org.objectweb.asm
Class Frame

java.lang.Object
  org.objectweb.asm.Frame

final class Frame
extends java.lang.Object

Information about the input and output stack map frames of a basic block.

Author:

Eric Bruneton

Field Summary

(package private) static int	ARRAY_OF Constant to be added to a type to get a type with one more dimension.
(package private) static int	BASE Kind of the types that are not relative to an input stack map frame.
(package private) static int	BASE_KIND Mask to get the kind of base types.
(package private) static int	BASE_VALUE Mask to get the value of base types.
(package private) static int	BOOLEAN The BOOLEAN type.
(package private) static int	BYTE The BYTE type.
(package private) static int	CHAR The CHAR type.
(package private) static int	DIM Mask to get the dimension of a frame type.
(package private) static int	DOUBLE The DOUBLE type.
(package private) static int	ELEMENT_OF Constant to be added to a type to get a type with one less dimension.
(package private) static int	FLOAT The FLOAT type.
private int	initializationCount Number of types that are initialized in the basic block.
private int[]	initializations The types that are initialized in the basic block.
(package private) int[]	inputLocals The input stack map frame locals.
(package private) int[]	inputStack The input stack map frame stack.
(package private) static int	INTEGER The INTEGER type.
(package private) static int	KIND Mask to get the kind of a frame type.
private static int	LOCAL Kind of the types that are relative to the local variable types of an input stack map frame.
(package private) static int	LONG The LONG type.
(package private) static int	NULL The NULL type.
(package private) static int	OBJECT Base kind of the base reference types.
private int[]	outputLocals The output stack map frame locals.
private int[]	outputStack The output stack map frame stack.
private int	outputStackTop Relative size of the output stack.
(package private) Label	owner The label (i.e.
(package private) static int	SHORT The SHORT type.
(package private) static int[]	SIZE The stack size variation corresponding to each JVM instruction.
private static int	STACK Kind of the the types that are relative to the stack of an input stack map frame.
(package private) static int	TOP The TOP type.
(package private) static int	UNINITIALIZED Base kind of the uninitialized base types.
(package private) static int	UNINITIALIZED_THIS The UNINITIALIZED_THIS type.
(package private) static int	VALUE Mask to get the value of a frame type.

Constructor Summary

Frame()

Method Summary

(package private) void	execute(int opcode, int arg, ClassWriter cw, Item item) Simulates the action of the given instruction on the output stack frame.
private int	get(int local) Returns the output frame local variable type at the given index.
private int	init(ClassWriter cw, int t) Replaces the given type with the appropriate type if it is one of the types on which a constructor is invoked in the basic block.
private void	init(int var) Adds a new type to the list of types on which a constructor is invoked in the basic block.
(package private) void	initInputFrame(ClassWriter cw, int access, Type[] args, int maxLocals) Initializes the input frame of the first basic block from the method descriptor.
(package private) boolean	merge(ClassWriter cw, Frame frame, int edge) Merges the input frame of the given basic block with the input and output frames of this basic block.
private boolean	merge(ClassWriter cw, int t, int[] types, int index) Merges the type at the given index in the given type array with the given type.
private int	pop() Pops a type from the output frame stack and returns its value.
private void	pop(int elements) Pops the given number of types from the output frame stack.
private void	pop(java.lang.String desc) Pops a type from the output frame stack.
private void	push(ClassWriter cw, java.lang.String desc) Pushes a new type onto the output frame stack.
private void	push(int type) Pushes a new type onto the output frame stack.
private void	set(int local, int type) Sets the output frame local variable type at the given index.
private int	type(ClassWriter cw, java.lang.String desc) Returns the int encoding of the given type.

Methods inherited from class java.lang.Object

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

Field Detail

DIM

static final int DIM

Mask to get the dimension of a frame type. This dimension is a signed integer between -8 and 7.

See Also:

Constant Field Values

ARRAY_OF

static final int ARRAY_OF

Constant to be added to a type to get a type with one more dimension.

