com.groupbyinc.common.apache.commons.collections4.trie.AbstractPatriciaTrie Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.commons.collections4.trie;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.SortedMap;
import org.apache.commons.collections4.OrderedMapIterator;
/**
* This class implements the base PATRICIA algorithm and everything that
* is related to the {@link Map} interface.
*
* @since 4.0
* @version $Id: AbstractPatriciaTrie.java 1648941 2015-01-01 21:10:46Z tn $
*/
abstract class AbstractPatriciaTrie extends AbstractBitwiseTrie {
private static final long serialVersionUID = 5155253417231339498L;
/** The root node of the {@link Trie}. */
private transient TrieEntry root = new TrieEntry(null, null, -1);
/**
* Each of these fields are initialized to contain an instance of the
* appropriate view the first time this view is requested. The views are
* stateless, so there's no reason to create more than one of each.
*/
private transient volatile Set keySet;
private transient volatile Collection values;
private transient volatile Set> entrySet;
/** The current size of the {@link Trie}. */
private transient int size = 0;
/**
* The number of times this {@link Trie} has been modified.
* It's used to detect concurrent modifications and fail-fast the {@link Iterator}s.
*/
protected transient int modCount = 0;
protected AbstractPatriciaTrie(final KeyAnalyzer keyAnalyzer) {
super(keyAnalyzer);
}
/**
* Constructs a new {@link org.apache.commons.collections4.Trie Trie} using the given
* {@link KeyAnalyzer} and initializes the {@link org.apache.commons.collections4.Trie Trie}
* with the values from the provided {@link Map}.
*/
protected AbstractPatriciaTrie(final KeyAnalyzer keyAnalyzer,
final Map map) {
super(keyAnalyzer);
putAll(map);
}
//-----------------------------------------------------------------------
@Override
public void clear() {
root.key = null;
root.bitIndex = -1;
root.value = null;
root.parent = null;
root.left = root;
root.right = null;
root.predecessor = root;
size = 0;
incrementModCount();
}
@Override
public int size() {
return size;
}
/**
* A helper method to increment the {@link Trie} size and the modification counter.
*/
void incrementSize() {
size++;
incrementModCount();
}
/**
* A helper method to decrement the {@link Trie} size and increment the modification counter.
*/
void decrementSize() {
size--;
incrementModCount();
}
/**
* A helper method to increment the modification counter.
*/
private void incrementModCount() {
++modCount;
}
@Override
public V put(final K key, final V value) {
if (key == null) {
throw new NullPointerException("Key cannot be null");
}
final int lengthInBits = lengthInBits(key);
// The only place to store a key with a length
// of zero bits is the root node
if (lengthInBits == 0) {
if (root.isEmpty()) {
incrementSize();
} else {
incrementModCount();
}
return root.setKeyValue(key, value);
}
final TrieEntry found = getNearestEntryForKey(key, lengthInBits);
if (compareKeys(key, found.key)) {
if (found.isEmpty()) { // <- must be the root
incrementSize();
} else {
incrementModCount();
}
return found.setKeyValue(key, value);
}
final int bitIndex = bitIndex(key, found.key);
if (!KeyAnalyzer.isOutOfBoundsIndex(bitIndex)) {
if (KeyAnalyzer.isValidBitIndex(bitIndex)) { // in 99.999...9% the case
/* NEW KEY+VALUE TUPLE */
final TrieEntry t = new TrieEntry(key, value, bitIndex);
addEntry(t, lengthInBits);
incrementSize();
return null;
} else if (KeyAnalyzer.isNullBitKey(bitIndex)) {
// A bits of the Key are zero. The only place to
// store such a Key is the root Node!
/* NULL BIT KEY */
if (root.isEmpty()) {
incrementSize();
} else {
incrementModCount();
}
return root.setKeyValue(key, value);
} else if (KeyAnalyzer.isEqualBitKey(bitIndex)) {
// This is a very special and rare case.
/* REPLACE OLD KEY+VALUE */
if (found != root) {
incrementModCount();
return found.setKeyValue(key, value);
}
}
}
throw new IllegalArgumentException("Failed to put: " + key + " -> " + value + ", " + bitIndex);
}
/**
* Adds the given {@link TrieEntry} to the {@link Trie}.
*/
TrieEntry addEntry(final TrieEntry entry, final int lengthInBits) {
TrieEntry current = root.left;
TrieEntry path = root;
while(true) {
if (current.bitIndex >= entry.bitIndex
|| current.bitIndex <= path.bitIndex) {
entry.predecessor = entry;
if (!isBitSet(entry.key, entry.bitIndex, lengthInBits)) {
entry.left = entry;
entry.right = current;
} else {
entry.left = current;
entry.right = entry;
}
entry.parent = path;
if (current.bitIndex >= entry.bitIndex) {
current.parent = entry;
}
// if we inserted an uplink, set the predecessor on it
if (current.bitIndex <= path.bitIndex) {
current.predecessor = entry;
}
if (path == root || !isBitSet(entry.key, path.bitIndex, lengthInBits)) {
path.left = entry;
} else {
path.right = entry;
}
return entry;
}
path = current;
if (!isBitSet(entry.key, current.bitIndex, lengthInBits)) {
current = current.left;
} else {
current = current.right;
}
}
}
@Override
public V get(final Object k) {
final TrieEntry entry = getEntry(k);
return entry != null ? entry.getValue() : null;
}
/**
* Returns the entry associated with the specified key in the
* PatriciaTrieBase. Returns null if the map contains no mapping
* for this key.
*
* This may throw ClassCastException if the object is not of type K.
*/
TrieEntry getEntry(final Object k) {
final K key = castKey(k);
if (key == null) {
return null;
}
final int lengthInBits = lengthInBits(key);
final TrieEntry entry = getNearestEntryForKey(key, lengthInBits);
return !entry.isEmpty() && compareKeys(key, entry.key) ? entry : null;
}
/**
* Returns the {@link Entry} whose key is closest in a bitwise XOR
* metric to the given key. This is NOT lexicographic closeness.
* For example, given the keys:
*
*
* - D = 1000100
*
- H = 1001000
*
- L = 1001100
*
*
* 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.
*
* @param key the key to use in the search
* @return the {@link Entry} whose key is closest in a bitwise XOR metric
* to the provided key
*/
public Map.Entry select(final K key) {
final int lengthInBits = lengthInBits(key);
final Reference> reference = new Reference>();
if (!selectR(root.left, -1, key, lengthInBits, reference)) {
return reference.get();
}
return null;
}
/**
* 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:
*
*
* - D = 1000100
*
- H = 1001000
*
- L = 1001100
*
*
* 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.
*
* @param key the key to use in the search
* @return the key that is closest in a bitwise XOR metric to the provided key
*/
public K selectKey(final K key) {
final Map.Entry entry = select(key);
if (entry == null) {
return null;
}
return entry.getKey();
}
/**
* 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:
*
*
* - D = 1000100
*
- H = 1001000
*
- L = 1001100
*
*
* 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.
