com.sun.msv.grammar

Class ExpressionPool

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

Nested Class Summary
static classExpressionPool.ClosedHash
expression cache by closed hash.
Constructor Summary
ExpressionPool(ExpressionPool parent)
creates new expression pool as a child pool of the given parent pool.
ExpressionPool()
Method Summary
ExpressioncreateAnyString()
ExpressioncreateAttribute(NameClass nameClass)
ExpressioncreateAttribute(NameClass nameClass, Expression content)
ExpressioncreateChoice(Expression left, Expression right)
ExpressioncreateConcur(Expression left, Expression right)
ExpressioncreateData(XSDatatype dt)
ExpressioncreateData(Datatype dt, StringPair typeName)
ExpressioncreateData(Datatype dt, StringPair typeName, Expression except)
ExpressioncreateEpsilon()
ExpressioncreateInterleave(Expression left, Expression right)
ExpressioncreateList(Expression exp)
ExpressioncreateMixed(Expression body)
ExpressioncreateNullSet()
ExpressioncreateOneOrMore(Expression child)
ExpressioncreateOptional(Expression child)
ExpressioncreateSequence(Expression left, Expression right)
ExpressioncreateValue(XSDatatype dt, Object value)
ExpressioncreateValue(Datatype dt, StringPair typeName, Object value)
ExpressioncreateZeroOrMore(Expression child)

Constructor Detail

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 Detail

createAnyString

public final Expression createAnyString()

createAttribute

public final Expression createAttribute(NameClass nameClass)

createAttribute

public final Expression createAttribute(NameClass nameClass, Expression content)

createChoice

public final Expression createChoice(Expression left, Expression right)

createConcur

public final Expression createConcur(Expression left, Expression right)

createData

public final Expression createData(XSDatatype dt)

createData

public final Expression createData(Datatype dt, StringPair typeName)

createData

public final Expression createData(Datatype dt, StringPair typeName, Expression except)

createEpsilon

public final Expression createEpsilon()

createInterleave

public final Expression createInterleave(Expression left, Expression right)

createList

public final Expression createList(Expression exp)

createMixed

public final Expression createMixed(Expression body)

createNullSet

public final Expression createNullSet()

createOneOrMore

public final Expression createOneOrMore(Expression child)

createOptional

public final Expression createOptional(Expression child)

createSequence

public final Expression createSequence(Expression left, Expression right)

createValue

public final Expression createValue(XSDatatype dt, Object value)

createValue

public final Expression createValue(Datatype dt, StringPair typeName, Object value)

createZeroOrMore

public final Expression createZeroOrMore(Expression child)