/// <summary>
/// Capacity specifies the initial size of the StringDictionary. The StringDictionary grows too accomodate more entries as they are added.
/// </summary>
/// <param name="capacity"></param>
public StringDictionary(int capacity)
{
_capacity = (capacity > _minCapacity ? GetNextCapacity(capacity) : _minCapacity);
_capacityLess1 = _capacity - 1;
// Minimum capacity of StringDictionary = 1024 entries
_entries = new StringDictionaryEntry <T> [_capacity];
// Initialize the space map
_spaceMap = new BitArray(_capacity);
}
/// <summary>
/// This methods adds a given Key value pair to the StringDictionary. Keys need to be unique. Values need not be unique.
/// Complexity Average Case: O(log((n + 1/)n)), Worst Case: O(n)
/// </summary>
/// <param name="key"></param>
/// <param name="keyValue"></param>
public void Add(string key, T keyValue)
{
//GetHashCodes(key, out hashA, out hashB);
uint hashA = 0, hashB = 0;
for (int i = 0; i < key.Length; i++)
{
hashA = ((hashA << 5) + hashA ^ (uint)key[i]);
hashB = ((hashB << 6) + (hashB << 16) - hashB + (uint)key[i]);
}
uint hash;
bool inserted = false;
lock (_syncRoot)
{
for (int i = 0; i < _numHashes; i++)
{
hash = hashA + _primes[i] * hashB;
if (!_spaceMap[(int)(hash & _capacityLess1)])
{
_entries[hash & _capacityLess1] = new StringDictionaryEntry <T>(hashA, hashB, keyValue);
inserted = true;
_spaceMap[(int)(hash & (_capacityLess1))] = true;
break;
}
}
if (!inserted)
{
while (!inserted)
{
Resize();
for (int i = 0; i < _numHashes; i++)
{
hash = hashA + _primes[i] * hashB;
if (!_spaceMap[(int)(hash & _capacityLess1)])
{
_entries[hash & _capacityLess1] = new StringDictionaryEntry <T>(hashA, hashB, keyValue);
inserted = true;
_spaceMap[(int)(hash & _capacityLess1)] = true;
break;
}
}
}
}
Count++;
}
}
///// <summary>
///// Determines whether a given key exists in the StringDictionary.
///// Complexity O(1)
///// </summary>
///// <param name="key"></param>
///// <returns></returns>
//public bool Remove(string key)
//{
// //GetHashCodes(key, out hashA, out hashB);
// uint hashA = 0, hashB = 0;
// for (int i = 0; i < key.Length; i++)
// {
// hashA = ((hashA << 5) + hashA ^ (uint)key[i]);
// hashB = ((hashB << 6) + (hashB << 16) - hashB + (uint)key[i]);
// }
// int index;
// uint hash;
// lock (_syncRoot)
// {
// for (int i = 0; i < _numHashes; i++)
// {
// hash = hashA + _primes[i] * hashB;
// index = (int)(hash & _capacityLess1);
// if (!_spaceMap[index])
// {
// break;
// }
// else if (_entries[index].HashA == hashA && _entries[index].HashB == hashB)
// {
// _entries[index] = null;
// _spaceMap[index] = false;
// return true;
// }
// }
// }
// return false;
//}
/// <summary>
/// The number of hashes to generate for insertions / lookups in the StringDictionary.
/// The default value is 31. Possible values range from 5 to 277 inclusive. A lower value leads to greater performance at the cost of a low load factor.
/// A higher value leads to lesser performance but higher load factor.
/// </summary>
//public int NumHashes
//{
// get { return _numHashes; }
// set { _numHashes = ((value < 16) && (value > 278) ? value : 31); }
//}
// Indexer
//public T this[string key]
//{
// get
// {
// //int index;
// //if ((index = ContainsKeyInternal(key)) >= 0)
// // return _entries[index].Value;
// //else
// // return default(T);
// return this.GetContainsKey(key);
// }
// //set
// //{
// // int index;
// // if ((index = ContainsKeyInternal(key)) >= 0)
// // _entries[index].Value = value;
// // else
// // throw new KeyNotFoundException("Key not found. Key: " + key);
// //}
//}
#endregion
#region Utility Functions
/// <summary>
///// The internal method used by ContainsKey(string) method.
///// </summary>
///// <param name="key"></param>
///// <returns></returns>
//private int ContainsKeyInternal(string key)
//{
// uint hashA, hashB;
// uint hash;
// GetHashCodes(key, out hashA, out hashB);
// for (int i = 0; i < _numHashes; i++)
// {
// hash = hashA + _primes[i] * hashB;
// if (!_spaceMap[(int)(hash & _capacityLess1)])
// break;
// else if (_entries[hash & _capacityLess1].HashA == hashA && _entries[hash & _capacityLess1].HashB == hashB)
// return (int)(hash & _capacityLess1);
// }
// return -1;
//}
/// <summary>
/// The internal method called to resize the _entries array.
/// Complexity O(n)
/// </summary>
private void Resize()
{
start:
_capacity = _capacity << 1;
_capacityLess1 = _capacity - 1;
StringDictionaryEntry <T>[] newEntries = new StringDictionaryEntry <T> [_capacity];
BitArray newSpaceMap = new BitArray(_capacity);
uint hash;
for (int i = 0; i < _entries.Length; i++)
{
if (_spaceMap[i])
{
//for (int j = 0; j < _numHashes; j++)
//{
// hash = _entries[i].HashA + _primes[j] * _entries[i].HashB;
// if (! newSpaceMap[(int)(hash & _capacityLess1)])
// {
// newEntries[hash & _capacityLess1] = _entries[i];
// newSpaceMap[(int)(hash & _capacityLess1)] = true;
// break;
// }
//}
bool rehashed = false;
for (int j = 0; j < _numHashes; j++)
{
hash = _entries[i].HashA + _primes[j] * _entries[i].HashB;
if (!newSpaceMap[(int)(hash & _capacityLess1)])
{
newEntries[hash & _capacityLess1] = _entries[i];
newSpaceMap[(int)(hash & _capacityLess1)] = true;
rehashed = true;
break;
}
}
if (!rehashed)
{
//Debug.Assert(false, "rehash goto accured.");
goto start;
}
}
}
_entries = newEntries;
_spaceMap = newSpaceMap;
}
