cf
Class CodeAttribute

java.lang.Object
  cf.CodeAttribute

 class CodeAttribute
extends Object

An instance of class CodeAttribute is an in-core representation of a “Code” attribute of a method.

Version:

$Id: CodeAttribute.java,v 1.59 2004/04/28 14:01:41 rl Exp $

Author:

Zvi Har’El

See Also:

Class source code

Field Summary

(package private) Vector	attributes Attributes of this code.
(package private) ClassFile	cf The ClassFile object to which this code belongs.
(package private) byte[]	code The actual JVM bytecode for this method.
(package private) int	codeLength Number of bytes in the code array.
(package private) Vector	exceptionTable The exception table.
(package private) short	maxLocals Maximum number of words in the local variable pool of this method.
(package private) short	maxStack Maximum number of words on the operand stack during the method execution.

Constructor Summary

CodeAttribute(ClassFile cf)
Constructs an empty CodeAttribute object for a new method.

CodeAttribute(DataInputStream in, ClassFile cf)
Constructs a new CodeAttribute object by reading an input stream.

Method Summary

(package private) void	addException(int start, int end, int handler, String type) Adds an exception to the exception table of a method.
(package private) void	ldc(double c) Generates code to push a DOUBLE constant into the stack.
(package private) void	ldc(float c) Generates code to push a FLOAT constant into the stack.
(package private) void	ldc(int c) Generates code to push a INTEGER constant into the stack.
(package private) void	ldc(long c) Generates code to push a LONG constant into the stack.
private void	ldc(short i) Generates code to push an INTEGER, a FLOAT, or a STRING constant into the stack.
(package private) void	ldc(String c) Generates code to push null or a STRING constant into the stack.
(package private) void	move(int n, byte op) Generates byte code to move data to or from a local variable.
(package private) void	pad() Pads the code array with zero bytes.
(package private) void	pad(int n) Pads the code array with zero bytes.
(package private) void	put(byte i) Puts a byte in the first available location of the code array.
(package private) void	put(byte i, int l) Puts a byte in a specified location of the code array.
(package private) void	put(byte tag, short i, String s1, String s2) Puts an index to the constant pool in the first available location of the code array.
(package private) void	put(byte tag, String s) Puts an index to the constant pool in the first available location of the code array.
(package private) void	put(byte tag, String s1, String s2, String s3) Puts an index to the constant pool in the first available location of the code array.
(package private) void	put(short i) Puts two bytes in the first available location of the code array.
(package private) void	put(short i, int l) Puts two bytes in a specified location of the code array.
(package private) void	strip() Strip attributes.
(package private) void	trim() Trim the code array to actual code length.
(package private) void	write(DataOutputStream out) Writes the CodeAttribute object on an output stream.

Methods inherited from class java.lang.Object

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

Field Detail

maxStack

short maxStack

Maximum number of words on the operand stack during the method execution.

maxLocals

short maxLocals

Maximum number of words in the local variable pool of this method.

codeLength

int codeLength

Number of bytes in the code array.

code

byte[] code

The actual JVM bytecode for this method.

exceptionTable

final Vector exceptionTable

The exception table. Each entry is an Long object, packing four short values, as follows: The start and end of the code for which the exception handler is active, the start of the exception handler, and the type of the handled exception given as an index to a CLASS constant.

attributes

final Vector attributes

Attributes of this code. The attributes possible at this level are “LineNumberTable” and “LocalVariableTable”. Each entry is a byte array.

cf

ClassFile cf

The ClassFile object to which this code belongs. Used to access the constant pool.

Constructor Detail

CodeAttribute

CodeAttribute(DataInputStream in,
              ClassFile cf)
        throws IOException

Constructs a new CodeAttribute object by reading an input stream.

Parameters:

in - the input stream

cf - the ClassFile object to which this CodeAttribute object belongs

Throws:

IOException - if input error occurs

CodeAttribute

CodeAttribute(ClassFile cf)

Constructs an empty CodeAttribute object for a new method. The code array initial allocation is 256 bytes.

