/Include/object.h

  1#ifndef Py_OBJECT_H
  2#define Py_OBJECT_H
  3#ifdef __cplusplus
  4extern "C" {
  5#endif
  6
  7
  8/* Object and type object interface */
  9
 10/*
 11Objects are structures allocated on the heap.  Special rules apply to
 12the use of objects to ensure they are properly garbage-collected.
 13Objects are never allocated statically or on the stack; they must be
 14accessed through special macros and functions only.  (Type objects are
 15exceptions to the first rule; the standard types are represented by
 16statically initialized type objects, although work on type/class unification
 17for Python 2.2 made it possible to have heap-allocated type objects too).
 18
 19An object has a 'reference count' that is increased or decreased when a
 20pointer to the object is copied or deleted; when the reference count
 21reaches zero there are no references to the object left and it can be
 22removed from the heap.
 23
 24An object has a 'type' that determines what it represents and what kind
 25of data it contains.  An object's type is fixed when it is created.
 26Types themselves are represented as objects; an object contains a
 27pointer to the corresponding type object.  The type itself has a type
 28pointer pointing to the object representing the type 'type', which
 29contains a pointer to itself!).
 30
 31Objects do not float around in memory; once allocated an object keeps
 32the same size and address.  Objects that must hold variable-size data
 33can contain pointers to variable-size parts of the object.  Not all
 34objects of the same type have the same size; but the size cannot change
 35after allocation.  (These restrictions are made so a reference to an
 36object can be simply a pointer -- moving an object would require
 37updating all the pointers, and changing an object's size would require
 38moving it if there was another object right next to it.)
 39
 40Objects are always accessed through pointers of the type 'PyObject *'.
 41The type 'PyObject' is a structure that only contains the reference count
 42and the type pointer.  The actual memory allocated for an object
 43contains other data that can only be accessed after casting the pointer
 44to a pointer to a longer structure type.  This longer type must start
 45with the reference count and type fields; the macro PyObject_HEAD should be
 46used for this (to accommodate for future changes).  The implementation
 47of a particular object type can cast the object pointer to the proper
 48type and back.
 49
 50A standard interface exists for objects that contain an array of items
 51whose size is determined when the object is allocated.
 52*/
 53
 54/* Py_DEBUG implies Py_TRACE_REFS. */
 55#if defined(Py_DEBUG) && !defined(Py_TRACE_REFS)
 56#define Py_TRACE_REFS
 57#endif
 58
 59/* Py_TRACE_REFS implies Py_REF_DEBUG. */
 60#if defined(Py_TRACE_REFS) && !defined(Py_REF_DEBUG)
 61#define Py_REF_DEBUG
 62#endif
 63
 64#ifdef Py_TRACE_REFS
 65/* Define pointers to support a doubly-linked list of all live heap objects. */
 66#define _PyObject_HEAD_EXTRA		\
 67	struct _object *_ob_next;	\
 68	struct _object *_ob_prev;
 69
 70#define _PyObject_EXTRA_INIT 0, 0,
 71
 72#else
 73#define _PyObject_HEAD_EXTRA
 74#define _PyObject_EXTRA_INIT
 75#endif
 76
 77/* PyObject_HEAD defines the initial segment of every PyObject.  Keep
 78   this in sync with Util/PyTypeBuilder.h. */
 79#define PyObject_HEAD			\
 80	_PyObject_HEAD_EXTRA		\
 81	Py_ssize_t ob_refcnt;		\
 82	struct _typeobject *ob_type;
 83
 84#define PyObject_HEAD_INIT(type)	\
 85	_PyObject_EXTRA_INIT		\
 86	1, type,
 87
 88#define PyVarObject_HEAD_INIT(type, size)	\
 89	PyObject_HEAD_INIT(type) size,
 90
 91/* PyObject_VAR_HEAD defines the initial segment of all variable-size
 92 * container objects.  These end with a declaration of an array with 1
 93 * element, but enough space is malloc'ed so that the array actually
 94 * has room for ob_size elements.  Note that ob_size is an element count,
 95 * not necessarily a byte count.
 96 */
 97#define PyObject_VAR_HEAD		\
 98	PyObject_HEAD			\
 99	Py_ssize_t ob_size; /* Number of items in variable part */
100#define Py_INVALID_SIZE (Py_ssize_t)-1
101
102/* Nothing is actually declared to be a PyObject, but every pointer to
103 * a Python object can be cast to a PyObject*.  This is inheritance built
104 * by hand.  Similarly every pointer to a variable-size Python object can,
105 * in addition, be cast to PyVarObject*.
106 */
107typedef struct _object {
108	PyObject_HEAD
109} PyObject;
110
111typedef struct PyVarObject {
112	PyObject_VAR_HEAD
113} PyVarObject;
114
115#define Py_REFCNT(ob)		(((PyObject*)(ob))->ob_refcnt)
116#define Py_TYPE(ob)		(((PyObject*)(ob))->ob_type)
117#define Py_SIZE(ob)		(((PyVarObject*)(ob))->ob_size)
118
119/*
120Type objects contain a string containing the type name (to help somewhat
121in debugging), the allocation parameters (see PyObject_New() and
122PyObject_NewVar()),
123and methods for accessing objects of the type.  Methods are optional, a
124nil pointer meaning that particular kind of access is not available for
125this type.  The Py_DECREF() macro uses the tp_dealloc method without
126checking for a nil pointer; it should always be implemented except if
127the implementation can guarantee that the reference count will never
128reach zero (e.g., for statically allocated type objects).
129
130NB: the methods for certain type groups are now contained in separate
131method blocks.
