| /* |
| * Copyright 2005-2010 Roger Kapsi, Sam Berlin |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.cassandra.index.sasi.utils.trie; |
| |
| import java.util.Map; |
| import java.util.SortedMap; |
| |
| import org.apache.cassandra.index.sasi.utils.trie.Cursor.Decision; |
| |
| /** |
| * This class is taken from https://github.com/rkapsi/patricia-trie (v0.6), and slightly modified |
| * to correspond to Cassandra code style, as the only Patricia Trie implementation, |
| * which supports pluggable key comparators (e.g. commons-collections PatriciaTrie (which is based |
| * on rkapsi/patricia-trie project) only supports String keys) |
| * but unfortunately is not deployed to the maven central as a downloadable artifact. |
| */ |
| |
| /** |
| * 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 the {@link Map.Entry} whose key is closest in a bitwise XOR |
| * metric to the given key. This is NOT lexicographic closeness. |
| * For example, given the keys: |
| * |
| * <ol> |
| * <li>D = 1000100 |
| * <li>H = 1001000 |
| * <li>L = 1001100 |
| * </ol> |
| * |
| * If the {@link 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. |
| * |
| * @return The {@link Map.Entry} whose key is closest in a bitwise XOR metric |
| * to the provided key. |
| */ |
| Map.Entry<K, V> select(K key); |
| |
| /** |
| * Returns the key that is closest in a bitwise XOR metric to the |
| * provided key. This is NOT lexicographic closeness! |
| * |
| * For example, given the keys: |
| * |
| * <ol> |
| * <li>D = 1000100 |
| * <li>H = 1001000 |
| * <li>L = 1001100 |
| * </ol> |
| * |
| * If the {@link 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. |
| * |
| * @return The key that is closest in a bitwise XOR metric to the provided key. |
| */ |
| @SuppressWarnings("unused") |
| K selectKey(K key); |
| |
| /** |
| * Returns the value whose key is closest in a bitwise XOR metric to |
| * the provided key. This is NOT lexicographic closeness! |
| * |
| * For example, given the keys: |
| * |
| * <ol> |
| * <li>D = 1000100 |
| * <li>H = 1001000 |
| * <li>L = 1001100 |
| * </ol> |
| * |
| * If the {@link 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. |
| * |
| * @return The value whose key is closest in a bitwise XOR metric |
| * to the provided key. |
| */ |
| @SuppressWarnings("unused") |
| V selectValue(K key); |
| |
| /** |
| * Iterates through the {@link 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 {@link 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 {@link Decision#EXIT}. |
| * |
| * <p>The cursor can return {@link Decision#CONTINUE} to continue traversing. |
| * |
| * <p>{@link Decision#REMOVE_AND_EXIT} is used to remove the current element |
| * and stop traversing. |
| * |
| * <p>Note: The {@link Decision#REMOVE} operation is not supported. |
| * |
| * @return The entry the cursor returned {@link Decision#EXIT} on, or null |
| * if it continued till the end. |
| */ |
| Map.Entry<K,V> select(K key, Cursor<? super K, ? super V> cursor); |
| |
| /** |
| * Traverses the {@link Trie} in lexicographical order. |
| * {@link Cursor#select(java.util.Map.Entry)} will be called on each entry. |
| * |
| * <p>The traversal will stop when the cursor returns {@link Decision#EXIT}, |
| * {@link Decision#CONTINUE} is used to continue traversing and |
| * {@link Decision#REMOVE} is used to remove the element that was selected |
| * and continue traversing. |
| * |
| * <p>{@link Decision#REMOVE_AND_EXIT} is used to remove the current element |
| * and stop traversing. |
| * |
| * @return The entry the cursor returned {@link Decision#EXIT} on, or null |
| * if it continued till the end. |
| */ |
| Map.Entry<K,V> traverse(Cursor<? super K, ? super V> cursor); |
| |
| /** |
| * Returns a view of this {@link Trie} of all elements that are prefixed |
| * by the given key. |
| * |
| * <p>In a {@link Trie} with fixed size keys, this is essentially a |
| * {@link #get(Object)} operation. |
| * |
| * <p>For example, if the {@link Trie} contains 'Anna', 'Anael', |
| * 'Analu', 'Andreas', 'Andrea', 'Andres', and 'Anatole', then |
| * a lookup of 'And' would return 'Andreas', 'Andrea', and 'Andres'. |
| */ |
| SortedMap<K, V> prefixMap(K prefix); |
| } |