org.codehaus.janino

Class CodeContext

java.lang.Object

org.codehaus.janino.CodeContext

public class CodeContext
extends Object

The context of the compilation of a function (constructor or method). Manages generation of byte code, the exception table, generation of line number tables, allocation of local variables, determining of stack size and local variable table size and flow analysis.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	CodeContext.FixUp A throw-in interface that marks CodeContext.Offsets as "fix-ups": During the execution of fixUp(), all "fix-ups" are invoked and can do last touches to the code attribute.
class	CodeContext.Inserter A class that implements an insertion point into a "Code" attribute.
class	CodeContext.LineNumberOffset An CodeContext.Offset who#s sole purpose is to later create a 'LneNumberTable' attribute.
class	CodeContext.Offset A class that represents an offset within a "Code" attribute.

Constructor Summary

Constructors

Constructor and Description
CodeContext(ClassFile classFile, String functionName) Creates an empty "Code" attribute.

Method Summary

Modifier and Type	Method and Description
void	addExceptionTableEntry(CodeContext.Offset startPc, CodeContext.Offset endPc, CodeContext.Offset handlerPc, String catchTypeFd) Adds another entry to the "exception_table" of this code attribute (see JVMS 4.7.3).
short	allocateLocalVariable(short size) Allocates space for a local variable of the given size (1 or 2) on the local variable array.
Java.LocalVariableSlot	allocateLocalVariable(short size, String name, IClass type) Allocates space for a local variable of the given size (1 or 2) on the local variable array.
CodeContext.Inserter	currentInserter()
void	fixUpAndRelocate() Fixes up all of the offsets and relocate() all relocatables.
void	flowAnalysis(String functionName) Checks the code for consistency; updates the "maxStack" member.
List<Java.LocalVariableSlot>	getAllLocalVars()
ClassFile	getClassFile() The ClassFile this context is related to.
void	makeSpace(short lineNumber, int size) Adds space for size bytes at current offset.
CodeContext.Inserter	newInserter() Allocates an CodeContext.Inserter, set it to the current offset, and inserts it before the current offset.
CodeContext.Offset	newOffset() Creates and inserts an CodeContext.Offset at the current inserter's current position.
void	popInserter() Replaces the current CodeContext.Inserter with the remembered one (see pushInserter(CodeContext.Inserter)).
void	pushInserter(CodeContext.Inserter ins) Remembers the current CodeContext.Inserter, then replaces it with the new one.
void	removeCode(CodeContext.Offset from, CodeContext.Offset to) Removes all code between from and to.
void	restoreLocalVariables() Restores the previous size of the local variables array.
List<Java.LocalVariableSlot>	saveLocalVariables() Remembers the current size of the local variables array.
protected void	storeCodeAttributeBody(DataOutputStream dos, short lineNumberTableAttributeNameIndex, short localVariableTableAttributeNameIndex)
protected ClassFile.AttributeInfo	storeLocalVariableTable(DataOutputStream dos, short localVariableTableAttributeNameIndex)
void	write(short lineNumber, byte b1) Inserts a byte at the current insertion position.
void	write(short lineNumber, byte[] b) Inserts a sequence of bytes at the current insertion position.
void	write(short lineNumber, byte b1, byte b2) Inserts bytes at the current insertion position.
void	write(short lineNumber, byte b1, byte b2, byte b3) Inserts bytes at the current insertion position.
void	write(short lineNumber, byte b1, byte b2, byte b3, byte b4) Inserts bytes at the current insertion position.
void	writeBranch(short lineNumber, int opcode, CodeContext.Offset dst)
void	writeOffset(short lineNumber, CodeContext.Offset src, CodeContext.Offset dst) Writes a four-byte offset (as it is used in TABLESWITCH and LOOKUPSWITCH) into this code context.
void	writeShort(short lineNumber, int v)

Methods inherited from class java.lang.Object

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

Constructor Detail

CodeContext

public CodeContext(ClassFile classFile,
                   String functionName)

Creates an empty "Code" attribute.

Method Detail

getClassFile

public ClassFile getClassFile()

The ClassFile this context is related to.

allocateLocalVariable

public short allocateLocalVariable(short size)

Allocates space for a local variable of the given size (1 or 2) on the local variable array.

As a side effect, the "max_locals" field of the "Code" attribute is updated.

The only way to deallocate local variables is to saveLocalVariables() and later restoreLocalVariables().

Parameters:

size - The number of slots to allocate (1 or 2)

Returns:

The slot index of the allocated variable

allocateLocalVariable

public Java.LocalVariableSlot allocateLocalVariable(short size,
                                                    @Nullable
                                                    String name,
                                                    @Nullable
                                                    IClass type)

Allocates space for a local variable of the given size (1 or 2) on the local variable array. As a side effect, the "max_locals" field of the "Code" attribute is updated.

The only way to deallocate local variables is to saveLocalVariables() and later restoreLocalVariables().

