Class SimulaCodeTransform

java.lang.Object

simula.compiler.transform.SimulaCodeTransform

All Implemented Interfaces:

ClassFileTransform<CodeTransform, CodeElement, CodeBuilder>, CodeTransform

final class SimulaCodeTransform
extends Object
implements CodeTransform

Simula .class file transformer.

To easily modify the code, the Simula Compiler generates certain method call in the .java file:
Process the stream of CodeElements looking for two particular code sequences:

CASE 1: Repair the JUMPTABLE(_JTX, n).

This method-call is a placeholder for where to put in a Jump-Table.
The parameter 'n' is the number of cases.

JUMPTABLE will always occur before any any labels.

Locate the instruction sequence:

   ... any instruction(s)
   GETFIELD _JTX
   ICONST n   or  BIPUSH  or SIPUSH
   INVOKESTATIC _JUMPTABLE

Replace it by:

   ... any instruction(s)
   GETFIELD _JTX
   TABLESWITCH ... uses 'n' labels which is binded later.

CASE 2: Repair a LABEL(n).

This method-call is used to signal the occurrence of a Simula Label.
The label 'n' in the TABLESWITCH is binded.

Locate the instruction sequence:

   ICONST n   or  BIPUSH  or SIPUSH
   INVOKESTATIC _SIM_LABEL
   NEXT-INSTRUCTION

Replace it by:

   PREV-INSTRUCTION
   LABELBINDING( case n )
   NEXT-INSTRUCTION

Link to GitHub: Source File.

Author:

Øystein Myhre Andersen

Field Summary

Fields

Modifier and Type	Field	Description
private List<SwitchCase>	cases	The switch cases.
private CodeElement	prevElement	The previous CodeElement

Fields inherited from interface java.lang.classfile.CodeTransform

ACCEPT_ALL

Constructor Summary

Constructors

Constructor	Description
SimulaCodeTransform()	Default Constructor.

Method Summary

Modifier and Type	Method	Description
void	accept(CodeBuilder builder, CodeElement element)
void	atEnd(CodeBuilder builder)
private int	getConst(CodeElement element)	ConstantInstruction: ICONST n or BIPUSH or SIPUSH
String	toString()

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.classfile.ClassFileTransform

atStart

Methods inherited from interface java.lang.classfile.CodeTransform

andThen

Field Details

cases

private List<SwitchCase> cases

The switch cases.

prevElement

private CodeElement prevElement

The previous CodeElement

Constructor Details

SimulaCodeTransform

SimulaCodeTransform()

Default Constructor.

Method Details

atEnd

public void atEnd(CodeBuilder builder)

Specified by:

atEnd in interface ClassFileTransform<CodeTransform, CodeElement, CodeBuilder>

accept

public void accept(CodeBuilder builder,
 CodeElement element)

Specified by:

accept in interface ClassFileTransform<CodeTransform, CodeElement, CodeBuilder>

getConst

private int getConst(CodeElement element)

ConstantInstruction: ICONST n or BIPUSH or SIPUSH

Parameters:

element - a CodeElement: ICONST n or BIPUSH or SIPUSH

Returns:

the integer constant value

Throws:

RuntimeException - if something went wrong

toString

public String toString()

Overrides:

toString in class Object