*
* @param key the key to use in the search
* @return the value whose key is closest in a bitwise XOR metric
* to the provided key
*/
public V selectValue(final K key) {
final Map.Entry entry = select(key);
if (entry == null) {
return null;
}
return entry.getValue();
}
/**
* This is equivalent to the other {@link #selectR(TrieEntry, int, Object, int, Cursor, Reference)}
* method but without its overhead because we're selecting only one best matching Entry from the {@link Trie}.
*/
private boolean selectR(final TrieEntry h, final int bitIndex,
final K key, final int lengthInBits,
final Reference> reference) {
if (h.bitIndex <= bitIndex) {
// If we hit the root Node and it is empty
// we have to look for an alternative best
// matching node.
if (!h.isEmpty()) {
reference.set(h);
return false;
}
return true;
}
if (!isBitSet(key, h.bitIndex, lengthInBits)) {
if (selectR(h.left, h.bitIndex, key, lengthInBits, reference)) {
return selectR(h.right, h.bitIndex, key, lengthInBits, reference);
}
} else {
if (selectR(h.right, h.bitIndex, key, lengthInBits, reference)) {
return selectR(h.left, h.bitIndex, key, lengthInBits, reference);
}
}
return false;
}
@Override
public boolean containsKey(final Object k) {
if (k == null) {
return false;
}
final K key = castKey(k);
final int lengthInBits = lengthInBits(key);
final TrieEntry entry = getNearestEntryForKey(key, lengthInBits);
return !entry.isEmpty() && compareKeys(key, entry.key);
}
@Override
public Set> entrySet() {
if (entrySet == null) {
entrySet = new EntrySet();
}
return entrySet;
}
@Override
public Set keySet() {
if (keySet == null) {
keySet = new KeySet();
}
return keySet;
}
@Override
public Collection values() {
if (values == null) {
values = new Values();
}
return values;
}
/**
* {@inheritDoc}
*
* @throws ClassCastException if provided key is of an incompatible type
*/
@Override
public V remove(final Object k) {
if (k == null) {
return null;
}
final K key = castKey(k);
final int lengthInBits = lengthInBits(key);
TrieEntry current = root.left;
TrieEntry path = root;
while (true) {
if (current.bitIndex <= path.bitIndex) {
if (!current.isEmpty() && compareKeys(key, current.key)) {
return removeEntry(current);
}
return null;
}
path = current;
if (!isBitSet(key, current.bitIndex, lengthInBits)) {
current = current.left;
} else {
current = current.right;
}
}
}
/**
* Returns the nearest entry for a given key. This is useful
* for finding knowing if a given key exists (and finding the value
* for it), or for inserting the key.
*
* The actual get implementation. This is very similar to
* selectR but with the exception that it might return the
* root Entry even if it's empty.
*/
TrieEntry getNearestEntryForKey(final K key, final int lengthInBits) {
TrieEntry current = root.left;
TrieEntry path = root;
while(true) {
if (current.bitIndex <= path.bitIndex) {
return current;
}
path = current;
if (!isBitSet(key, current.bitIndex, lengthInBits)) {
current = current.left;
} else {
current = current.right;
}
}
}
/**
* Removes a single entry from the {@link Trie}.
*
* If we found a Key (Entry h) then figure out if it's
* an internal (hard to remove) or external Entry (easy
* to remove)
*/
V removeEntry(final TrieEntry h) {
if (h != root) {
if (h.isInternalNode()) {
removeInternalEntry(h);
} else {
removeExternalEntry(h);
}
}
decrementSize();
return h.setKeyValue(null, null);
}
/**
* Removes an external entry from the {@link Trie}.
*
* If it's an external Entry then just remove it.
* This is very easy and straight forward.
*/
private void removeExternalEntry(final TrieEntry h) {
if (h == root) {
throw new IllegalArgumentException("Cannot delete root Entry!");
} else if (!h.isExternalNode()) {
throw new IllegalArgumentException(h + " is not an external Entry!");
}
final TrieEntry parent = h.parent;
final TrieEntry child = h.left == h ? h.right : h.left;
if (parent.left == h) {
parent.left = child;
} else {
parent.right = child;
}
// either the parent is changing, or the predecessor is changing.
if (child.bitIndex > parent.bitIndex) {
child.parent = parent;
} else {
child.predecessor = parent;
}
}
/**
* Removes an internal entry from the {@link Trie}.
*
* If it's an internal Entry then "good luck" with understanding
* this code. The Idea is essentially that Entry p takes Entry h's
* place in the trie which requires some re-wiring.
*/
private void removeInternalEntry(final TrieEntry h) {
if (h == root) {
throw new IllegalArgumentException("Cannot delete root Entry!");
} else if (!h.isInternalNode()) {
throw new IllegalArgumentException(h + " is not an internal Entry!");
}
final TrieEntry p = h.predecessor;
// Set P's bitIndex
p.bitIndex = h.bitIndex;
// Fix P's parent, predecessor and child Nodes
{
final TrieEntry parent = p.parent;
final TrieEntry child = p.left == h ? p.right : p.left;
// if it was looping to itself previously,
// it will now be pointed from it's parent
// (if we aren't removing it's parent --
// in that case, it remains looping to itself).
// otherwise, it will continue to have the same
// predecessor.
if (p.predecessor == p && p.parent != h) {
p.predecessor = p.parent;
}
if (parent.left == p) {
parent.left = child;
} else {
parent.right = child;
}
if (child.bitIndex > parent.bitIndex) {
child.parent = parent;
}
}
// Fix H's parent and child Nodes
{
// If H is a parent of its left and right child
// then change them to P
if (h.left.parent == h) {
h.left.parent = p;
}
if (h.right.parent == h) {
h.right.parent = p;
}
// Change H's parent
if (h.parent.left == h) {
h.parent.left = p;
} else {
h.parent.right = p;
}
}
// Copy the remaining fields from H to P
//p.bitIndex = h.bitIndex;
p.parent = h.parent;
p.left = h.left;
p.right = h.right;
// Make sure that if h was pointing to any uplinks,
// p now points to them.
if (isValidUplink(p.left, p)) {
p.left.predecessor = p;
}
if (isValidUplink(p.right, p)) {
p.right.predecessor = p;
}
}
/**
* Returns the entry lexicographically after the given entry.
* If the given entry is null, returns the first node.
*/
TrieEntry nextEntry(final TrieEntry node) {
if (node == null) {
return firstEntry();
}
return nextEntryImpl(node.predecessor, node, null);
}
/**
* Scans for the next node, starting at the specified point, and using 'previous'
* as a hint that the last node we returned was 'previous' (so we know not to return
* it again). If 'tree' is non-null, this will limit the search to the given tree.
*
* The basic premise is that each iteration can follow the following steps:
*
* 1) Scan all the way to the left.
* a) If we already started from this node last time, proceed to Step 2.
* b) If a valid uplink is found, use it.
* c) If the result is an empty node (root not set), break the scan.
* d) If we already returned the left node, break the scan.
*
* 2) Check the right.
* a) If we already returned the right node, proceed to Step 3.
