PatriciaTrie.java
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phex.common.collections |
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Phex |
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| Metric | Description | |
|---|---|---|
| LINE_COMMENT | Number of line comments |  |
| CYCLOMATIC | Cyclomatic complexity | |
| JAVA0034 | JAVA0034 Missing braces in if statement | |
| RETURNS | Number of return points from functions | |
| COMPARISONS | Number of comparison operators | |
| INTERFACE_COMPLEXITY | Interface complexity | |
| SIZE | Size of the file in bytes | |
| DECL_COMMENTS | Comments in declarations | |
| FUNCTIONS | Number of function declarations | |
| EXEC_COMMENTS | Comments in executable code | |
| BLOCKS | Number of blocks | |
| OPERATORS | Number of operators | |
| PROGRAM_LENGTH | Halstead program length | |
| LINES | Number of lines in the source file | |
| PARAMS | Number of formal parameter declarations | |
| OPERANDS | Number of operands | |
| ELOC | Effective lines of code | |
| LOC | Lines of code | |
| JAVA0108 | JAVA0108 Incorrect javadoc: no @param tag for 'parameter' | |
| LOGICAL_LINES | Number of statements | |
| COMMENTS | Comment lines | |
| JAVA0110 | JAVA0110 Incorrect javadoc: no @return tag | |
| DOC_COMMENT | Number of javadoc comment lines | |
| UNIQUE_OPERANDS | Number of unique operands | |
| PROGRAM_VOCAB | Halstead program vocabulary | |
| WHITESPACE | Number of whitespace lines | |
| EXITS | Procedure exits | |
| LOOPS | Number of loops | |
| JAVA0096 | JAVA0096 Field in nested class hides outer field | |
| JAVA0277 | JAVA0277 Iterator.next() implementation does not throw NoSuchElementException | |
| JAVA0242 | JAVA0242 Transient field in non-Serializable class | |
| JAVA0031 | JAVA0031 Case statement not properly closed | |
| JAVA0163 | JAVA0163 Empty statement | |
| JAVA0075 | JAVA0075 Method parameter hides field | |
| JAVA0036 | JAVA0036 Missing braces in while statement | |
| JAVA0177 | JAVA0177 Variable declaration missing initializer | |
| JAVA0117 | JAVA0117 Missing javadoc: method 'method' | |
| UNIQUE_OPERATORS | Number of unique operators | |
| JAVA0244 | JAVA0244 Field or method name in subclass differs only by case from inherited field or method | |
| JAVA0032 | JAVA0032 Switch statement missing default | |
| JAVA0179 | JAVA0179 Local variable hides visible field | |
| JAVA0254 | JAVA0254 Use enhanced for loop construct instead of Iterator | |
| JAVA0137 | JAVA0137 Non-abstract class missing constructor | |
| JAVA0128 | JAVA0128 Public constructor in non-public class | |
| PROGRAM_VOLUME | Halstead program volume | |
| JAVA0136 | JAVA0136 N methods defined in class (maximum: M) | |
| JAVA0138 | JAVA0138 N parameters defined for method (maximum: M) | |
| JAVA0126 | JAVA0126 Method declares unchecked exception in throws | |
| JAVA0109 | JAVA0109 Incorrect javadoc: no parameter 'parameter' | |
| JAVA0141 | JAVA0141 Unnecessary modifier for method in interface | |
| JAVA0029 | JAVA0029 Private method not used | |
| JAVA0145 | JAVA0145 Tab character used in source file | |
/*
* PHEX - The pure-java Gnutella-servent.
* Copyright (C) 2001 - 2007 Phex Development Group
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* --- SVN Information ---
* $Id: PatriciaTrie.java 3714 2007-02-08 14:22:13Z gregork $
*/
package phex.common.collections;
// Modified version (1.3 2007-01-17 11:36:08) of /java/org/limewire/collection/PatriciaTrie.java
// Copyright by Limewire
import java.io.Serializable;
import java.util.AbstractCollection;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.Collection;
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.collections.iterators.EmptyIterator;
/**
* A PATRICIA Trie.
*
* PATRICIA = Practical Algorithm to Retrieve Information Coded in Alphanumeric
*
* A PATRICIA Trie is a compressed Trie. Instead of storing all data at the
* edges of the Trie (and having empty internal nodes), PATRICIA stores data
* in every node. This allows for very efficient traversal, insert, delete,
* predecessor, successor, prefix, range, and 'select' operations. All operations
* are performed at worst in O(K) time, where K is the number of bits in the
* largest item in the tree. In practice, operations actually take O(A(K))
* time, where A(K) is the average number of bits of all items in the tree.
*
* Most importantly, PATRICIA requires very few comparisons to keys while
* doing any operation. While performing a lookup, each comparison
* (at most K of them, described above) will perform a single bit comparison
* against the given key, instead of comparing the entire key to another key.
*
* The Trie can return operations in lexographical order using the 'traverse',
* 'prefix', 'submap', or 'iterator' methods. The Trie can also scan for items
* that are 'bitwise' (using an XOR metric) by the 'select' method. Bitwise
* closeness is determined by the KeyAnalyzer returning true or false for
* a bit being set or not in a given key.
*
* This PATRICIA Trie supports both variable length & fixed length keys.
* Some methods, such as getPrefixedBy(...) are suited only to variable
* length keys, whereas getPrefixedByBits(...) is suited to fixed-size keys.
*
* See http://www.csse.monash.edu.au/~lloyd/tildeAlgDS/Tree/PATRICIA/ for
* more information.
*
* Any methods here that take an Object may throw a ClassCastException if
* the method is expecting an instance of K (and it isn't K).
*
* @author Roger Kapsi
* @author Sam Berlin
*/
public class PatriciaTrie<K, V> extends AbstractMap<K, V> implements Trie<K, V>, Serializable {
private static final long serialVersionUID = 110232526181493307L;
/** The root element of the Trie. */
private final TrieEntry<K, V> root = new TrieEntry<K, V>(null, null, -1);
/** The current size (total number of elements) of the Trie. */
private int size = 0;
/** The number of times this has been modified (to fail-fast the iterators). */
private transient int modCount = 0;
/** The keyAnalyzer used to analyze bit values of keys. */
private final KeyAnalyzer<? super K> keyAnalyzer;
/** Constructs a new PatriciaTrie using the given keyAnalyzer. */
public PatriciaTrie(KeyAnalyzer<? super K> keyAnalyzer) {
this.keyAnalyzer = keyAnalyzer;
}
/** Returns the KeyAnalyzer that constructed the trie. */
public KeyAnalyzer<? super K> getKeyAnalyzer() {
return keyAnalyzer;
}
/** Returns the KeyAnalyzer as a comparator. */
public Comparator<? super K> comparator() {
return keyAnalyzer;
}
/** Clears the Trie (i.e. removes all emelemnts). */
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();
}
/** Returns true if the Trie is empty */
public boolean isEmpty() {
return size == 0;
}
/** Returns the number items in the Trie */
public int size() {
return size;
}
/** Increments both the size and mod counter. */
private void incrementSize() {
size++;
incrementModCount();
}
/** Decrements the size and increments the mod counter. */
private void decrementSize() {
size--;
incrementModCount();
}
/** Increments the mod counter. */
private void incrementModCount() {
modCount++;
}
/**
* Adds a new <key, value> pair to the Trie and if a pair already
* exists it will be replaced. In the latter case it will return
* the old value.