132*/
133
134typedef PyObject * (*unaryfunc)(PyObject *);
135typedef PyObject * (*binaryfunc)(PyObject *, PyObject *);
136typedef PyObject * (*ternaryfunc)(PyObject *, PyObject *, PyObject *);
137typedef int (*inquiry)(PyObject *);
138typedef Py_ssize_t (*lenfunc)(PyObject *);
139typedef int (*coercion)(PyObject **, PyObject **);
140typedef PyObject *(*intargfunc)(PyObject *, int) Py_DEPRECATED(2.5);
141typedef PyObject *(*intintargfunc)(PyObject *, int, int) Py_DEPRECATED(2.5);
142typedef PyObject *(*ssizeargfunc)(PyObject *, Py_ssize_t);
143typedef PyObject *(*ssizessizeargfunc)(PyObject *, Py_ssize_t, Py_ssize_t);
144typedef int(*intobjargproc)(PyObject *, int, PyObject *);
145typedef int(*intintobjargproc)(PyObject *, int, int, PyObject *);
146typedef int(*ssizeobjargproc)(PyObject *, Py_ssize_t, PyObject *);
147typedef int(*ssizessizeobjargproc)(PyObject *, Py_ssize_t, Py_ssize_t, PyObject *);
148typedef int(*objobjargproc)(PyObject *, PyObject *, PyObject *);
149
150
151
152/* int-based buffer interface */
153typedef int (*getreadbufferproc)(PyObject *, int, void **);
154typedef int (*getwritebufferproc)(PyObject *, int, void **);
155typedef int (*getsegcountproc)(PyObject *, int *);
156typedef int (*getcharbufferproc)(PyObject *, int, char **);
157/* ssize_t-based buffer interface */
158typedef Py_ssize_t (*readbufferproc)(PyObject *, Py_ssize_t, void **);
159typedef Py_ssize_t (*writebufferproc)(PyObject *, Py_ssize_t, void **);
160typedef Py_ssize_t (*segcountproc)(PyObject *, Py_ssize_t *);
161typedef Py_ssize_t (*charbufferproc)(PyObject *, Py_ssize_t, char **);
162
163/* Py3k buffer interface */
164
165typedef struct bufferinfo {
166	void *buf;
167	PyObject *obj;        /* borrowed reference */
168        Py_ssize_t len;
169        Py_ssize_t itemsize;  /* This is Py_ssize_t so it can be
170                                 pointed to by strides in simple case.*/
171        int readonly;
172        int ndim;
173        char *format;
174        Py_ssize_t *shape;
175        Py_ssize_t *strides;
176        Py_ssize_t *suboffsets;
177        void *internal;
178} Py_buffer;
179
180typedef int (*getbufferproc)(PyObject *, Py_buffer *, int);
181typedef void (*releasebufferproc)(PyObject *, Py_buffer *);
182
183        /* Flags for getting buffers */
184#define PyBUF_SIMPLE 0
185#define PyBUF_WRITABLE 0x0001
186/*  we used to include an E, backwards compatible alias  */
187#define PyBUF_WRITEABLE PyBUF_WRITABLE
188#define PyBUF_FORMAT 0x0004
189#define PyBUF_ND 0x0008
190#define PyBUF_STRIDES (0x0010 | PyBUF_ND)
191#define PyBUF_C_CONTIGUOUS (0x0020 | PyBUF_STRIDES)
192#define PyBUF_F_CONTIGUOUS (0x0040 | PyBUF_STRIDES)
193#define PyBUF_ANY_CONTIGUOUS (0x0080 | PyBUF_STRIDES)
194#define PyBUF_INDIRECT (0x0100 | PyBUF_STRIDES)
195
196#define PyBUF_CONTIG (PyBUF_ND | PyBUF_WRITABLE)
197#define PyBUF_CONTIG_RO (PyBUF_ND)
198
199#define PyBUF_STRIDED (PyBUF_STRIDES | PyBUF_WRITABLE)
200#define PyBUF_STRIDED_RO (PyBUF_STRIDES)
201
202#define PyBUF_RECORDS (PyBUF_STRIDES | PyBUF_WRITABLE | PyBUF_FORMAT)
203#define PyBUF_RECORDS_RO (PyBUF_STRIDES | PyBUF_FORMAT)
204
205#define PyBUF_FULL (PyBUF_INDIRECT | PyBUF_WRITABLE | PyBUF_FORMAT)
206#define PyBUF_FULL_RO (PyBUF_INDIRECT | PyBUF_FORMAT)
207
208
209#define PyBUF_READ  0x100
210#define PyBUF_WRITE 0x200
211#define PyBUF_SHADOW 0x400
212/* end Py3k buffer interface */
213
214typedef int (*objobjproc)(PyObject *, PyObject *);
215typedef int (*visitproc)(PyObject *, void *);
216typedef int (*traverseproc)(PyObject *, visitproc, void *);
217
218typedef struct PyNumberMethods {
219	/* For numbers without flag bit Py_TPFLAGS_CHECKTYPES set, all
220	   arguments are guaranteed to be of the object's type (modulo
221	   coercion hacks -- i.e. if the type's coercion function
222	   returns other types, then these are allowed as well).  Numbers that
223	   have the Py_TPFLAGS_CHECKTYPES flag bit set should check *both*
224	   arguments for proper type and implement the necessary conversions
225	   in the slot functions themselves. */
226
227	binaryfunc nb_add;
228	binaryfunc nb_subtract;
229	binaryfunc nb_multiply;
230	binaryfunc nb_divide;
231	binaryfunc nb_remainder;
232	binaryfunc nb_divmod;
233	ternaryfunc nb_power;
234	unaryfunc nb_negative;
235	unaryfunc nb_positive;
236	unaryfunc nb_absolute;
237	inquiry nb_nonzero;
238	unaryfunc nb_invert;
239	binaryfunc nb_lshift;
240	binaryfunc nb_rshift;
241	binaryfunc nb_and;
242	binaryfunc nb_xor;
243	binaryfunc nb_or;
244	coercion nb_coerce;
245	unaryfunc nb_int;
246	unaryfunc nb_long;
247	unaryfunc nb_float;
248	unaryfunc nb_oct;
249	unaryfunc nb_hex;
250	/* Added in release 2.0 */
251	binaryfunc nb_inplace_add;
252	binaryfunc nb_inplace_subtract;
253	binaryfunc nb_inplace_multiply;
254	binaryfunc nb_inplace_divide;