* b) If it is a valid uplink, use it.
* c) Do Step 1 from the right node.
*
* 3) Back up through the parents until we encounter find a parent
* that we're not the right child of.
*
* 4) If there's no right child of that parent, the iteration is finished.
* Otherwise continue to Step 5.
*
* 5) Check to see if the right child is a valid uplink.
* a) If we already returned that child, proceed to Step 6.
* Otherwise, use it.
*
* 6) If the right child of the parent is the parent itself, we've
* already found & returned the end of the Trie, so exit.
*
* 7) Do Step 1 on the parent's right child.
*/
TrieEntry nextEntryImpl(final TrieEntry start,
final TrieEntry previous, final TrieEntry tree) {
TrieEntry current = start;
// Only look at the left if this was a recursive or
// the first check, otherwise we know we've already looked
// at the left.
if (previous == null || start != previous.predecessor) {
while (!current.left.isEmpty()) {
// stop traversing if we've already
// returned the left of this node.
if (previous == current.left) {
break;
}
if (isValidUplink(current.left, current)) {
return current.left;
}
current = current.left;
}
}
// If there's no data at all, exit.
if (current.isEmpty()) {
return null;
}
// If we've already returned the left,
// and the immediate right is null,
// there's only one entry in the Trie
// which is stored at the root.
//
// / ("") <-- root
// \_/ \
// null <-- 'current'
//
if (current.right == null) {
return null;
}
// If nothing valid on the left, try the right.
if (previous != current.right) {
// See if it immediately is valid.
if (isValidUplink(current.right, current)) {
return current.right;
}
// Must search on the right's side if it wasn't initially valid.
return nextEntryImpl(current.right, previous, tree);
}
// Neither left nor right are valid, find the first parent
// whose child did not come from the right & traverse it.
while (current == current.parent.right) {
// If we're going to traverse to above the subtree, stop.
if (current == tree) {
return null;
}
current = current.parent;
}
// If we're on the top of the subtree, we can't go any higher.
if (current == tree) {
return null;
}
// If there's no right, the parent must be root, so we're done.
if (current.parent.right == null) {
return null;
}
// If the parent's right points to itself, we've found one.
if (previous != current.parent.right
&& isValidUplink(current.parent.right, current.parent)) {
return current.parent.right;
}
// If the parent's right is itself, there can't be any more nodes.
if (current.parent.right == current.parent) {
return null;
}
// We need to traverse down the parent's right's path.
return nextEntryImpl(current.parent.right, previous, tree);
}
/**
* Returns the first entry the {@link Trie} is storing.
*
* This is implemented by going always to the left until
* we encounter a valid uplink. That uplink is the first key.
*/
TrieEntry firstEntry() {
// if Trie is empty, no first node.
if (isEmpty()) {
return null;
}
return followLeft(root);
}
/**
* Goes left through the tree until it finds a valid node.
*/
TrieEntry followLeft(TrieEntry node) {
while(true) {
TrieEntry child = node.left;
// if we hit root and it didn't have a node, go right instead.
if (child.isEmpty()) {
child = node.right;
}
if (child.bitIndex <= node.bitIndex) {
return child;
}
node = child;
}
}
//-----------------------------------------------------------------------
public Comparator comparator() {
return getKeyAnalyzer();
}
public K firstKey() {
if (size() == 0) {
throw new NoSuchElementException();
}
return firstEntry().getKey();
}
public K lastKey() {
final TrieEntry entry = lastEntry();
if (entry != null) {
return entry.getKey();
}
throw new NoSuchElementException();
}
public K nextKey(final K key) {
if (key == null) {
throw new NullPointerException();
}
final TrieEntry entry = getEntry(key);
if (entry != null) {
final TrieEntry nextEntry = nextEntry(entry);
return nextEntry != null ? nextEntry.getKey() : null;
}
return null;
}
public K previousKey(final K key) {
if (key == null) {
throw new NullPointerException();
}
final TrieEntry entry = getEntry(key);
if (entry != null) {
final TrieEntry prevEntry = previousEntry(entry);
return prevEntry != null ? prevEntry.getKey() : null;
}
return null;
}
public OrderedMapIterator mapIterator() {
return new TrieMapIterator();
}
public SortedMap prefixMap(final K key) {
return getPrefixMapByBits(key, 0, lengthInBits(key));
}
/**
* Returns a view of this {@link Trie} of all elements that are prefixed
* by the number of bits in the given Key.
*
* The view that this returns is optimized to have a very efficient
* {@link Iterator}. The {@link SortedMap#firstKey()},
* {@link SortedMap#lastKey()} & {@link Map#size()} methods must
* iterate over all possible values in order to determine the results.
* This information is cached until the PATRICIA {@link Trie} changes.
* All other methods (except {@link Iterator}) must compare the given
* key to the prefix to ensure that it is within the range of the view.
* The {@link Iterator}'s remove method must also relocate the subtree
* that contains the prefixes if the entry holding the subtree is
* removed or changes. Changing the subtree takes O(K) time.
*
* @param key the key to use in the search
* @param offsetInBits the prefix offset
* @param lengthInBits the number of significant prefix bits
* @return a {@link SortedMap} view of this {@link Trie} with all elements whose
* key is prefixed by the search key
*/
private SortedMap getPrefixMapByBits(final K key, final int offsetInBits, final int lengthInBits) {
final int offsetLength = offsetInBits + lengthInBits;
if (offsetLength > lengthInBits(key)) {
throw new IllegalArgumentException(offsetInBits + " + "
+ lengthInBits + " > " + lengthInBits(key));
}
if (offsetLength == 0) {
return this;
}
return new PrefixRangeMap(key, offsetInBits, lengthInBits);
}
public SortedMap headMap(final K toKey) {
return new RangeEntryMap(null, toKey);
}
public SortedMap subMap(final K fromKey, final K toKey) {
return new RangeEntryMap(fromKey, toKey);
}
public SortedMap tailMap(final K fromKey) {
return new RangeEntryMap(fromKey, null);
}
/**
* Returns an entry strictly higher than the given key,
* or null if no such entry exists.
*/
TrieEntry higherEntry(final K key) {
// TODO: Cleanup so that we don't actually have to add/remove from the
// tree. (We do it here because there are other well-defined
// functions to perform the search.)
final int lengthInBits = lengthInBits(key);
if (lengthInBits == 0) {
if (!root.isEmpty()) {
// If data in root, and more after -- return it.
if (size() > 1) {
return nextEntry(root);
}
// If no more after, no higher entry.
return null;
}
// Root is empty & we want something after empty, return first.
return firstEntry();
}
final TrieEntry found = getNearestEntryForKey(key, lengthInBits);
if (compareKeys(key, found.key)) {
return nextEntry(found);
}
final int bitIndex = bitIndex(key, found.key);
if (KeyAnalyzer.isValidBitIndex(bitIndex)) {
final TrieEntry added = new TrieEntry(key, null, bitIndex);
addEntry(added, lengthInBits);
incrementSize(); // must increment because remove will decrement
final TrieEntry ceil = nextEntry(added);
removeEntry(added);
modCount -= 2; // we didn't really modify it.
return ceil;
} else if (KeyAnalyzer.isNullBitKey(bitIndex)) {
if (!root.isEmpty()) {
return firstEntry();
} else if (size() > 1) {
return nextEntry(firstEntry());
} else {
return null;
}
} else if (KeyAnalyzer.isEqualBitKey(bitIndex)) {
return nextEntry(found);
}
// we should have exited above.
throw new IllegalStateException("invalid lookup: " + key);
}
/**
* Returns a key-value mapping associated with the least key greater
* than or equal to the given key, or null if there is no such key.
