org.logicalcobwebs.asm
Class ClassWriter

java.lang.Object
  org.logicalcobwebs.asm.ClassWriter

All Implemented Interfaces:

ClassVisitor

Direct Known Subclasses:

DebuggingClassWriter

public class ClassWriter
extends java.lang.Object
implements ClassVisitor

A ClassVisitor that generates Java class files. More precisely this visitor generates a byte array conforming to the Java class file format. It can be used alone, to generate a Java class "from scratch", or with one or more ClassReader and adapter class visitor to generate a modified class from one or more existing Java classes.

Field Summary

private int	access The access flags of this class.
private Attribute	attrs The non standard attributes of the class.
(package private) static int	CLASS The type of CONSTANT_Class constant pool items.
private boolean	computeMaxs true if the maximum stack size and number of local variables must be automatically computed.
(package private) static int	DOUBLE The type of CONSTANT_Double constant pool items.
(package private) static int	FIELD The type of CONSTANT_Fieldref constant pool items.
private int	fieldCount Number of fields of this class.
(package private) static int	FIELDORMETH_INSN The type of field and method invocations instructions.
private ByteVector	fields The fields of this class.
(package private) CodeWriter	firstMethod The methods of this class.
(package private) static int	FLOAT The type of CONSTANT_Float constant pool items.
(package private) static int	IINC_INSN The type of the IINC instruction.
(package private) static int	IMETH The type of CONSTANT_InterfaceMethodref constant pool items.
(package private) static int	IMPLVAR_INSN The type of instructions with an implicit local variable index label.
private short	index Index of the next item to be added in the constant pool.
private ByteVector	innerClasses The InnerClasses attribute.
private int	innerClassesCount The number of entries in the InnerClasses attribute.
(package private) static int	INT The type of CONSTANT_Integer constant pool items.
private int	interfaceCount Number of interfaces implemented or extended by this class or interface.
private int[]	interfaces The interfaces implemented or extended by this class or interface.
(package private) static int	ITFMETH_INSN The type of the INVOKEINTERFACE instruction.
(package private) Item	key A reusable key used to look for items in the hash table.
(package private) Item	key2 A reusable key used to look for items in the hash table.
(package private) Item	key3 A reusable key used to look for items in the hash table.
(package private) static int	LABEL_INSN The type of instructions with a 2 bytes bytecode offset label.
(package private) static int	LABELW_INSN The type of instructions with a 4 bytes bytecode offset label.
(package private) CodeWriter	lastMethod The methods of this class.
(package private) static int	LDC_INSN The type of the LDC instruction.
(package private) static int	LDCW_INSN The type of the LDC_W and LDC2_W instructions.
(package private) static int	LONG The type of CONSTANT_Long constant pool items.
(package private) static int	LOOK_INSN The type of the LOOKUPSWITCH instruction.
(package private) static int	MANA_INSN The type of the MULTIANEWARRAY instruction.
(package private) static int	METH The type of CONSTANT_Methodref constant pool items.
private int	name The constant pool item that contains the internal name of this class.
(package private) static int	NAME_TYPE The type of CONSTANT_NameAndType constant pool items.
(package private) static int	NOARG_INSN The type of instructions without any label.
private ByteVector	pool The constant pool of this class.
(package private) static int	SBYTE_INSN The type of instructions with an signed byte label.
(package private) static int	SHORT_INSN The type of instructions with an signed short label.
private int	sourceFile The index of the constant pool item that contains the name of the source file from which this class was compiled.
(package private) static int	STR The type of CONSTANT_String constant pool items.
private int	superName The constant pool item that contains the internal name of the super class of this class.
(package private) static int	TABL_INSN The type of the TABLESWITCH instruction.
private Item[]	table The constant pool's hash table data.
private int	threshold The threshold of the constant pool's hash table.
(package private) static byte[]	TYPE The instruction types of all JVM opcodes.
(package private) static int	TYPE_INSN The type of instructions with a type descriptor argument.
(package private) static int	UTF8 The type of CONSTANT_Utf8 constant pool items.
(package private) static int	VAR_INSN The type of instructions with a local variable index label.
(package private) static int	WIDE_INSN The type of the WIDE instruction.

