Package org.apache.sling.scripting.jsp.jasper.xmlparser

Class SymbolTable

java.lang.Object
org.apache.sling.scripting.jsp.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.
Version:
$Id: SymbolTable.java 467222 2006-10-24 03:17:11Z markt $
Author:
Andy Clark

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    protected static final class 
    SymbolTable.Entry
    This class is a symbol table entry.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected SymbolTable.Entry[]
    fBuckets
    Buckets.
    protected int
    fTableSize
     
    protected static final int
    TABLE_SIZE
    Default table size.

  • Constructor Summary

    Constructors
    Constructor
    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
    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.
    String
    addSymbol(String symbol)
    Adds the specified symbol to the symbol table and returns a reference to the unique symbol.
    boolean
    containsSymbol(char[] buffer, int offset, int length)
    Returns true if the symbol table already contains the specified symbol.
    boolean
    containsSymbol(String symbol)
    Returns true if the symbol table already contains the specified symbol.
    int
    hash(char[] buffer, int offset, int length)
    Returns a hashcode value for the specified symbol information.
    int
    hash(String symbol)
    Returns a hashcode value for the specified symbol.

    Methods inherited from class java.lang.Object

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

  • Field Details

    • TABLE_SIZE

      protected static final int TABLE_SIZE
      Default table size.
      See Also:

    • fBuckets

      protected SymbolTable.Entry[] fBuckets
      Buckets.

    • fTableSize

      protected int fTableSize

  • Constructor Details

    • 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.

  • Method Details

    • addSymbol

      public String addSymbol(String symbol)
      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:
      symbol - The new symbol.

    • 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.

    • hash

      public int hash(String symbol)
      Returns a hashcode value for the specified symbol. The value returned by this method must be identical to the value returned by the hash(char[],int,int) method when called with the character array that comprises the symbol string.
      Parameters:
      symbol - The symbol to hash.

    • 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.

    • containsSymbol

      public boolean containsSymbol(String symbol)
      Returns true if the symbol table already contains the specified symbol.
      Parameters:
      symbol - The symbol to look for.

    • containsSymbol

      public boolean containsSymbol(char[] buffer, int offset, int length)
      Returns true if the symbol table already contains the specified symbol.
      Parameters:
      buffer - The buffer containing the symbol to look for.
      offset - The offset into the buffer.
      length - The length of the symbol in the buffer.