*/
TrieEntry ceilingEntry(final K key) {
// Basically:
// Follow the steps of adding an entry, but instead...
//
// - If we ever encounter a situation where we found an equal
// key, we return it immediately.
//
// - If we hit an empty root, return the first iterable item.
//
// - If we have to add a new item, we temporarily add it,
// find the successor to it, then remove the added item.
//
// These steps ensure that the returned value is either the
// entry for the key itself, or the first entry directly after
// the key.
// TODO: Cleanup so that we don't actually have to add/remove from the
// tree. (We do it here because there are other well-defined
// functions to perform the search.)
final int lengthInBits = lengthInBits(key);
if (lengthInBits == 0) {
if (!root.isEmpty()) {
return root;
}
return firstEntry();
}
final TrieEntry found = getNearestEntryForKey(key, lengthInBits);
if (compareKeys(key, found.key)) {
return found;
}
final int bitIndex = bitIndex(key, found.key);
if (KeyAnalyzer.isValidBitIndex(bitIndex)) {
final TrieEntry added = new TrieEntry(key, null, bitIndex);
addEntry(added, lengthInBits);
incrementSize(); // must increment because remove will decrement
final TrieEntry ceil = nextEntry(added);
removeEntry(added);
modCount -= 2; // we didn't really modify it.
return ceil;
} else if (KeyAnalyzer.isNullBitKey(bitIndex)) {
if (!root.isEmpty()) {
return root;
}
return firstEntry();
} else if (KeyAnalyzer.isEqualBitKey(bitIndex)) {
return found;
}
// we should have exited above.
throw new IllegalStateException("invalid lookup: " + key);
}
/**
* Returns a key-value mapping associated with the greatest key
* strictly less than the given key, or null if there is no such key.
*/
TrieEntry lowerEntry(final K key) {
// Basically:
// Follow the steps of adding an entry, but instead...
//
// - If we ever encounter a situation where we found an equal
// key, we return it's previousEntry immediately.
//
// - If we hit root (empty or not), return null.
//
// - If we have to add a new item, we temporarily add it,
// find the previousEntry to it, then remove the added item.
//
// These steps ensure that the returned value is always just before
// the key or null (if there was nothing before it).
// TODO: Cleanup so that we don't actually have to add/remove from the
// tree. (We do it here because there are other well-defined
// functions to perform the search.)
final int lengthInBits = lengthInBits(key);
if (lengthInBits == 0) {
return null; // there can never be anything before root.
}
final TrieEntry found = getNearestEntryForKey(key, lengthInBits);
if (compareKeys(key, found.key)) {
return previousEntry(found);
}
final int bitIndex = bitIndex(key, found.key);
if (KeyAnalyzer.isValidBitIndex(bitIndex)) {
final TrieEntry added = new TrieEntry(key, null, bitIndex);
addEntry(added, lengthInBits);
incrementSize(); // must increment because remove will decrement
final TrieEntry prior = previousEntry(added);
removeEntry(added);
modCount -= 2; // we didn't really modify it.
return prior;
} else if (KeyAnalyzer.isNullBitKey(bitIndex)) {
return null;
} else if (KeyAnalyzer.isEqualBitKey(bitIndex)) {
return previousEntry(found);
}
// we should have exited above.
throw new IllegalStateException("invalid lookup: " + key);
}
/**
* Returns a key-value mapping associated with the greatest key
* less than or equal to the given key, or null if there is no such key.
*/
TrieEntry floorEntry(final K key) {
// TODO: Cleanup so that we don't actually have to add/remove from the
// tree. (We do it here because there are other well-defined
// functions to perform the search.)
final int lengthInBits = lengthInBits(key);
if (lengthInBits == 0) {
if (!root.isEmpty()) {
return root;
}
return null;
}
final TrieEntry found = getNearestEntryForKey(key, lengthInBits);
if (compareKeys(key, found.key)) {
return found;
}
final int bitIndex = bitIndex(key, found.key);
if (KeyAnalyzer.isValidBitIndex(bitIndex)) {
final TrieEntry added = new TrieEntry(key, null, bitIndex);
addEntry(added, lengthInBits);
incrementSize(); // must increment because remove will decrement
final TrieEntry floor = previousEntry(added);
removeEntry(added);
modCount -= 2; // we didn't really modify it.
return floor;
} else if (KeyAnalyzer.isNullBitKey(bitIndex)) {
if (!root.isEmpty()) {
return root;
}
return null;
} else if (KeyAnalyzer.isEqualBitKey(bitIndex)) {
return found;
}
// we should have exited above.
throw new IllegalStateException("invalid lookup: " + key);
}
/**
* Finds the subtree that contains the prefix.
*
* This is very similar to getR but with the difference that
* we stop the lookup if h.bitIndex > lengthInBits.
*/
TrieEntry subtree(final K prefix, final int offsetInBits, final int lengthInBits) {
TrieEntry current = root.left;
TrieEntry path = root;
while(true) {
if (current.bitIndex <= path.bitIndex || lengthInBits <= current.bitIndex) {
break;
}
path = current;
if (!isBitSet(prefix, offsetInBits + current.bitIndex, offsetInBits + lengthInBits)) {
current = current.left;
} else {
current = current.right;
}
}
// Make sure the entry is valid for a subtree.
final TrieEntry entry = current.isEmpty() ? path : current;
// If entry is root, it can't be empty.
if (entry.isEmpty()) {
return null;
}
final int endIndexInBits = offsetInBits + lengthInBits;
// if root && length of root is less than length of lookup,
// there's nothing.
// (this prevents returning the whole subtree if root has an empty
// string and we want to lookup things with "\0")
if (entry == root && lengthInBits(entry.getKey()) < endIndexInBits) {
return null;
}
// Found key's length-th bit differs from our key
// which means it cannot be the prefix...
if (isBitSet(prefix, endIndexInBits - 1, endIndexInBits)
!= isBitSet(entry.key, lengthInBits - 1, lengthInBits(entry.key))) {
return null;
}
// ... or there are less than 'length' equal bits
final int bitIndex = getKeyAnalyzer().bitIndex(prefix, offsetInBits, lengthInBits,
entry.key, 0, lengthInBits(entry.getKey()));
if (bitIndex >= 0 && bitIndex < lengthInBits) {
return null;
}
return entry;
}
/**
* Returns the last entry the {@link Trie} is storing.
*
* This is implemented by going always to the right until
* we encounter a valid uplink. That uplink is the last key.