Constructor Summary

ClassWriter(boolean computeMaxs)
Constructs a new ClassWriter object.

Method Summary

private Item	get(Item key) Returns the constant pool's hash table item which is equal to the given item.
protected int	newClass(java.lang.String value) Adds a class reference to the constant pool of the class being build.
(package private) Item	newConst(java.lang.Object cst) Adds a number or string constant to the constant pool of the class being build.
protected int	newCst(java.lang.Object cst) Adds a number or string constant to the constant pool of the class being build.
private Item	newDouble(double value) Adds a double to the constant pool of the class being build.
protected int	newField(java.lang.String owner, java.lang.String name, java.lang.String desc) Adds a field reference to the constant pool of the class being build.
private Item	newFloat(float value) Adds a float to the constant pool of the class being build.
private Item	newInteger(int value) Adds an integer to the constant pool of the class being build.
private Item	newLong(long value) Adds a long to the constant pool of the class being build.
protected int	newMethod(java.lang.String owner, java.lang.String name, java.lang.String desc, boolean itf) Adds a method reference to the constant pool of the class being build.
(package private) Item	newMethodItem(java.lang.String owner, java.lang.String name, java.lang.String desc, boolean itf) Adds a method reference to the constant pool of the class being build.
protected int	newNameType(java.lang.String name, java.lang.String desc) Adds a name and type to the constant pool of the class being build.
private Item	newString(java.lang.String value) Adds a string to the constant pool of the class being build.
protected int	newUTF8(java.lang.String value) Adds an UTF8 string to the constant pool of the class being build.
private void	put(Item i) Puts the given item in the constant pool's hash table.
private void	put122(int b, int s1, int s2) Puts one byte and two shorts into the constant pool.
byte[]	toByteArray() Returns the bytecode of the class that was build with this class writer.
void	visit(int access, java.lang.String name, java.lang.String superName, java.lang.String[] interfaces, java.lang.String sourceFile) Visits the header of the class.
void	visitAttribute(Attribute attr) Visits a non standard attribute of the class.
void	visitEnd() Visits the end of the class.
void	visitField(int access, java.lang.String name, java.lang.String desc, java.lang.Object value, Attribute attrs) Visits a field of the class.
void	visitInnerClass(java.lang.String name, java.lang.String outerName, java.lang.String innerName, int access) Visits information about an inner class.
CodeVisitor	visitMethod(int access, java.lang.String name, java.lang.String desc, java.lang.String[] exceptions, Attribute attrs) Visits a method of the class.
protected byte[]	writeAttribute(Attribute attr) Converts the content of the given attribute to a byte array.

Methods inherited from class java.lang.Object

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

Field Detail

CLASS

static final int CLASS

The type of CONSTANT_Class constant pool items.

See Also:

Constant Field Values

FIELD

static final int FIELD

The type of CONSTANT_Fieldref constant pool items.

See Also:

Constant Field Values

METH

static final int METH

The type of CONSTANT_Methodref constant pool items.

See Also:

Constant Field Values

IMETH

static final int IMETH

The type of CONSTANT_InterfaceMethodref constant pool items.

See Also:

Constant Field Values

STR

static final int STR

The type of CONSTANT_String constant pool items.

See Also:

Constant Field Values

INT

static final int INT

The type of CONSTANT_Integer constant pool items.

See Also:

Constant Field Values

FLOAT

static final int FLOAT

The type of CONSTANT_Float constant pool items.

See Also:

Constant Field Values

LONG

static final int LONG

The type of CONSTANT_Long constant pool items.

See Also:

Constant Field Values

DOUBLE

static final int DOUBLE

The type of CONSTANT_Double constant pool items.

