jawa.util.bytecode module

Utilities for reading & writing JVM method bytecode.

class jawa.util.bytecode.Instruction

Bases: jawa.util.bytecode.Instruction

Represents a single JVM instruction, consisting of an opcode and its potential operands.

classmethod create(mnemonic_or_op, operands=None)

details

Extended opcode information.

name

Alias for mnemonic.

size_on_disk(start_pos=0)

Returns the size of this instruction and its operands when packed. start_pos is required for the tableswitch and lookupswitch instruction as the padding depends on alignment.

wide

True if this instruction needs to be prefixed by the WIDE opcode.

class jawa.util.bytecode.Operand(op_type, value)

Bases: tuple

op_type

Alias for field number 0

value

Alias for field number 1

class jawa.util.bytecode.OperandFmts

Bases: enum.Enum

An enumeration.

BYTE = <Struct object>

INTEGER = <Struct object>

SHORT = <Struct object>

UBYTE = <Struct object>

USHORT = <Struct object>

class jawa.util.bytecode.OperandTypes

Bases: enum.IntEnum

Constants used to determine the “type” of operand on an opcode, such as a BRANCH [offset] or a LITERAL [value].

BRANCH = 40

CONSTANT_INDEX = 30

LITERAL = 10

LOCAL_INDEX = 20

PADDING = 50

jawa.util.bytecode.load_bytecode_definitions(*, path=None) → dict

Load bytecode definitions from JSON file.

If no path is provided the default bytecode.json will be loaded.

Parameters:path – Either None or a path to a JSON file to load containing bytecode definitions.

jawa.util.bytecode.read_instruction(fio, start_pos)

Reads a single instruction from fio and returns it, or None if the stream is empty.

Parameters:

• fio – Any file-like object providing read().
• start_pos – The current position in the stream.

jawa.util.bytecode.write_instruction(fout, start_pos, ins)

Writes a single instruction of opcode with operands to fout.

Parameters:

• fout – Any file-like object providing write().
• start_pos – The current position in the stream.
• ins – The Instruction to write.