darleybarreto
commented
3 years ago CPython Ctypes
Important types
typedef struct tagPyCArgObject PyCArgObject;
typedef struct tagCDataObject CDataObject;
typedef PyObject *(* GETFUNC)(void *, Py_ssize_t size);
typedef PyObject *(* SETFUNC)(void *, PyObject *value, Py_ssize_t size);
typedef PyCArgObject *(* PARAMFUNC)(CDataObject *obj);
struct tagCDataObject {
PyObject_HEAD
char *b_ptr; /* pointer to memory block */
int b_needsfree; /* need _we_ free the memory? */
CDataObject *b_base; /* pointer to base object or NULL */
Py_ssize_t b_size; /* size of memory block in bytes */
Py_ssize_t b_length; /* number of references we need */
Py_ssize_t b_index; /* index of this object into base's
b_object list */
PyObject *b_objects; /* dictionary of references we need to keep, or Py_None */
union value b_value;
};
typedef struct {
PyObject_VAR_HEAD
ffi_closure *pcl_write; /* the C callable, writeable */
void *pcl_exec; /* the C callable, executable */
ffi_cif cif;
int flags;
PyObject *converters;
PyObject *callable;
PyObject *restype;
SETFUNC setfunc;
ffi_type *ffi_restype;
ffi_type *atypes[1];
} CThunkObject;
extern PyTypeObject PyCThunk_Type;
#define CThunk_CheckExact(v) Py_IS_TYPE(v, &PyCThunk_Type)
typedef struct {
/* First part identical to tagCDataObject */
PyObject_HEAD
char *b_ptr; /* pointer to memory block */
int b_needsfree; /* need _we_ free the memory? */
CDataObject *b_base; /* pointer to base object or NULL */
Py_ssize_t b_size; /* size of memory block in bytes */
Py_ssize_t b_length; /* number of references we need */
Py_ssize_t b_index; /* index of this object into base's
b_object list */
PyObject *b_objects; /* list of references we need to keep */
union value b_value;
/* end of tagCDataObject, additional fields follow */
CThunkObject *thunk;
PyObject *callable;
/* These two fields will override the ones in the type's stgdict if
they are set */
PyObject *converters;
PyObject *argtypes;
PyObject *restype;
PyObject *checker;
PyObject *errcheck;
#ifdef MS_WIN32
int index;
GUID *iid;
#endif
PyObject *paramflags;
} PyCFuncPtrObject;
/* a table entry describing a predefined ctypes type */
struct fielddesc {
char code;
SETFUNC setfunc;
GETFUNC getfunc;
ffi_type *pffi_type; /* always statically allocated */
SETFUNC setfunc_swapped;
GETFUNC getfunc_swapped;
};
typedef struct {
PyObject_HEAD
Py_ssize_t offset;
Py_ssize_t size;
Py_ssize_t index; /* Index into CDataObject's
object array */
PyObject *proto; /* a type or NULL */
GETFUNC getfunc; /* getter function if proto is NULL */
SETFUNC setfunc; /* setter function if proto is NULL */
int anonymous;
} CFieldObject;
/* A subclass of PyDictObject, used as the instance dictionary of ctypes
metatypes */
typedef struct {
PyDictObject dict; /* first part identical to PyDictObject */
Py_ssize_t size; /* number of bytes */
Py_ssize_t align; /* alignment requirements */
Py_ssize_t length; /* number of fields */
ffi_type ffi_type_pointer;
PyObject *proto; /* Only for Pointer/ArrayObject */
SETFUNC setfunc; /* Only for simple objects */
GETFUNC getfunc; /* Only for simple objects */
PARAMFUNC paramfunc;
/* Following fields only used by PyCFuncPtrType_Type instances */
PyObject *argtypes; /* tuple of CDataObjects */
PyObject *converters; /* tuple([t.from_param for t in argtypes]) */
PyObject *restype; /* CDataObject or NULL */
PyObject *checker;
int flags; /* calling convention and such */
/* pep3118 fields, pointers neeed PyMem_Free */
char *format;
int ndim;
Py_ssize_t *shape;
/* Py_ssize_t *strides; */ /* unused in ctypes */
/* Py_ssize_t *suboffsets; */ /* unused in ctypes */
} StgDictObject;
struct tagPyCArgObject {
PyObject_HEAD
ffi_type *pffi_type;
char tag;
union {
char c;
char b;
short h;
int i;
long l;
long long q;
long double D;
double d;
float f;
void *p;
} value;
PyObject *obj;
Py_ssize_t size; /* for the 'V' tag */
};I didn't give a deeper look into types like StgDictObject and tagPyCArgObject.
