/// <summary>
/// Delete data from the hash table by key.
/// </summary>
/// <param name="key"> Key. </param>
/// <exception cref="ArgumentNullException"><paramref name="key"/> is <c>null</c>.</exception>
/// <exception cref="ArgumentException"></exception>
public void Delete(TKey key)
{
// Check the input for correctness.
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
if (key.ToString().Length > maxSize)
{
throw new ArgumentException($"The maximum key length is {maxSize} characters.", nameof(key));
}
// Get a key hash.
int hash = GetHash(key);
// If the value with this hash is not in the table, then terminate the method.
if (!items.ContainsKey(hash))
{
return;
}
// Get a collection of elements by key hash.
List <OpenHashingItem <TKey, TValue> > hashTableItem = items[hash];
// Get a collection item by key.
OpenHashingItem <TKey, TValue> item = hashTableItem.SingleOrDefault(i => i.Key.Equals(key));
// If a collection item is found, delete it from the collection.
if (item != null)
{
hashTableItem.Remove(item);
}
}
/// <summary>
/// Add data to the hash table.
/// </summary>
/// <param name="key"> Stored data key. </param>
/// <param name="value"> Stored data. </param>
/// <exception cref="ArgumentNullException"></exception>
/// <exception cref="ArgumentException"></exception>
public void Insert(TKey key, TValue value)
{
// Check the input for correctness.
if (key == null || value == null)
{
throw new ArgumentNullException(nameof(key), nameof(value));
}
if (key.ToString().Length > maxSize)
{
throw new ArgumentException($"The maximum key length is {maxSize} characters.", nameof(key));
}
// Create a new copy of the data.
OpenHashingItem <TKey, TValue> item = new OpenHashingItem <TKey, TValue>(key, value);
// Get a key hash.
int hash = GetHash(item.Key);
// Get a collection of items with the same key hash.
List <OpenHashingItem <TKey, TValue> > hashTableItem = null;
// If the collection is not empty, then values with such a hash already exist.
if (items.ContainsKey(hash))
{
// Get a hash table element.
hashTableItem = items[hash];
// Check the value inside the collection with the received key.
OpenHashingItem <TKey, TValue> oldElementWithKey = hashTableItem.SingleOrDefault(i => i.Key.Equals(item.Key));
// If such an element is found, we report an error.
if (oldElementWithKey != null)
{
throw new ArgumentException($"The hash table already contains an element with a key {key}. The key must be unique.", nameof(key));
}
// Add a data item to the hash table item collection.
items[hash].Add(item);
}
// Else the collection is empty, so there were no values with such a key hash before
else
{
// Create a new collection.
hashTableItem = new List <OpenHashingItem <TKey, TValue> >()
{
item
};
// Add data to the table.
items.Add(hash, hashTableItem);
}
}
/// <summary>
/// Search for a value by key.
/// </summary>
/// <param name="key"> Key. </param>
/// <returns> Stored data found by key. </returns>
/// <exception cref="ArgumentNullException"><paramref name="key"/> is <c>null</c>.</exception>
/// <exception cref="ArgumentException"></exception>
public string Search(TKey key)
{
// Check the input for correctness.
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
if (key.ToString().Length > maxSize)
{
throw new ArgumentException($"The maximum key length is {maxSize} characters.", nameof(key));
}
// Get a key hash.
int hash = GetHash(key);
// If the table does not contain such hash, we finish execution of a method having returned null.
if (!items.ContainsKey(hash))
{
return(null);
}
// Get a collection of elements by key hash.
List <OpenHashingItem <TKey, TValue> > hashTableItem = items[hash];
// If a hash is found, then look for the value in the collection by key.
if (hashTableItem != null)
{
// Get a collection item by key.
OpenHashingItem <TKey, TValue> item = hashTableItem.SingleOrDefault(i => i.Key.Equals(key));
// If a collection item is found, we return the stored data.
if (item != null)
{
return(item.Value.ToString());
}
}
// We return null if nothing is found.
return(null);
}
