3.5.1. Atom Protocol#

Caterpillar provides a special protocol for working with atoms. It is designed to incorporate packing and unpacking of data streams as well as calculating its size and measuring its type.

Changed in version 2.6.0: Reworked the CAPI and its components.

type CpAtomObject#: All classes that implement capabilities of an atom should inherit from this class. It stores optional C slots for __pack__, __pack_many__, __unpack__, __unpack_many__, __size__, __type__ and __bits__. Slots that are not configured raise NotImplementedError when called through the Python methods.

PyTypeObject CpAtom_Type#: The type object of the CpAtom class.

Atoms may be implemented either as native CpAtomObject subclasses or as normal Python objects exposing the corresponding special methods. The CpAtom_* helpers use the native slot when available and fall back to Python attribute/method lookup otherwise.

int CpAtom_HasPack(PyObject *o)#
int CpAtom_FastCanPack(PyObject *o, _coremodulestate *state)#: Return 1 if the object provides an interface of packing other objects and 0 otherwise. Note that it returns 1 for classes with a __pack__() method, since the type of objects to be packed can not be determined by introspection.

int CpAtom_HasPackMany(PyObject *o)#: Return 1 if the object exposes __pack_many__ and 0 otherwise.

int CpAtom_HasUnpack(PyObject *o)#: Return 1 if the object provides an interface of unpacking other objects and 0 otherwise. Note that it returns 1 for classes with a __unpack__() method, since the type of objects to be unpacked can not be determined by introspection.

int CpAtom_HasUnpackMany(PyObject *o)#: Return 1 if the object exposes __unpack_many__ and 0 otherwise.

int CpAtom_HasType(PyObject *o)#: Returns 1 if the object provides a method of determining the type this object (usually an atom) represents and 0 otherwise. As all other functions, this one will simply check for the presence of the __type__() method.

int CpAtom_HasSize(PyObject *o)#: Searches for __size__(), returns 1 if it is present and 0 otherwise.

int CpAtom_HasBits(PyObject *o)#: Searches for __bits__ and returns 1 if present. __bits__ is used by bitfield and repeated native atoms and may be implemented as either a callable or an integer attribute on Python objects.