255	binaryfunc nb_inplace_remainder;
256	ternaryfunc nb_inplace_power;
257	binaryfunc nb_inplace_lshift;
258	binaryfunc nb_inplace_rshift;
259	binaryfunc nb_inplace_and;
260	binaryfunc nb_inplace_xor;
261	binaryfunc nb_inplace_or;
262
263	/* Added in release 2.2 */
264	/* The following require the Py_TPFLAGS_HAVE_CLASS flag */
265	binaryfunc nb_floor_divide;
266	binaryfunc nb_true_divide;
267	binaryfunc nb_inplace_floor_divide;
268	binaryfunc nb_inplace_true_divide;
269
270	/* Added in release 2.5 */
271	unaryfunc nb_index;
272} PyNumberMethods;
273
274typedef struct PySequenceMethods {
275	lenfunc sq_length;
276	binaryfunc sq_concat;
277	ssizeargfunc sq_repeat;
278	ssizeargfunc sq_item;
279	ssizessizeargfunc sq_slice;
280	ssizeobjargproc sq_ass_item;
281	ssizessizeobjargproc sq_ass_slice;
282	objobjproc sq_contains;
283	/* Added in release 2.0 */
284	binaryfunc sq_inplace_concat;
285	ssizeargfunc sq_inplace_repeat;
286} PySequenceMethods;
287
288typedef struct PyMappingMethods {
289	lenfunc mp_length;
290	binaryfunc mp_subscript;
291	objobjargproc mp_ass_subscript;
292} PyMappingMethods;
293
294typedef struct PyBufferProcs {
295	readbufferproc bf_getreadbuffer;
296	writebufferproc bf_getwritebuffer;
297	segcountproc bf_getsegcount;
298	charbufferproc bf_getcharbuffer;
299        getbufferproc bf_getbuffer;
300	releasebufferproc bf_releasebuffer;
301} PyBufferProcs;
302
303
304typedef void (*freefunc)(void *);
305typedef void (*destructor)(PyObject *);
306typedef int (*printfunc)(PyObject *, FILE *, int);
307typedef PyObject *(*getattrfunc)(PyObject *, char *);
308typedef PyObject *(*getattrofunc)(PyObject *, PyObject *);
309typedef int (*setattrfunc)(PyObject *, char *, PyObject *);
310typedef int (*setattrofunc)(PyObject *, PyObject *, PyObject *);
311typedef int (*cmpfunc)(PyObject *, PyObject *);
312typedef PyObject *(*reprfunc)(PyObject *);
313typedef long (*hashfunc)(PyObject *);
314typedef PyObject *(*richcmpfunc) (PyObject *, PyObject *, int);
315typedef PyObject *(*getiterfunc) (PyObject *);
316typedef PyObject *(*iternextfunc) (PyObject *);
317typedef PyObject *(*descrgetfunc) (PyObject *, PyObject *, PyObject *);
318typedef int (*descrsetfunc) (PyObject *, PyObject *, PyObject *);
319typedef int (*initproc)(PyObject *, PyObject *, PyObject *);
320typedef PyObject *(*newfunc)(struct _typeobject *, PyObject *, PyObject *);
321typedef PyObject *(*allocfunc)(struct _typeobject *, Py_ssize_t);
322
323typedef struct _typeobject {
324	PyObject_VAR_HEAD
325	const char *tp_name; /* For printing, in format "<module>.<name>" */
326	Py_ssize_t tp_basicsize, tp_itemsize; /* For allocation */
327
328	/* Methods to implement standard operations */
329
330	destructor tp_dealloc;
331	printfunc tp_print;
332	getattrfunc tp_getattr;
333	setattrfunc tp_setattr;
334	cmpfunc tp_compare;
335	reprfunc tp_repr;
336
337	/* Method suites for standard classes */
338
339	PyNumberMethods *tp_as_number;
340	PySequenceMethods *tp_as_sequence;
341	PyMappingMethods *tp_as_mapping;
342
343	/* More standard operations (here for binary compatibility) */
344
345	hashfunc tp_hash;
346	ternaryfunc tp_call;
347	reprfunc tp_str;
348	getattrofunc tp_getattro;
349	setattrofunc tp_setattro;
350
351	/* Functions to access object as input/output buffer */
352	PyBufferProcs *tp_as_buffer;
353
354	/* Flags to define presence of optional/expanded features */
355	long tp_flags;
356
357	const char *tp_doc; /* Documentation string */
358
359	/* Assigned meaning in release 2.0 */
360	/* call function for all accessible objects */
361	traverseproc tp_traverse;
362
363	/* delete references to contained objects */
364	inquiry tp_clear;
365
366	/* Assigned meaning in release 2.1 */
367	/* rich comparisons */
368	richcmpfunc tp_richcompare;
369
370	/* weak reference enabler */
371	Py_ssize_t tp_weaklistoffset;
372
373	/* Added in release 2.2 */
374	/* Iterators */
375	getiterfunc tp_iter;
376	iternextfunc tp_iternext;
377
378	/* Attribute descriptor and subclassing stuff */
379	struct PyMethodDef *tp_methods;
380	struct PyMemberDef *tp_members;
381	struct PyGetSetDef *tp_getset;
382	struct _typeobject *tp_base;
383	PyObject *tp_dict;
384	descrgetfunc tp_descr_get;
385	descrsetfunc tp_descr_set;
386	Py_ssize_t tp_dictoffset;
387	initproc tp_init;
388	allocfunc tp_alloc;
389	newfunc tp_new;
390	freefunc tp_free; /* Low-level free-memory routine */
391	inquiry tp_is_gc; /* For PyObject_IS_GC */
392	PyObject *tp_bases;
393	PyObject *tp_mro; /* method resolution order */
394	PyObject *tp_cache;
395	PyObject *tp_subclasses;
396	PyObject *tp_weaklist;
397	destructor tp_del;
398
399	/* Type attribute cache version tag. Added in version 2.6 */
400	unsigned int tp_version_tag;
401
402        /* A list of weakrefs to code objects listening for modifications.
