class ClassFile(object):
"""
Implements the JVM ClassFile (files typically ending in ``.class``).
To open an existing ClassFile::
>>> with open('HelloWorld.class', 'rb') as fin:
... cf = ClassFile(fin)
To save a newly created or modified ClassFile::
>>> cf = ClassFile.create('HelloWorld')
>>> with open('HelloWorld.class', 'wb') as out:
... cf.save(out)
:meth:`~ClassFile.create` sets up some reasonable defaults equivalent to:
.. code-block:: java
public class HelloWorld extends java.lang.Object{
}
:param source: any file-like object providing ``.read()``.
"""
#: The JVM ClassFile magic number.
MAGIC = 0xCAFEBABE
def __init__(self, source: IO = None):
# Default to J2SE_7
self._version = ClassVersion(0x32, 0)
self._constants = ConstantPool()
self.access_flags = Flags(
'>H', {
'acc_public': 0x0001,
'acc_final': 0x0010,
'acc_super': 0x0020,
'acc_interface': 0x0200,
'acc_abstract': 0x0400,
'acc_synthetic': 0x1000,
'acc_annotation': 0x2000,
'acc_enum': 0x4000
})
self._this = 0
self._super = 0
self._interfaces = []
self.fields = FieldTable(self)
self.methods = MethodTable(self)
self.attributes = AttributeTable(self)
#: The ClassLoader bound to this ClassFile, if any.
self.classloader = None
if source:
self._from_io(source)
@classmethod
def create(cls,
this: str,
super_: str = u'java/lang/Object') -> 'ClassFile':
"""
A utility which sets up reasonable defaults for a new public class.
:param this: The name of this class.
:param super_: The name of this class's superclass.
"""
cf = ClassFile()
cf.access_flags.acc_public = True
cf.access_flags.acc_super = True
cf.this = cf.constants.create_class(this)
cf.super_ = cf.constants.create_class(super_)
return cf
def save(self, source: IO):
"""
Saves the class to the file-like object `source`.
:param source: Any file-like object providing write().
"""
write = source.write
write(
pack('>IHH', ClassFile.MAGIC, self.version.minor,
self.version.major))
self._constants.pack(source)
write(self.access_flags.pack())
write(
pack(f'>HHH{len(self._interfaces)}H', self._this, self._super,
len(self._interfaces), *self._interfaces))
self.fields.pack(source)
self.methods.pack(source)
self.attributes.pack(source)
def _from_io(self, source: IO):
"""
Loads an existing JVM ClassFile from any file-like object.
"""
read = source.read
if unpack('>I', source.read(4))[0] != ClassFile.MAGIC:
raise ValueError('invalid magic number')
# The version is swapped on disk to (minor, major), so swap it back.
self.version = unpack('>HH', source.read(4))[::-1]
self._constants.unpack(source)
# ClassFile access_flags, see section #4.1 of the JVM specs.
self.access_flags.unpack(read(2))
# The CONSTANT_Class indexes for "this" class and its superclass.
# Interfaces are a simple list of CONSTANT_Class indexes.
self._this, self._super, interfaces_count = unpack('>HHH', read(6))
self._interfaces = unpack(f'>{interfaces_count}H',
read(2 * interfaces_count))
self.fields.unpack(source)
self.methods.unpack(source)
self.attributes.unpack(source)
@property
def version(self) -> ClassVersion:
"""
The :class:`~jawa.cf.ClassVersion` for this class.
Example::
>>> cf = ClassFile.create('HelloWorld')
>>> cf.version = 51, 0
>>> print(cf.version)
ClassVersion(major=51, minor=0)
>>> print(cf.version.major)
51
"""
return self._version
@version.setter
def version(self, major_minor: Union[ClassVersion, Sequence]):
self._version = ClassVersion(*major_minor)
@property
def constants(self) -> ConstantPool:
"""
The :class:`~jawa.cp.ConstantPool` for this class.
"""
return self._constants
@property
def this(self) -> ConstantClass:
"""
The :class:`~jawa.constants.ConstantClass` which represents this class.
