This page hosts a formal specification of .class file format using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.
The Python runtime library can be installed from PyPI:
python3 -m pip install kaitaistructParse a local file and get structure in memory:
data = JavaClass.from_file("path/to/local/file.class")
Or parse structure from a bytes:
from kaitaistruct import KaitaiStream, BytesIO
raw = b"\x00\x01\x02..."
data = JavaClass(KaitaiStream(BytesIO(raw)))
After that, one can get various attributes from the structure by invoking getter methods like:
data.magic # => get magic
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import Enum
if getattr(kaitaistruct, 'API_VERSION', (0, 9)) < (0, 9):
raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))
class JavaClass(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.1
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.magic = self._io.read_bytes(4)
if not self.magic == b"\xCA\xFE\xBA\xBE":
raise kaitaistruct.ValidationNotEqualError(b"\xCA\xFE\xBA\xBE", self.magic, self._io, u"/seq/0")
self.version_minor = self._io.read_u2be()
self.version_major = self._io.read_u2be()
if not self.version_major >= 43:
raise kaitaistruct.ValidationLessThanError(43, self.version_major, self._io, u"/seq/2")
self.constant_pool_count = self._io.read_u2be()
self.constant_pool = []
for i in range((self.constant_pool_count - 1)):
self.constant_pool.append(JavaClass.ConstantPoolEntry((self.constant_pool[(i - 1)].is_two_entries if i != 0 else False), self._io, self, self._root))
self.access_flags = self._io.read_u2be()
self.this_class = self._io.read_u2be()
self.super_class = self._io.read_u2be()
self.interfaces_count = self._io.read_u2be()
self.interfaces = []
for i in range(self.interfaces_count):
self.interfaces.append(self._io.read_u2be())
self.fields_count = self._io.read_u2be()
self.fields = []
for i in range(self.fields_count):
self.fields.append(JavaClass.FieldInfo(self._io, self, self._root))
self.methods_count = self._io.read_u2be()
self.methods = []
for i in range(self.methods_count):
self.methods.append(JavaClass.MethodInfo(self._io, self, self._root))
self.attributes_count = self._io.read_u2be()
self.attributes = []
for i in range(self.attributes_count):
self.attributes.append(JavaClass.AttributeInfo(self._io, self, self._root))
class FloatCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.5
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.value = self._io.read_f4be()
class AttributeInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.name_index = self._io.read_u2be()
self.attribute_length = self._io.read_u4be()
_on = self.name_as_str
if _on == u"SourceFile":
self._raw_info = self._io.read_bytes(self.attribute_length)
_io__raw_info = KaitaiStream(BytesIO(self._raw_info))
self.info = JavaClass.AttributeInfo.AttrBodySourceFile(_io__raw_info, self, self._root)
elif _on == u"LineNumberTable":
self._raw_info = self._io.read_bytes(self.attribute_length)
_io__raw_info = KaitaiStream(BytesIO(self._raw_info))
self.info = JavaClass.AttributeInfo.AttrBodyLineNumberTable(_io__raw_info, self, self._root)
elif _on == u"Exceptions":
self._raw_info = self._io.read_bytes(self.attribute_length)
_io__raw_info = KaitaiStream(BytesIO(self._raw_info))
self.info = JavaClass.AttributeInfo.AttrBodyExceptions(_io__raw_info, self, self._root)
elif _on == u"Code":
self._raw_info = self._io.read_bytes(self.attribute_length)
_io__raw_info = KaitaiStream(BytesIO(self._raw_info))
self.info = JavaClass.AttributeInfo.AttrBodyCode(_io__raw_info, self, self._root)
else:
self.info = self._io.read_bytes(self.attribute_length)
class AttrBodyCode(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.3
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.max_stack = self._io.read_u2be()
self.max_locals = self._io.read_u2be()
self.code_length = self._io.read_u4be()
self.code = self._io.read_bytes(self.code_length)
self.exception_table_length = self._io.read_u2be()
self.exception_table = []
for i in range(self.exception_table_length):
self.exception_table.append(JavaClass.AttributeInfo.AttrBodyCode.ExceptionEntry(self._io, self, self._root))
self.attributes_count = self._io.read_u2be()
self.attributes = []
for i in range(self.attributes_count):
self.attributes.append(JavaClass.AttributeInfo(self._io, self, self._root))
class ExceptionEntry(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.3
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.start_pc = self._io.read_u2be()
self.end_pc = self._io.read_u2be()
self.handler_pc = self._io.read_u2be()
self.catch_type = self._io.read_u2be()
@property
def catch_exception(self):
if hasattr(self, '_m_catch_exception'):
return self._m_catch_exception
if self.catch_type != 0:
self._m_catch_exception = self._root.constant_pool[(self.catch_type - 1)]
return getattr(self, '_m_catch_exception', None)
class AttrBodyExceptions(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.5
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.number_of_exceptions = self._io.read_u2be()
self.exceptions = []
for i in range(self.number_of_exceptions):
self.exceptions.append(JavaClass.AttributeInfo.AttrBodyExceptions.ExceptionTableEntry(self._io, self, self._root))
class ExceptionTableEntry(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.index = self._io.read_u2be()
@property
def as_info(self):
if hasattr(self, '_m_as_info'):
return self._m_as_info
self._m_as_info = self._root.constant_pool[(self.index - 1)].cp_info