Metaclasses
PyTypeObject PyCArrayType_Type;
PyTypeObject PyCPointerType_Type;
PyTypeObject PyCFuncPtrType_Type;
PyTypeObject PyCStructType_Type;
PyTypeObject UnionType_Type;
PyTypeObject PyCSimpleType_Type;All these metaclasses but PyCPointerType_Type and PyCSimpleType_Type implements CDataType_methods:
static PyMethodDef CDataType_methods[] = {
{ "from_param", CDataType_from_param, METH_O, from_param_doc },
{ "from_address", CDataType_from_address, METH_O, from_address_doc },
{ "from_buffer", CDataType_from_buffer, METH_VARARGS, from_buffer_doc, },
{ "from_buffer_copy", CDataType_from_buffer_copy, METH_VARARGS, from_buffer_copy_doc, },
{ "in_dll", CDataType_in_dll, METH_VARARGS, in_dll_doc },
};PyCSimpleType_Type uses PyCSimpleType_methods:
static PyMethodDef PyCSimpleType_methods[] = {
{ "from_param", PyCSimpleType_from_param, METH_O, from_param_doc },
{ "from_address", CDataType_from_address, METH_O, from_address_doc },
{ "from_buffer", CDataType_from_buffer, METH_VARARGS, from_buffer_doc, },
{ "from_buffer_copy", CDataType_from_buffer_copy, METH_VARARGS, from_buffer_copy_doc, },
{ "in_dll", CDataType_in_dll, METH_VARARGS, in_dll_doc},
};PyCPointerType_Type uses PyCPointerType_methods:
static PyMethodDef PyCPointerType_methods[] = {
{ "from_address", CDataType_from_address, METH_O, from_address_doc },
{ "from_buffer", CDataType_from_buffer, METH_VARARGS, from_buffer_doc, },
{ "from_buffer_copy", CDataType_from_buffer_copy, METH_VARARGS, from_buffer_copy_doc, },
{ "in_dll", CDataType_in_dll, METH_VARARGS, in_dll_doc},
{ "from_param", (PyCFunction)PyCPointerType_from_param, METH_O, from_param_doc},
{ "set_type", (PyCFunction)PyCPointerType_set_type, METH_O },
};Al the above classes use CDataType_as_sequence as tp_as_sequence (sequence protocol):
static PySequenceMethods CDataType_as_sequence = {
0, /* inquiry sq_length; */
0, /* binaryfunc sq_concat; */
CDataType_repeat, /* intargfunc sq_repeat; */
0, /* intargfunc sq_item; */
0, /* intintargfunc sq_slice; */
0, /* intobjargproc sq_ass_item; */
0, /* intintobjargproc sq_ass_slice; */
0, /* objobjproc sq_contains; */
0, /* binaryfunc sq_inplace_concat; */
0, /* intargfunc sq_inplace_repeat; */
};Classes
PyTypeObject PyCData_Type;
PyTypeObject PyCArray_Type; // subclass of PyCArrayType_Type
PyTypeObject PyCPointer_Type; // subclass of PyCPointerType_Type
PyTypeObject PyCFuncPtr_Type; // subclass of PyCFuncPtrType_Type
PyTypeObject Struct_Type; // subclass of PyCStructType_Type
PyTypeObject Union_Type; // subclass of UnionType_Type
PyTypeObject Simple_Type; // subclass of PyCSimpleType_TypeAll the above classes but PyCFuncPtr_Type have tp_basicsize as sizeof(CDataObject), PyCFuncPtr_Type has sizeof(PyCFuncPtrObject). They're all subclass of PyCData_Type.
Each class has some particular methods, which needs to be explored individually. Some of the shared methods, for instance Struct_Type, Union_Type, PyCArray_Type and Simple_Type have the same new. Another example is that they all have the same method on tp_as_buffer slot.
PyPy implements PyCData_Type as a metaclass, if I'm not mistaken. CDataObject is it's subclass, all the above classes implements CDataObject and their respective superclasses.
rodrigocam
This is the
#1(first) tracking issue w.r.t the implementation of_ctypes. The main goal is to discuss the core ideas of the some interpreters such as CPython, PyPy and IronPython.