*/
TrieEntry lastEntry() {
return followRight(root.left);
}
/**
* Traverses down the right path until it finds an uplink.
*/
TrieEntry followRight(TrieEntry node) {
// if Trie is empty, no last entry.
if (node.right == null) {
return null;
}
// Go as far right as possible, until we encounter an uplink.
while (node.right.bitIndex > node.bitIndex) {
node = node.right;
}
return node.right;
}
/**
* Returns the node lexicographically before the given node (or null if none).
*
* This follows four simple branches:
* - If the uplink that returned us was a right uplink:
* - If predecessor's left is a valid uplink from predecessor, return it.
* - Else, follow the right path from the predecessor's left.
* - If the uplink that returned us was a left uplink:
* - Loop back through parents until we encounter a node where
* node != node.parent.left.
* - If node.parent.left is uplink from node.parent:
* - If node.parent.left is not root, return it.
* - If it is root & root isEmpty, return null.
* - If it is root & root !isEmpty, return root.
* - If node.parent.left is not uplink from node.parent:
* - Follow right path for first right child from node.parent.left
*
* @param start the start entry
*/
TrieEntry previousEntry(final TrieEntry start) {
if (start.predecessor == null) {
throw new IllegalArgumentException("must have come from somewhere!");
}
if (start.predecessor.right == start) {
if (isValidUplink(start.predecessor.left, start.predecessor)) {
return start.predecessor.left;
}
return followRight(start.predecessor.left);
}
TrieEntry node = start.predecessor;
while (node.parent != null && node == node.parent.left) {
node = node.parent;
}
if (node.parent == null) { // can be null if we're looking up root.
return null;
}
if (isValidUplink(node.parent.left, node.parent)) {
if (node.parent.left == root) {
if (root.isEmpty()) {
return null;
}
return root;
}
return node.parent.left;
}
return followRight(node.parent.left);
}
/**
* Returns the entry lexicographically after the given entry.
* If the given entry is null, returns the first node.
*
* This will traverse only within the subtree. If the given node
* is not within the subtree, this will have undefined results.
*/
TrieEntry nextEntryInSubtree(final TrieEntry node,
final TrieEntry parentOfSubtree) {
if (node == null) {
return firstEntry();
}
return nextEntryImpl(node.predecessor, node, parentOfSubtree);
}
/**
* Returns true if 'next' is a valid uplink coming from 'from'.
*/
static boolean isValidUplink(final TrieEntry next, final TrieEntry from) {
return next != null && next.bitIndex <= from.bitIndex && !next.isEmpty();
}
/**
* A {@link Reference} allows us to return something through a Method's
* argument list. An alternative would be to an Array with a length of
* one (1) but that leads to compiler warnings. Computationally and memory
* wise there's no difference (except for the need to load the
* {@link Reference} Class but that happens only once).
*/
private static class Reference {
private E item;
public void set(final E item) {
this.item = item;
}
public E get() {
return item;
}
}
/**
* A {@link Trie} is a set of {@link TrieEntry} nodes.
*/
protected static class TrieEntry extends BasicEntry {
private static final long serialVersionUID = 4596023148184140013L;
/** The index this entry is comparing. */
protected int bitIndex;
/** The parent of this entry. */
protected TrieEntry parent;
/** The left child of this entry. */
protected TrieEntry left;
/** The right child of this entry. */
protected TrieEntry right;
/** The entry who uplinks to this entry. */
protected TrieEntry predecessor;
public TrieEntry(final K key, final V value, final int bitIndex) {
super(key, value);
this.bitIndex = bitIndex;
this.parent = null;
this.left = this;
this.right = null;
this.predecessor = this;
}
/**
* Whether or not the entry is storing a key.
* Only the root can potentially be empty, all other
* nodes must have a key.
*/
public boolean isEmpty() {
return key == null;
}
/**
* Neither the left nor right child is a loopback.
*/
public boolean isInternalNode() {
return left != this && right != this;
}
/**
* Either the left or right child is a loopback.
*/
public boolean isExternalNode() {
return !isInternalNode();
}
@Override
public String toString() {
final StringBuilder buffer = new StringBuilder();
if (bitIndex == -1) {
buffer.append("RootEntry(");
} else {
buffer.append("Entry(");
}
buffer.append("key=").append(getKey()).append(" [").append(bitIndex).append("], ");
buffer.append("value=").append(getValue()).append(", ");
//buffer.append("bitIndex=").append(bitIndex).append(", ");
if (parent != null) {
if (parent.bitIndex == -1) {
buffer.append("parent=").append("ROOT");
} else {
buffer.append("parent=").append(parent.getKey()).append(" [").append(parent.bitIndex).append("]");
}
} else {
buffer.append("parent=").append("null");
}
buffer.append(", ");
if (left != null) {
if (left.bitIndex == -1) {
buffer.append("left=").append("ROOT");
} else {
buffer.append("left=").append(left.getKey()).append(" [").append(left.bitIndex).append("]");
}
} else {
buffer.append("left=").append("null");
}
buffer.append(", ");
if (right != null) {
if (right.bitIndex == -1) {
buffer.append("right=").append("ROOT");
} else {
buffer.append("right=").append(right.getKey()).append(" [").append(right.bitIndex).append("]");
}
} else {
buffer.append("right=").append("null");
}
buffer.append(", ");
if (predecessor != null) {
if(predecessor.bitIndex == -1) {
buffer.append("predecessor=").append("ROOT");
} else {
buffer.append("predecessor=").append(predecessor.getKey()).append(" [").
append(predecessor.bitIndex).append("]");
}
}
buffer.append(")");
return buffer.toString();
}
}
/**
* This is a entry set view of the {@link Trie} as returned by {@link Map#entrySet()}.
*/
private class EntrySet extends AbstractSet> {
@Override
public Iterator> iterator() {
return new EntryIterator();
}
@Override
public boolean contains(final Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
final TrieEntry candidate = getEntry(((Map.Entry)o).getKey());
return candidate != null && candidate.equals(o);
}
@Override
public boolean remove(final Object obj) {
if (obj instanceof Map.Entry == false) {
return false;
}
if (contains(obj) == false) {
return false;
}
final Map.Entry entry = (Map.Entry) obj;
AbstractPatriciaTrie.this.remove(entry.getKey());
return true;
}
@Override
public int size() {
return AbstractPatriciaTrie.this.size();
}
@Override
public void clear() {
AbstractPatriciaTrie.this.clear();
}
/**
* An {@link Iterator} that returns {@link Entry} Objects.
*/
private class EntryIterator extends TrieIterator> {
public Map.Entry next() {
return nextEntry();
}
}
}
/**
* This is a key set view of the {@link Trie} as returned by {@link Map#keySet()}.
*/
private class KeySet extends AbstractSet {
@Override
public Iterator iterator() {
return new KeyIterator();
}
@Override
public int size() {
return AbstractPatriciaTrie.this.size();
}
@Override
public boolean contains(final Object o) {
return containsKey(o);
}
@Override
public boolean remove(final Object o) {
final int size = size();
AbstractPatriciaTrie.this.remove(o);
return size != size();
}
@Override
public void clear() {
AbstractPatriciaTrie.this.clear();
}
/**
* An {@link Iterator} that returns Key Objects.
