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):
return self._cf.constants[self._descriptor_index]
@property
def name(self):
return self._cf.constants[self._name_index]
@property
def access_flags(self):
return self._access_flags
@property
def attributes(self):
return self._attributes
@property
def value(self):
"""
A shortcut for the field's ConstantValue attribute, should one exist.
"""
constant_value = self.attributes.find_one(name='ConstantValue')
return constant_value
def _from_io(self, fio):
self.access_flags.unpack(fio.read(2))
self._name_index, self._descriptor_index = unpack('>HH', fio.read(4))
self._attributes._from_io(fio)
def _to_io(self, fout):
fout.write(self.access_flags.pack())
fout.write(pack('>HH', self._name_index, self._descriptor_index))
self._attributes._to_io(fout)
class ClassFile(object):
"""
Implements the JVM ClassFile (files typically ending in ``.class``).
To open an existing ClassFile::
from jawa import ClassFile
with open('HelloWorld.class') as fin:
cf = ClassFile(fin)
To save a newly created or modified ClassFile::
with open('HelloWorld.class', 'wb') as fout:
cf.save(fout)
To create a new ClassFile, use the helper :meth:`~ClassFile.create`::
from jawa import ClassFile
cf = ClassFile.create('HelloWorld')
with open('HelloWorld.class', 'wb') as fout:
cf.save(fout)
:meth:`~ClassFile.create` sets up some reasonable defaults equivelent to:
.. code-block:: java
public class HelloWorld extends java.lang.Object{
}
:param fio: any file-like object providing ``.read()``.
"""
#: The JVM ClassFile magic number.
MAGIC = 0xCAFEBABE
def __init__(self, fio=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)
if fio:
self._from_io(fio)
@classmethod
def create(cls, this, super_='java/lang/Object'):
"""
A utility method 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).index
cf._super = cf.constants.create_class(super_).index
return cf
def save(self, fout):
"""
Saves the class to the file-like object `fout`.
"""
write = fout.write
write(pack('>IHH',
ClassFile.MAGIC,
self.version.minor,
self.version.major
))
self._constants._to_io(fout)
write(self.access_flags.pack())
write(pack('>HHH{0}H'.format(len(self._interfaces)),
self._this,
self._super,
len(self._interfaces),
*self._interfaces
))
self._fields._to_io(fout)
self._methods._to_io(fout)
self._attributes._to_io(fout)
# ------------
# Internal
# ------------
def _from_io(self, fio):
"""
Loads an existing JVM ClassFile from any file-like object.
"""
read = fio.read
if unpack('>I', fio.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', fio.read(4))[::-1]
self._constants._from_io(fio)
# 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(
'>{0}H'.format(interfaces_count),
read(2 * interfaces_count)
)
self._fields._from_io(fio)
self._methods._from_io(fio)
self._attributes._from_io(fio)
# -------------
# Properties
# -------------
@property
def version(self):
"""
The :class:`~jawa.cf.ClassVersion` for this class.
Example::
>>> 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)):
self._version = ClassVersion(major, minor)
class CodeAttribute(Attribute):
@classmethod
def create(cls, cf):
c = cls(cf, cf.constants.create_utf8('Code').index)
c._max_stack = 0
c._max_locals = 0
c._ex_table = []
c._attributes = AttributeTable(cf)
c._code = ''
return c
def unpack(self, info):
fio = StringIO(info)
self._max_stack, self._max_locals, c_len = unpack('>HHI', fio.read(8))
self._code = fio.read(c_len)
# The exception table
ex_table_len = unpack('>H', fio.read(2))[0]
self._ex_table = []
for _ in repeat(None, ex_table_len):
self._ex_table.append(CodeException(
*unpack('>HHHH', fio.read(8))
))
self._attributes = AttributeTable(self._cf)
self._attributes._from_io(fio)
fio.close()
@property
def info(self):
fout = StringIO()
fout.write(pack(
'>HHI',
self._max_stack,
self._max_locals,
len(self._code)
))
fout.write(self._code)
fout.write(pack('>H', len(self._ex_table)))
for exception in self._ex_table:
fout.write(pack('>HHHH', *exception))
self._attributes._to_io(fout)
return fout.getvalue()
@property
def max_stack(self):
return self._max_stack
@max_stack.setter
def max_stack(self, value):
self._max_stack = value
@property
def max_locals(self):
return self._max_locals
@max_locals.setter
def max_locals(self, value):
self._max_locals = value
@property
def exception_table(self):
return self._ex_table
@property
def code(self):
return self._code
@property
def attributes(self):
return self._attributes
def assemble(self, code):
"""
Assembles an iterable of :class:`~jawa.util.bytecode.Instruction`
objects into a methods code body.
"""
fout = StringIO()
for ins in code:
write_instruction(fout, fout.tell(), ins)
self._code = fout.getvalue()
fout.close()
def disassemble(self):
"""
Disassembles this method.
"""
fio = StringIO(self._code)
for ins in iter(lambda: read_instruction(fio, fio.tell()), None):
yield ins
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):
return self._cf.constants[self._descriptor_index]
@property
def name(self):
return self._cf.constants[self._name_index]
@property
def access_flags(self):
return self._access_flags
@property
def attributes(self):
return self._attributes
@property
def returns(self):
return method_descriptor(self.descriptor.value).returns
@property
def args(self):
return method_descriptor(self.descriptor.value).args
@property
def code(self):
"""
A shortcut for::
method.attributes.find_one(name='Code')
"""
return self.attributes.find_one(name='Code')
def _from_io(self, fio):
self.access_flags.unpack(fio.read(2))
self._name_index, self._descriptor_index = unpack('>HH', fio.read(4))
self._attributes._from_io(fio)
def _to_io(self, fout):
fout.write(self.access_flags.pack())
fout.write(pack('>HH',
self._name_index,
self._descriptor_index
))
self._attributes._to_io(fout)
