/// <summary>
/// This operation will grow the inner array and sweep up deleted nodes
/// This is an expensive operation that we should minimize the usage of if possible
/// </summary>
/// <returns></returns>
protected void GrowInnerArray()
{
var oldNodes = InnerArray;
int newArraySize;
if (PrimeNumberEnumerator.MoveNext() != false)
{
newArraySize = (int)PrimeNumberEnumerator.Current;
}
else
{
throw new ArgumentOutOfRangeException("The ODDictionary has reached its maximum capacity.");
}
InnerArray = new ODDictionaryNode <TKey, TValue> [newArraySize];
foreach (var node in oldNodes)
{
if (node != null && node.IsDeleted == false)
{
// get the initial probe value
int keyLocation = GetIndexForKey(node.Key);
// confirm that key is not present and get first available insert location
bool keyAlreadyPresent;
keyLocation = FirstAvailable(keyLocation, node.Key, out keyAlreadyPresent);
//we don't need to worry about keyAlreadyPresent because we're repopulating a new array
InnerArray[keyLocation] = node;
}
}
}
/// <summary>
/// Finds the first available non-key location in the index to perform an insert. Or the key location if it is already present.
/// Instead of an out parameter, throw could be used, but in this case, finding a key is to be expected, and try/catch should not be used
/// for control flow.
/// </summary>
/// <param name="keyLocation">Starting index to probe</param>
/// <param name="key">The to be inserted</param>
/// <param name="keyAlreadyPresent">Outpool boolean, flag is true is the key is already present</param>
/// <returns>Location to perform insert or the location of the key if already present</returns>
protected int FirstAvailable(int keyLocation, TKey key, out bool keyAlreadyPresent)
{
ODDictionaryNode <TKey, TValue> currentNode = InnerArray[keyLocation];
int firstGoodLocation = -1;
keyAlreadyPresent = false;
// probe the values, if it's null we're good
while (currentNode != null)
{
// We found an indentical key, insert is not logically possible, stop searching
if (currentNode.Key.Equals(key) && !currentNode.IsDeleted)
{
keyAlreadyPresent = true;
break;
}
// we found a deleted location, remember it for later to use it
if (currentNode.IsDeleted && firstGoodLocation == -1)
{
firstGoodLocation = keyLocation;
}
keyLocation = (keyLocation + 1) % InnerArray.Length;
currentNode = InnerArray[keyLocation];
}
// if we didn't find the key, but we found a first location that's prior to our first null, then return that.
if (!keyAlreadyPresent && firstGoodLocation != -1)
{
keyLocation = firstGoodLocation;
}
return(keyLocation);
}
private bool OptimisticConcurrencyControl; // simple control to detect concurrency exceptions rather than locking resources
public ODDictionary()
{
PrimeNumberEnumerator = SetPrimeNumbers();
PrimeNumberEnumerator.MoveNext();
CurrentSize = 0;
InnerArray = new ODDictionaryNode <TKey, TValue> [(int)PrimeNumberEnumerator.Current];
EnumeratorsToInvalidate = new List <ODDictionaryEnumerator <TKey, TValue> >();
OptimisticConcurrencyControl = false;
}
/// <summary>
/// Allows the user to set the initial value of the inner array
/// </summary>
/// <param name="initialArraySize">Int32 for the size of the inner array</param>
public ODDictionary(int initialArraySize)
{
PrimeNumberEnumerator = SetPrimeNumbers();
while (PrimeNumberEnumerator.MoveNext() != false)
{
// next grow will be at least initialArraySize *2
if ((int)PrimeNumberEnumerator.Current > (initialArraySize * 2))
{
break;
}
}
CurrentSize = 0;
InnerArray = new ODDictionaryNode <TKey, TValue> [initialArraySize];
EnumeratorsToInvalidate = new List <ODDictionaryEnumerator <TKey, TValue> >();
OptimisticConcurrencyControl = false;
}
/// <summary>
/// Add a Key/Value pair to the collection. Throws exception if key already present.
/// </summary>
/// <param name="key">Key to be used for retrieval, may not be null</param>
/// <param name="value">Value to be returned on retrieval</param>
public void Add(TKey key, TValue value)
{
// check concurrency control
if (OptimisticConcurrencyControl == true)
{
throw new Exception("Optimistic concurrency control violated");
}
// set control
OptimisticConcurrencyControl = true;
// validation
if (key == null || value == null)
{
OptimisticConcurrencyControl = false;
throw new ArgumentNullException("Neither key nor value may be null.");
}
// To minimize collisions, we will grow the collection when it is half full
if (CurrentSize > InnerArray.Length / 2)
{
GrowInnerArray();
}
// get the initial probe value
int keyLocation = GetIndexForKey(key);
// confirm that key is not present and get first available insert location
bool keyAlreadyPresent;
keyLocation = FirstAvailable(keyLocation, key, out keyAlreadyPresent);
if (keyAlreadyPresent)
{
OptimisticConcurrencyControl = false;
throw new ArgumentException("An item with the same key has already been added.");
}
var odDictionaryNode = new ODDictionaryNode <TKey, TValue>(key, value);
InnerArray[keyLocation] = odDictionaryNode;
OptimisticConcurrencyControl = false; // release control
InvalidateEnumerators();
CurrentSize++;
}
/// <summary>
/// The find & return method. Specify a key and get the return value requested or set value.
/// </summary>
/// <param name="key"></param>
/// <returns></returns>
public TValue this[TKey key]
{
get
{
// check concurrency control
if (OptimisticConcurrencyControl == true)
{
throw new Exception("Optimistic concurrency control violated");
}
OptimisticConcurrencyControl = true;
// validation
if (key == null)
{
OptimisticConcurrencyControl = false;
throw new ArgumentNullException("Key may not be null.");
}
int keyLocation = GetIndexForKey(key);
// Find the key
bool keyAlreadyPresent;
keyLocation = FirstAvailable(keyLocation, key, out keyAlreadyPresent);
if (!keyAlreadyPresent)
{
OptimisticConcurrencyControl = false;
throw new KeyNotFoundException("The given key was not present in the dictionary.");
}
var value = InnerArray[keyLocation].Value;
OptimisticConcurrencyControl = false;
return(value);
}
set
{
// check concurrency control
if (OptimisticConcurrencyControl == true)
{
throw new Exception("Optimistic concurrency control violated");
}
OptimisticConcurrencyControl = true;
int keyLocation = GetIndexForKey(key);
// Find the key
bool keyAlreadyPresent;
keyLocation = FirstAvailable(keyLocation, key, out keyAlreadyPresent);
// if it's not yet in the dictionary, add it
if (!keyAlreadyPresent)
{
var odDictionaryNode = new ODDictionaryNode <TKey, TValue>(key, value);
InnerArray[keyLocation] = odDictionaryNode;
CurrentSize++;
OptimisticConcurrencyControl = false;
}
else
{
// else just update the value
InnerArray[keyLocation].Value = value;
OptimisticConcurrencyControl = false;
}
InvalidateEnumerators();
}
}