*/
private class KeyIterator extends TrieIterator {
public K next() {
return nextEntry().getKey();
}
}
}
/**
* This is a value view of the {@link Trie} as returned by {@link Map#values()}.
*/
private class Values extends AbstractCollection {
@Override
public Iterator iterator() {
return new ValueIterator();
}
@Override
public int size() {
return AbstractPatriciaTrie.this.size();
}
@Override
public boolean contains(final Object o) {
return containsValue(o);
}
@Override
public void clear() {
AbstractPatriciaTrie.this.clear();
}
@Override
public boolean remove(final Object o) {
for (final Iterator it = iterator(); it.hasNext(); ) {
final V value = it.next();
if (compare(value, o)) {
it.remove();
return true;
}
}
return false;
}
/**
* An {@link Iterator} that returns Value Objects.
*/
private class ValueIterator extends TrieIterator {
public V next() {
return nextEntry().getValue();
}
}
}
/**
* An iterator for the entries.
*/
abstract class TrieIterator implements Iterator {
/** For fast-fail. */
protected int expectedModCount = AbstractPatriciaTrie.this.modCount;
protected TrieEntry next; // the next node to return
protected TrieEntry current; // the current entry we're on
/**
* Starts iteration from the root.
*/
protected TrieIterator() {
next = AbstractPatriciaTrie.this.nextEntry(null);
}
/**
* Starts iteration at the given entry.
*/
protected TrieIterator(final TrieEntry firstEntry) {
next = firstEntry;
}
/**
* Returns the next {@link TrieEntry}.
*/
protected TrieEntry nextEntry() {
if (expectedModCount != AbstractPatriciaTrie.this.modCount) {
throw new ConcurrentModificationException();
}
final TrieEntry e = next;
if (e == null) {
throw new NoSuchElementException();
}
next = findNext(e);
current = e;
return e;
}
/**
* @see PatriciaTrie#nextEntry(TrieEntry)
*/
protected TrieEntry findNext(final TrieEntry prior) {
return AbstractPatriciaTrie.this.nextEntry(prior);
}
public boolean hasNext() {
return next != null;
}
public void remove() {
if (current == null) {
throw new IllegalStateException();
}
if (expectedModCount != AbstractPatriciaTrie.this.modCount) {
throw new ConcurrentModificationException();
}
final TrieEntry node = current;
current = null;
AbstractPatriciaTrie.this.removeEntry(node);
expectedModCount = AbstractPatriciaTrie.this.modCount;
}
}
/**
* An {@link OrderedMapIterator} for a {@link Trie}.
*/
private class TrieMapIterator extends TrieIterator implements OrderedMapIterator {
protected TrieEntry previous; // the previous node to return
public K next() {
return nextEntry().getKey();
}
public K getKey() {
if (current == null) {
throw new IllegalStateException();
}
return current.getKey();
}
public V getValue() {
if (current == null) {
throw new IllegalStateException();
}
return current.getValue();
}
public V setValue(final V value) {
if (current == null) {
throw new IllegalStateException();
}
return current.setValue(value);
}
public boolean hasPrevious() {
return previous != null;
}
public K previous() {
return previousEntry().getKey();
}
@Override
protected TrieEntry nextEntry() {
final TrieEntry nextEntry = super.nextEntry();
previous = nextEntry;
return nextEntry;
}
protected TrieEntry previousEntry() {
if (expectedModCount != AbstractPatriciaTrie.this.modCount) {
throw new ConcurrentModificationException();
}
final TrieEntry e = previous;
if (e == null) {
throw new NoSuchElementException();
}
previous = AbstractPatriciaTrie.this.previousEntry(e);
next = current;
current = e;
return current;
}
}
/**
* A range view of the {@link Trie}.
*/
private abstract class RangeMap extends AbstractMap
implements SortedMap {
/** The {@link #entrySet()} view. */
private transient volatile Set> entrySet;
/**
* Creates and returns an {@link #entrySet()} view of the {@link RangeMap}.
*/
protected abstract Set> createEntrySet();
/**
* Returns the FROM Key.
*/
protected abstract K getFromKey();
/**
* Whether or not the {@link #getFromKey()} is in the range.
*/
protected abstract boolean isFromInclusive();
/**
* Returns the TO Key.
*/
protected abstract K getToKey();
/**
* Whether or not the {@link #getToKey()} is in the range.
*/
protected abstract boolean isToInclusive();
public Comparator comparator() {
return AbstractPatriciaTrie.this.comparator();
}
@Override
public boolean containsKey(final Object key) {
if (!inRange(castKey(key))) {
return false;
}
return AbstractPatriciaTrie.this.containsKey(key);
}
@Override
public V remove(final Object key) {
if (!inRange(castKey(key))) {
return null;
}
return AbstractPatriciaTrie.this.remove(key);
}
@Override
public V get(final Object key) {
if (!inRange(castKey(key))) {
return null;
}
return AbstractPatriciaTrie.this.get(key);
}
@Override
public V put(final K key, final V value) {
if (!inRange(key)) {
throw new IllegalArgumentException("Key is out of range: " + key);
}
return AbstractPatriciaTrie.this.put(key, value);
}
@Override
public Set> entrySet() {
if (entrySet == null) {
entrySet = createEntrySet();
}
return entrySet;
}
public SortedMap subMap(final K fromKey, final K toKey) {
if (!inRange2(fromKey)) {
throw new IllegalArgumentException("FromKey is out of range: " + fromKey);
}
if (!inRange2(toKey)) {
throw new IllegalArgumentException("ToKey is out of range: " + toKey);
}
return createRangeMap(fromKey, isFromInclusive(), toKey, isToInclusive());
}
public SortedMap headMap(final K toKey) {
if (!inRange2(toKey)) {
throw new IllegalArgumentException("ToKey is out of range: " + toKey);
}
return createRangeMap(getFromKey(), isFromInclusive(), toKey, isToInclusive());
}
public SortedMap tailMap(final K fromKey) {
if (!inRange2(fromKey)) {
throw new IllegalArgumentException("FromKey is out of range: " + fromKey);
}
return createRangeMap(fromKey, isFromInclusive(), getToKey(), isToInclusive());
}
/**
* Returns true if the provided key is greater than TO and less than FROM.
*/
protected boolean inRange(final K key) {
final K fromKey = getFromKey();
final K toKey = getToKey();
return (fromKey == null || inFromRange(key, false)) && (toKey == null || inToRange(key, false));
}
/**
* This form allows the high endpoint (as well as all legit keys).
*/
protected boolean inRange2(final K key) {
final K fromKey = getFromKey();
final K toKey = getToKey();
return (fromKey == null || inFromRange(key, false)) && (toKey == null || inToRange(key, true));
}
/**
* Returns true if the provided key is in the FROM range of the {@link RangeMap}.
