mirror of
https://git.notmuchmail.org/git/notmuch
synced 2024-12-29 12:51:43 +01:00
238 lines
8.2 KiB
Python
238 lines
8.2 KiB
Python
import abc
|
|
import collections.abc
|
|
|
|
from notmuch2 import _capi as capi
|
|
from notmuch2 import _errors as errors
|
|
|
|
|
|
__all__ = ['NotmuchObject', 'BinString']
|
|
|
|
|
|
class NotmuchObject(metaclass=abc.ABCMeta):
|
|
"""Base notmuch object syntax.
|
|
|
|
This base class exists to define the memory management handling
|
|
required to use the notmuch library. It is meant as an interface
|
|
definition rather than a base class, though you can use it as a
|
|
base class to ensure you don't forget part of the interface. It
|
|
only concerns you if you are implementing this package itself
|
|
rather then using it.
|
|
|
|
libnotmuch uses a hierarchical memory allocator, where freeing the
|
|
memory of a parent object also frees the memory of all child
|
|
objects. To make this work seamlessly in Python this package
|
|
keeps references to parent objects which makes them stay alive
|
|
correctly under normal circumstances. When an object finally gets
|
|
deleted the :meth:`__del__` method will be called to free the
|
|
memory.
|
|
|
|
However during some peculiar situations, e.g. interpreter
|
|
shutdown, it is possible for the :meth:`__del__` method to have
|
|
been called, whele there are still references to an object. This
|
|
could result in child objects asking their memory to be freed
|
|
after the parent has already freed the memory, making things
|
|
rather unhappy as double frees are not taken lightly in C. To
|
|
handle this case all objects need to follow the same protocol to
|
|
destroy themselves, see :meth:`destroy`.
|
|
|
|
Once an object has been destroyed trying to use it should raise
|
|
the :exc:`ObjectDestroyedError` exception. For this see also the
|
|
convenience :class:`MemoryPointer` descriptor in this module which
|
|
can be used as a pointer to libnotmuch memory.
|
|
"""
|
|
|
|
@abc.abstractmethod
|
|
def __init__(self, parent, *args, **kwargs):
|
|
"""Create a new object.
|
|
|
|
Other then for the toplevel :class:`Database` object
|
|
constructors are only ever called by internal code and not by
|
|
the user. Per convention their signature always takes the
|
|
parent object as first argument. Feel free to make the rest
|
|
of the signature match the object's requirement. The object
|
|
needs to keep a reference to the parent, so it can check the
|
|
parent is still alive.
|
|
"""
|
|
|
|
@property
|
|
@abc.abstractmethod
|
|
def alive(self):
|
|
"""Whether the object is still alive.
|
|
|
|
This indicates whether the object is still alive. The first
|
|
thing this needs to check is whether the parent object is
|
|
still alive, if it is not then this object can not be alive
|
|
either. If the parent is alive then it depends on whether the
|
|
memory for this object has been freed yet or not.
|
|
"""
|
|
|
|
def __del__(self):
|
|
self._destroy()
|
|
|
|
@abc.abstractmethod
|
|
def _destroy(self):
|
|
"""Destroy the object, freeing all memory.
|
|
|
|
This method needs to destroy the object on the
|
|
libnotmuch-level. It must ensure it's not been destroyed by
|
|
it's parent object yet before doing so. It also must be
|
|
idempotent.
|
|
"""
|
|
|
|
|
|
class MemoryPointer:
|
|
"""Data Descriptor to handle accessing libnotmuch pointers.
|
|
|
|
Most :class:`NotmuchObject` instances will have one or more CFFI
|
|
pointers to C-objects. Once an object is destroyed this pointer
|
|
should no longer be used and a :exc:`ObjectDestroyedError`
|
|
exception should be raised on trying to access it. This
|
|
descriptor simplifies implementing this, allowing the creation of
|
|
an attribute which can be assigned to, but when accessed when the
|
|
stored value is *None* it will raise the
|
|
:exc:`ObjectDestroyedError` exception::
|
|
|
|
class SomeOjb:
|
|
_ptr = MemoryPointer()
|
|
|
|
def __init__(self, ptr):
|
|
self._ptr = ptr
|
|
|
|
def destroy(self):
|
|
somehow_free(self._ptr)
|
|
self._ptr = None
|
|
|
|
def do_something(self):
|
|
return some_libnotmuch_call(self._ptr)
|
|
"""
|
|
|
|
def __get__(self, instance, owner):
|
|
try:
|
|
val = getattr(instance, self.attr_name, None)
|
|
except AttributeError:
|
|
# We're not on 3.6+ and self.attr_name does not exist
|
|
self.__set_name__(instance, 'dummy')
|
|
val = getattr(instance, self.attr_name, None)
|
|
if val is None:
|
|
raise errors.ObjectDestroyedError()
|
|
return val
|
|
|
|
def __set__(self, instance, value):
|
|
try:
|
|
setattr(instance, self.attr_name, value)
|
|
except AttributeError:
|
|
# We're not on 3.6+ and self.attr_name does not exist
|
|
self.__set_name__(instance, 'dummy')
|
|
setattr(instance, self.attr_name, value)
|
|
|
|
def __set_name__(self, instance, name):
|
|
self.attr_name = '_memptr_{}_{:x}'.format(name, id(instance))
|
|
|
|
|
|
class BinString(str):
|
|
"""A str subclass with binary data.