403           Added in Unladen.  */
404        PyObject *tp_code_listeners;
405
406#ifdef COUNT_ALLOCS
407	/* these must be last and never explicitly initialized */
408	Py_ssize_t tp_allocs;
409	Py_ssize_t tp_frees;
410	Py_ssize_t tp_maxalloc;
411	struct _typeobject *tp_prev;
412	struct _typeobject *tp_next;
413#endif
414} PyTypeObject;
415
416
417/* The *real* layout of a type object when allocated on the heap */
418typedef struct _heaptypeobject {
419	/* Note: there's a dependency on the order of these members
420	   in slotptr() in typeobject.c . */
421	PyTypeObject ht_type;
422	PyNumberMethods as_number;
423	PyMappingMethods as_mapping;
424	PySequenceMethods as_sequence; /* as_sequence comes after as_mapping,
425					  so that the mapping wins when both
426					  the mapping and the sequence define
427					  a given operator (e.g. __getitem__).
428					  see add_operators() in typeobject.c . */
429	PyBufferProcs as_buffer;
430	PyObject *ht_name, *ht_slots;
431	/* here are optional user slots, followed by the members. */
432} PyHeapTypeObject;
433
434/* access macro to the members which are floating "behind" the object */
435#define PyHeapType_GET_MEMBERS(etype) \
436    ((PyMemberDef *)(((char *)etype) + Py_TYPE(etype)->tp_basicsize))
437
438
439/* Generic type check */
440PyAPI_FUNC(int) PyType_IsSubtype(PyTypeObject *, PyTypeObject *);
441#define PyObject_TypeCheck(ob, tp) \
442	(Py_TYPE(ob) == (tp) || PyType_IsSubtype(Py_TYPE(ob), (tp)))
443
444PyAPI_DATA(PyTypeObject) PyType_Type; /* built-in 'type' */
445PyAPI_DATA(PyTypeObject) PyBaseObject_Type; /* built-in 'object' */
446PyAPI_DATA(PyTypeObject) PySuper_Type; /* built-in 'super' */
447
448#define PyType_Check(op) \
449	PyType_FastSubclass(Py_TYPE(op), Py_TPFLAGS_TYPE_SUBCLASS)
450#define PyType_CheckExact(op) (Py_TYPE(op) == &PyType_Type)
451
452PyAPI_FUNC(int) PyType_Ready(PyTypeObject *);
453PyAPI_FUNC(PyObject *) PyType_GenericAlloc(PyTypeObject *, Py_ssize_t);
454PyAPI_FUNC(PyObject *) PyType_GenericNew(PyTypeObject *,
455					       PyObject *, PyObject *);
456PyAPI_FUNC(PyObject *) _PyType_Lookup(PyTypeObject *, PyObject *);
457PyAPI_FUNC(unsigned int) PyType_ClearCache(void);
458PyAPI_FUNC(void) PyType_Modified(PyTypeObject *);
459PyAPI_FUNC(int) _PyType_AddCodeListener(PyTypeObject *type, PyObject *code);
460
461/* Generic operations on objects */
462PyAPI_FUNC(int) PyObject_Print(PyObject *, FILE *, int);
463PyAPI_FUNC(void) _PyObject_Dump(PyObject *);
464PyAPI_FUNC(PyObject *) PyObject_Repr(PyObject *);
465PyAPI_FUNC(PyObject *) _PyObject_Str(PyObject *);
466PyAPI_FUNC(PyObject *) PyObject_Str(PyObject *);
467#define PyObject_Bytes PyObject_Str
468#ifdef Py_USING_UNICODE
469PyAPI_FUNC(PyObject *) PyObject_Unicode(PyObject *);
470#endif
471PyAPI_FUNC(int) PyObject_Compare(PyObject *, PyObject *);
472PyAPI_FUNC(PyObject *) PyObject_RichCompare(PyObject *, PyObject *, int);
473PyAPI_FUNC(int) PyObject_RichCompareBool(PyObject *, PyObject *, int);
474PyAPI_FUNC(PyObject *) PyObject_GetAttrString(PyObject *, const char *);
475PyAPI_FUNC(int) PyObject_SetAttrString(PyObject *, const char *, PyObject *);
476PyAPI_FUNC(int) PyObject_HasAttrString(PyObject *, const char *);
477PyAPI_FUNC(PyObject *) PyObject_GetAttr(PyObject *, PyObject *);
478PyAPI_FUNC(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
479PyAPI_FUNC(int) PyObject_HasAttr(PyObject *, PyObject *);
480PyAPI_FUNC(PyObject **) _PyObject_GetDictPtr(PyObject *);
481PyAPI_FUNC(PyObject *) PyObject_SelfIter(PyObject *);
482PyAPI_FUNC(PyObject *) PyObject_GenericGetAttr(PyObject *, PyObject *);
483PyAPI_FUNC(int) PyObject_GenericSetAttr(PyObject *,
484					      PyObject *, PyObject *);
485PyAPI_FUNC(long) PyObject_Hash(PyObject *);
486PyAPI_FUNC(long) PyObject_HashNotImplemented(PyObject *);
487PyAPI_FUNC(int) PyObject_IsTrue(PyObject *);
488PyAPI_FUNC(int) PyObject_Not(PyObject *);
489PyAPI_FUNC(int) PyCallable_Check(PyObject *);
490PyAPI_FUNC(int) PyNumber_Coerce(PyObject **, PyObject **);
491PyAPI_FUNC(int) PyNumber_CoerceEx(PyObject **, PyObject **);
492PyAPI_FUNC(int) _PyObject_ShouldBindMethod(PyObject *, PyObject *);
493PyAPI_FUNC(PyObject *) PyObject_GetMethod(PyObject *, PyObject *);
494
495PyAPI_FUNC(void) PyObject_ClearWeakRefs(PyObject *);
496
497/* A slot function whose address we need to compare */
498extern int _PyObject_SlotCompare(PyObject *, PyObject *);
499
500
501/* PyObject_Dir(obj) acts like Python __builtin__.dir(obj), returning a
502   list of strings.  PyObject_Dir(NULL) is like __builtin__.dir(),
503   returning the names of the current locals.  In this case, if there are
504   no current locals, NULL is returned, and PyErr_Occurred() is false.
