org.apache.jasper.xmlparser

Class SymbolTable

java.lang.Object

org.apache.jasper.xmlparser.SymbolTable

public class SymbolTable
extends Object

This class is a symbol table implementation that guarantees that strings used as identifiers are unique references. Multiple calls to addSymbol will always return the same string reference.

The symbol table performs the same task as String.intern() with the following differences:

• A new string object does not need to be created in order to retrieve a unique reference. Symbols can be added by using a series of characters in a character array.
• Users of the symbol table can provide their own symbol hashing implementation. For example, a simple string hashing algorithm may fail to produce a balanced set of hashcodes for symbols that are mostly unique. Strings with similar leading characters are especially prone to this poor hashing behavior.

Author:

Andy Clark

Constructor Summary

Constructors

Constructor and Description
SymbolTable() Constructs a symbol table with a default number of buckets.
SymbolTable(int tableSize) Constructs a symbol table with a specified number of buckets.

Method Summary

Modifier and Type	Method and Description
String	addSymbol(char[] buffer, int offset, int length) Adds the specified symbol to the symbol table and returns a reference to the unique symbol.
int	hash(char[] buffer, int offset, int length) Returns a hashcode value for the specified symbol information.

Methods inherited from class java.lang.Object

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

Constructor Detail

SymbolTable

public SymbolTable()

Constructs a symbol table with a default number of buckets.

SymbolTable

public SymbolTable(int tableSize)

Constructs a symbol table with a specified number of buckets.

Parameters:

tableSize - The table size (default is 101)

Method Detail

addSymbol

public String addSymbol(char[] buffer,
                        int offset,
                        int length)

Adds the specified symbol to the symbol table and returns a reference to the unique symbol. If the symbol already exists, the previous symbol reference is returned instead, in order guarantee that symbol references remain unique.

Parameters:

buffer - The buffer containing the new symbol.

offset - The offset into the buffer of the new symbol.

length - The length of the new symbol in the buffer.

Returns:

the symbol added

hash

public int hash(char[] buffer,
                int offset,
                int length)

Returns a hashcode value for the specified symbol information. The value returned by this method must be identical to the value returned by the hash(String) method when called with the string object created from the symbol information.

Parameters:

buffer - The character buffer containing the symbol.

offset - The offset into the character buffer of the start of the symbol.

length - The length of the symbol.

Returns:

the hash value