*/
public V put(K key, V value) {
if (key == null) {
throw new NullPointerException("Key cannot be null");
}
int keyLength = length(key);
// The only place to store a key with a length
// of zero bits is the root node
if (keyLength == 0) {
if (root.isEmpty()) {
incrementSize();
} else {
incrementModCount();
}
return root.setKeyValue(key, value);
}
TrieEntry<K, V> found = getNearestEntryForKey(key, keyLength);
if (key.equals(found.key)) {
if (found.isEmpty()) { // <- must be the root
incrementSize();
} else {
incrementModCount();
}
return found.setKeyValue(key, value);
}
int bitIndex = bitIndex(key, found.key);
if (isValidBitIndex(bitIndex)) { // in 99.999...9% the case
/* NEW KEY+VALUE TUPLE */
TrieEntry<K, V> t = new TrieEntry<K, V>(key, value, bitIndex);
addEntry(t, keyLength);
incrementSize();
return null;
} else if (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 (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 IndexOutOfBoundsException("Failed to put: " + key + " -> " + value + ", " + bitIndex);
}
/** Adds the given entry into the Trie. */
private TrieEntry<K, V> addEntry(TrieEntry<K, V> toAdd, int keyLength) {
TrieEntry<K, V> current = root.left;
TrieEntry<K, V> path = root;
while(true) {
if(current.bitIndex >= toAdd.bitIndex || current.bitIndex <= path.bitIndex) {
toAdd.predecessor = toAdd;
if (!isBitSet(toAdd.key, keyLength, toAdd.bitIndex)) {
toAdd.left = toAdd;
toAdd.right = current;
} else {
toAdd.left = current;
toAdd.right = toAdd;
}
toAdd.parent = path;
if (current.bitIndex >= toAdd.bitIndex) {
current.parent = toAdd;
}
// if we inserted an uplink, set the predecessor on it
if(current.bitIndex <= path.bitIndex) {
current.predecessor = toAdd;
}
if (path == root || !isBitSet(toAdd.key, keyLength, path.bitIndex))
path.left = toAdd;
else
path.right = toAdd;
return toAdd;
}
path = current;
if(!isBitSet(toAdd.key, keyLength, current.bitIndex))
current = current.left;
else
current = current.right;
}
}
@Override
public Set<Map.Entry<K,V>> entrySet() {
Set<Map.Entry<K,V>> es = entrySet;
return (es != null ? es : (entrySet = new EntrySet()));
}
/**
* Returns the Value whose Key equals our lookup Key
* or null if no such key exists.
*/
public V get(Object k) {
TrieEntry<K, V> entry = getEntry(k);
return entry != null ? entry.getValue() : null;
}
/**
* Returns the entry associated with the specified key in the
* PatriciaTrie. Returns null if the map contains no mapping
* for this key.
*
* This may throw ClassCastException if the object is not of type K.
*/
TrieEntry<K,V> getEntry(Object k) {
K key = asKey(k);
if(key == null)
return null;
int keyLength = length(key);
TrieEntry<K,V> entry = getNearestEntryForKey(key, keyLength);
return !entry.isEmpty() && key.equals(entry.key) ? entry : null;
}
/** Gets the key as a 'K'. */
@SuppressWarnings("unchecked")
protected final K asKey(Object key) {
try {
return (K)key;
} catch(ClassCastException cce) {
// Because the type is erased, the cast & return are
// actually doing nothing, making this CCE impossible.
// However, it's still here on the off-chance it may
// work.
return null;
}
}
/**
* 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.
*/
private TrieEntry<K, V> getNearestEntryForKey(K key, int keyLength) {
TrieEntry<K, V> current = root.left;
TrieEntry<K, V> path = root;
while(true) {
if(current.bitIndex <= path.bitIndex)
return current;
path = current;
if(!isBitSet(key, keyLength, current.bitIndex))
current = current.left;
else
current = current.right;
}
}
/**
* Returns the Value whose Key has the longest prefix
* in common with our lookup key.
*/
@SuppressWarnings("unchecked")
public V select(K key) {
int keyLength = length(key);
TrieEntry[] result = new TrieEntry[1];
if (!selectR(root.left, -1, key, keyLength, result)) {
TrieEntry<K, V> e = result[0];
return e.getValue();
}
return null;
}
/**
* This is eqivalent to the other selectR() method but without
* its overhead because we're selecting only one best matching
* Entry from the Trie.
*/
private boolean selectR(TrieEntry<K, V> h, int bitIndex,
final K key, final int keyLength, final TrieEntry[] result) {
if (h.bitIndex <= bitIndex) {
// If we hit the root Node and it is empty
// we have to look for an alternative best
// mathcing node.
if (!h.isEmpty()) {
result[0] = h;
return false;
}
return true;
}
if (!isBitSet(key, keyLength, h.bitIndex)) {
if (selectR(h.left, h.bitIndex, key, keyLength, result)) {
return selectR(h.right, h.bitIndex, key, keyLength, result);
}
} else {
if (selectR(h.right, h.bitIndex, key, keyLength, result)) {
return selectR(h.left, h.bitIndex, key, keyLength, result);
}
}
return false;
}
@SuppressWarnings("unchecked")
public Map.Entry<K,V> select(K key, Cursor<? super K, ? super V> cursor) {
int keyLength = length(key);
TrieEntry[] result = new TrieEntry[]{ null };
selectR(root.left, -1, key, keyLength, cursor, result);
return result[0];
}
private boolean selectR(TrieEntry<K,V> h, int bitIndex,
final K key,
final int keyLength,
final Cursor<? super K, ? super V> cursor,
final TrieEntry[] result) {
if (h.bitIndex <= bitIndex) {
if(!h.isEmpty()) {
Cursor.SelectStatus ret = cursor.select(h);
switch(ret) {
case REMOVE:
throw new UnsupportedOperationException("cannot remove during select");
case EXIT:
result[0] = h;
return false; // exit
case REMOVE_AND_EXIT:
TrieEntry<K, V> entry = new TrieEntry<K, V>(h.getKey(), h.getValue(), -1);
result[0] = entry;
removeEntry(h);
return false;
case CONTINUE:
// fallthrough.
}
}
return true; // continue
}
if (!isBitSet(key, keyLength, h.bitIndex)) {
if (selectR(h.left, h.bitIndex, key, keyLength, cursor, result)) {
return selectR(h.right, h.bitIndex, key, keyLength, cursor, result);
}
} else {
if (selectR(h.right, h.bitIndex, key, keyLength, cursor, result)) {
return selectR(h.left, h.bitIndex, key, keyLength, cursor, result);
}
}
return false;
}
/**
* Returns a view of this Trie of all elements that are
* prefixed by the given key.
*
* In a fixed-keysize Trie, this is essentially a 'get' operation.
*
* 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'.
*
* The view that this returns is optimized to have a very efficient
* Iterator. The firstKey, lastKey & size methods must iterate
* over all possible values in order to determine the results. This
* information is cached until the Patricia tree changes. All other
* methods (except Iterator) must compare the given key to the prefix
* to ensure that it is within the range of the view. The 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
* @return
*/
public SortedMap<K, V> getPrefixedBy(K key) {
return getPrefixedByBits(key, 0, keyAnalyzer.length(key));
}
/**
* Returns a view of this Trie of all elements that are
* prefixed by the length of the key.
