com.github.wuic.servlet.jetty

Class ArrayTernaryTrie<V>

java.lang.Object

com.github.wuic.servlet.jetty.ArrayTernaryTrie<V>

Type Parameters:

V - the Entry type

public class ArrayTernaryTrie<V>
extends Object

A Ternary Trie String lookup data structure.

This Trie is of a fixed size and cannot grow (which can be a good thing with regards to DOS when used as a cache).

The Trie is stored in 3 arrays:

char[] _tree

This is semantically 2 dimensional array flattened into a 1 dimensional char array. The second dimension is that every 4 sequential elements represents a row of: character; hi index; eq index; low index, used to build a ternary trie of key strings.

String[] _key

An array of key values where each element matches a row in the _tree array. A non zero key element indicates that the _tree row is a complete key rather than an intermediate character of a longer key.

V[] _value

An array of values corresponding to the _key array

The lookup of a value will iterate through the _tree array matching characters. If the equal tree branch is followed, then the _key array is looked up to see if this is a complete match. If a match is found then the _value array is looked up to return the matching value.

This Trie may be instantiated either as case sensitive or insensitive.

This Trie is not Threadsafe and contains no mutual exclusion or deliberate memory barriers. It is intended for an ArrayTrie to be built by a single thread and then used concurrently by multiple threads and not mutated during that access. If concurrent mutations of the Trie is required external locks need to be applied.

Constructor Summary

Constructors

Constructor and Description
ArrayTernaryTrie() Create a case insensitive Trie of default capacity.
ArrayTernaryTrie(ArrayTernaryTrie<V> trie, double factor) Copy Trie and change capacity by a factor
ArrayTernaryTrie(boolean insensitive) Create a Trie of default capacity
ArrayTernaryTrie(boolean insensitive, int capacity) Create a Trie
ArrayTernaryTrie(int capacity) Create a case insensitive Trie

Method Summary

Methods

Modifier and Type	Method and Description
void	dump()
V	get(ByteBuffer b)
V	get(ByteBuffer b, int offset, int len) Get and exact match from a segment of a ByteBuufer as key
V	get(String s)
V	get(String s, int offset, int len) Get and exact match from a String key
V	getBest(ByteBuffer b, int offset, int len)
V	getBest(String s)
V	getBest(String s, int offset, int length) Get the best match from key in a String.
static int	hilo(int diff)
boolean	isCaseInsensitive()
boolean	isFull()
Set<String>	keySet()
boolean	put(String s, V v) Put and entry into the Trie
boolean	put(V v)
V	remove(String s)
String	toString()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ArrayTernaryTrie

public ArrayTernaryTrie()

Create a case insensitive Trie of default capacity.

ArrayTernaryTrie

public ArrayTernaryTrie(boolean insensitive)

Create a Trie of default capacity

Parameters:

insensitive - true if the Trie is insensitive to the case of the key.

ArrayTernaryTrie

public ArrayTernaryTrie(int capacity)

Create a case insensitive Trie

Parameters:

capacity - The capacity of the Trie, which is in the worst case is the total number of characters of all keys stored in the Trie. The capacity needed is dependent of the shared prefixes of the keys. For example, a capacity of 6 nodes is required to store keys "foo" and "bar", but a capacity of only 4 is required to store "bar" and "bat".

ArrayTernaryTrie

public ArrayTernaryTrie(boolean insensitive,
                int capacity)

Create a Trie

Parameters:

insensitive - true if the Trie is insensitive to the case of the key.

capacity - The capacity of the Trie, which is in the worst case is the total number of characters of all keys stored in the Trie. The capacity needed is dependent of the shared prefixes of the keys. For example, a capacity of 6 nodes is required to store keys "foo" and "bar", but a capacity of only 4 is required to store "bar" and "bat".

ArrayTernaryTrie

public ArrayTernaryTrie(ArrayTernaryTrie<V> trie,
                double factor)

Copy Trie and change capacity by a factor

Parameters:

trie - the trie to copy from

factor - the factor to grow the capacity by

Method Detail

put

public boolean put(String s,
          V v)

Put and entry into the Trie

Parameters:

s - The key for the entry

v - The value of the entry

Returns:

True if the Trie had capacity to add the field.

get

public V get(String s,
    int offset,
    int len)

Get and exact match from a String key

Parameters:

s - The key

offset - The offset within the string of the key

len - the length of the key

Returns:

the value for the string / offset / length

get

public V get(ByteBuffer b,
    int offset,
    int len)

Get and exact match from a segment of a ByteBuufer as key

Parameters:

b - The buffer

offset - The offset within the buffer of the key

len - the length of the key

Returns:

The value or null if not found

getBest

public V getBest(String s)

getBest

public V getBest(String s,
        int offset,
        int length)

Get the best match from key in a String.

Parameters:

s - The string

offset - The offset within the string of the key

length - the length of the key

Returns:

The value or null if not found

getBest

public V getBest(ByteBuffer b,
        int offset,
        int len)

toString

public String toString()

Overrides:

toString in class Object

keySet

public Set<String> keySet()

isFull

public boolean isFull()

hilo

public static int hilo(int diff)

dump

public void dump()

put

public boolean put(V v)

remove

public V remove(String s)

get

public V get(String s)

get

public V get(ByteBuffer b)

isCaseInsensitive

public boolean isCaseInsensitive()