Package com.sun.msv.grammar

Class ExpressionPool

java.lang.Object

com.sun.msv.grammar.ExpressionPool

All Implemented Interfaces:

Serializable

public class ExpressionPool
extends Object
implements Serializable

Creates a new Expression by combining existing expressions. all expressions are memorized and unified so that every subexpression will be shared and reused. Optimization will be also done transparently. For example, createChoice(P,P) will result in P. createSequence(P,nullSet) will result in nullSet. Furthermore, associative operators are grouped to the left. createChoice( (P|Q), (R|S) ) will be ((P|Q)|R)|S.

Although this unification is essential, this is also the performance bottle neck. In particular, createChoice and createSequence are two most commonly called methods.

For example, when validating a DocBook XML (150KB) twice against DocBook.trex(237KB), createChoice is called 63000 times and createSequence called 23000 times. (the third is the createOptional method and only 1560 times.) And they took more than 10% of validation time, which is the worst time-consuming method.

Therefore, please beware that this class includes several ugly code optimization.

Author:

Kohsuke KAWAGUCHI

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	ExpressionPool.ClosedHash	expression cache by closed hash.

Constructor Summary

Constructors

Constructor	Description
ExpressionPool()
ExpressionPool(ExpressionPool parent)	creates new expression pool as a child pool of the given parent pool.

Method Summary

Modifier and Type	Method	Description
final Expression	createAnyString()
final Expression	createAttribute(NameClass nameClass)
final Expression	createAttribute(NameClass nameClass, Expression content, String defaultValue)
final Expression	createChoice(Expression left, Expression right)
final Expression	createConcur(Expression left, Expression right)
final Expression	createData(XSDatatype dt)
final Expression	createData(org.relaxng.datatype.Datatype dt, StringPair typeName)
final Expression	createData(org.relaxng.datatype.Datatype dt, StringPair typeName, Expression except)
final Expression	createEpsilon()
final Expression	createInterleave(Expression left, Expression right)
final Expression	createList(Expression exp)
final Expression	createMixed(Expression body)
final Expression	createNullSet()
final Expression	createOneOrMore(Expression child)
final Expression	createOptional(Expression child)
final Expression	createSequence(Expression left, Expression right)
final Expression	createValue(XSDatatype dt, Object value)
final Expression	createValue(org.relaxng.datatype.Datatype dt, StringPair typeName, Object value)
final Expression	createZeroOrMore(Expression child)
protected final Expression	unify(Expression exp)	unifies expressions.

Methods inherited from class java.lang.Object

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

Constructor Details

ExpressionPool

public ExpressionPool(ExpressionPool parent)

creates new expression pool as a child pool of the given parent pool.

Every expression memorized in the parent pool can be retrieved, but update operations are only performed upon the child pool. In this way, the parent pool can be shared among the multiple threads without interfering performance.

Furthermore, you can throw away a child pool after a certain time period to prevent it from eating up memory.

ExpressionPool

public ExpressionPool()

Method Details

createAttribute

public final Expression createAttribute(NameClass nameClass)

createAttribute

public final Expression createAttribute(NameClass nameClass,
 Expression content,
 String defaultValue)

createEpsilon

public final Expression createEpsilon()

createNullSet

public final Expression createNullSet()

createAnyString

public final Expression createAnyString()

createChoice

public final Expression createChoice(Expression left,
 Expression right)

createOneOrMore

public final Expression createOneOrMore(Expression child)

createZeroOrMore

public final Expression createZeroOrMore(Expression child)

createOptional

public final Expression createOptional(Expression child)

createData

public final Expression createData(XSDatatype dt)

createData

public final Expression createData(org.relaxng.datatype.Datatype dt,
 StringPair typeName)

createData

public final Expression createData(org.relaxng.datatype.Datatype dt,
 StringPair typeName,
 Expression except)

createValue

public final Expression createValue(XSDatatype dt,
 Object value)

createValue

public final Expression createValue(org.relaxng.datatype.Datatype dt,
 StringPair typeName,
 Object value)

createList

public final Expression createList(Expression exp)

createMixed

public final Expression createMixed(Expression body)

createSequence

public final Expression createSequence(Expression left,
 Expression right)

createConcur

public final Expression createConcur(Expression left,
 Expression right)

createInterleave

public final Expression createInterleave(Expression left,
 Expression right)

unify

protected final Expression unify(Expression exp)

unifies expressions. If the equivalent expression is already registered in the table, destroy newly created one (so that no two objects represents same expression structure). If it's not registered, then register it and return it.