"""
return self.constants.get(self._this)
@this.setter
def this(self, value):
self._this = value.index
@property
def super_(self) -> ConstantClass:
"""
The :class:`~jawa.constants.ConstantClass` which represents this
class's superclass.
"""
return self.constants.get(self._super)
@super_.setter
def super_(self, value: ConstantClass):
self._super = value.index
@property
def interfaces(self) -> Iterable[ConstantClass]:
"""
A list of direct superinterfaces of this class as indexes into
the constant pool, in left-to-right order.
"""
return [self._constants[idx] for idx in self._interfaces]
@property
def bootstrap_methods(self) -> BootstrapMethod:
"""
Returns the bootstrap methods table from the BootstrapMethods attribute,
if one exists. If it does not, one will be created.
:returns: Table of `BootstrapMethod` objects.
"""
bootstrap = self.attributes.find_one(name='BootstrapMethods')
if bootstrap is None:
bootstrap = self.attributes.create(
ATTRIBUTE_CLASSES['BootstrapMethods'])
return bootstrap.table
def __repr__(self):
return f'<ClassFile(this={self.this.name.value!r})>'
class Field(object):
def __init__(self, cf):
self._cf = cf
self.access_flags = Flags('>H', {
'acc_public': 0x0001,
'acc_private': 0x0002,
'acc_protected': 0x0004,
'acc_static': 0x0008,
'acc_final': 0x0010,
'acc_volatile': 0x0040,
'acc_transient': 0x0080,
'acc_synthetic': 0x1000,
'acc_enum': 0x4000
})
self._name_index = 0
self._descriptor_index = 0
self.attributes = AttributeTable(cf)
@property
def descriptor(self) -> UTF8:
"""
The UTF8 Constant containing the field's descriptor.
"""
return self._cf.constants[self._descriptor_index]
@property
def type(self):
"""
A :class:`~jawa.util.descriptor.JVMType` representing the field's
type.
"""
return field_descriptor(self.descriptor.value)
@property
def name(self) -> UTF8:
"""
The UTF8 Constant containing the field's name.
"""
return self._cf.constants[self._name_index]
@property
def value(self) -> ConstantValueAttribute:
"""
A shortcut for the field's ConstantValue attribute, should one exist.
"""
return self.attributes.find_one(name='ConstantValue')
def unpack(self, source: IO):
"""
Read the Field from the file-like object `fio`.
.. note::
Advanced usage only. You will typically never need to call this
method as it will be called for you when loading a ClassFile.
:param source: Any file-like object providing `read()`
"""
self.access_flags.unpack(source.read(2))
self._name_index, self._descriptor_index = unpack('>HH', source.read(4))
self.attributes.unpack(source)
def pack(self, out: IO):
"""
Write the Field to the file-like object `out`.
.. note::
Advanced usage only. You will typically never need to call this
method as it will be called for you when saving a ClassFile.
:param out: Any file-like object providing `write()`
"""
out.write(self.access_flags.pack())
out.write(pack('>HH', self._name_index, self._descriptor_index))
self.attributes.pack(out)
class Field(object):
def __init__(self, cf):
self._cf = cf
self.access_flags = Flags(
'>H', {
'acc_public': 0x0001,
'acc_private': 0x0002,
'acc_protected': 0x0004,
'acc_static': 0x0008,
'acc_final': 0x0010,
'acc_volatile': 0x0040,
'acc_transient': 0x0080,
'acc_synthetic': 0x1000,
'acc_enum': 0x4000
})
self._name_index = 0
self._descriptor_index = 0
self.attributes = AttributeTable(cf)
@property
def descriptor(self) -> UTF8:
"""
The UTF8 Constant containing the field's descriptor.
"""
return self._cf.constants[self._descriptor_index]
@property
def type(self):
"""
A :class:`~jawa.util.descriptor.JVMType` representing the field's
type.
"""
return field_descriptor(self.descriptor.value)
@property
def name(self) -> UTF8:
"""
The UTF8 Constant containing the field's name.
"""
return self._cf.constants[self._name_index]
@property
def value(self) -> ConstantValueAttribute:
"""
A shortcut for the field's ConstantValue attribute, should one exist.