*/
protected boolean inFromRange(final K key, final boolean forceInclusive) {
final K fromKey = getFromKey();
final boolean fromInclusive = isFromInclusive();
final int ret = getKeyAnalyzer().compare(key, fromKey);
if (fromInclusive || forceInclusive) {
return ret >= 0;
}
return ret > 0;
}
/**
* Returns true if the provided key is in the TO range of the {@link RangeMap}.
*/
protected boolean inToRange(final K key, final boolean forceInclusive) {
final K toKey = getToKey();
final boolean toInclusive = isToInclusive();
final int ret = getKeyAnalyzer().compare(key, toKey);
if (toInclusive || forceInclusive) {
return ret <= 0;
}
return ret < 0;
}
/**
* Creates and returns a sub-range view of the current {@link RangeMap}.
*/
protected abstract SortedMap createRangeMap(K fromKey, boolean fromInclusive,
K toKey, boolean toInclusive);
}
/**
* A {@link RangeMap} that deals with {@link Entry}s.
*/
private class RangeEntryMap extends RangeMap {
/** The key to start from, null if the beginning. */
private final K fromKey;
/** The key to end at, null if till the end. */
private final K toKey;
/** Whether or not the 'from' is inclusive. */
private final boolean fromInclusive;
/** Whether or not the 'to' is inclusive. */
private final boolean toInclusive;
/**
* Creates a {@link RangeEntryMap} with the fromKey included and
* the toKey excluded from the range.
*/
protected RangeEntryMap(final K fromKey, final K toKey) {
this(fromKey, true, toKey, false);
}
/**
* Creates a {@link RangeEntryMap}.
*/
protected RangeEntryMap(final K fromKey, final boolean fromInclusive,
final K toKey, final boolean toInclusive) {
if (fromKey == null && toKey == null) {
throw new IllegalArgumentException("must have a from or to!");
}
if (fromKey != null && toKey != null && getKeyAnalyzer().compare(fromKey, toKey) > 0) {
throw new IllegalArgumentException("fromKey > toKey");
}
this.fromKey = fromKey;
this.fromInclusive = fromInclusive;
this.toKey = toKey;
this.toInclusive = toInclusive;
}
public K firstKey() {
Map.Entry e = null;
if (fromKey == null) {
e = firstEntry();
} else {
if (fromInclusive) {
e = ceilingEntry(fromKey);
} else {
e = higherEntry(fromKey);
}
}
final K first = e != null ? e.getKey() : null;
if (e == null || toKey != null && !inToRange(first, false)) {
throw new NoSuchElementException();
}
return first;
}
public K lastKey() {
Map.Entry e;
if (toKey == null) {
e = lastEntry();
} else {
if (toInclusive) {
e = floorEntry(toKey);
} else {
e = lowerEntry(toKey);
}
}
final K last = e != null ? e.getKey() : null;
if (e == null || fromKey != null && !inFromRange(last, false)) {
throw new NoSuchElementException();
}
return last;
}
@Override
protected Set> createEntrySet() {
return new RangeEntrySet(this);
}
@Override
public K getFromKey() {
return fromKey;
}
@Override
public K getToKey() {
return toKey;
}
@Override
public boolean isFromInclusive() {
return fromInclusive;
}
@Override
public boolean isToInclusive() {
return toInclusive;
}
@Override
protected SortedMap createRangeMap(final K fromKey, final boolean fromInclusive,
final K toKey, final boolean toInclusive) {
return new RangeEntryMap(fromKey, fromInclusive, toKey, toInclusive);
}
}
/**
* A {@link Set} view of a {@link RangeMap}.
*/
private class RangeEntrySet extends AbstractSet> {
private final RangeMap delegate;
private transient int size = -1;
private transient int expectedModCount;
/**
* Creates a {@link RangeEntrySet}.
*/
public RangeEntrySet(final RangeMap delegate) {
if (delegate == null) {
throw new NullPointerException("delegate");
}
this.delegate = delegate;
}
@Override
public Iterator> iterator() {
final K fromKey = delegate.getFromKey();
final K toKey = delegate.getToKey();
TrieEntry first = null;
if (fromKey == null) {
first = firstEntry();
} else {
first = ceilingEntry(fromKey);
}
TrieEntry last = null;
if (toKey != null) {
last = ceilingEntry(toKey);
}
return new EntryIterator(first, last);
}
@Override
public int size() {
if (size == -1 || expectedModCount != AbstractPatriciaTrie.this.modCount) {
size = 0;
for (final Iterator it = iterator(); it.hasNext(); it.next()) {
++size;
}
expectedModCount = AbstractPatriciaTrie.this.modCount;
}
return size;
}
@Override
public boolean isEmpty() {
return !iterator().hasNext();
}
@SuppressWarnings("unchecked")
@Override
public boolean contains(final Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
final Map.Entry entry = (Map.Entry) o;
final K key = entry.getKey();
if (!delegate.inRange(key)) {
return false;
}
final TrieEntry node = getEntry(key);
return node != null && compare(node.getValue(), entry.getValue());
}
@SuppressWarnings("unchecked")
@Override
public boolean remove(final Object o) {
if (!(o instanceof Map.Entry)) {
return false;
}
final Map.Entry entry = (Map.Entry) o;
final K key = entry.getKey();
if (!delegate.inRange(key)) {
return false;
}
final TrieEntry node = getEntry(key);
if (node != null && compare(node.getValue(), entry.getValue())) {
removeEntry(node);
return true;
}
return false;
}
/**
* An {@link Iterator} for {@link RangeEntrySet}s.
*/
private final class EntryIterator extends TrieIterator> {
private final K excludedKey;
/**
* Creates a {@link EntryIterator}.
*/
private EntryIterator(final TrieEntry first, final TrieEntry last) {
super(first);
this.excludedKey = last != null ? last.getKey() : null;
}
@Override
public boolean hasNext() {
return next != null && !compare(next.key, excludedKey);
}
public Map.Entry next() {
if (next == null || compare(next.key, excludedKey)) {
throw new NoSuchElementException();
}
return nextEntry();
}
}
}
/**
* A submap used for prefix views over the {@link Trie}.
*/
private class PrefixRangeMap extends RangeMap {
private final K prefix;
private final int offsetInBits;
private final int lengthInBits;
private K fromKey = null;
private K toKey = null;
private transient int expectedModCount = 0;
private int size = -1;
/**
* Creates a {@link PrefixRangeMap}.
*/
private PrefixRangeMap(final K prefix, final int offsetInBits, final int lengthInBits) {
this.prefix = prefix;
this.offsetInBits = offsetInBits;
this.lengthInBits = lengthInBits;
}
/**
* This method does two things. It determines the FROM
* and TO range of the {@link PrefixRangeMap} and the number
* of elements in the range. This method must be called every
* time the {@link Trie} has changed.