Parameters:

cf - the ClassFile object to which this CodeAttribute object belongs

Method Detail

write

final void write(DataOutputStream out)
          throws IOException

Writes the CodeAttribute object on an output stream.

Parameters:

out - the output stream

Throws:

IOException - if output error occurs

strip

final void strip()

Strip attributes.

addException

final void addException(int start,
                        int end,
                        int handler,
                        String type)

Adds an exception to the exception table of a method.

Parameters:

start - the start of the code for which the handler is active

end - the end of the code for which the handler is active

handler - the start of the exception handler

type - the type of exception caught by this handler

See Also:

JVM Spec §4.7.4

trim

final void trim()

Trim the code array to actual code length.

put

final void put(byte i,
               int l)
        throws IndexOutOfBoundsException

Puts a byte in a specified location of the code array.

Parameters:

i - the byte

l - the location

Throws:

IndexOutOfBoundsException - if the reqested location is outside the code array

put

final void put(short i,
               int l)
        throws IndexOutOfBoundsException

Puts two bytes in a specified location of the code array.

Parameters:

i - the bytes

l - the location

Throws:

IndexOutOfBoundsException - if the reqested location is outside the code array

put

final void put(byte i)

Puts a byte in the first available location of the code array. If the code array becomes full, doubles its capacity.

Parameters:

i - the byte

put

final void put(short i)

Puts two bytes in the first available location of the code array.

Parameters:

i - the bytes

put

final void put(byte tag,
               String s)

Puts an index to the constant pool in the first available location of the code array.

Parameters:

tag - a constant pool tag

s - a String value

See Also:

ClassFile.cp(byte,String)

put

final void put(byte tag,
               String s1,
               String s2,
               String s3)

Puts an index to the constant pool in the first available location of the code array.

Parameters:

tag - a constant pool tag

s1 - a String value

s2 - a String value

s3 - a String value

See Also:

ClassFile.cp(byte,String,String,String)

put

final void put(byte tag,
               short i,
               String s1,
               String s2)

Puts an index to the constant pool in the first available location of the code array.

Parameters:

tag - a constant pool tag

i - a short value

s1 - a String value

s2 - a String value

See Also:

ClassFile.cp(byte,short,String,String)

pad

final void pad(int n)

Pads the code array with zero bytes.

Parameters:

n - the number of padding bytes

pad

final void pad()

Pads the code array with zero bytes. The next available location will be aligned to a multiple of four bytes.

See Also:

JVM Spec §6.4: tableswitch

ldc

private final void ldc(short i)

Generates code to push an INTEGER, a FLOAT, or a STRING constant into the stack. The JVM operation most efficient for the size of the index of the constant in the pool is selected.

Parameters:

i - an index to the constant pool

See Also:

JVM Spec §6.4: ldc, ldc_w

ldc

final void ldc(int c)

Generates code to push a INTEGER constant into the stack.

Parameters:

c - a int value

See Also:

ldc(short), JVM Spec §6.4: iconst_<i>, bipush, sipush

ldc

final void ldc(long c)

Generates code to push a LONG constant into the stack.

Parameters:

c - a long value

See Also:

JVM Spec §6.4: lconst_<l>, ldc2_w

ldc

final void ldc(float c)

Generates code to push a FLOAT constant into the stack.

Parameters:

c - a float value

See Also:

ldc(short), JVM Spec §6.4: fconst_<f>

ldc

final void ldc(double c)

Generates code to push a DOUBLE constant into the stack.

Parameters:

c - a double value

See Also:

JVM Spec §6.4: dconst_<d>, ldc2_w

ldc

final void ldc(String c)

Generates code to push null or a STRING constant into the stack.

Parameters:

c - null or a String value

See Also:

ldc(short), JVM Spec §6.4: aconst_null

move

final void move(int n,
                byte op)

Generates byte code to move data to or from a local variable. The JVM operation most efficient for the given local variable is selected.

Parameters:

n - the local variable

op - the opcode: ILOAD, ISTORE, etc.

See Also:

JVM Spec §6.4: iload, iload_<n>, wide