See Also:

Constant Field Values

NAME_TYPE

static final int NAME_TYPE

The type of CONSTANT_NameAndType constant pool items.

See Also:

Constant Field Values

UTF8

static final int UTF8

The type of CONSTANT_Utf8 constant pool items.

See Also:

Constant Field Values

index

private short index

Index of the next item to be added in the constant pool.

pool

private ByteVector pool

The constant pool of this class.

table

private Item[] table

The constant pool's hash table data.

threshold

private int threshold

The threshold of the constant pool's hash table.

access

private int access

The access flags of this class.

name

private int name

The constant pool item that contains the internal name of this class.

superName

private int superName

The constant pool item that contains the internal name of the super class of this class.

interfaceCount

private int interfaceCount

Number of interfaces implemented or extended by this class or interface.

interfaces

private int[] interfaces

The interfaces implemented or extended by this class or interface. More precisely, this array contains the indexes of the constant pool items that contain the internal names of these interfaces.

sourceFile

private int sourceFile

The index of the constant pool item that contains the name of the source file from which this class was compiled.

fieldCount

private int fieldCount

Number of fields of this class.

fields

private ByteVector fields

The fields of this class.

computeMaxs

private boolean computeMaxs

true if the maximum stack size and number of local variables must be automatically computed.

firstMethod

CodeWriter firstMethod

The methods of this class. These methods are stored in a linked list of CodeWriter objects, linked to each other by their CodeWriter.next field. This field stores the first element of this list.

lastMethod

CodeWriter lastMethod

The methods of this class. These methods are stored in a linked list of CodeWriter objects, linked to each other by their CodeWriter.next field. This field stores the last element of this list.

innerClassesCount

private int innerClassesCount

The number of entries in the InnerClasses attribute.

innerClasses

private ByteVector innerClasses

The InnerClasses attribute.

attrs

private Attribute attrs

The non standard attributes of the class.

key

Item key

A reusable key used to look for items in the hash table.

key2

Item key2

A reusable key used to look for items in the hash table.

key3

Item key3

A reusable key used to look for items in the hash table.

NOARG_INSN

static final int NOARG_INSN

The type of instructions without any label.

See Also:

Constant Field Values

SBYTE_INSN

static final int SBYTE_INSN

The type of instructions with an signed byte label.

See Also:

Constant Field Values

SHORT_INSN

static final int SHORT_INSN

The type of instructions with an signed short label.

See Also:

Constant Field Values

VAR_INSN

static final int VAR_INSN

The type of instructions with a local variable index label.

See Also:

Constant Field Values

IMPLVAR_INSN

static final int IMPLVAR_INSN

The type of instructions with an implicit local variable index label.

See Also:

Constant Field Values

TYPE_INSN

static final int TYPE_INSN

The type of instructions with a type descriptor argument.

See Also:

Constant Field Values

FIELDORMETH_INSN

static final int FIELDORMETH_INSN

The type of field and method invocations instructions.

See Also:

Constant Field Values

ITFMETH_INSN

static final int ITFMETH_INSN

The type of the INVOKEINTERFACE instruction.

See Also:

Constant Field Values

LABEL_INSN

static final int LABEL_INSN

The type of instructions with a 2 bytes bytecode offset label.

See Also:

Constant Field Values

LABELW_INSN

static final int LABELW_INSN

The type of instructions with a 4 bytes bytecode offset label.

See Also:

Constant Field Values

LDC_INSN

static final int LDC_INSN

The type of the LDC instruction.

See Also:

Constant Field Values

LDCW_INSN

static final int LDCW_INSN

The type of the LDC_W and LDC2_W instructions.

See Also:

Constant Field Values

IINC_INSN

static final int IINC_INSN

The type of the IINC instruction.

See Also:

Constant Field Values

TABL_INSN

static final int TABL_INSN

The type of the TABLESWITCH instruction.

See Also:

Constant Field Values

LOOK_INSN

static final int LOOK_INSN

The type of the LOOKUPSWITCH instruction.