*
* Fixed-keysize Tries will not support this operation
* (because all keys will be the same length).
*
* 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'.
*
* The view that this returns is optimized to have a very efficient
* Iterator. The firstKey, lastKey & size methods must iterate
* over all possible values in order to determine the results. This
* information is cached until the Patricia tree changes. All other
* methods (except Iterator) must compare the given key to the prefix
* to ensure that it is within the range of the view. The 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
* @param length
* @return
*/
public SortedMap<K, V> getPrefixedBy(K key, int length) {
return getPrefixedByBits(key, 0, length * keyAnalyzer.bitsPerElement());
}
/**
* 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.
*
* Fixed-keysize Tries will not support this operation
* (because all keys are the same length).
*
* 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'.
*
* The view that this returns is optimized to have a very efficient
* Iterator. The firstKey, lastKey & size methods must iterate
* over all possible values in order to determine the results. This
* information is cached until the Patricia tree changes. All other
* methods (except Iterator) must compare the given key to the prefix
* to ensure that it is within the range of the view. The 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
* @param offset
* @param length
* @return
*/
public SortedMap<K, V> getPrefixedBy(K key, int offset, int length) {
return getPrefixedByBits(key, offset * keyAnalyzer.bitsPerElement(), length * keyAnalyzer.bitsPerElement());
}
/**
* Returns a view of this Trie of all elements that are prefixed
* by the number of bits in the given Key.
*
* 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'.
*
* The view that this returns is optimized to have a very efficient
* Iterator. The firstKey, lastKey & size methods must iterate
* over all possible values in order to determine the results. This
* information is cached until the Patricia tree changes. All other
* methods (except Iterator) must compare the given key to the prefix
* to ensure that it is within the range of the view. The 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
* @param length
* @return
*/
public SortedMap<K, V> getPrefixedByBits(K key, int bitLength) {
return getPrefixedByBits(key, 0, bitLength);
}
/**
* Returns a view of this map, with entries containing only those that
* are prefixed by a value whose bits matches the bits between 'offset'
* and 'length' in the given key.
*
* The view that this returns is optimized to have a very efficient
* Iterator. The firstKey, lastKey & size methods must iterate
* over all possible values in order to determine the results. This
* information is cached until the Patricia tree changes. All other
* methods (except Iterator) must compare the given key to the prefix
* to ensure that it is within the range of the view. The 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
* @param offset
* @param length
* @return
*/
private SortedMap<K, V> getPrefixedByBits(K key, int offset, int length) {
int offsetLength = offset + length;
if (offsetLength > length(key)) {
throw new IllegalArgumentException(offset + " + " + length + " > " + length(key));
}
if(offsetLength == 0)
return this;
return new PrefixSubMap(key, offset, length);
}
/**
* Returns true if this trie contains the specified Key
*
* This may throw ClassCastException if the object is not
* of type K.
*/
public boolean containsKey(Object k) {
K key = asKey(k);
if(key == null)
return false;
int keyLength = length(key);
TrieEntry entry = getNearestEntryForKey(key, keyLength);
return !entry.isEmpty() && key.equals(entry.key);
}
/** Returns true if this Trie contains the specified value. */
public boolean containsValue(Object o) {
for(V v : values())
if(valEquals(v, o))
return true;
return false;
}
/**
* Removes a Key from the Trie if one exists
*
* This may throw ClassCastException if the object is not of type K.
*
* @param key the Key to delete
* @return Returns the deleted Value
*/
public V remove(Object k) {
K key = asKey(k);
if(key == null)
return null;
int keyLength = length(key);
TrieEntry<K, V> current = root.left;
TrieEntry<K, V> path = root;
while(true) {
if(current.bitIndex <= path.bitIndex) {
if(!current.isEmpty() && key.equals(current.key))
return removeEntry(current);
else
return null;
}
path = current;
if(!isBitSet(key, keyLength, current.bitIndex))
current = current.left;
else
current = current.right;
}
}
/**
* Removes a single entry from the 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)
*/
private V removeEntry(TrieEntry<K, V> h) {
if (h != root) {
if (h.isInternalNode()) {
removeInternalEntry(h);
} else {
removeExternalEntry(h);
}
}
decrementSize();
return h.setKeyValue(null, null);
}
/**
* Removes an external entry from the Trie.
*
* If it's an external Entry then just remove it.
* This is very easy and straight forward.
*/
private void removeExternalEntry(TrieEntry<K, V> h) {
if (h == root) {
throw new IllegalArgumentException("Cannot delete root Entry!");
} else if (!h.isExternalNode()) {
throw new IllegalArgumentException(h + " is not an external Entry!");
}
TrieEntry<K, V> parent = h.parent;
TrieEntry<K, V> 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 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-wireing.
*/
private void removeInternalEntry(TrieEntry<K, V> h) {
if (h == root) {
throw new IllegalArgumentException("Cannot delete root Entry!");
} else if (!h.isInternalNode()) {
throw new IllegalArgumentException(h + " is not an internal Entry!");
}
TrieEntry<K, V> p = h.predecessor;
// Set P's bitIndex
p.bitIndex = h.bitIndex;
// Fix P's parent, predecessor and child Nodes
{
TrieEntry<K, V> parent = p.parent;
TrieEntry<K, V> 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 childs
// 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 node lexographically 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
* @return
*/
private TrieEntry<K, V> previousEntry(TrieEntry<K, V> 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;
} else {
return followRight(start.predecessor.left);
}
} else {
TrieEntry<K, V> 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;
else
return root;
} else {
return node.parent.left;
}
} else {
return followRight(node.parent.left);
}
}
}
/**
* Returns the entry lexographically after the given entry.
* If the given entry is null, returns the first node.
*/
private TrieEntry<K, V> nextEntry(TrieEntry<K, V> node) {
if(node == null) {
return firstEntry();
} else {
return nextEntryImpl(node.predecessor, node, null);
}
}
/**
* Returns the entry lexographically 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.
*/
private TrieEntry<K, V> nextEntryInSubtree(TrieEntry<K, V> node, TrieEntry<K, V> parentOfSubtree) {
if(node == null) {
return firstEntry();
} else {
return nextEntryImpl(node.predecessor, node, parentOfSubtree);
}
}
/**
* 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.
*/
private TrieEntry<K, V> nextEntryImpl(TrieEntry<K, V> start, TrieEntry<K, V> previous, TrieEntry<K, V> tree) {
TrieEntry<K, V> 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 each entry as a string. */
public String toString() {
StringBuilder buffer = new StringBuilder();
buffer.append("Trie[").append(size()).append("]={\n");
for(Iterator<Map.Entry<K, V>> i = newEntryIterator(); i.hasNext(); ) {
buffer.append(" ").append(i.next().toString()).append("\n");
}
buffer.append("}\n");
return buffer.toString();
}
public Map.Entry<K, V> traverse(Cursor<? super K, ? super V> cursor) {
TrieEntry<K, V> entry = nextEntry(null);
while(entry != null) {
TrieEntry<K, V> current = entry;
Cursor.SelectStatus ret = cursor.select(current);
entry = nextEntry(current);
switch(ret) {
case EXIT:
return current;
case REMOVE:
removeEntry(current);
break; // out of switch, stay in while loop
case REMOVE_AND_EXIT:
Map.Entry<K, V> value = new TrieEntry<K, V>(current.getKey(), current.getValue(), -1);
removeEntry(current);
return value;
case CONTINUE: // do nothing.
