com.sun.jdo.spi.persistence.support.sqlstore.query.util.scope

Class SymbolTable

java.lang.Object

com.sun.jdo.spi.persistence.support.sqlstore.query.util.scope.SymbolTable

public class SymbolTable
extends Object

The symbol table handling declared identifies.

Version:

0.1

Author:

Michael Bouschen

Field Summary

Fields

Modifier and Type	Field and Description
protected int	actualScope The actual scope level.
protected Stack	nestings Stack of old definitions.
protected Hashtable	symbols The table of declared identifier (symbols).

Constructor Summary

Constructors

Constructor and Description
SymbolTable()

Method Summary

Modifier and Type	Method and Description
Definition	declare(String ident, Definition def) Add identifier to the actual scope.
void	enterScope() Opens a new scope.
protected void	forgetNesting(Nesting nesting) Internal method to reinstall the old definitions.
int	getActualScope() Returns the level of the actual scope.
Definition	getDefinition(String ident) Checks the symbol table for the actual definition of the specified identifier.
boolean	isDeclared(String ident) Checks whether the specified identifier is declared.
void	leaveScope() Closes the actual scope.

Methods inherited from class java.lang.Object

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

Field Detail

actualScope

protected int actualScope

The actual scope level.

nestings

protected Stack nestings

Stack of old definitions.

symbols

protected Hashtable symbols

The table of declared identifier (symbols).

Constructor Detail

SymbolTable

public SymbolTable()

Method Detail

enterScope

public void enterScope()

Opens a new scope. Prepare everything to handle old definitions when a identifier declaration is hidden.

leaveScope

public void leaveScope()

Closes the actual scope. Hidden definitions are reinstalled.

getActualScope

public int getActualScope()

Returns the level of the actual scope.

Returns:

actual scope level.

declare

public Definition declare(String ident,
                          Definition def)

Add identifier to the actual scope. If the identifier was already declared in the actual scope the symbol table is NOT changed and the old definition is returned. Otherwise a possible definition of a lower level scope is saved in the actual nesting and the new definition is stored in the symbol table. This allows to reinstall the old definition when the sctaul scope is closed.

Parameters:

ident - identifier to be declared

def - new definition of identifier

Returns:

the old definition if the identifier was already declared in the actual scope; null otherwise

isDeclared

public boolean isDeclared(String ident)

Checks whether the specified identifier is declared.

Parameters:

ident - the name of identifier to be tested

Returns:

true if the identifier is declared; false otherwise.

getDefinition

public Definition getDefinition(String ident)

Checks the symbol table for the actual definition of the specified identifier. If the identifier is declared the definition is returned, otherwise null.

Parameters:

ident - the name of identifier

Returns:

the actual definition of ident is declared; null otherise.

forgetNesting

protected void forgetNesting(Nesting nesting)

Internal method to reinstall the old definitions. The method is called when a scope is closed. For all identifier that were declared in the closed scope their former definition (that was hidden) is reinstalled.

Parameters:

nesting - list of hidden definitions