505*/
506PyAPI_FUNC(PyObject *) PyObject_Dir(PyObject *);
507
508
509/* Helpers for printing recursive container types */
510PyAPI_FUNC(int) Py_ReprEnter(PyObject *);
511PyAPI_FUNC(void) Py_ReprLeave(PyObject *);
512
513/* Helpers for hash functions */
514PyAPI_FUNC(long) _Py_HashDouble(double);
515PyAPI_FUNC(long) _Py_HashPointer(void*);
516
517/* Helper for passing objects to printf and the like */
518#define PyObject_REPR(obj) PyString_AS_STRING(PyObject_Repr(obj))
519
520/* Flag bits for printing: */
521#define Py_PRINT_RAW	1	/* No string quotes etc. */
522
523/*
524`Type flags (tp_flags)
525
526These flags are used to extend the type structure in a backwards-compatible
527fashion. Extensions can use the flags to indicate (and test) when a given
528type structure contains a new feature. The Python core will use these when
529introducing new functionality between major revisions (to avoid mid-version
530changes in the PYTHON_API_VERSION).
531
532Arbitration of the flag bit positions will need to be coordinated among
533all extension writers who publically release their extensions (this will
534be fewer than you might expect!)..
535
536Python 1.5.2 introduced the bf_getcharbuffer slot into PyBufferProcs.
537
538Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
539
540Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
541given type object has a specified feature.
542
543NOTE: when building the core, Py_TPFLAGS_DEFAULT includes
544Py_TPFLAGS_HAVE_VERSION_TAG; outside the core, it doesn't.  This is so
545that extensions that modify tp_dict of their own types directly don't
546break, since this was allowed in 2.5.  In 3.0 they will have to
547manually remove this flag though!
548*/
549
550/* PyBufferProcs contains bf_getcharbuffer */
551#define Py_TPFLAGS_HAVE_GETCHARBUFFER  (1L<<0)
552
553/* PySequenceMethods contains sq_contains */
554#define Py_TPFLAGS_HAVE_SEQUENCE_IN (1L<<1)
555
556/* This is here for backwards compatibility.  Extensions that use the old GC
557 * API will still compile but the objects will not be tracked by the GC. */
558#define Py_TPFLAGS_GC 0 /* used to be (1L<<2) */
559
560/* PySequenceMethods and PyNumberMethods contain in-place operators */
561#define Py_TPFLAGS_HAVE_INPLACEOPS (1L<<3)
562
563/* PyNumberMethods do their own coercion */
564#define Py_TPFLAGS_CHECKTYPES (1L<<4)
565
566/* tp_richcompare is defined */
567#define Py_TPFLAGS_HAVE_RICHCOMPARE (1L<<5)
568
569/* Objects which are weakly referencable if their tp_weaklistoffset is >0 */
570#define Py_TPFLAGS_HAVE_WEAKREFS (1L<<6)
571
572/* tp_iter is defined */
573#define Py_TPFLAGS_HAVE_ITER (1L<<7)
574
575/* New members introduced by Python 2.2 exist */
576#define Py_TPFLAGS_HAVE_CLASS (1L<<8)
577
578/* Set if the type object is dynamically allocated */
579#define Py_TPFLAGS_HEAPTYPE (1L<<9)
580
581/* Set if the type allows subclassing */
582#define Py_TPFLAGS_BASETYPE (1L<<10)
583
584/* Set if the type is 'ready' -- fully initialized */
585#define Py_TPFLAGS_READY (1L<<12)
586
587/* Set while the type is being 'readied', to prevent recursive ready calls */
588#define Py_TPFLAGS_READYING (1L<<13)
589
590/* Objects support garbage collection (see objimp.h) */
591#define Py_TPFLAGS_HAVE_GC (1L<<14)
592
593/* These two bits are preserved for Stackless Python, next after this is 17 */
594#ifdef STACKLESS
595#define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION (3L<<15)
596#else
597#define Py_TPFLAGS_HAVE_STACKLESS_EXTENSION 0
598#endif
599
600/* Objects support nb_index in PyNumberMethods */
601#define Py_TPFLAGS_HAVE_INDEX (1L<<17)
602
603/* Objects support type attribute cache */
604#define Py_TPFLAGS_HAVE_VERSION_TAG   (1L<<18)
605#define Py_TPFLAGS_VALID_VERSION_TAG  (1L<<19)
606
607/* Type is abstract and cannot be instantiated */
608#define Py_TPFLAGS_IS_ABSTRACT (1L<<20)
609
610/* Has the new buffer protocol */
611#define Py_TPFLAGS_HAVE_NEWBUFFER (1L<<21)
612
613/* These flags are used to determine if a type is a subclass. */