}
}
return null;
}
/** Returns true if 'next' is a valid uplink coming from 'from'. */
private boolean isValidUplink(TrieEntry<K, V> next, TrieEntry<K, V> from) {
return next != null && next.bitIndex <= from.bitIndex && !next.isEmpty();
}
/** Returns true if bitIndex is a valid index */
private static boolean isValidBitIndex(int bitIndex) {
return 0 <= bitIndex && bitIndex <= Integer.MAX_VALUE;
}
/** Returns true if bitIndex is a NULL_BIT_KEY */
private static boolean isNullBitKey(int bitIndex) {
return bitIndex == KeyAnalyzer.NULL_BIT_KEY;
}
/** Returns true if bitIndex is a EQUAL_BIT_KEY */
private static boolean isEqualBitKey(int bitIndex) {
return bitIndex == KeyAnalyzer.EQUAL_BIT_KEY;
}
/** Returns the length of the key, or 0 if the key is null. */
private int length(K key) {
if (key == null) {
return 0;
}
return keyAnalyzer.length(key);
}
/**
* Returns whether or not the given bit on the
* key is set, or false if the key is null
*/
private boolean isBitSet(K key, int keyLength, int bitIndex) {
if (key == null) { // root's might be null!
return false;
}
return keyAnalyzer.isBitSet(key, keyLength, bitIndex);
}
/**
* Utility method for calling
* keyAnalyzer.bitIndex(key, 0, length(key), foundKey, 0, length(foundKey))
*/
private int bitIndex(K key, K foundKey) {
return keyAnalyzer.bitIndex(key, 0, length(key), foundKey, 0, length(foundKey));
}
/** The actual Trie nodes. */
private static class TrieEntry<K,V> implements Map.Entry<K,V>, Serializable {
private static final long serialVersionUID = 4596023148184140013L;
private K key;
private V value;
/** The index this entry is comparing. */
private int bitIndex;
/** The parent of this entry. */
private TrieEntry<K,V> parent;
/** The left child of this entry. */
private TrieEntry<K,V> left;
/** The right child of this entry. */
private TrieEntry<K,V> right;
/** The entry who uplinks to this entry. */
private TrieEntry<K,V> predecessor;
private TrieEntry(K key, V value, int bitIndex) {
this.key = key;
this.value = value;
this.bitIndex = bitIndex;
this.parent = null;
this.left = this;
this.right = null;
this.predecessor = this;
}
public boolean equals(Object o) {
if(o == this) {
return true;
} else if(o instanceof Map.Entry) {
Map.Entry e = (Map.Entry)o;
Object k1 = getKey();
Object k2 = e.getKey();
if (k1 == k2 || (k1 != null && k1.equals(k2))) {
Object v1 = getValue();
Object v2 = e.getValue();
if (v1 == v2 || (v1 != null && v1.equals(v2)))
return true;
}
return false;
} else {
return false;
}
}
/**
* 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;
}
public K getKey() {
return key;
}
public V getValue() {
return value;
}
public V setValue(V value) {
V o = this.value;
this.value = value;
return o;
}
/**
* Replaces the old key and value with the new ones.
* Returns the old vlaue.
*/
private V setKeyValue(K key, V value) {
this.key = key;
return setValue(value);
}
/** Neither the left nor right child is a loopback */
private boolean isInternalNode() {
return left != this && right != this;
}
/** Either the left or right child is a loopback */
private boolean isExternalNode() {
return !isInternalNode();
}
public String toString() {
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();
}
}
/** Analyzes keys on a bit level. */
public static interface KeyAnalyzer<K> extends Comparator<K>, Serializable {
/** Returned by bitIndex if key's bits are all 0 */
public static final int NULL_BIT_KEY = -1;
/**
* Returned by bitIndex if key and found key are
* equal. This is a very very specific case and
* shouldn't happen on a regular basis
*/
public static final int EQUAL_BIT_KEY = -2;
/**
* Returns the length of the Key in bits.
*/
public int length(K key);
/** Returns whether or not a bit is set */
public boolean isBitSet(K key, int keyLength, int bitIndex);
/**
* Returns the n-th different bit between key and found.
* This starts the comparison in key at 'keyStart' and goes
* for 'keyLength' bits, and compares to the found key
* starting at 'foundStart' and going for 'foundLength' bits.
*/
public int bitIndex(K key, int keyStart, int keyLength,
K found, int foundStart, int foundLength);
/**
* Returns the number of bits per element in the key.
* This is only useful for variable-length keys, such as Strings.
*/
public int bitsPerElement();
/**
* Determines whether or not the given prefix (from offset to length)
* is a prefix of the given key.
*/
public boolean isPrefix(K prefix, int offset, int length, K key);
}
/** An iterator that stores a single TrieEntry. */
private class SingletonIterator implements Iterator<Map.Entry<K, V>> {
private final TrieEntry<K, V> entry;
private int hit = 0;
public SingletonIterator(TrieEntry<K, V> entry) {
this.entry = entry;
}
public boolean hasNext() {
return hit == 0;
}
public Map.Entry<K, V> next() {
if(hit != 0)
throw new NoSuchElementException();
hit++;
return entry;
}
public void remove() {
if(hit != 1)
throw new IllegalStateException();
hit++;
PatriciaTrie.this.removeEntry(entry);
}
}
/** An iterator for the entries. */
private abstract class NodeIterator<E> implements Iterator<E> {
protected int expectedModCount = modCount; // For fast-fail
protected TrieEntry<K, V> next; // the next node to return
protected TrieEntry<K, V> current; // the current entry we're on
// Starts iteration from the beginning.
protected NodeIterator() {
next = PatriciaTrie.this.nextEntry(null);
}
// Starts iteration at the given entry.
protected NodeIterator(TrieEntry<K, V> firstEntry) {
next = firstEntry;
}
public boolean hasNext() {
return next != null;
}
TrieEntry<K,V> nextEntry() {
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
TrieEntry<K,V> e = next;
if (e == null)
throw new NoSuchElementException();
next = findNext(e);
current = e;
return e;
}
protected TrieEntry<K, V> findNext(TrieEntry<K, V> prior) {
return PatriciaTrie.this.nextEntry(prior);
}
public void remove() {
if (current == null)
throw new IllegalStateException();
if (modCount != expectedModCount)
throw new ConcurrentModificationException();
TrieEntry<K, V> node = current;
current = null;
PatriciaTrie.this.removeEntry(node);
expectedModCount = modCount;
}
}
private class ValueIterator extends NodeIterator<V> {
public V next() {
return nextEntry().value;
}
}
private class KeyIterator extends NodeIterator<K> {
public K next() {
return nextEntry().getKey();
}
}
private class EntryIterator extends NodeIterator<Map.Entry<K,V>> {
public Map.Entry<K,V> next() {
return nextEntry();
}
}
/** An iterator for iterating over a prefix search. */
private class PrefixEntryIterator extends NodeIterator<Map.Entry<K, V>> {
// values to reset the subtree if we remove it.
protected final K prefix;
protected final int offset;
protected final int length;
protected boolean lastOne;
protected TrieEntry<K, V> subtree; // the subtree to search within
// Starts iteration at the given entry & search only within the given subtree.
