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/Include/objimpl.h

http://unladen-swallow.googlecode.com/
C++ Header | 336 lines | 138 code | 45 blank | 153 comment | 13 complexity | bf4809637db88c9f9b5c9bace995a22a MD5 | raw file
  1/* The PyObject_ memory family:  high-level object memory interfaces.
  2   See pymem.h for the low-level PyMem_ family.
  3*/
  4
  5#ifndef Py_OBJIMPL_H
  6#define Py_OBJIMPL_H
  7
  8#include "pymem.h"
  9
 10#ifdef __cplusplus
 11extern "C" {
 12#endif
 13
 14/* BEWARE:
 15
 16   Each interface exports both functions and macros.  Extension modules should
 17   use the functions, to ensure binary compatibility across Python versions.
 18   Because the Python implementation is free to change internal details, and
 19   the macros may (or may not) expose details for speed, if you do use the
 20   macros you must recompile your extensions with each Python release.
 21
 22   Never mix calls to PyObject_ memory functions with calls to the platform
 23   malloc/realloc/ calloc/free, or with calls to PyMem_.
 24*/
 25
 26/*
 27Functions and macros for modules that implement new object types.
 28
 29 - PyObject_New(type, typeobj) allocates memory for a new object of the given
 30   type, and initializes part of it.  'type' must be the C structure type used
 31   to represent the object, and 'typeobj' the address of the corresponding
 32   type object.  Reference count and type pointer are filled in; the rest of
 33   the bytes of the object are *undefined*!  The resulting expression type is
 34   'type *'.  The size of the object is determined by the tp_basicsize field
 35   of the type object.
 36
 37 - PyObject_NewVar(type, typeobj, n) is similar but allocates a variable-size
 38   object with room for n items.  In addition to the refcount and type pointer
 39   fields, this also fills in the ob_size field.
 40
 41 - PyObject_Del(op) releases the memory allocated for an object.  It does not
 42   run a destructor -- it only frees the memory.  PyObject_Free is identical.
 43
 44 - PyObject_Init(op, typeobj) and PyObject_InitVar(op, typeobj, n) don't
 45   allocate memory.  Instead of a 'type' parameter, they take a pointer to a
 46   new object (allocated by an arbitrary allocator), and initialize its object
 47   header fields.
 48
 49Note that objects created with PyObject_{New, NewVar} are allocated using the
 50specialized Python allocator (implemented in obmalloc.c), if WITH_PYMALLOC is
 51enabled.  In addition, a special debugging allocator is used if PYMALLOC_DEBUG
 52is also #defined.
 53
 54In case a specific form of memory management is needed (for example, if you
 55must use the platform malloc heap(s), or shared memory, or C++ local storage or
 56operator new), you must first allocate the object with your custom allocator,
 57then pass its pointer to PyObject_{Init, InitVar} for filling in its Python-
 58specific fields:  reference count, type pointer, possibly others.  You should
 59be aware that Python no control over these objects because they don't
 60cooperate with the Python memory manager.  Such objects may not be eligible
 61for automatic garbage collection and you have to make sure that they are
 62released accordingly whenever their destructor gets called (cf. the specific
 63form of memory management you're using).
 64
 65Unless you have specific memory management requirements, use
 66PyObject_{New, NewVar, Del}.
 67*/
 68
 69/*
 70 * Raw object memory interface
 71 * ===========================
 72 */
 73
 74/* Functions to call the same malloc/realloc/free as used by Python's
 75   object allocator.  If WITH_PYMALLOC is enabled, these may differ from
 76   the platform malloc/realloc/free.  The Python object allocator is
 77   designed for fast, cache-conscious allocation of many "small" objects,
 78   and with low hidden memory overhead.
 79
 80   PyObject_Malloc(0) returns a unique non-NULL pointer if possible.
 81
 82   PyObject_Realloc(NULL, n) acts like PyObject_Malloc(n).
 83   PyObject_Realloc(p != NULL, 0) does not return  NULL, or free the memory
 84   at p.
 85
 86   Returned pointers must be checked for NULL explicitly; no action is
 87   performed on failure other than to return NULL (no warning it printed, no
 88   exception is set, etc).
