//credits: https://stackoverflow.com/a/14354311/4499267
public static int GetCardinality(this BitArray bitArray)
{
bitArray.AssertNotNull("bitArray");
int[] ints = new int[(bitArray.Count >> 5) + 1];
bitArray.CopyTo(ints, 0);
int count = 0;
// fix for not truncated bits in last integer that may have been set to true with SetAll()
ints[ints.Length - 1] &= ~(-1 << (bitArray.Count % 32));
for (int i = 0; i < ints.Length; i++)
{
int c = ints[i];
// magic (http://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel)
unchecked
{
c = c - ((c >> 1) & 0x55555555);
c = (c & 0x33333333) + ((c >> 2) & 0x33333333);
c = ((c + (c >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
}
count += c;
}
return(count);
}
//credits: https://stackoverflow.com/a/37072636/4499267
public static int IndexOfMaxSignificantBit(this BitArray array)
{
array.AssertNotNull("array");
int[] intArray = (int[])array.GetType().GetField("m_array", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic).GetValue(array);
int pos = -1;
int maxPos = -1;
for (int j = 0; j < intArray.Length; ++j)
{
var b = intArray[j];
if (b != 0)
{
pos = 31;
for (int bit = 31; bit >= 0; --bit)
{
if ((b & (1 << bit)) != 0)
{
break;
}
pos--;
}
}
maxPos = Math.Max(maxPos, pos);
}
return(maxPos);
}
public static bool[] ToArray(this BitArray bitArray)
{
bitArray.AssertNotNull("bitArray");
bool[] bits = new bool[bitArray.Count];
bitArray.CopyTo(bits, 0);
return(bits);
}
public static BitArray ToMaxSignificantBits(this BitArray bitArray, out int maxSignificantBit)
{
bitArray.AssertNotNull("bitArray");
maxSignificantBit = bitArray.IndexOfMaxSignificantBit();
IList <bool> list = new List <bool>();
for (int j = 0; j < bitArray.Length; j += 32)
{
for (int i = j; i < (j + 32); ++i)
{
if (i <= (maxSignificantBit + j))
{
list.Add(bitArray[i]);
}
}
}
return(new BitArray(list.ToArray()));
}