PrefixEntryIterator(TrieEntry<K, V> startScan, K prefix, int offset, int length) {
subtree = startScan;
next = PatriciaTrie.this.followLeft(startScan);
this.prefix = prefix;
this.offset = offset;
this.length = length;
}
public Map.Entry<K,V> next() {
Map.Entry<K, V> entry = nextEntry();
if(lastOne)
next = null;
return entry;
}
@Override
protected TrieEntry<K, V> findNext(TrieEntry<K, V> prior) {
return PatriciaTrie.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;
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, length);
// If the subtree's bitIndex is less than the
// length of our prefix, it's the last item
// in the prefix tree.
if(length >= subtree.bitIndex)
lastOne = true;
}
}
/** An iterator for submaps. */
private class SubMapEntryIterator extends NodeIterator<Map.Entry<K,V>> {
private final K firstExcludedKey;
SubMapEntryIterator(TrieEntry<K,V> first, TrieEntry<K,V> firstExcluded) {
super(first);
firstExcludedKey =
(firstExcluded == null ? null : firstExcluded.key);
}
public boolean hasNext() {
return next != null && next.key != firstExcludedKey;
}
public Map.Entry<K,V> next() {
if (next == null || next.key == firstExcludedKey)
throw new NoSuchElementException();
return nextEntry();
}
}
Iterator<K> newKeyIterator() {
return new KeyIterator();
}
Iterator<V> newValueIterator() {
return new ValueIterator();
}
Iterator<Map.Entry<K,V>> newEntryIterator() {
return new EntryIterator();
}
/**
* 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<K> keySet = null;
private transient volatile Collection<V> values = null;
private transient volatile Set<Map.Entry<K,V>> entrySet = null;
private class EntrySet extends AbstractSet<Map.Entry<K,V>> {
public Iterator<Map.Entry<K,V>> iterator() {
return newEntryIterator();
}
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
TrieEntry<K,V> candidate = getEntry(((Map.Entry)o).getKey());
return candidate != null && candidate.equals(o);
}
public boolean remove(Object o) {
int size = size();
PatriciaTrie.this.remove(o);
return size != size();
}
public int size() {
return size;
}
public void clear() {
PatriciaTrie.this.clear();
}
}
/**
* Returns a set view of the keys contained in this map. The set is
* backed by the map, so changes to the map are reflected in the set, and
* vice-versa. The set supports element removal, which removes the
* corresponding mapping from this map, via the <tt>Iterator.remove</tt>,
* <tt>Set.remove</tt>, <tt>removeAll</tt>, <tt>retainAll</tt>, and
* <tt>clear</tt> operations. It does not support the <tt>add</tt> or
* <tt>addAll</tt> operations.
*
* @return a set view of the keys contained in this map.
*/
public Set<K> keySet() {
Set<K> ks = keySet;
return (ks != null ? ks : (keySet = new KeySet()));
}
private class KeySet extends AbstractSet<K> {
public Iterator<K> iterator() {
return newKeyIterator();
}
public int size() {
return size;
}
public boolean contains(Object o) {
return containsKey(o);
}
public boolean remove(Object o) {
int size = size();
PatriciaTrie.this.remove(o);
return size != size();
}
public void clear() {
PatriciaTrie.this.clear();
}
}
/**
* Returns a collection view of the values contained in this map. The
* collection is backed by the map, so changes to the map are reflected in
* the collection, and vice-versa. The collection supports element
* removal, which removes the corresponding mapping from this map, via the
* <tt>Iterator.remove</tt>, <tt>Collection.remove</tt>,
* <tt>removeAll</tt>, <tt>retainAll</tt>, and <tt>clear</tt> operations.
* It does not support the <tt>add</tt> or <tt>addAll</tt> operations.
*
* @return a collection view of the values contained in this map.
*/
public Collection<V> values() {
Collection<V> vs = values;
return (vs != null ? vs : (values = new Values()));
}
/** Test two values for equality. Works with null values. */
private static boolean valEquals(Object o1, Object o2) {
return (o1==null ? o2==null : o1.equals(o2));
}
private class Values extends AbstractCollection<V> {
public Iterator<V> iterator() {
return newValueIterator();
}
public int size() {
return size;
}
public boolean contains(Object o) {
return containsValue(o);
}
public void clear() {
PatriciaTrie.this.clear();
}
public boolean remove(Object o) {
for(Iterator<V> i = iterator(); i.hasNext(); ) {
V v = i.next();
if(valEquals(v, o)) {
i.remove();
return true;
}
}
return false;
}
}
/**
* Returns the first entry the Trie is storing.
*
* This is implemented by going always to the left until
* we encounter a valid uplink. That uplink is the first key.
*/
private TrieEntry<K, V> 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. */
private TrieEntry<K, V> followLeft(TrieEntry<K, V> node) {
while(true) {
TrieEntry<K, V> 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;
}
}
/**
* Returns the last entry the Trie is storing.
*
* This is implemented by going always to the right until
* we encounter a valid uplink. That uplink is the last key.
*/
private TrieEntry<K, V> lastEntry() {
return followRight(root.left);
}
/** Traverses down the right path until it finds an uplink. */
protected TrieEntry<K, V> followRight(TrieEntry<K, V> 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;
}
public K firstKey() {
return firstEntry().getKey();
}
public SortedMap<K, V> headMap(K toKey) {
return new SubMap(null, toKey);
}
public K lastKey() {
TrieEntry<K, V> entry = lastEntry();
if(entry != null)
return entry.getKey();
else
return null;
}
public SortedMap<K, V> subMap(K fromKey, K toKey) {
return new SubMap(fromKey, toKey);
}
public SortedMap<K, V> tailMap(K fromKey) {
return new SubMap(fromKey, null);
}
/**
* Returns an entry strictly higher than the given key,
* or null if no such entry exists.
*/
protected TrieEntry<K,V> higherEntry(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.)
int keyLength = length(key);
if (keyLength == 0) {
if(!root.isEmpty()) {
// If data in root, and more after -- return it.
if(size() > 1) {
return nextEntry(root);
} else { // If no more after, no higher entry.
return null;
}
} else {
// Root is empty & we want something after empty, return first.
return firstEntry();
}
}
TrieEntry<K, V> found = getNearestEntryForKey(key, keyLength);
if (key.equals(found.key))
return nextEntry(found);
int bitIndex = bitIndex(key, found.key);
if (isValidBitIndex(bitIndex)) {
TrieEntry<K, V> added = new TrieEntry<K, V>(key, null, bitIndex);
addEntry(added, keyLength);
incrementSize(); // must increment because remove will decrement
TrieEntry<K, V> ceil = nextEntry(added);
removeEntry(added);
modCount -= 2; // we didn't really modify it.
return ceil;
} else if (isNullBitKey(bitIndex)) {
if (!root.isEmpty())
return firstEntry();
else if(size() > 1)
return nextEntry(firstEntry());
else
return null;
} else if (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.