See Also:

Constant Field Values

MANA_INSN

static final int MANA_INSN

The type of the MULTIANEWARRAY instruction.

See Also:

Constant Field Values

WIDE_INSN

static final int WIDE_INSN

The type of the WIDE instruction.

See Also:

Constant Field Values

TYPE

static byte[] TYPE

The instruction types of all JVM opcodes.

Constructor Detail

ClassWriter

public ClassWriter(boolean computeMaxs)

Constructs a new ClassWriter object.

Parameters:

computeMaxs - true if the maximum stack size and the maximum number of local variables must be automatically computed. If this flag is true, then the arguments of the visitMaxs method of the CodeVisitor returned by the visitMethod method will be ignored, and computed automatically from the signature and the bytecode of each method.

Method Detail

visit

public void visit(int access,
                  java.lang.String name,
                  java.lang.String superName,
                  java.lang.String[] interfaces,
                  java.lang.String sourceFile)

Description copied from interface: ClassVisitor

Visits the header of the class.

Specified by:

visit in interface ClassVisitor

Parameters:

access - the class's access flags (see Constants). This parameter also indicates if the class is deprecated.

name - the internal name of the class (see getInternalName).

superName - the internal of name of the super class (see getInternalName). For interfaces, the super class is Object. May be null, but only for the java.lang.Object class.

interfaces - the internal names of the class's interfaces (see getInternalName). May be null.

sourceFile - the name of the source file from which this class was compiled. May be null.

visitInnerClass

public void visitInnerClass(java.lang.String name,
                            java.lang.String outerName,
                            java.lang.String innerName,
                            int access)

Description copied from interface: ClassVisitor

Visits information about an inner class. This inner class is not necessarily a member of the class being visited.

Specified by:

visitInnerClass in interface ClassVisitor

Parameters:

name - the internal name of an inner class (see getInternalName).

outerName - the internal name of the class to which the inner class belongs (see getInternalName). May be null.

innerName - the (simple) name of the inner class inside its enclosing class. May be null for anonymous inner classes.

access - the access flags of the inner class as originally declared in the enclosing class.

visitField

public void visitField(int access,
                       java.lang.String name,
                       java.lang.String desc,
                       java.lang.Object value,
                       Attribute attrs)

Description copied from interface: ClassVisitor

Visits a field of the class.

Specified by:

visitField in interface ClassVisitor

Parameters:

access - the field's access flags (see Constants). This parameter also indicates if the field is synthetic and/or deprecated.

name - the field's name.

desc - the field's descriptor (see Type).

value - the field's initial value. This parameter, which may be null if the field does not have an initial value, must be an Integer, a Float, a Long, a Double or a String. This parameter is only used for static fields. Its value is ignored for non static fields, which must be initialized through bytecode instructions in constructors or methods.

attrs - the non standard method attributes, linked together by their next field. May be null.

visitMethod

public CodeVisitor visitMethod(int access,
                               java.lang.String name,
                               java.lang.String desc,
                               java.lang.String[] exceptions,
                               Attribute attrs)

Description copied from interface: ClassVisitor

Visits a method of the class. This method must return a new CodeVisitor instance (or null) each time it is called, i.e., it should not return a previously returned visitor.

Specified by:

visitMethod in interface ClassVisitor

Parameters:

access - the method's access flags (see Constants). This parameter also indicates if the method is synthetic and/or deprecated.

name - the method's name.

desc - the method's descriptor (see Type).

exceptions - the internal names of the method's exception classes (see getInternalName). May be null.

attrs - the non standard method attributes, linked together by their next field. May be null.

Returns:

an object to visit the byte code of the method, or null if this class visitor is not interested in visiting the code of this method.

visitAttribute

public void visitAttribute(Attribute attr)

Description copied from interface: ClassVisitor

Visits a non standard attribute of the class. This method must visit only the first attribute in the given attribute list.