 89
 90   For allocating objects, use PyObject_{New, NewVar} instead whenever
 91   possible.  The PyObject_{Malloc, Realloc, Free} family is exposed
 92   so that you can exploit Python's small-block allocator for non-object
 93   uses.  If you must use these routines to allocate object memory, make sure
 94   the object gets initialized via PyObject_{Init, InitVar} after obtaining
 95   the raw memory.
 96*/
 97PyAPI_FUNC(void *) PyObject_Malloc(size_t);
 98PyAPI_FUNC(void *) PyObject_Realloc(void *, size_t);
 99PyAPI_FUNC(void) PyObject_Free(void *);
100
101
102/* Macros */
103#ifdef WITH_PYMALLOC
104#ifdef PYMALLOC_DEBUG	/* WITH_PYMALLOC && PYMALLOC_DEBUG */
105PyAPI_FUNC(void *) _PyObject_DebugMalloc(size_t nbytes);
106PyAPI_FUNC(void *) _PyObject_DebugRealloc(void *p, size_t nbytes);
107PyAPI_FUNC(void) _PyObject_DebugFree(void *p);
108PyAPI_FUNC(void) _PyObject_DebugDumpAddress(const void *p);
109PyAPI_FUNC(void) _PyObject_DebugCheckAddress(const void *p);
110PyAPI_FUNC(void) _PyObject_DebugMallocStats(void);
111#define PyObject_MALLOC		_PyObject_DebugMalloc
112#define PyObject_Malloc		_PyObject_DebugMalloc
113#define PyObject_REALLOC	_PyObject_DebugRealloc
114#define PyObject_Realloc	_PyObject_DebugRealloc
115#define PyObject_FREE		_PyObject_DebugFree
116#define PyObject_Free		_PyObject_DebugFree
117
118#else	/* WITH_PYMALLOC && ! PYMALLOC_DEBUG */
119#define PyObject_MALLOC		PyObject_Malloc
120#define PyObject_REALLOC	PyObject_Realloc
121#define PyObject_FREE		PyObject_Free
122#endif
123
124#else	/* ! WITH_PYMALLOC */
125#define PyObject_MALLOC		PyMem_MALLOC
126#define PyObject_REALLOC	PyMem_REALLOC
127#define PyObject_FREE		PyMem_FREE
128
129#endif	/* WITH_PYMALLOC */
130
131#define PyObject_Del		PyObject_Free
132#define PyObject_DEL		PyObject_FREE
133
134/* for source compatibility with 2.2 */
135#define _PyObject_Del		PyObject_Free
136
137/*
138 * Generic object allocator interface
139 * ==================================
140 */
141
142/* Functions */
143PyAPI_FUNC(PyObject *) PyObject_Init(PyObject *, PyTypeObject *);
144PyAPI_FUNC(PyVarObject *) PyObject_InitVar(PyVarObject *,
145                                                 PyTypeObject *, Py_ssize_t);
146PyAPI_FUNC(PyObject *) _PyObject_New(PyTypeObject *);
147PyAPI_FUNC(PyVarObject *) _PyObject_NewVar(PyTypeObject *, Py_ssize_t);
148
149#define PyObject_New(type, typeobj) \
150		( (type *) _PyObject_New(typeobj) )
151#define PyObject_NewVar(type, typeobj, n) \
152		( (type *) _PyObject_NewVar((typeobj), (n)) )
153
154/* Macros trading binary compatibility for speed. See also pymem.h.
155   Note that these macros expect non-NULL object pointers.*/
156#define PyObject_INIT(op, typeobj) \
157	( Py_TYPE(op) = (typeobj), _Py_NewReference((PyObject *)(op)), (op) )
158#define PyObject_INIT_VAR(op, typeobj, size) \
159	( Py_SIZE(op) = (size), PyObject_INIT((op), (typeobj)) )
160
161#define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize )
162
163/* _PyObject_VAR_SIZE returns the number of bytes (as size_t) allocated for a
164   vrbl-size object with nitems items, exclusive of gc overhead (if any).  The
165   value is rounded up to the closest multiple of sizeof(void *), in order to
166   ensure that pointer fields at the end of the object are correctly aligned
167   for the platform (this is of special importance for subclasses of, e.g.,
168   str or long, so that pointers can be stored after the embedded data).
169
170   Note that there's no memory wastage in doing this, as malloc has to
171   return (at worst) pointer-aligned memory anyway.
