi.ToArray()));
}
