package org.limewire.collection;
import java.util.Map;
import java.util.SortedMap;
/**
* Defines the interface for a prefix tree, an ordered tree data structure. For
* more information, see <a href= "http://en.wikipedia.org/wiki/Trie">Tries</a>.
*
* @author Roger Kapsi
* @author Sam Berlin
*/
public interface Trie<K, V> extends SortedMap<K, V> {
/**
* Returns a view of this Trie of all elements that are
* prefixed by the given key.
* <p>
* In a fixed-keysize Trie, this is essentially a 'get' operation.
* <p>
* For example, if the Trie contains 'Lime', 'LimeWire',
* 'LimeRadio', 'Lax', 'Later', 'Lake', and 'Lovely', then
* a lookup of 'Lime' would return 'Lime', 'LimeRadio', and 'LimeWire'.
*/
public SortedMap<K, V> getPrefixedBy(K key);
/**
* Returns a view of this Trie of all elements that are
* prefixed by the length of the key.
* <p>
* Fixed-keysize Tries will not support this operation
* (because all keys will be the same length).
* <p>
* For example, if the Trie contains 'Lime', 'LimeWire',
* 'LimeRadio', 'Lax', 'Later', 'Lake', and 'Lovely', then
* a lookup of 'LimePlastics' with a length of 4 would
* return 'Lime', 'LimeRadio', and 'LimeWire'.
*/
public SortedMap<K, V> getPrefixedBy(K key, int length);
/**
* Returns a view of this Trie of all elements that are prefixed
* by the key, starting at the given offset and for the given length.
* <p>
* Fixed-keysize Tries will not support this operation
* (because all keys are the same length).
* <p>
* For example, if the Trie contains 'Lime', 'LimeWire',
* 'LimeRadio', 'Lax', 'Later', 'Lake', and 'Lovely', then
* a lookup of 'The Lime Plastics' with an offset of 4 and a
* length of 4 would return 'Lime', 'LimeRadio', and 'LimeWire'.
*/
public SortedMap<K, V> getPrefixedBy(K key, int offset, int length);
/**
* Returns a view of this Trie of all elements that are prefixed
* by the number of bits in the given Key.
* <p>
* Fixed-keysize Tries can support this operation as a way to do
* lookups of partial keys. That is, if the Trie is storing IP
* addresses, you can lookup all addresses that begin with
* '192.168' by providing the key '192.168.X.X' and a length of 16
* would return all addresses that begin with '192.168'.
*/
public SortedMap<K, V> getPrefixedByBits(K key, int bitLength);
/**
* Returns the value for the entry whose key is closest in a bitwise
* XOR metric to the given key. This is NOT lexicographic closeness.
* For example, given the keys:<p>
* D = 1000100 <br>
* H = 1001000 <br>
* L = 1001100 <br>
* <p>
* If the Trie contained 'H' and 'L', a lookup of 'D' would return 'L',
* because the XOR distance between D & L is smaller than the XOR distance
* between D & H.
*/
public V select(K key);
/**
* Iterates through the Trie, starting with the entry whose bitwise
* value is closest in an XOR metric to the given key. After the closest
* entry is found, the Trie will call select on that entry and continue
* calling select for each entry (traversing in order of XOR closeness,
* NOT lexicographically) until the cursor returns
* <code>Cursor.SelectStatus.EXIT</code>.<p>
* The cursor can return <code>Cursor.SelectStatus.CONTINUE</code> to
* continue traversing.<p>
* <code>Cursor.SelectStatus.REMOVE_AND_EXIT</code> is used to remove the current element
* and stop traversing.
* <p>
* Note: The {@link Cursor.SelectStatus#REMOVE} operation is not supported.
*
* @return The entry the cursor returned EXIT on, or null if it continued
* till the end.
*/
public Map.Entry<K,V> select(K key, Cursor<? super K, ? super V> cursor);
/**
* Traverses the Trie in lexicographical order. <code>Cursor.select</code>
* will be called on each entry.<p>
* The traversal will stop when the cursor returns <code>Cursor.SelectStatus.EXIT</code>.<p>
* <code>Cursor.SelectStatus.CONTINUE</code> is used to continue traversing.<p>
* <code>Cursor.SelectStatus.REMOVE</code> is used to remove the element that was
* selected and continue traversing.<p>
* <code>Cursor.SelectStatus.REMOVE_AND_EXIT</code> is used to remove the current element
* and stop traversing.
*
* @return The entry the cursor returned EXIT on, or null if it continued
* till the end.
*/
public Map.Entry<K,V> traverse(Cursor<? super K, ? super V> cursor);
/**
* An interface used by a {@link Trie}. A {@link Trie} selects items by
* closeness and passes the items to the <code>Cursor</code>. You can then
* decide what to do with the key-value pair and the return value
* from {@link #select(java.util.Map.Entry)} tells the <code>Trie</code>
* what to do next.
* <p>
* <code>Cursor</code> returns status/selection status might be:
* <table cellspace="5">
* <tr><td><b>Return Value</b></td><td><b>Status</b></td></tr>
* <tr><td>EXIT</td><td>Finish the Trie operation</td></tr>
* <tr><td>CONTINUE</td><td>Look at the next element in the traversal</td></tr>
* <tr><td>REMOVE_AND_EXIT</td><td>Remove the entry and stop iterating</td></tr>
* <tr><td>REMOVE</td><td>Remove the entry and continue iterating</td></tr>
* </table>
* <p>
* Note: {@link Trie#select(Object, org.limewire.collection.Trie.Cursor)} does
* not support <code>REMOVE</code>.
*
* @param <K> Key Type
* @param <V> Key Value
*/
public static interface Cursor<K, V> {
/**
* Notification that the Trie is currently looking at the given entry.
* Return <code>EXIT</code> to finish the Trie operation,
* <code>CONTINUE</code> to look at the next entry, <code>REMOVE</code>
* to remove the entry and continue iterating, or
* <code>REMOVE_AND_EXIT</code> to remove the entry and stop iterating.
* Not all operations support <code>REMOVE</code>.
*
*/
public SelectStatus select(Map.Entry<? extends K, ? extends V> entry);
/** The mode during selection. */
public static enum SelectStatus {
EXIT, CONTINUE, REMOVE, REMOVE_AND_EXIT
}
}
}