org.biojava.utils.bytecode

Class IfExpression

java.lang.Object

org.biojava.utils.bytecode.IfExpression

All Implemented Interfaces:

CodeGenerator

public class IfExpression
extends Object
implements CodeGenerator

A CodeGenerator that provides something semanticaly identical to if.

It generates code of the form:

conditional branch to trueLabel
ifFalse instructions here
branch to endLabel
trueLabel
ifTrue instructions here
endLabel

Author:

Matthew Pocock

Constructor Summary

Constructors

Constructor and Description
IfExpression(byte ifInstruction, CodeGenerator ifTrue, CodeGenerator ifFalse)

Method Summary

Methods

Modifier and Type	Method and Description
CodeGenerator	getIfFalse()
Instruction	getIfInstruction()
CodeGenerator	getIfTrue()
int	stackDelta() Return the change in the stack dept this generator will cause.
int	stackDepth() Return the total depth of the stack required by this CodeGenerator.
void	writeCode(CodeContext ctx) Write the byte or bytes for this CodeGenerator to a CodeContext.

Methods inherited from class java.lang.Object

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

Constructor Detail

IfExpression

public IfExpression(byte ifInstruction,
            CodeGenerator ifTrue,
            CodeGenerator ifFalse)

Method Detail

getIfInstruction

public Instruction getIfInstruction()

getIfTrue

public CodeGenerator getIfTrue()

getIfFalse

public CodeGenerator getIfFalse()

writeCode

public void writeCode(CodeContext ctx)
               throws CodeException

Description copied from interface: CodeGenerator

Write the byte or bytes for this CodeGenerator to a CodeContext.

Specified by:

writeCode in interface CodeGenerator

Parameters:

ctx - a CodeContext to write to

Throws:

CodeException - if there was some failure in writing to the context

stackDepth

public int stackDepth()

Description copied from interface: CodeGenerator

Return the total depth of the stack required by this CodeGenerator.

For single byte-code instructions, this will be the same as stackDelta() if stackDelta() is positive, zero otherwise. For a compound instruction, this will be the maximum stack depth required to execute all sub-instructions.

Specified by:

stackDepth in interface CodeGenerator

Returns:

the stack depth needed

stackDelta

public int stackDelta()

Description copied from interface: CodeGenerator

Return the change in the stack dept this generator will cause.

In the case of an instruction that adds items to the stack, stackDelta will be positive. For instructions that removes items from the stack, this will be negative.

Specified by:

stackDelta in interface CodeGenerator

Returns:

the change between stack depth before and after execution of this code