public class BloomFilter
  {
  private BitArray hashbits;
  private int numKeys;
  private int[] hashKeys;

  public BloomFilter(int tableSize, int nKeys)
  {
  numKeys = nKeys;
  hashKeys = new int[numKeys];
  hashbits = new BitArray(tableSize);
  }

  private int HashString(string s)
  {
  int hash = 0;
  for (int i = 0; i < s.Length; i++)
  {
  hash += s[i];
  hash += (hash << 10);
  hash ^= (hash >> 6);
  }
  hash += (hash << 3);
  hash ^= (hash >> 11);
  hash += (hash << 15);

  return hash;
  }

  private void CreateHashes(string str)
  {
  int hash1 = str.GetHashCode();
  int hash2 = HashString(str);

  hashKeys[0] = Math.Abs(hash1 % hashbits.Count);
  if (numKeys > 1)
  {
  for (int i = 1; i < numKeys; i++)
  {
  hashKeys[i] = Math.Abs((hash1 + (i * hash2))
  % hashbits.Count);
  }
  }
  }
  public bool Contains(string str)
  {
  CreateHashes(str);
  // Test each hash key. Return false if any 
  // one of the bits is not set.
  foreach (int hash in hashKeys)
  {
  if (!hashbits[hash])
  return false;
  }
  // All bits set. The item is there.
  return true;
  }
  public bool Add(string str)
  {
  // Initially assume that the item is in the table
  bool rslt = true;
  CreateHashes(str);
  foreach (int hash in hashKeys)
  {
  if (!hashbits[hash])
  {
  // One of the bits wasn't set, so show that
  // the item wasn't in the table, and set that bit.
  rslt = false;
  hashbits[hash] = true;
  }
  }
  return rslt;
  }