Parameters:

size - Number of slots to use (1 or 2)

name - The variable name; if null, then the variable won't be written to the localvariabletable

type - The variable type; if the name is not null, then the type is needed to write to the localvariabletable

saveLocalVariables

public List<Java.LocalVariableSlot> saveLocalVariables()

Remembers the current size of the local variables array.

restoreLocalVariables

public void restoreLocalVariables()

Restores the previous size of the local variables array. This MUST to be called for every call to saveLocalVariables as it closes the variable extent for all the active local variables in the current block.

storeCodeAttributeBody

protected void storeCodeAttributeBody(DataOutputStream dos,
                                      short lineNumberTableAttributeNameIndex,
                                      short localVariableTableAttributeNameIndex)
                               throws IOException

Parameters:

dos -

lineNumberTableAttributeNameIndex - 0 == don't generate a "LineNumberTable" attribute

Throws:

IOException

storeLocalVariableTable

@Nullable
protected ClassFile.AttributeInfo storeLocalVariableTable(DataOutputStream dos,
                                                                     short localVariableTableAttributeNameIndex)

Returns:

A ClassFile.LocalVariableTableAttribute for this CodeContext

flowAnalysis

public void flowAnalysis(String functionName)

Checks the code for consistency; updates the "maxStack" member.

Notice: On inconsistencies, a "RuntimeException" is thrown (KLUDGE).

fixUpAndRelocate

public void fixUpAndRelocate()

Fixes up all of the offsets and relocate() all relocatables.

write

public void write(short lineNumber,
                  byte[] b)

Inserts a sequence of bytes at the current insertion position. Creates CodeContext.LineNumberOffsets as necessary.

Parameters:

lineNumber - The line number that corresponds to the byte code, or -1

b -

write

public void write(short lineNumber,
                  byte b1)

Inserts a byte at the current insertion position. Creates CodeContext.LineNumberOffsets as necessary.

This method is an optimization to avoid allocating small byte[] and ease GC load.

Parameters:

lineNumber - The line number that corresponds to the byte code, or -1

b1 -

write

public void write(short lineNumber,
                  byte b1,
                  byte b2)

Inserts bytes at the current insertion position. Creates CodeContext.LineNumberOffsets as necessary.

This method is an optimization to avoid allocating small byte[] and ease GC load.

Parameters:

lineNumber - The line number that corresponds to the byte code, or -1

b1 -

b2 -

write

public void write(short lineNumber,
                  byte b1,
                  byte b2,
                  byte b3)

Inserts bytes at the current insertion position. Creates CodeContext.LineNumberOffsets as necessary.

This method is an optimization to avoid allocating small byte[] and ease GC load.

Parameters:

lineNumber - The line number that corresponds to the byte code, or -1

b1 -

b2 -

b3 -

write

public void write(short lineNumber,
                  byte b1,
                  byte b2,
                  byte b3,
                  byte b4)

Inserts bytes at the current insertion position. Creates CodeContext.LineNumberOffsets as necessary.

This method is an optimization to avoid allocating small byte[] and ease GC load.

Parameters:

lineNumber - The line number that corresponds to the byte code, or -1

b1 -

b2 -

b3 -

b4 -

makeSpace

public void makeSpace(short lineNumber,
                      int size)

Adds space for size bytes at current offset. Creates CodeContext.LineNumberOffsets as necessary.

Parameters:

lineNumber - The line number that corresponds to the byte code, or -1

size - The size in bytes to inject

writeShort

public void writeShort(short lineNumber,
                       int v)

Parameters:

lineNumber - The line number that corresponds to the byte code, or -1

writeBranch

public void writeBranch(short lineNumber,
                        int opcode,
                        CodeContext.Offset dst)

Parameters:

lineNumber - The line number that corresponds to the byte code, or -1

writeOffset

public void writeOffset(short lineNumber,
                        CodeContext.Offset src,
                        CodeContext.Offset dst)

Writes a four-byte offset (as it is used in TABLESWITCH and LOOKUPSWITCH) into this code context.

newOffset

public CodeContext.Offset newOffset()

Creates and inserts an CodeContext.Offset at the current inserter's current position.

newInserter

public CodeContext.Inserter newInserter()

Allocates an CodeContext.Inserter, set it to the current offset, and inserts it before the current offset.

In clear text, this means that you can continue writing to the "Code" attribute, then pushInserter(CodeContext.Inserter) the CodeContext.Inserter, then write again (which inserts bytes into the "Code" attribute at the previously remembered position), and then popInserter().

currentInserter

public CodeContext.Inserter currentInserter()

Returns:

The current inserter

pushInserter

public void pushInserter(CodeContext.Inserter ins)

Remembers the current CodeContext.Inserter, then replaces it with the new one.

popInserter

public void popInserter()

Replaces the current CodeContext.Inserter with the remembered one (see pushInserter(CodeContext.Inserter)).

addExceptionTableEntry

public void addExceptionTableEntry(CodeContext.Offset startPc,
                                   CodeContext.Offset endPc,
                                   CodeContext.Offset handlerPc,
                                   @Nullable
                                   String catchTypeFd)

Adds another entry to the "exception_table" of this code attribute (see JVMS 4.7.3).

Parameters:

catchTypeFd - null means finally clause

getAllLocalVars

public List<Java.LocalVariableSlot> getAllLocalVars()

Returns:

All the local variables that are allocated in any block in this CodeContext

removeCode

public void removeCode(CodeContext.Offset from,
                       CodeContext.Offset to)

Removes all code between from and to. Also removes any CodeContext.Relocatables existing in that range.