"""
return self.attributes.find_one(name='ConstantValue')
def unpack(self, source: IO):
"""
Read the Field from the file-like object `fio`.
.. note::
Advanced usage only. You will typically never need to call this
method as it will be called for you when loading a ClassFile.
:param source: Any file-like object providing `read()`
"""
self.access_flags.unpack(source.read(2))
self._name_index, self._descriptor_index = unpack(
'>HH', source.read(4))
self.attributes.unpack(source)
def pack(self, out: IO):
"""
Write the Field to the file-like object `out`.
.. note::
Advanced usage only. You will typically never need to call this
method as it will be called for you when saving a ClassFile.
:param out: Any file-like object providing `write()`
"""
out.write(self.access_flags.pack())
out.write(pack('>HH', self._name_index, self._descriptor_index))
self.attributes.pack(out)
class Method(object):
def __init__(self, cf):
self._cf = cf
self.access_flags = Flags('>H', {
'acc_public': 0x0001,
'acc_private': 0x0002,
'acc_protected': 0x0004,
'acc_static': 0x0008,
'acc_final': 0x0010,
'acc_synchronized': 0x0020,
'acc_bridge': 0x0040,
'acc_varargs': 0x0080,
'acc_native': 0x0100,
'acc_abstract': 0x0400,
'acc_strict': 0x0800,
'acc_synthetic': 0x1000
})
self._name_index = 0
self._descriptor_index = 0
self.attributes = AttributeTable(cf)
@property
def descriptor(self) -> UTF8:
"""
The UTF8 Constant containing the method's descriptor.
"""
return self._cf.constants[self._descriptor_index]
@property
def name(self) -> UTF8:
"""
The UTF8 Constant containing the method's name.
"""
return self._cf.constants[self._name_index]
@property
def returns(self) -> JVMType:
"""
A :class:`~jawa.util.descriptor.JVMType` representing the method's
return type.
"""
return method_descriptor(self.descriptor.value).returns
@property
def args(self) -> List[JVMType]:
"""
A list of :class:`~jawa.util.descriptor.JVMType` representing the
method's argument list.
"""
return method_descriptor(self.descriptor.value).args
@property
def code(self) -> CodeAttribute:
"""
A shortcut for :code:`method.attributes.find_one(name='Code')`.
"""
return self.attributes.find_one(name='Code')
def __repr__(self):
return f'<Method(name={self.name})>'
def unpack(self, source: IO):
"""
Read the Method from the file-like object `fio`.
.. note::
Advanced usage only. You will typically never need to call this
method as it will be called for you when loading a ClassFile.
:param source: Any file-like object providing `read()`
"""
self.access_flags.unpack(source.read(2))
self._name_index, self._descriptor_index = unpack('>HH', source.read(4))
self.attributes.unpack(source)
def pack(self, out: IO):
"""
Write the Method to the file-like object `out`.
.. note::
Advanced usage only. You will typically never need to call this
method as it will be called for you when saving a ClassFile.
:param out: Any file-like object providing `write()`
"""
out.write(self.access_flags.pack())
out.write(pack(
'>HH',
self._name_index,
self._descriptor_index
))
self.attributes.pack(out)
class ClassFile(object):
"""
Implements the JVM ClassFile (files typically ending in ``.class``).
To open an existing ClassFile::
>>> with open('HelloWorld.class', 'rb') as fin:
... cf = ClassFile(fin)
To save a newly created or modified ClassFile::
>>> cf = ClassFile.create('HelloWorld')
>>> with open('HelloWorld.class', 'wb') as out:
... cf.save(out)
:meth:`~ClassFile.create` sets up some reasonable defaults equivalent to:
.. code-block:: java
public class HelloWorld extends java.lang.Object{
}
:param source: any file-like object providing ``.read()``.
"""
#: The JVM ClassFile magic number.