614#define Py_TPFLAGS_INT_SUBCLASS		(1L<<23)
615#define Py_TPFLAGS_LONG_SUBCLASS	(1L<<24)
616#define Py_TPFLAGS_LIST_SUBCLASS	(1L<<25)
617#define Py_TPFLAGS_TUPLE_SUBCLASS	(1L<<26)
618#define Py_TPFLAGS_STRING_SUBCLASS	(1L<<27)
619#define Py_TPFLAGS_UNICODE_SUBCLASS	(1L<<28)
620#define Py_TPFLAGS_DICT_SUBCLASS	(1L<<29)
621#define Py_TPFLAGS_BASE_EXC_SUBCLASS	(1L<<30)
622#define Py_TPFLAGS_TYPE_SUBCLASS	(1L<<31)
623
624#define Py_TPFLAGS_DEFAULT_EXTERNAL ( \
625                             Py_TPFLAGS_HAVE_GETCHARBUFFER | \
626                             Py_TPFLAGS_HAVE_SEQUENCE_IN | \
627                             Py_TPFLAGS_HAVE_INPLACEOPS | \
628                             Py_TPFLAGS_HAVE_RICHCOMPARE | \
629                             Py_TPFLAGS_HAVE_WEAKREFS | \
630                             Py_TPFLAGS_HAVE_ITER | \
631                             Py_TPFLAGS_HAVE_CLASS | \
632                             Py_TPFLAGS_HAVE_STACKLESS_EXTENSION | \
633                             Py_TPFLAGS_HAVE_INDEX | \
634                             0)
635#define Py_TPFLAGS_DEFAULT_CORE (Py_TPFLAGS_DEFAULT_EXTERNAL | \
636                                 Py_TPFLAGS_HAVE_VERSION_TAG)
637
638#ifdef Py_BUILD_CORE
639#define Py_TPFLAGS_DEFAULT Py_TPFLAGS_DEFAULT_CORE
640#else
641#define Py_TPFLAGS_DEFAULT Py_TPFLAGS_DEFAULT_EXTERNAL
642#endif
643
644#define PyType_HasFeature(t,f)  (((t)->tp_flags & (f)) != 0)
645#define PyType_FastSubclass(t,f)  PyType_HasFeature(t,f)
646
647
648/*
649The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
650reference counts.  Py_DECREF calls the object's deallocator function when
651the refcount falls to 0; for
652objects that don't contain references to other objects or heap memory
653this can be the standard function free().  Both macros can be used
654wherever a void expression is allowed.  The argument must not be a
655NULL pointer.  If it may be NULL, use Py_XINCREF/Py_XDECREF instead.
656The macro _Py_NewReference(op) initialize reference counts to 1, and
657in special builds (Py_REF_DEBUG, Py_TRACE_REFS) performs additional
658bookkeeping appropriate to the special build.
659
660We assume that the reference count field can never overflow; this can
661be proven when the size of the field is the same as the pointer size, so
662we ignore the possibility.  Provided a C int is at least 32 bits (which
663is implicitly assumed in many parts of this code), that's enough for
664about 2**31 references to an object.
665
666XXX The following became out of date in Python 2.2, but I'm not sure
667XXX what the full truth is now.  Certainly, heap-allocated type objects
668XXX can and should be deallocated.
669Type objects should never be deallocated; the type pointer in an object
670is not considered to be a reference to the type object, to save
671complications in the deallocation function.  (This is actually a
672decision that's up to the implementer of each new type so if you want,
673you can count such references to the type object.)
674
675*** WARNING*** The Py_DECREF macro must have a side-effect-free argument
676since it may evaluate its argument multiple times.  (The alternative
677would be to mace it a proper function or assign it to a global temporary
678variable first, both of which are slower; and in a multi-threaded
679environment the global variable trick is not safe.)
680*/
681
682/* First define a pile of simple helper macros, one set per special
683 * build symbol.  These either expand to the obvious things, or to
684 * nothing at all when the special mode isn't in effect.  The main
685 * macros can later be defined just once then, yet expand to different
686 * things depending on which special build options are and aren't in effect.
687 * Trust me <wink>:  while painful, this is 20x easier to understand than,
688 * e.g, defining _Py_NewReference five different times in a maze of nested
689 * #ifdefs (we used to do that -- it was impenetrable).