|
|
|
|
Most data in libnotmuch should be valid ASCII or valid UTF-8.
|
|
However since it is a C library these are represented as
|
|
bytestrings instead which means on an API level we can not
|
|
guarantee that decoding this to UTF-8 will both succeed and be
|
|
lossless. This string type converts bytes to unicode in a lossy
|
|
way, but also makes the raw bytes available.
|
|
|
|
This object is a normal unicode string for most intents and
|
|
purposes, but you can get the original bytestring back by calling
|
|
``bytes()`` on it.
|
|
"""
|
|
|
|
def __new__(cls, data, encoding='utf-8', errors='ignore'):
|
|
if not isinstance(data, bytes):
|
|
data = bytes(data, encoding=encoding)
|
|
strdata = str(data, encoding=encoding, errors=errors)
|
|
inst = super().__new__(cls, strdata)
|
|
inst._bindata = data
|
|
return inst
|
|
|
|
@classmethod
|
|
def from_cffi(cls, cdata):
|
|
"""Create a new string from a CFFI cdata pointer."""
|
|
return cls(capi.ffi.string(cdata))
|
|
|
|
def __bytes__(self):
|
|
return self._bindata
|
|
|
|
|
|
class NotmuchIter(NotmuchObject, collections.abc.Iterator):
|
|
"""An iterator for libnotmuch iterators.
|
|
|
|
It is tempting to use a generator function instead, but this would
|
|
not correctly respect the :class:`NotmuchObject` memory handling
|
|
protocol and in some unsuspecting cornercases cause memory
|
|
trouble. You probably want to sublcass this in order to wrap the
|
|
value returned by :meth:`__next__`.
|
|
|
|
:param parent: The parent object.
|
|
:type parent: NotmuchObject
|
|
:param iter_p: The CFFI pointer to the C iterator.
|
|
:type iter_p: cffi.cdata
|
|
:param fn_destory: The CFFI notmuch_*_destroy function.
|
|
:param fn_valid: The CFFI notmuch_*_valid function.
|
|
:param fn_get: The CFFI notmuch_*_get function.
|
|
:param fn_next: The CFFI notmuch_*_move_to_next function.
|
|
"""
|
|
_iter_p = MemoryPointer()
|
|
|
|
def __init__(self, parent, iter_p,
|
|
*, fn_destroy, fn_valid, fn_get, fn_next):
|
|
self._parent = parent
|
|
self._iter_p = iter_p
|
|
self._fn_destroy = fn_destroy
|
|
self._fn_valid = fn_valid
|
|
self._fn_get = fn_get
|
|
self._fn_next = fn_next
|
|
|
|
def __del__(self):
|
|
self._destroy()
|
|
|
|
@property
|
|
def alive(self):
|
|
if not self._parent.alive:
|
|
return False
|
|
try:
|
|
self._iter_p
|
|
except errors.ObjectDestroyedError:
|
|
return False
|
|
else:
|
|
return True
|
|
|
|
def _destroy(self):
|
|
if self.alive:
|
|
try:
|
|
self._fn_destroy(self._iter_p)
|
|
except errors.ObjectDestroyedError:
|
|
pass
|
|
self._iter_p = None
|
|
|
|
def __iter__(self):
|
|
"""Return the iterator itself.
|
|
|
|
Note that as this is an iterator and not a container this will
|
|
not return a new iterator. Thus any elements already consumed
|
|
will not be yielded by the :meth:`__next__` method anymore.
|
|
"""
|
|
return self
|
|
|
|
def __next__(self):
|
|
if not self._fn_valid(self._iter_p):
|
|
self._destroy()
|
|
raise StopIteration()
|
|
obj_p = self._fn_get(self._iter_p)
|
|
self._fn_next(self._iter_p)
|
|
return obj_p
|
|
|
|
def __repr__(self):
|
|
try:
|
|
self._iter_p
|
|
except errors.ObjectDestroyedError:
|
|
return '<NotmuchIter (exhausted)>'
|
|
else:
|
|
return '<NotmuchIter>'
|