MAGIC = 0xCAFEBABE
def __init__(self, source: IO=None):
# Default to J2SE_7
self._version = ClassVersion(0x32, 0)
self._constants = ConstantPool()
self.access_flags = Flags('>H', {
'acc_public': 0x0001,
'acc_final': 0x0010,
'acc_super': 0x0020,
'acc_interface': 0x0200,
'acc_abstract': 0x0400,
'acc_synthetic': 0x1000,
'acc_annotation': 0x2000,
'acc_enum': 0x4000
})
self._this = 0
self._super = 0
self._interfaces = []
self.fields = FieldTable(self)
self.methods = MethodTable(self)
self.attributes = AttributeTable(self)
#: The ClassLoader bound to this ClassFile, if any.
self.classloader = None
if source:
self._from_io(source)
@classmethod
def create(cls, this: str, super_: str=u'java/lang/Object') -> 'ClassFile':
"""
A utility which sets up reasonable defaults for a new public class.
:param this: The name of this class.
:param super_: The name of this class's superclass.
"""
cf = ClassFile()
cf.access_flags.acc_public = True
cf.access_flags.acc_super = True
cf.this = cf.constants.create_class(this)
cf.super_ = cf.constants.create_class(super_)
return cf
def save(self, source: IO):
"""
Saves the class to the file-like object `source`.
:param source: Any file-like object providing write().
"""
write = source.write
write(pack(
'>IHH',
ClassFile.MAGIC,
self.version.minor,
self.version.major
))
self._constants.pack(source)
write(self.access_flags.pack())
write(pack(
f'>HHH{len(self._interfaces)}H',
self._this,
self._super,
len(self._interfaces),
*self._interfaces
))
self.fields.pack(source)
self.methods.pack(source)
self.attributes.pack(source)
def _from_io(self, source: IO):
"""
Loads an existing JVM ClassFile from any file-like object.
"""
read = source.read
if unpack('>I', source.read(4))[0] != ClassFile.MAGIC:
raise ValueError('invalid magic number')
# The version is swapped on disk to (minor, major), so swap it back.
self.version = unpack('>HH', source.read(4))[::-1]
self._constants.unpack(source)
# ClassFile access_flags, see section #4.1 of the JVM specs.
self.access_flags.unpack(read(2))
# The CONSTANT_Class indexes for "this" class and its superclass.
# Interfaces are a simple list of CONSTANT_Class indexes.
self._this, self._super, interfaces_count = unpack('>HHH', read(6))
self._interfaces = unpack(
f'>{interfaces_count}H',
read(2 * interfaces_count)
)
self.fields.unpack(source)
self.methods.unpack(source)
self.attributes.unpack(source)
@property
def version(self) -> ClassVersion:
"""
The :class:`~jawa.cf.ClassVersion` for this class.
Example::
>>> cf = ClassFile.create('HelloWorld')
>>> cf.version = 51, 0
>>> print(cf.version)
ClassVersion(major=51, minor=0)
>>> print(cf.version.major)
51
"""
return self._version
@version.setter
def version(self, major_minor: Union[ClassVersion, Sequence]):
self._version = ClassVersion(*major_minor)
@property
def constants(self) -> ConstantPool:
"""
The :class:`~jawa.cp.ConstantPool` for this class.
"""
return self._constants
@property
def this(self) -> ConstantClass:
"""
The :class:`~jawa.constants.ConstantClass` which represents this class.
"""
return self.constants.get(self._this)
@this.setter
def this(self, value):
self._this = value.index
@property
def super_(self) -> ConstantClass:
"""
The :class:`~jawa.constants.ConstantClass` which represents this
class's superclass.
"""
return self.constants.get(self._super)
@super_.setter
def super_(self, value: ConstantClass):
self._super = value.index
@property
def interfaces(self) -> Iterable[ConstantClass]:
"""
A list of direct superinterfaces of this class as indexes into
the constant pool, in left-to-right order.
"""
return [self._constants[idx] for idx in self._interfaces]
@property
def bootstrap_methods(self) -> BootstrapMethod:
"""
Returns the bootstrap methods table from the BootstrapMethods attribute,
if one exists. If it does not, one will be created.
:returns: Table of `BootstrapMethod` objects.
"""
bootstrap = self.attributes.find_one(name='BootstrapMethods')
if bootstrap is None:
bootstrap = self.attributes.create(
ATTRIBUTE_CLASSES['BootstrapMethods']
)
return bootstrap.table
def __repr__(self):
return f'<ClassFile(this={self.this.name.value!r})>'