See Also:

Constant Field Values

ELEMENT_OF

static final int ELEMENT_OF

Constant to be added to a type to get a type with one less dimension.

See Also:

Constant Field Values

KIND

static final int KIND

Mask to get the kind of a frame type.

See Also:

BASE, LOCAL, STACK, Constant Field Values

VALUE

static final int VALUE

Mask to get the value of a frame type.

See Also:

Constant Field Values

BASE_KIND

static final int BASE_KIND

Mask to get the kind of base types.

See Also:

Constant Field Values

BASE_VALUE

static final int BASE_VALUE

Mask to get the value of base types.

See Also:

Constant Field Values

BASE

static final int BASE

Kind of the types that are not relative to an input stack map frame.

See Also:

Constant Field Values

OBJECT

static final int OBJECT

Base kind of the base reference types. The BASE_VALUE of such types is an index into the type table.

See Also:

Constant Field Values

UNINITIALIZED

static final int UNINITIALIZED

Base kind of the uninitialized base types. The BASE_VALUE of such types in an index into the type table (the Item at that index contains both an instruction offset and an internal class name).

See Also:

Constant Field Values

LOCAL

private static final int LOCAL

Kind of the types that are relative to the local variable types of an input stack map frame. The value of such types is a local variable index.

See Also:

Constant Field Values

STACK

private static final int STACK

Kind of the the types that are relative to the stack of an input stack map frame. The value of such types is a position relatively to the top of this stack.

See Also:

Constant Field Values

TOP

static final int TOP

The TOP type. This is a BASE type.

See Also:

Constant Field Values

BOOLEAN

static final int BOOLEAN

The BOOLEAN type. This is a BASE type mainly used for array types.

See Also:

Constant Field Values

BYTE

static final int BYTE

The BYTE type. This is a BASE type mainly used for array types.

See Also:

Constant Field Values

CHAR

static final int CHAR

The CHAR type. This is a BASE type mainly used for array types.

See Also:

Constant Field Values

SHORT

static final int SHORT

The SHORT type. This is a BASE type mainly used for array types.

See Also:

Constant Field Values

INTEGER

static final int INTEGER

The INTEGER type. This is a BASE type.

See Also:

Constant Field Values

FLOAT

static final int FLOAT

The FLOAT type. This is a BASE type.

See Also:

Constant Field Values

DOUBLE

static final int DOUBLE

The DOUBLE type. This is a BASE type.

See Also:

Constant Field Values

LONG

static final int LONG

The LONG type. This is a BASE type.

See Also:

Constant Field Values

NULL

static final int NULL

The NULL type. This is a BASE type.

See Also:

Constant Field Values

UNINITIALIZED_THIS

static final int UNINITIALIZED_THIS

The UNINITIALIZED_THIS type. This is a BASE type.

See Also:

Constant Field Values

SIZE

static final int[] SIZE

The stack size variation corresponding to each JVM instruction. This stack variation is equal to the size of the values produced by an instruction, minus the size of the values consumed by this instruction.

owner

Label owner

The label (i.e. basic block) to which these input and output stack map frames correspond.

inputLocals

int[] inputLocals

The input stack map frame locals.

inputStack

int[] inputStack

The input stack map frame stack.

outputLocals

private int[] outputLocals

The output stack map frame locals.

outputStack

private int[] outputStack

The output stack map frame stack.

outputStackTop

private int outputStackTop

Relative size of the output stack. The exact semantics of this field depends on the algorithm that is used. When only the maximum stack size is computed, this field is the size of the output stack relatively to the top of the input stack. When the stack map frames are completely computed, this field is the actual number of types in outputStack.

initializationCount

private int initializationCount

Number of types that are initialized in the basic block.

