com.saxonica.bytecode
Class ToItemCompiler

java.lang.Object
  com.saxonica.bytecode.ExpressionCompiler
      com.saxonica.bytecode.ToItemCompiler

Direct Known Subclasses:

ArithmeticCompiler, BaseURICompiler, CastExpressionCompiler, CastToUnionCompiler, ComponentCompiler, ContextItemCompiler, CountCompiler, DateTimeConstructorCompiler, DocCompiler, FirstItemExpressionCompiler, FunctionItemExpressionCompiler, IdentityComparisonCompiler, ItemAtCompiler, LastCompiler, LastItemExpressionCompiler, MinimaxCompiler, NamespaceUriFnCompiler, NegateExpressionCompiler, NodeNameFnCompiler, NumberFnCompiler, PartialApplyCompiler, PositionCompiler, QNameFnCompiler, RootExpressionCompiler, RootFunctionCompiler, RoundingCompiler, SingletonAtomizerCompiler, StringLengthCompiler, SumCompiler, ToStringCompiler, TupleExpressionCompiler

public abstract class ToItemCompiler
extends ExpressionCompiler

Abstract superclass for expression compilers that handle expressions returning a single item (or nothing). The compilers for such expressions must implement the compileToItem() method; they may optionally implement other methods such as compileToIterator().

Constructor Summary

ToItemCompiler()

Method Summary

void	compileToBoolean(CompilerService compiler, Expression expression) Generate bytecode to evaluate the expression as a boolean Precondition: none.
void	compileToIterator(CompilerService compiler, Expression expression) Generate bytecode to evaluate the expression as a SequenceIterator Precondition: none.
void	compileToPush(CompilerService compiler, Expression expression) Generate bytecode to evaluate the expression in push mode Precondition: none.
protected void	returnZeroLengthStringIfNull(Expression arg, Generator ga, GeneratedMethodInfo methodInfo, LabelInfo returnLabel, int extraPops) Utility method for use by subclasses to generate code that causes an empty string to be returned if the first argument is an empty sequence.

Methods inherited from class com.saxonica.bytecode.ExpressionCompiler

allocateStatic, compileItemFromInt, compileItemFromString, compileToItem, compileToLoop, compileToPrimitive, generateMethod, getConfiguration, handleEmptyStringResult, setConfiguration, throwXPathException, throwXPathException, unboxItem, verify, visitAnnotation, visitLineNumber

Methods inherited from class java.lang.Object

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

Constructor Detail

ToItemCompiler

public ToItemCompiler()

Method Detail

compileToIterator

public void compileToIterator(CompilerService compiler,
                              Expression expression)
                       throws CannotCompileException

Description copied from class: ExpressionCompiler

Generate bytecode to evaluate the expression as a SequenceIterator Precondition: none. Postcondition: at execution time, the stack contains a SequenceIterator representing the result of the expression

Specified by:

compileToIterator in class ExpressionCompiler

Parameters:

compiler - the compiler service

expression - the expression to be compiled

Throws:

CannotCompileException

compileToBoolean

public void compileToBoolean(CompilerService compiler,
                             Expression expression)
                      throws CannotCompileException

Description copied from class: ExpressionCompiler

Generate bytecode to evaluate the expression as a boolean Precondition: none. Postcondition: at execution time, the stack contains an integer (0=false, 1=true) representing the result of the expression

Specified by:

compileToBoolean in class ExpressionCompiler

Parameters:

compiler - the compiler service

expression - the expression to be compiled

Throws:

CannotCompileException

compileToPush

public void compileToPush(CompilerService compiler,
                          Expression expression)
                   throws CannotCompileException

Description copied from class: ExpressionCompiler

Generate bytecode to evaluate the expression in push mode Precondition: none. Postcondition: at execution time, the stack is unchanged, and the value of the expression has been written to the current receiver

Specified by:

compileToPush in class ExpressionCompiler

Parameters:

compiler - the compiler service

expression - the expression to be compiled

Throws:

CannotCompileException

returnZeroLengthStringIfNull

protected void returnZeroLengthStringIfNull(Expression arg,
                                            Generator ga,
                                            GeneratedMethodInfo methodInfo,
                                            LabelInfo returnLabel,
                                            int extraPops)

Utility method for use by subclasses to generate code that causes an empty string to be returned if the first argument is an empty sequence. Precondition: the value of the first argument is on the stack, either as a string or as an item Postcondition: either the control has jumped to the return label with a zero-length string on the stack, or control drops through with the value of the first argument still on the stack (as supplied).

Parameters:

arg - the first argument

ga - the Generator

methodInfo - the method information

returnLabel - the label to jump to on completion

extraPops - items (other than the string being tested) that need to be popped of the stack if jumping to the return label