/// <summary>
/// Initializes hashtable with given equality comparer of T and capacity equal to smallest prime number bigger than provided value.
/// </summary>
public HashTable(int capacity, EqualityComparer <T> equalityComparer)
{
if (equalityComparer == null)
{
throw new ArgumentNullException("Comparer is null");
}
this.equalityComparer = equalityComparer;
if (capacity < 0)
{
throw new ArgumentException("Capacity can't be negative");
}
// set buckets capacity to next smallest prime
if (capacity < 17)
{
capacity = 17;
}
else
{
ulong cap = NumericAlgorithms.FindNextPrime((ulong)capacity);
capacity = cap > int.MaxValue ? int.MaxValue : (int)cap; //int.MaxValue is prime
}
bucketsCapacity = capacity;
buckets = new LinkedList <T> [bucketsCapacity];
}
/// <summary>
/// Initializes hashtable with given equality comparer and capacity equal to smallest prime number bigger than collection.count
/// </summary>
public HashTable(IEnumerable <T> collection, EqualityComparer <T> equalityComparer)
{
if (equalityComparer == null)
{
throw new ArgumentNullException("Comparer is null");
}
this.equalityComparer = equalityComparer;
// set buckets capacity to next smallest prime
if (collection == null)
{
throw new ArgumentNullException("Collection is null");
}
if (collection is IList <T> )
{
bucketsCapacity = (collection as IList <T>).Count;
}
else
{
int cap = 0;
foreach (var item in collection)
{
cap++;
}
bucketsCapacity = cap;
}
if (bucketsCapacity < 17)
{
bucketsCapacity = 17;
}
else
{
ulong cap = NumericAlgorithms.FindNextPrime((ulong)bucketsCapacity);
bucketsCapacity = cap > int.MaxValue ? int.MaxValue : (int)cap; //int.MaxValue is prime
}
buckets = new LinkedList <T> [bucketsCapacity];
// add collection elements to hashtable
foreach (var item in collection)
{
this.Add(item);
}
}
/// <summary>
/// Adds new item to hashtable. Might cause a reallocation.
/// </summary>
public void Add(T item)
{
int hashCode = equalityComparer.GetHashCode(item);
int bucketIndex = hashCode % bucketsCapacity;
if (buckets[bucketIndex] == null)
{
buckets[bucketIndex] = new LinkedList <T>();
bucketsCount++;
}
buckets[bucketIndex].Add(item);
elementsCount++;
//-------------------------- reallocate the buckets collection if required
// get new bucket capacity if required
if (LoadFactor <= MaxLoadFactor)
{
return;
}
ulong newBucketsCapacity = 17;
if (bucketsCapacity < int.MaxValue / 2)
{
newBucketsCapacity = (ulong)bucketsCapacity * 2;
newBucketsCapacity = NumericAlgorithms.FindNextPrime((ulong)newBucketsCapacity);
}
else
{
newBucketsCapacity = int.MaxValue; //its prime
}
// for each value in hash table get new index in new reallocated array, copy that value and count new buckets
var newBuckets = new LinkedList <T> [newBucketsCapacity];
int newBucketsCount = 0;
for (int i = 0; i < buckets.Length; i++)
{
if (buckets[i] != null)
{
var list = buckets[i];
if (list.Count != 0)
{
foreach (T value in list)
{
hashCode = equalityComparer.GetHashCode(value);
int newBucketIndex = hashCode % (int)newBucketsCapacity;
if (newBuckets[newBucketIndex] == null)
{
newBuckets[newBucketIndex] = new LinkedList <T>();
newBucketsCount++;
}
newBuckets[newBucketIndex].Add(value);
}
}
}
}
// copy new values
buckets = newBuckets;
bucketsCapacity = (int)newBucketsCapacity;
bucketsCount = newBucketsCount;
}