*/
private int fixup() {
// The trie has changed since we last found our toKey / fromKey
if (size == - 1 || AbstractPatriciaTrie.this.modCount != expectedModCount) {
final Iterator> it = super.entrySet().iterator();
size = 0;
Map.Entry entry = null;
if (it.hasNext()) {
entry = it.next();
size = 1;
}
fromKey = entry == null ? null : entry.getKey();
if (fromKey != null) {
final TrieEntry prior = previousEntry((TrieEntry)entry);
fromKey = prior == null ? null : prior.getKey();
}
toKey = fromKey;
while (it.hasNext()) {
++size;
entry = it.next();
}
toKey = entry == null ? null : entry.getKey();
if (toKey != null) {
entry = nextEntry((TrieEntry)entry);
toKey = entry == null ? null : entry.getKey();
}
expectedModCount = AbstractPatriciaTrie.this.modCount;
}
return size;
}
public K firstKey() {
fixup();
Map.Entry e = null;
if (fromKey == null) {
e = firstEntry();
} else {
e = higherEntry(fromKey);
}
final K first = e != null ? e.getKey() : null;
if (e == null || !getKeyAnalyzer().isPrefix(prefix, offsetInBits, lengthInBits, first)) {
throw new NoSuchElementException();
}
return first;
}
public K lastKey() {
fixup();
Map.Entry e = null;
if (toKey == null) {
e = lastEntry();
} else {
e = lowerEntry(toKey);
}
final K last = e != null ? e.getKey() : null;
if (e == null || !getKeyAnalyzer().isPrefix(prefix, offsetInBits, lengthInBits, last)) {
throw new NoSuchElementException();
}
return last;
}
/**
* Returns true if this {@link PrefixRangeMap}'s key is a prefix of the provided key.
*/
@Override
protected boolean inRange(final K key) {
return getKeyAnalyzer().isPrefix(prefix, offsetInBits, lengthInBits, key);
}
/**
* Same as {@link #inRange(Object)}.
*/
@Override
protected boolean inRange2(final K key) {
return inRange(key);
}
/**
* Returns true if the provided Key is in the FROM range of the {@link PrefixRangeMap}.
*/
@Override
protected boolean inFromRange(final K key, final boolean forceInclusive) {
return getKeyAnalyzer().isPrefix(prefix, offsetInBits, lengthInBits, key);
}
/**
* Returns true if the provided Key is in the TO range of the {@link PrefixRangeMap}.
*/
@Override
protected boolean inToRange(final K key, final boolean forceInclusive) {
return getKeyAnalyzer().isPrefix(prefix, offsetInBits, lengthInBits, key);
}
@Override
protected Set> createEntrySet() {
return new PrefixRangeEntrySet(this);
}
@Override
public K getFromKey() {
return fromKey;
}
@Override
public K getToKey() {
return toKey;
}
@Override
public boolean isFromInclusive() {
return false;
}
@Override
public boolean isToInclusive() {
return false;
}
@Override
protected SortedMap createRangeMap(final K fromKey, final boolean fromInclusive,
final K toKey, final boolean toInclusive) {
return new RangeEntryMap(fromKey, fromInclusive, toKey, toInclusive);
}
}
/**
* A prefix {@link RangeEntrySet} view of the {@link Trie}.
*/
private final class PrefixRangeEntrySet extends RangeEntrySet {
private final PrefixRangeMap delegate;
private TrieEntry prefixStart;
private int expectedModCount = 0;
/**
* Creates a {@link PrefixRangeEntrySet}.
*/
public PrefixRangeEntrySet(final PrefixRangeMap delegate) {
super(delegate);
this.delegate = delegate;
}
@Override
public int size() {
return delegate.fixup();
}
@Override
public Iterator> iterator() {
if (AbstractPatriciaTrie.this.modCount != expectedModCount) {
prefixStart = subtree(delegate.prefix, delegate.offsetInBits, delegate.lengthInBits);
expectedModCount = AbstractPatriciaTrie.this.modCount;
}
if (prefixStart == null) {
final Set> empty = Collections.emptySet();
return empty.iterator();
} else if (delegate.lengthInBits > prefixStart.bitIndex) {
return new SingletonIterator(prefixStart);
} else {
return new EntryIterator(prefixStart, delegate.prefix, delegate.offsetInBits, delegate.lengthInBits);
}
}
/**
* An {@link Iterator} that holds a single {@link TrieEntry}.
*/
private final class SingletonIterator implements Iterator> {
private final TrieEntry entry;
private int hit = 0;
public SingletonIterator(final TrieEntry entry) {
this.entry = entry;
}
public boolean hasNext() {
return hit == 0;
}
public Map.Entry next() {
if (hit != 0) {
throw new NoSuchElementException();
}
++hit;
return entry;
}
public void remove() {
if (hit != 1) {
throw new IllegalStateException();
}
++hit;
AbstractPatriciaTrie.this.removeEntry(entry);
}
}
/**
* An {@link Iterator} for iterating over a prefix search.
*/
private final class EntryIterator extends TrieIterator> {
// values to reset the subtree if we remove it.
private final K prefix;
private final int offset;
private final int lengthInBits;
private boolean lastOne;
private TrieEntry subtree; // the subtree to search within
/**
* Starts iteration at the given entry & search only
* within the given subtree.
*/
EntryIterator(final TrieEntry startScan, final K prefix,
final int offset, final int lengthInBits) {
subtree = startScan;
next = AbstractPatriciaTrie.this.followLeft(startScan);
this.prefix = prefix;
this.offset = offset;
this.lengthInBits = lengthInBits;
}
public Map.Entry next() {
final Map.Entry entry = nextEntry();
if (lastOne) {
next = null;
}
return entry;
}
@Override
protected TrieEntry findNext(final TrieEntry prior) {
return AbstractPatriciaTrie.this.nextEntryInSubtree(prior, subtree);
}
@Override
public void remove() {
// If the current entry we're removing is the subtree
// then we need to find a new subtree parent.
boolean needsFixing = false;
final int bitIdx = subtree.bitIndex;
if (current == subtree) {
needsFixing = true;
}
super.remove();
// If the subtree changed its bitIndex or we
// removed the old subtree, get a new one.
if (bitIdx != subtree.bitIndex || needsFixing) {
subtree = subtree(prefix, offset, lengthInBits);
}
// If the subtree's bitIndex is less than the
// length of our prefix, it's the last item
// in the prefix tree.
if (lengthInBits >= subtree.bitIndex) {
lastOne = true;
}
}
}
}
//-----------------------------------------------------------------------
/**
* Reads the content of the stream.
*/
@SuppressWarnings("unchecked") // This will fail at runtime if the stream is incorrect
private void readObject(final ObjectInputStream stream) throws IOException, ClassNotFoundException{
stream.defaultReadObject();
root = new TrieEntry(null, null, -1);
int size = stream.readInt();
for(int i = 0; i < size; i++){
K k = (K) stream.readObject();
V v = (V) stream.readObject();
put(k, v);
}
}
/**
* Writes the content to the stream for serialization.
*/
private void writeObject(final ObjectOutputStream stream) throws IOException{
stream.defaultWriteObject();
stream.writeInt(this.size());
for (final Entry entry : entrySet()) {
stream.writeObject(entry.getKey());
stream.writeObject(entry.getValue());
}
}
}