*/
protected TrieEntry<K,V> ceilingEntry(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.)
int keyLength = length(key);
if (keyLength == 0) {
if(!root.isEmpty())
return root;
else
return firstEntry();
}
TrieEntry<K, V> found = getNearestEntryForKey(key, keyLength);
if (key.equals(found.key))
return found;
int bitIndex = bitIndex(key, found.key);
if (isValidBitIndex(bitIndex)) {
TrieEntry<K, V> added = new TrieEntry<K, V>(key, null, bitIndex);
addEntry(added, keyLength);
incrementSize(); // must increment because remove will decrement
TrieEntry<K, V> ceil = nextEntry(added);
removeEntry(added);
modCount -= 2; // we didn't really modify it.
return ceil;
} else if (isNullBitKey(bitIndex)) {
if (!root.isEmpty())
return root;
else
return firstEntry();
} else if (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.
*/
protected TrieEntry<K,V> lowerEntry(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.)
int keyLength = length(key);
if (keyLength == 0) {
return null; // there can never be anything before root.
}
TrieEntry<K, V> found = getNearestEntryForKey(key, keyLength);
if (key.equals(found.key))
return previousEntry(found);
int bitIndex = bitIndex(key, found.key);
if (isValidBitIndex(bitIndex)) {
TrieEntry<K, V> added = new TrieEntry<K, V>(key, null, bitIndex);
addEntry(added, keyLength);
incrementSize(); // must increment because remove will decrement
TrieEntry<K, V> prior = previousEntry(added);
removeEntry(added);
modCount -= 2; // we didn't really modify it.
return prior;
} else if (isNullBitKey(bitIndex)) {
return null;
} else if (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.
*/
protected TrieEntry<K,V> floorEntry(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.)
int keyLength = length(key);
if (keyLength == 0) {
if(!root.isEmpty())
return root;
else
return null;
}
TrieEntry<K, V> found = getNearestEntryForKey(key, keyLength);
if (key.equals(found.key))
return found;
int bitIndex = bitIndex(key, found.key);
if (isValidBitIndex(bitIndex)) {
TrieEntry<K, V> added = new TrieEntry<K, V>(key, null, bitIndex);
addEntry(added, keyLength);
incrementSize(); // must increment because remove will decrement
TrieEntry<K, V> floor = previousEntry(added);
removeEntry(added);
modCount -= 2; // we didn't really modify it.
return floor;
} else if (isNullBitKey(bitIndex)) {
if (!root.isEmpty())
return root;
else
return null;
} else if (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 > keyLength.
*/
private TrieEntry<K, V> subtree(K prefix, int offset, int length) {
TrieEntry<K, V> current = root.left;
TrieEntry<K, V> path = root;
while(true) {
if(current.bitIndex <= path.bitIndex || length < current.bitIndex)
break;
path = current;
if(!isBitSet(prefix, length+offset, current.bitIndex+offset)) {
current = current.left;
} else {
current = current.right;
}
}
// Make sure the entry is valid for a subtree.
TrieEntry<K, V> entry = current.isEmpty() ? path : current;
// If entry is root, it can't be empty.
if (entry.isEmpty())
return null;
int offsetLength = offset + length;
// 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 && length(entry.getKey()) < offsetLength)
return null;
// Found key's length-th bit differs from our key
// which means it cannot be the prefix...
if(isBitSet(prefix, offsetLength, offsetLength) !=
isBitSet(entry.key, length(entry.key), length)) {
return null;
}
// ... or there are less than 'length' equal bits
int bitIndex = keyAnalyzer.bitIndex(prefix, offset, length,
entry.key, 0, length(entry.getKey()));
if (bitIndex >= 0 && bitIndex < length)
return null;
return entry;
}
/** A submap used for prefix views over the Trie. */
private class PrefixSubMap extends SubMap {
protected final K prefix;
protected final int offset;
protected final int length;
private transient int keyModCount = 0;
protected int size;
PrefixSubMap(K prefix, int offset, int length) {
this.prefix = prefix;
this.offset = offset;
this.length = length;
fromInclusive = false;
}
public K firstKey() {
fixup();
TrieEntry<K,V> e;
if(fromKey == null) {
e = firstEntry();
} else {
e = higherEntry(fromKey);
}
K first = e != null ? e.getKey() : null;
if (e == null || !keyAnalyzer.isPrefix(prefix, offset, length, first))
throw new NoSuchElementException();
return first;
}
public K lastKey() {
fixup();
TrieEntry<K,V> e;
if(toKey == null) {
e = lastEntry();
} else {
e = lowerEntry(toKey);
}
K last = e != null ? e.getKey() : null;
if (e == null || !keyAnalyzer.isPrefix(prefix, offset, length, last))
throw new NoSuchElementException();
return last;
}
protected boolean inRange(K key) {
return keyAnalyzer.isPrefix(prefix, offset, length, key);
}
protected boolean inRange2(K key) {
return keyAnalyzer.isPrefix(prefix, offset, length, key);
}
protected boolean inToRange(K key, boolean forceInclusive) {
return keyAnalyzer.isPrefix(prefix, offset, length, key);
}
protected boolean inFromRange(K key, boolean forceInclusive) {
return keyAnalyzer.isPrefix(prefix, offset, length, key);
}
private void fixup() {
// The trie has changed since we last
// found our toKey / fromKey
if(modCount != keyModCount) {
Iterator<Map.Entry<K, V>> iter = entrySet().iterator();
size = 0;
Map.Entry<K, V> entry = null;
if(iter.hasNext()) {
entry = iter.next();
size = 1;
}
fromKey = entry == null ? null : entry.getKey();
if(fromKey != null) {
TrieEntry<K, V> prior = previousEntry((TrieEntry<K, V>)entry);
fromKey = prior == null ? null : prior.getKey();
}
toKey = fromKey;
while(iter.hasNext()) {
size++;
entry = iter.next();
}
toKey = entry == null ? null : entry.getKey();
if(toKey != null) {
entry = nextEntry((TrieEntry<K, V>)entry);
toKey = entry == null ? null : entry.getKey();
}
keyModCount = modCount;
}
}
protected Set<Map.Entry<K, V>> newSubMapEntrySet() {
return new PrefixEntrySetView();
}
private class PrefixEntrySetView extends SubMap.EntrySetView {
private TrieEntry<K, V> prefixStart;
private int iterModCount = 0;
public int size() {
fixup();
return PrefixSubMap.this.size;
}
public Iterator<Map.Entry<K,V>> iterator() {
if(modCount != iterModCount) {
prefixStart = subtree(prefix, offset, length);
iterModCount = modCount;
}
if(prefixStart == null) {
return EmptyIterator.INSTANCE;
} else if(length >= prefixStart.bitIndex){
return new SingletonIterator(prefixStart);
} else {
return new PrefixEntryIterator(prefixStart, prefix, offset, length);
}
}
}
}