Specified by:

visitAttribute in interface ClassVisitor

Parameters:

attr - a non standard class attribute. Must not be null.

visitEnd

public void visitEnd()

Description copied from interface: ClassVisitor

Visits the end of the class. This method, which is the last one to be called, is used to inform the visitor that all the fields and methods of the class have been visited.

Specified by:

visitEnd in interface ClassVisitor

toByteArray

public byte[] toByteArray()

Returns the bytecode of the class that was build with this class writer.

Returns:

the bytecode of the class that was build with this class writer.

newConst

Item newConst(java.lang.Object cst)

Adds a number or string constant to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

cst - the value of the constant to be added to the constant pool. This parameter must be an Integer, a Float, a Long, a Double or a String.

Returns:

a new or already existing constant item with the given value.

newCst

protected int newCst(java.lang.Object cst)

Adds a number or string constant to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

cst - the value of the constant to be added to the constant pool. This parameter must be an Integer, a Float, a Long, a Double or a String.

Returns:

the index of a new or already existing constant item with the given value.

newUTF8

protected int newUTF8(java.lang.String value)

Adds an UTF8 string to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

value - the String value.

Returns:

the index of a new or already existing UTF8 item.

newClass

protected int newClass(java.lang.String value)

Adds a class reference to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

value - the internal name of the class.

Returns:

the index of a new or already existing class reference item.

newField

protected int newField(java.lang.String owner,
                       java.lang.String name,
                       java.lang.String desc)

Adds a field reference to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

owner - the internal name of the field's owner class.

name - the field's name.

desc - the field's descriptor.

Returns:

the index of a new or already existing field reference item.

newMethodItem

Item newMethodItem(java.lang.String owner,
                   java.lang.String name,
                   java.lang.String desc,
                   boolean itf)

Adds a method reference to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

owner - the internal name of the method's owner class.

name - the method's name.

desc - the method's descriptor.

itf - true if owner is an interface.

Returns:

a new or already existing method reference item.

newMethod

protected int newMethod(java.lang.String owner,
                        java.lang.String name,
                        java.lang.String desc,
                        boolean itf)

Adds a method reference to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

owner - the internal name of the method's owner class.

name - the method's name.

desc - the method's descriptor.

itf - true if owner is an interface.

Returns:

the index of a new or already existing method reference item.

newInteger

private Item newInteger(int value)

Adds an integer to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

value - the int value.

Returns:

a new or already existing int item.

newFloat

private Item newFloat(float value)

Adds a float to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

value - the float value.

Returns:

a new or already existing float item.

newLong

private Item newLong(long value)

Adds a long to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

value - the long value.

Returns:

a new or already existing long item.

newDouble

private Item newDouble(double value)

Adds a double to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

value - the double value.

Returns:

a new or already existing double item.

newString

private Item newString(java.lang.String value)

Adds a string to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

value - the String value.

Returns:

a new or already existing string item.

newNameType

protected int newNameType(java.lang.String name,
                          java.lang.String desc)

Adds a name and type to the constant pool of the class being build. Does nothing if the constant pool already contains a similar item.

Parameters:

name - a name.

desc - a type descriptor.

Returns:

the index of a new or already existing name and type item.

get

private Item get(Item key)

Returns the constant pool's hash table item which is equal to the given item.

Parameters:

key - a constant pool item.

Returns:

the constant pool's hash table item which is equal to the given item, or null if there is no such item.

put

private void put(Item i)

Puts the given item in the constant pool's hash table. The hash table must not already contains this item.

Parameters:

i - the item to be added to the constant pool's hash table.

put122

private void put122(int b,
                    int s1,
                    int s2)

Puts one byte and two shorts into the constant pool.

Parameters:

b - a byte.

s1 - a short.

s2 - another short.

writeAttribute

protected byte[] writeAttribute(Attribute attr)

Converts the content of the given attribute to a byte array.

Parameters:

attr - the attribute that must be converted to a byte array.

Returns:

a byte array containing the content of the given attribute (and this content only, i.e. the 6 attribute header bytes must not be included in the returned array).