return getattr(self, '_m_as_info', None)
@property
def name_as_str(self):
if hasattr(self, '_m_name_as_str'):
return self._m_name_as_str
self._m_name_as_str = self.as_info.name_as_str
return getattr(self, '_m_name_as_str', None)
class AttrBodySourceFile(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.10
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.sourcefile_index = self._io.read_u2be()
@property
def sourcefile_as_str(self):
if hasattr(self, '_m_sourcefile_as_str'):
return self._m_sourcefile_as_str
self._m_sourcefile_as_str = self._root.constant_pool[(self.sourcefile_index - 1)].cp_info.value
return getattr(self, '_m_sourcefile_as_str', None)
class AttrBodyLineNumberTable(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.7.12
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.line_number_table_length = self._io.read_u2be()
self.line_number_table = []
for i in range(self.line_number_table_length):
self.line_number_table.append(JavaClass.AttributeInfo.AttrBodyLineNumberTable.LineNumberTableEntry(self._io, self, self._root))
class LineNumberTableEntry(KaitaiStruct):
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.start_pc = self._io.read_u2be()
self.line_number = self._io.read_u2be()
@property
def name_as_str(self):
if hasattr(self, '_m_name_as_str'):
return self._m_name_as_str
self._m_name_as_str = self._root.constant_pool[(self.name_index - 1)].cp_info.value
return getattr(self, '_m_name_as_str', None)
class MethodRefCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.2
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.class_index = self._io.read_u2be()
self.name_and_type_index = self._io.read_u2be()
@property
def class_as_info(self):
if hasattr(self, '_m_class_as_info'):
return self._m_class_as_info
self._m_class_as_info = self._root.constant_pool[(self.class_index - 1)].cp_info
return getattr(self, '_m_class_as_info', None)
@property
def name_and_type_as_info(self):
if hasattr(self, '_m_name_and_type_as_info'):
return self._m_name_and_type_as_info
self._m_name_and_type_as_info = self._root.constant_pool[(self.name_and_type_index - 1)].cp_info
return getattr(self, '_m_name_and_type_as_info', None)
class FieldInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.5
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.access_flags = self._io.read_u2be()
self.name_index = self._io.read_u2be()
self.descriptor_index = self._io.read_u2be()
self.attributes_count = self._io.read_u2be()
self.attributes = []
for i in range(self.attributes_count):
self.attributes.append(JavaClass.AttributeInfo(self._io, self, self._root))
@property
def name_as_str(self):
if hasattr(self, '_m_name_as_str'):
return self._m_name_as_str
self._m_name_as_str = self._root.constant_pool[(self.name_index - 1)].cp_info.value
return getattr(self, '_m_name_as_str', None)
class DoubleCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.6
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.value = self._io.read_f8be()
class LongCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.5
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.value = self._io.read_u8be()
class InvokeDynamicCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.10
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.bootstrap_method_attr_index = self._io.read_u2be()
self.name_and_type_index = self._io.read_u2be()
class MethodHandleCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.8
"""
class ReferenceKindEnum(Enum):
get_field = 1
get_static = 2
put_field = 3
put_static = 4
invoke_virtual = 5
invoke_static = 6
invoke_special = 7
new_invoke_special = 8
invoke_interface = 9
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.reference_kind = KaitaiStream.resolve_enum(JavaClass.MethodHandleCpInfo.ReferenceKindEnum, self._io.read_u1())
self.reference_index = self._io.read_u2be()
class NameAndTypeCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.6
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.name_index = self._io.read_u2be()
self.descriptor_index = self._io.read_u2be()
@property
def name_as_info(self):
if hasattr(self, '_m_name_as_info'):
return self._m_name_as_info
self._m_name_as_info = self._root.constant_pool[(self.name_index - 1)].cp_info
return getattr(self, '_m_name_as_info', None)
@property
def name_as_str(self):
if hasattr(self, '_m_name_as_str'):
return self._m_name_as_str
self._m_name_as_str = self.name_as_info.value
return getattr(self, '_m_name_as_str', None)
@property
def descriptor_as_info(self):
if hasattr(self, '_m_descriptor_as_info'):
return self._m_descriptor_as_info
self._m_descriptor_as_info = self._root.constant_pool[(self.descriptor_index - 1)].cp_info
return getattr(self, '_m_descriptor_as_info', None)
@property
def descriptor_as_str(self):
if hasattr(self, '_m_descriptor_as_str'):
return self._m_descriptor_as_str
self._m_descriptor_as_str = self.descriptor_as_info.value
return getattr(self, '_m_descriptor_as_str', None)
class Utf8CpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.7
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.str_len = self._io.read_u2be()
self.value = (self._io.read_bytes(self.str_len)).decode(u"UTF-8")
class StringCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.3
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.string_index = self._io.read_u2be()
class MethodTypeCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.9
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.descriptor_index = self._io.read_u2be()
class InterfaceMethodRefCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.2
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.class_index = self._io.read_u2be()
self.name_and_type_index = self._io.read_u2be()
@property
def class_as_info(self):
if hasattr(self, '_m_class_as_info'):
return self._m_class_as_info
self._m_class_as_info = self._root.constant_pool[(self.class_index - 1)].cp_info
return getattr(self, '_m_class_as_info', None)
@property
def name_and_type_as_info(self):
if hasattr(self, '_m_name_and_type_as_info'):
return self._m_name_and_type_as_info
self._m_name_and_type_as_info = self._root.constant_pool[(self.name_and_type_index - 1)].cp_info
return getattr(self, '_m_name_and_type_as_info', None)
class ClassCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.1
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.name_index = self._io.read_u2be()
@property
def name_as_info(self):
if hasattr(self, '_m_name_as_info'):
return self._m_name_as_info
self._m_name_as_info = self._root.constant_pool[(self.name_index - 1)].cp_info
return getattr(self, '_m_name_as_info', None)
@property
def name_as_str(self):
if hasattr(self, '_m_name_as_str'):
return self._m_name_as_str
self._m_name_as_str = self.name_as_info.value
return getattr(self, '_m_name_as_str', None)
class ConstantPoolEntry(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4
"""
class TagEnum(Enum):
utf8 = 1
integer = 3
float = 4
long = 5
double = 6
class_type = 7
string = 8
field_ref = 9
method_ref = 10
interface_method_ref = 11
name_and_type = 12
method_handle = 15
method_type = 16
invoke_dynamic = 18
def __init__(self, is_prev_two_entries, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self.is_prev_two_entries = is_prev_two_entries
self._read()
def _read(self):
if not (self.is_prev_two_entries):
self.tag = KaitaiStream.resolve_enum(JavaClass.ConstantPoolEntry.TagEnum, self._io.read_u1())
if not (self.is_prev_two_entries):
_on = self.tag
if _on == JavaClass.ConstantPoolEntry.TagEnum.interface_method_ref:
self.cp_info = JavaClass.InterfaceMethodRefCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.class_type:
self.cp_info = JavaClass.ClassCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.utf8:
self.cp_info = JavaClass.Utf8CpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.method_type:
self.cp_info = JavaClass.MethodTypeCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.integer:
self.cp_info = JavaClass.IntegerCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.string:
self.cp_info = JavaClass.StringCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.float:
self.cp_info = JavaClass.FloatCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.long:
self.cp_info = JavaClass.LongCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.method_ref:
self.cp_info = JavaClass.MethodRefCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.double:
self.cp_info = JavaClass.DoubleCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.invoke_dynamic:
self.cp_info = JavaClass.InvokeDynamicCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.field_ref:
self.cp_info = JavaClass.FieldRefCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.method_handle:
self.cp_info = JavaClass.MethodHandleCpInfo(self._io, self, self._root)
elif _on == JavaClass.ConstantPoolEntry.TagEnum.name_and_type:
self.cp_info = JavaClass.NameAndTypeCpInfo(self._io, self, self._root)
@property
def is_two_entries(self):
if hasattr(self, '_m_is_two_entries'):
return self._m_is_two_entries
self._m_is_two_entries = (False if self.is_prev_two_entries else ((self.tag == JavaClass.ConstantPoolEntry.TagEnum.long) or (self.tag == JavaClass.ConstantPoolEntry.TagEnum.double)) )
return getattr(self, '_m_is_two_entries', None)
class MethodInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.6
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.access_flags = self._io.read_u2be()
self.name_index = self._io.read_u2be()
self.descriptor_index = self._io.read_u2be()
self.attributes_count = self._io.read_u2be()
self.attributes = []
for i in range(self.attributes_count):
self.attributes.append(JavaClass.AttributeInfo(self._io, self, self._root))
@property
def name_as_str(self):
if hasattr(self, '_m_name_as_str'):
return self._m_name_as_str
self._m_name_as_str = self._root.constant_pool[(self.name_index - 1)].cp_info.value
return getattr(self, '_m_name_as_str', None)
class IntegerCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.4
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.value = self._io.read_u4be()
class FieldRefCpInfo(KaitaiStruct):
"""
.. seealso::
Source - https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-4.html#jvms-4.4.2
"""
def __init__(self, _io, _parent=None, _root=None):
self._io = _io
self._parent = _parent
self._root = _root if _root else self
self._read()
def _read(self):
self.class_index = self._io.read_u2be()
self.name_and_type_index = self._io.read_u2be()
@property
def class_as_info(self):
if hasattr(self, '_m_class_as_info'):
return self._m_class_as_info
self._m_class_as_info = self._root.constant_pool[(self.class_index - 1)].cp_info
return getattr(self, '_m_class_as_info', None)
@property
def name_and_type_as_info(self):
if hasattr(self, '_m_name_and_type_as_info'):
return self._m_name_and_type_as_info
self._m_name_and_type_as_info = self._root.constant_pool[(self.name_and_type_index - 1)].cp_info
return getattr(self, '_m_name_and_type_as_info', None)