private class SubMap extends AbstractMap<K,V> implements SortedMap<K,V>, java.io.Serializable {
// TODO: add serialVersionUID
/** The key to start from, null if the beginning. */
protected K fromKey;
/** The key to end at, null if till the end. */
protected K toKey;
/** Whether or not the 'from' is inclusive. */
protected boolean fromInclusive;
/** Whether or not the 'to' is inclusive. */
protected boolean toInclusive;
/**
* Constructs a blank SubMap -- this should ONLY be used
* by subclasses that wish to lazily construct their
* fromKey or toKey
*/
protected SubMap() {}
SubMap(K fromKey, K toKey) {
if(fromKey == null && toKey == null)
throw new IllegalArgumentException("must have a from or to!");
if(fromKey != null && toKey != null && keyAnalyzer.compare(fromKey, toKey) > 0)
throw new IllegalArgumentException("fromKey > toKey");
this.fromKey = fromKey;
this.toKey = toKey;
fromInclusive = true;
}
public boolean isEmpty() {
return entrySet().isEmpty();
}
@SuppressWarnings("unchecked")
public boolean containsKey(Object key) {
return inRange((K) key) && PatriciaTrie.this.containsKey(key);
}
@SuppressWarnings("unchecked")
public V remove(Object key) {
if(!inRange((K)key))
return null;
return PatriciaTrie.this.remove(key);
}
@SuppressWarnings("unchecked")
public V get(Object key) {
if (!inRange((K) key))
return null;
return PatriciaTrie.this.get(key);
}
public V put(K key, V value) {
if (!inRange(key))
throw new IllegalArgumentException("key out of range");
return PatriciaTrie.this.put(key, value);
}
public Comparator<? super K> comparator() {
return keyAnalyzer;
}
public K firstKey() {
TrieEntry<K,V> e;
if(fromKey == null) {
e = firstEntry();
} else {
if(fromInclusive)
e = ceilingEntry(fromKey);
else
e = higherEntry(fromKey);
}
K first = e != null ? e.getKey() : null;
if (e == null || toKey != null && !inToRange(first, false))
throw new NoSuchElementException();
return first;
}
public K lastKey() {
TrieEntry<K,V> e;
if(toKey == null) {
e = lastEntry();
} else {
if(toInclusive)
e = floorEntry(toKey);
else
e = lowerEntry(toKey);
}
K last = e != null ? e.getKey() : null;
if (e == null || fromKey != null && !inFromRange(last, false))
throw new NoSuchElementException();
return last;
}
private transient Set<Map.Entry<K,V>> entrySet;
public Set<Map.Entry<K,V>> entrySet() {
if(entrySet == null)
entrySet = newSubMapEntrySet();
return entrySet;
}
protected Set<Map.Entry<K, V>> newSubMapEntrySet() {
return new EntrySetView();
}
class EntrySetView extends AbstractSet<Map.Entry<K,V>> {
private transient int size = -1, sizeModCount;
public int size() {
if (size == -1 || sizeModCount != PatriciaTrie.this.modCount) {
size = 0; sizeModCount = PatriciaTrie.this.modCount;
Iterator i = iterator();
while (i.hasNext()) {
size++;
i.next();
}
}
return size;
}
public boolean isEmpty() {
return !iterator().hasNext();
}
@SuppressWarnings("unchecked")
public boolean contains(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<K,V> entry = (Map.Entry<K,V>) o;
K key = entry.getKey();
if (!inRange(key))
return false;
TrieEntry<K, V> node = getEntry(key);
return node != null &&
valEquals(node.getValue(), entry.getValue());
}
@SuppressWarnings("unchecked")
public boolean remove(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry<K,V> entry = (Map.Entry<K,V>) o;
K key = entry.getKey();
if (!inRange(key))
return false;
TrieEntry<K,V> node = getEntry(key);
if (node!=null && valEquals(node.getValue(),entry.getValue())){
removeEntry(node);
return true;
}
return false;
}
public Iterator<Map.Entry<K,V>> iterator() {
return new SubMapEntryIterator(
(fromKey == null ? firstEntry() : ceilingEntry(fromKey)),
(toKey == null ? null : ceilingEntry(toKey)));
}
}
public SortedMap<K,V> subMap(K fromKey, K toKey) {
if (!inRange2(fromKey))
throw new IllegalArgumentException("fromKey out of range");
if (!inRange2(toKey))
throw new IllegalArgumentException("toKey out of range");
return new SubMap(fromKey, toKey);
}
public SortedMap<K,V> headMap(K toKey) {
if (!inRange2(toKey))
throw new IllegalArgumentException("toKey out of range");
return new SubMap(fromKey, toKey);
}
public SortedMap<K,V> tailMap(K fromKey) {
if (!inRange2(fromKey))
throw new IllegalArgumentException("fromKey out of range");
return new SubMap(fromKey, toKey);
}
protected boolean inRange(K key) {
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(K key) {
return (fromKey == null || inFromRange(key, false)) &&
(toKey == null || inToRange(key, true));
}
protected boolean inToRange(K key, boolean forceInclusive) {
int ret = keyAnalyzer.compare(key, toKey);
if(toInclusive || forceInclusive)
return ret <= 0;
else
return ret < 0;
}
protected boolean inFromRange(K key, boolean forceInclusive) {
int ret = keyAnalyzer.compare(key, fromKey);
if (fromInclusive || forceInclusive)
return ret >= 0;
else
return ret > 0;
}
}
}
The table below shows all metrics for PatriciaTrie.java.
| Metric | Value | Description | |
|---|---|---|---|
| BLOCKS | 297.00 | Number of blocks | |
| BLOCK_COMMENT | 24.00 | Number of block comment lines | |
| COMMENTS | 596.00 | Comment lines | |
| COMMENT_DENSITY | 0.57 | Comment density | |
| COMPARISONS | 279.00 | Number of comparison operators | |
| CYCLOMATIC | 414.00 | Cyclomatic complexity | |
| DECL_COMMENTS | 95.00 | Comments in declarations | |
| DOC_COMMENT | 439.00 | Number of javadoc comment lines | |
| ELOC | 1050.00 | Effective lines of code | |
| EXEC_COMMENTS | 59.00 | Comments in executable code | |
| EXITS | 113.00 | Procedure exits | |
| FUNCTIONS | 149.00 | Number of function declarations | |
| HALSTEAD_DIFFICULTY | 134.24 | Halstead difficulty | |
| HALSTEAD_EFFORT | 0.00 | Halstead effort | |
| INTERFACE_COMPLEXITY | 405.00 | Interface complexity | |
| JAVA0001 | 0.00 | JAVA0001 Package name does not contain only lower case letters | |
| JAVA0002 | 1.00 | JAVA0002 Package name does not begin with a top level domain name or country code | |
| JAVA0003 | 0.00 | JAVA0003 Minimize use of on-demand (.*) imports | |
| JAVA0004 | 0.00 | JAVA0004 Unnecessary import from java.lang | |
| JAVA0005 | 0.00 | JAVA0005 Imports not in specified order | |
| JAVA0006 | 0.00 | JAVA0006 Empty finally block | |
| JAVA0007 | 0.00 | JAVA0007 Should not declare public field | |
| JAVA0008 | 0.00 | JAVA0008 Empty catch block | |
| JAVA0009 | 0.00 | JAVA0009 Protected member in final class | |
| JAVA0010 | 0.00 | JAVA0010 Non-instantiable class does not contain a non-private static member | |