690 */
691#ifdef Py_REF_DEBUG
692PyAPI_DATA(Py_ssize_t) _Py_RefTotal;
693PyAPI_FUNC(void) _Py_NegativeRefcount(const char *fname,
694					    int lineno, PyObject *op);
695PyAPI_FUNC(PyObject *) _PyDict_Dummy(void);
696PyAPI_FUNC(PyObject *) _PySet_Dummy(void);
697PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
698#define _Py_INC_REFTOTAL	_Py_RefTotal++
699#define _Py_DEC_REFTOTAL	_Py_RefTotal--
700#define _Py_REF_DEBUG_COMMA	,
701#define _Py_CHECK_REFCNT(OP)					\
702{	if (((PyObject*)OP)->ob_refcnt < 0)				\
703		_Py_NegativeRefcount(__FILE__, __LINE__,	\
704				     (PyObject *)(OP));		\
705}
706#else
707#define _Py_INC_REFTOTAL
708#define _Py_DEC_REFTOTAL
709#define _Py_REF_DEBUG_COMMA
710#define _Py_CHECK_REFCNT(OP)	/* a semicolon */;
711#endif /* Py_REF_DEBUG */
712
713#ifdef COUNT_ALLOCS
714PyAPI_FUNC(void) inc_count(PyTypeObject *);
715PyAPI_FUNC(void) dec_count(PyTypeObject *);
716#define _Py_INC_TPALLOCS(OP)	inc_count(Py_TYPE(OP))
717#define _Py_INC_TPFREES(OP)	dec_count(Py_TYPE(OP))
718#define _Py_DEC_TPFREES(OP)	Py_TYPE(OP)->tp_frees--
719#define _Py_COUNT_ALLOCS_COMMA	,
720#else
721#define _Py_INC_TPALLOCS(OP)
722#define _Py_INC_TPFREES(OP)
723#define _Py_DEC_TPFREES(OP)
724#define _Py_COUNT_ALLOCS_COMMA
725#endif /* COUNT_ALLOCS */
726
727#ifdef Py_TRACE_REFS
728/* Py_TRACE_REFS is such major surgery that we call external routines. */
729PyAPI_FUNC(void) _Py_NewReference(PyObject *);
730PyAPI_FUNC(void) _Py_ForgetReference(PyObject *);
731PyAPI_FUNC(void) _Py_Dealloc(PyObject *);
732PyAPI_FUNC(void) _Py_PrintReferences(FILE *);
733PyAPI_FUNC(void) _Py_PrintReferenceAddresses(FILE *);
734PyAPI_FUNC(void) _Py_AddToAllObjects(PyObject *, int force);
735
736#else
737/* Without Py_TRACE_REFS, there's little enough to do that we expand code
738 * inline.
739 */
740#define _Py_NewReference(op) (				\
741	_Py_INC_TPALLOCS(op) _Py_COUNT_ALLOCS_COMMA	\
742	_Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA		\
743	Py_REFCNT(op) = 1)
744
745#define _Py_ForgetReference(op) _Py_INC_TPFREES(op)
746
747#define _Py_Dealloc(op) (				\
748	_Py_INC_TPFREES(op) _Py_COUNT_ALLOCS_COMMA	\
749	(*Py_TYPE(op)->tp_dealloc)((PyObject *)(op)))
750#endif /* !Py_TRACE_REFS */
751
752#define Py_INCREF(op) (				\
753	_Py_INC_REFTOTAL  _Py_REF_DEBUG_COMMA	\
754	((PyObject*)(op))->ob_refcnt++)
755
756#define Py_DECREF(op)					\
757	if (_Py_DEC_REFTOTAL  _Py_REF_DEBUG_COMMA	\
758	    --((PyObject*)(op))->ob_refcnt != 0)		\
759		_Py_CHECK_REFCNT(op)			\
760	else						\
761		_Py_Dealloc((PyObject *)(op))
762
763/* Safely decref `op` and set `op` to NULL, especially useful in tp_clear
764 * and tp_dealloc implementatons.
765 *
766 * Note that "the obvious" code can be deadly:
767 *
768 *     Py_XDECREF(op);
769 *     op = NULL;
770 *
771 * Typically, `op` is something like self->containee, and `self` is done
772 * using its `containee` member.  In the code sequence above, suppose
773 * `containee` is non-NULL with a refcount of 1.  Its refcount falls to
774 * 0 on the first line, which can trigger an arbitrary amount of code,
775 * possibly including finalizers (like __del__ methods or weakref callbacks)
776 * coded in Python, which in turn can release the GIL and allow other threads
777 * to run, etc.  Such code may even invoke methods of `self` again, or cause
778 * cyclic gc to trigger, but-- oops! --self->containee still points to the
779 * object being torn down, and it may be in an insane state while being torn
780 * down.  This has in fact been a rich historic source of miserable (rare &
781 * hard-to-diagnose) segfaulting (and other) bugs.
782 *
783 * The safe way is:
784 *
785 *      Py_CLEAR(op);
786 *
787 * That arranges to set `op` to NULL _before_ decref'ing, so that any code
788 * triggered as a side-effect of `op` getting torn down no longer believes
789 * `op` points to a valid object.
790 *
791 * There are cases where it's safe to use the naive code, but they're brittle.
792 * For example, if `op` points to a Python integer, you know that destroying
793 * one of those can't cause problems -- but in part that relies on that
794 * Python integers aren't currently weakly referencable.  Best practice is
795 * to use Py_CLEAR() even if you can't think of a reason for why you need to.
796 */
797#define Py_CLEAR(op)				\
798        do {                            	\
799                if (op) {			\
800                        PyObject *_py_tmp = (PyObject *)(op);	\
801                        (op) = NULL;		\
802                        Py_DECREF(_py_tmp);	\
803                }				\
804        } while (0)
805
806/* Macros to use in case the object pointer may be NULL: */
807#define Py_XINCREF(op) if ((op) == NULL) ; else Py_INCREF(op)
808#define Py_XDECREF(op) if ((op) == NULL) ; else Py_DECREF(op)
809
810/*
811These are provided as conveniences to Python runtime embedders, so that
812they can have object code that is not dependent on Python compilation flags.
813*/
814PyAPI_FUNC(void) Py_IncRef(PyObject *);
815PyAPI_FUNC(void) Py_DecRef(PyObject *);
816
817/*
818_Py_NoneStruct is an object of undefined type which can be used in contexts
819where NULL (nil) is not suitable (since NULL often means 'error').
820
821Don't forget to apply Py_INCREF() when returning this value!!!
822*/
823PyAPI_DATA(PyObject) _Py_NoneStruct; /* Don't use this directly */
824#define Py_None (&_Py_NoneStruct)
825
826/* Macro for returning Py_None from a function */
827#define Py_RETURN_NONE return Py_INCREF(Py_None), Py_None
828
829/*
830Py_NotImplemented is a singleton used to signal that an operation is
831not implemented for a given type combination.