See Also:

initializations

initializations

private int[] initializations

The types that are initialized in the basic block. A constructor invocation on an UNINITIALIZED or UNINITIALIZED_THIS type must replace every occurence of this type in the local variables and in the operand stack. This cannot be done during the first phase of the algorithm since, during this phase, the local variables and the operand stack are not completely computed. It is therefore necessary to store the types on which constructors are invoked in the basic block, in order to do this replacement during the second phase of the algorithm, where the frames are fully computed. Note that this array can contain types that are relative to input locals or to the input stack (see below for the description of the algorithm).

Constructor Detail

Frame

Frame()

Method Detail

get

private int get(int local)

Returns the output frame local variable type at the given index.

Parameters:

local - the index of the local that must be returned.

Returns:

the output frame local variable type at the given index.

set

private void set(int local,
                 int type)

Sets the output frame local variable type at the given index.

Parameters:

local - the index of the local that must be set.

type - the value of the local that must be set.

push

private void push(int type)

Pushes a new type onto the output frame stack.

Parameters:

type - the type that must be pushed.

push

private void push(ClassWriter cw,
                  java.lang.String desc)

Pushes a new type onto the output frame stack.

Parameters:

cw - the ClassWriter to which this label belongs.

desc - the descriptor of the type to be pushed. Can also be a method descriptor (in this case this method pushes its return type onto the output frame stack).

type

private int type(ClassWriter cw,
                 java.lang.String desc)

Returns the int encoding of the given type.

Parameters:

cw - the ClassWriter to which this label belongs.

desc - a type descriptor.

Returns:

the int encoding of the given type.

pop

private int pop()

Pops a type from the output frame stack and returns its value.

Returns:

the type that has been popped from the output frame stack.

pop

private void pop(int elements)

Pops the given number of types from the output frame stack.

Parameters:

elements - the number of types that must be popped.

pop

private void pop(java.lang.String desc)

Pops a type from the output frame stack.

Parameters:

desc - the descriptor of the type to be popped. Can also be a method descriptor (in this case this method pops the types corresponding to the method arguments).

init

private void init(int var)

Adds a new type to the list of types on which a constructor is invoked in the basic block.

Parameters:

var - a type on a which a constructor is invoked.

init

private int init(ClassWriter cw,
                 int t)

Replaces the given type with the appropriate type if it is one of the types on which a constructor is invoked in the basic block.

Parameters:

cw - the ClassWriter to which this label belongs.

t - a type

Returns:

t or, if t is one of the types on which a constructor is invoked in the basic block, the type corresponding to this constructor.

initInputFrame

void initInputFrame(ClassWriter cw,
                    int access,
                    Type[] args,
                    int maxLocals)

Initializes the input frame of the first basic block from the method descriptor.

Parameters:

cw - the ClassWriter to which this label belongs.

access - the access flags of the method to which this label belongs.

args - the formal parameter types of this method.

maxLocals - the maximum number of local variables of this method.

execute

void execute(int opcode,
             int arg,
             ClassWriter cw,
             Item item)

Simulates the action of the given instruction on the output stack frame.

Parameters:

opcode - the opcode of the instruction.

arg - the operand of the instruction, if any.

cw - the class writer to which this label belongs.

item - the operand of the instructions, if any.

merge

boolean merge(ClassWriter cw,
              Frame frame,
              int edge)

Merges the input frame of the given basic block with the input and output frames of this basic block. Returns true if the input frame of the given label has been changed by this operation.

Parameters:

cw - the ClassWriter to which this label belongs.

frame - the basic block whose input frame must be updated.

edge - the kind of the Edge between this label and 'label'. See Edge.info.

Returns:

true if the input frame of the given label has been changed by this operation.

merge

private boolean merge(ClassWriter cw,
                      int t,
                      int[] types,
                      int index)

Merges the type at the given index in the given type array with the given type. Returns true if the type array has been modified by this operation.

Parameters:

cw - the ClassWriter to which this label belongs.

t - the type with which the type array element must be merged.

types - an array of types.

index - the index of the type that must be merged in 'types'.

Returns:

true if the type array has been modified by this operation.