| JAVA0011 | 1.00 | JAVA0011 Abstract class does not contain an abstract method | |
| JAVA0012 | 0.00 | JAVA0012 Non-constructor method with same name as declaring class | |
| JAVA0013 | 0.00 | JAVA0013 Non-blank final field is not static | |
| JAVA0014 | 0.00 | JAVA0014 Class with only static members has non-private constructor | |
| JAVA0015 | 0.00 | JAVA0015 Package class contains public nested type | |
| JAVA0016 | 0.00 | JAVA0016 Abstract class contains public constructor | |
| JAVA0017 | 0.00 | JAVA0017 Class name does not have required form | |
| JAVA0018 | 0.00 | JAVA0018 Method name does not have required form | |
| JAVA0019 | 0.00 | JAVA0019 Interface name does not have required form | |
| JAVA0020 | 0.00 | JAVA0020 Field name does not have required form | |
| JAVA0021 | 0.00 | JAVA0021 Interface method name does not have required form | |
| JAVA0022 | 0.00 | JAVA0022 Static final field name does not have required form | |
| JAVA0023 | 0.00 | JAVA0023 Empty finalize method | |
| JAVA0024 | 0.00 | JAVA0024 Empty class | |
| JAVA0025 | 0.00 | JAVA0025 Method override is empty | |
| JAVA0026 | 0.00 | JAVA0026 Finalize method with parameters | |
| JAVA0029 | 1.00 | JAVA0029 Private method not used | |
| JAVA0030 | 0.00 | JAVA0030 Private field not used | |
| JAVA0031 | 2.00 | JAVA0031 Case statement not properly closed | |
| JAVA0032 | 2.00 | JAVA0032 Switch statement missing default | |
| JAVA0033 | 0.00 | JAVA0033 default: not last case in switch statement | |
| JAVA0034 | 90.00 | JAVA0034 Missing braces in if statement | |
| JAVA0035 | 0.00 | JAVA0035 Missing braces in for statement | |
| JAVA0036 | 2.00 | JAVA0036 Missing braces in while statement | |
| JAVA0038 | 0.00 | JAVA0038 Non-case label in switch statement | |
| JAVA0039 | 0.00 | JAVA0039 Break statement with label | |
| JAVA0040 | 0.00 | JAVA0040 Switch statement contains N cases (maximum: M) | |
| JAVA0041 | 0.00 | JAVA0041 Nested synchronized block | |
| JAVA0042 | 0.00 | JAVA0042 Empty synchronized statement | |
| JAVA0043 | 0.00 | JAVA0043 Inner class does not use outer class | |
| JAVA0044 | 0.00 | JAVA0044 Serializable class with no instance variables | |
| JAVA0045 | 0.00 | JAVA0045 Serializable class with only transient fields | |
| JAVA0046 | 0.00 | JAVA0046 Name of class not derived from Exception ends with 'Exception' | |
| JAVA0047 | 0.00 | JAVA0047 Serializable class derives from invalid base class | |
| JAVA0048 | 0.00 | JAVA0048 Name of class derived from Exception does not end with 'Exception' | |
| JAVA0049 | 0.00 | JAVA0049 Nested block at depth N (maximum: M) | |
| JAVA0050 | 0.00 | JAVA0050 Class derives from java.lang.Error | |
| JAVA0051 | 0.00 | JAVA0051 Class derives from java.lang.RuntimeException | |
| JAVA0052 | 0.00 | JAVA0052 Class derives from java.lang.Throwable | |
| JAVA0053 | 0.00 | JAVA0053 Unused label | |
| JAVA0054 | 0.00 | JAVA0054 Inheritance depth N exceeds maximum M | |
| JAVA0055 | 0.00 | JAVA0055 Class should be interface | |
| JAVA0056 | 0.00 | JAVA0056 Unnecessary abstract modifier for interface or annotation | |
| JAVA0057 | 0.00 | JAVA0057 Unnecessary default constructor | |
| JAVA0058 | 0.00 | JAVA0058 Constructor calls super() | |
| JAVA0059 | 0.00 | JAVA0059 Method override only calls super() | |
| JAVA0061 | 0.00 | JAVA0061 Inaccessible member in anonymous class | |
| JAVA0062 | 0.00 | JAVA0062 Public class missing public member or protected constructor | |
| JAVA0063 | 0.00 | JAVA0063 Identifier name should not contain '$' | |
| JAVA0064 | 0.00 | JAVA0064 N variations of identifier name (maximum: M) | |
| JAVA0065 | 0.00 | JAVA0065 Unnecessary final modifier for method in final class | |
| JAVA0066 | 0.00 | JAVA0066 Unnecessary modifier for interface nested type | |
| JAVA0067 | 0.00 | JAVA0067 Array descriptor on identifier name | |
| JAVA0068 | 0.00 | JAVA0068 Modifiers not declared in recommended order | |
| JAVA0071 | 0.00 | JAVA0071 Strings compared with == | |
| JAVA0073 | 0.00 | JAVA0073 Integer division in floating-point context | |
| JAVA0074 | 0.00 | JAVA0074 Use of Object.notify() | |
| JAVA0075 | 4.00 | JAVA0075 Method parameter hides field | |
| JAVA0076 | 0.00 | JAVA0076 Use of magic number | |
| JAVA0077 | 0.00 | JAVA0077 Private field not used in declaring class | |
| JAVA0078 | 0.00 | JAVA0078 Floating point values compared with == | |
| JAVA0079 | 0.00 | JAVA0079 Use of instance to reference static member | |
| JAVA0080 | 0.00 | JAVA0080 Import declaration not used | |
| JAVA0081 | 0.00 | JAVA0081 Boolean literal in comparison | |
| JAVA0082 | 0.00 | JAVA0082 Unnecessary widening cast | |
| JAVA0083 | 0.00 | JAVA0083 Unnecessary instanceof test | |
| JAVA0084 | 0.00 | JAVA0084 Should use compound assignment operator | |
| JAVA0085 | 0.00 | JAVA0085 Use of sun.* class | |
| JAVA0087 | 0.00 | JAVA0087 Use of Thread.sleep() | |
| JAVA0089 | 0.00 | JAVA0089 Use of restricted package | |
| JAVA0092 | 0.00 | JAVA0092 Use of restricted type | |
| JAVA0093 | 0.00 | JAVA0093 Redundant assignment | |
| JAVA0094 | 0.00 | JAVA0094 Field hides a superclass field | |
| JAVA0095 | 0.00 | JAVA0095 Uninitialized private field | |
| JAVA0096 | 4.00 | JAVA0096 Field in nested class hides outer field | |
| JAVA0098 | 2.00 | JAVA0098 Minimize use of implicit field initializers | |
| JAVA0100 | 0.00 | JAVA0100 Class contains N non-final fields (maximum: M) | |
| JAVA0101 | 2.00 | JAVA0101 Unnecessary modifier for field in interface | |
| JAVA0102 | 0.00 | JAVA0102 Last statement in finalize() not super.finalize() | |
| JAVA0103 | 0.00 | JAVA0103 Explicit call to finalize() | |
| JAVA0104 | 0.00 | JAVA0104 finalize() only calls super.finalize() | |
| JAVA0105 | 0.00 | JAVA0105 Duplicate import declaration | |
| JAVA0106 | 0.00 | JAVA0106 Unnecessary import from current package | |
| JAVA0108 | 59.00 | JAVA0108 Incorrect javadoc: no @param tag for 'parameter' | |
| JAVA0109 | 2.00 | JAVA0109 Incorrect javadoc: no parameter 'parameter' | |
| JAVA0110 | 45.00 | JAVA0110 Incorrect javadoc: no @return tag | |
| JAVA0111 | 0.00 | JAVA0111 Incorrect javadoc: @return tag for void method | |
| JAVA0112 | 0.00 | JAVA0112 Incorrect javadoc: no exception 'exception' in throws | |
| JAVA0113 | 0.00 | JAVA0113 Incorrect javadoc: no @author tag | |
| JAVA0114 | 1.00 | JAVA0114 Incorrect javadoc: no @v | |