832*/
833PyAPI_DATA(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
834#define Py_NotImplemented (&_Py_NotImplementedStruct)
835
836/* Rich comparison opcodes */
837#define Py_LT 0
838#define Py_LE 1
839#define Py_EQ 2
840#define Py_NE 3
841#define Py_GT 4
842#define Py_GE 5
843
844/* Maps Py_LT to Py_GT, ..., Py_GE to Py_LE.
845 * Defined in object.c.
846 */
847PyAPI_DATA(int) _Py_SwappedOp[];
848
849/*
850Define staticforward and statichere for source compatibility with old
851C extensions.
852
853The staticforward define was needed to support certain broken C
854compilers (notably SCO ODT 3.0, perhaps early AIX as well) botched the
855static keyword when it was used with a forward declaration of a static
856initialized structure.  Standard C allows the forward declaration with
857static, and we've decided to stop catering to broken C compilers.
858(In fact, we expect that the compilers are all fixed eight years later.)
859*/
860
861#define staticforward static
862#define statichere static
863
864
865/*
866More conventions
867================
868
869Argument Checking
870-----------------
871
872Functions that take objects as arguments normally don't check for nil
873arguments, but they do check the type of the argument, and return an
874error if the function doesn't apply to the type.
875
876Failure Modes
877-------------
878
879Functions may fail for a variety of reasons, including running out of
880memory.  This is communicated to the caller in two ways: an error string
881is set (see errors.h), and the function result differs: functions that
882normally return a pointer return NULL for failure, functions returning
883an integer return -1 (which could be a legal return value too!), and
884other functions return 0 for success and -1 for failure.
885Callers should always check for errors before using the result.  If
886an error was set, the caller must either explicitly clear it, or pass
887the error on to its caller.
888
889Reference Counts
890----------------
891
892It takes a while to get used to the proper usage of reference counts.
893
894Functions that create an object set the reference count to 1; such new
895objects must be stored somewhere or destroyed again with Py_DECREF().
896Some functions that 'store' objects, such as PyTuple_SetItem() and
897PyList_SetItem(),
898don't increment the reference count of the object, since the most
899frequent use is to store a fresh object.  Functions that 'retrieve'
900objects, such as PyTuple_GetItem() and PyDict_GetItemString(), also
901don't increment
902the reference count, since most frequently the object is only looked at
903quickly.  Thus, to retrieve an object and store it again, the caller
904must call Py_INCREF() explicitly.
905
906NOTE: functions that 'consume' a reference count, like
907PyList_SetItem(), consume the reference even if the object wasn't
908successfully stored, to simplify error handling.
909
910It seems attractive to make other functions that take an object as
911argument consume a reference count; however, this may quickly get
912confusing (even the current practice is already confusing).  Consider
913it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
914times.
915*/
916
917
918/* Trashcan mechanism, thanks to Christian Tismer.
919
920When deallocating a container object, it's possible to trigger an unbounded
921chain of deallocations, as each Py_DECREF in turn drops the refcount on "the
922next" object in the chain to 0.  This can easily lead to stack faults, and
923especially in threads (which typically have less stack space to work with).
924
925A container object that participates in cyclic gc can avoid this by
926bracketing the body of its tp_dealloc function with a pair of macros:
927
928static void
929mytype_dealloc(mytype *p)
930{
931        ... declarations go here ...
932
933 	PyObject_GC_UnTrack(p);	   // must untrack first
934	Py_TRASHCAN_SAFE_BEGIN(p)
935	... The body of the deallocator goes here, including all calls ...
936	... to Py_DECREF on contained objects.                         ...
937	Py_TRASHCAN_SAFE_END(p)
938}
939
940CAUTION:  Never return from the middle of the body!  If the body needs to
941"get out early", put a label immediately before the Py_TRASHCAN_SAFE_END
942call, and goto it.  Else the call-depth counter (see below) will stay
943above 0 forever, and the trashcan will never get emptied.
944
945How it works:  The BEGIN macro increments a call-depth counter.  So long
946as this counter is small, the body of the deallocator is run directly without
947further ado.  But if the counter gets large, it instead adds p to a list of
948objects to be deallocated later, skips the body of the deallocator, and
949resumes execution after the END macro.  The tp_dealloc routine then returns
950without deallocating anything (and so unbounded call-stack depth is avoided).
951
952When the call stack finishes unwinding again, code generated by the END macro
953notices this, and calls another routine to deallocate all the objects that
954may have been added to the list of deferred deallocations.  In effect, a
955chain of N deallocations is broken into N / PyTrash_UNWIND_LEVEL pieces,
956with the call stack never exceeding a depth of PyTrash_UNWIND_LEVEL.
957*/
958
959PyAPI_FUNC(void) _PyTrash_deposit_object(PyObject*);
960PyAPI_FUNC(void) _PyTrash_destroy_chain(void);
961PyAPI_DATA(int) _PyTrash_delete_nesting;
962PyAPI_DATA(PyObject *) _PyTrash_delete_later;
963
964#define PyTrash_UNWIND_LEVEL 50
965
966#define Py_TRASHCAN_SAFE_BEGIN(op) \
967	if (_PyTrash_delete_nesting < PyTrash_UNWIND_LEVEL) { \
968		++_PyTrash_delete_nesting;
969		/* The body of the deallocator is here. */
970#define Py_TRASHCAN_SAFE_END(op) \
971		--_PyTrash_delete_nesting; \
972		if (_PyTrash_delete_later && _PyTrash_delete_nesting <= 0) \
973			_PyTrash_destroy_chain(); \
974	} \
975	else \
976		_PyTrash_deposit_object((PyObject*)op);
977
978#ifdef __cplusplus
979}
980#endif
981#endif /* !Py_OBJECT_H */