172*/
173#if ((SIZEOF_VOID_P - 1) & SIZEOF_VOID_P) != 0
174#   error "_PyObject_VAR_SIZE requires SIZEOF_VOID_P be a power of 2"
175#endif
176
177#define _PyObject_VAR_SIZE(typeobj, nitems)	\
178	(size_t)				\
179	( ( (typeobj)->tp_basicsize +		\
180	    (nitems)*(typeobj)->tp_itemsize +	\
181	    (SIZEOF_VOID_P - 1)			\
182	  ) & ~(SIZEOF_VOID_P - 1)		\
183	)
184
185#define PyObject_NEW(type, typeobj) \
186( (type *) PyObject_Init( \
187	(PyObject *) PyObject_MALLOC( _PyObject_SIZE(typeobj) ), (typeobj)) )
188
189#define PyObject_NEW_VAR(type, typeobj, n) \
190( (type *) PyObject_InitVar( \
191      (PyVarObject *) PyObject_MALLOC(_PyObject_VAR_SIZE((typeobj),(n)) ),\
192      (typeobj), (n)) )
193
194/* This example code implements an object constructor with a custom
195   allocator, where PyObject_New is inlined, and shows the important
196   distinction between two steps (at least):
197       1) the actual allocation of the object storage;
198       2) the initialization of the Python specific fields
199          in this storage with PyObject_{Init, InitVar}.
200
201   PyObject *
202   YourObject_New(...)
203   {
204       PyObject *op;
205
206       op = (PyObject *) Your_Allocator(_PyObject_SIZE(YourTypeStruct));
207       if (op == NULL)
208           return PyErr_NoMemory();
209
210       PyObject_Init(op, &YourTypeStruct);
211
212       op->ob_field = value;
213       ...
214       return op;
215   }
216
217   Note that in C++, the use of the new operator usually implies that
218   the 1st step is performed automatically for you, so in a C++ class
219   constructor you would start directly with PyObject_Init/InitVar
220*/
221
222/*
223 * Garbage Collection Support
224 * ==========================
225 */
226
227/* C equivalent of gc.collect(). */
228PyAPI_FUNC(Py_ssize_t) PyGC_Collect(void);
229
230/* Test if a type has a GC head */
231#define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)
232
233/* Test if an object has a GC head */
234#define PyObject_IS_GC(o) (PyType_IS_GC(Py_TYPE(o)) && \
235	(Py_TYPE(o)->tp_is_gc == NULL || Py_TYPE(o)->tp_is_gc(o)))
236
237PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, Py_ssize_t);
238#define PyObject_GC_Resize(type, op, n) \
239		( (type *) _PyObject_GC_Resize((PyVarObject *)(op), (n)) )
240
241/* for source compatibility with 2.2 */
242#define _PyObject_GC_Del PyObject_GC_Del
243
244/* GC information is stored BEFORE the object structure. */
245typedef union _gc_head {
246	struct {
247		union _gc_head *gc_next;
248		union _gc_head *gc_prev;
249		Py_ssize_t gc_refs;
250	} gc;
251	long double dummy;  /* force worst-case alignment */
252} PyGC_Head;
253
254extern PyGC_Head *_PyGC_generation0;
255
256#define _Py_AS_GC(o) ((PyGC_Head *)(o)-1)
257
258#define _PyGC_REFS_UNTRACKED			(-2)
259#define _PyGC_REFS_REACHABLE			(-3)
260#define _PyGC_REFS_TENTATIVELY_UNREACHABLE	(-4)
261
262/* Tell the GC to track this object.  NB: While the object is tracked the
263 * collector it must be safe to call the ob_traverse method. */
264#define _PyObject_GC_TRACK(o) do { \
265	PyGC_Head *g = _Py_AS_GC(o); \
266	if (g->gc.gc_refs != _PyGC_REFS_UNTRACKED) \
267		Py_FatalError("GC object already tracked"); \
268	g->gc.gc_refs = _PyGC_REFS_REACHABLE; \
269	g->gc.gc_next = _PyGC_generation0; \
270	g->gc.gc_prev = _PyGC_generation0->gc.gc_prev; \
271	g->gc.gc_prev->gc.gc_next = g; \
272	_PyGC_generation0->gc.gc_prev = g; \
273    } while (0);
274
275/* Tell the GC to stop tracking this object.
276 * gc_next doesn't need to be set to NULL, but doing so is a good
277 * way to provoke memory errors if calling code is confused.
278 */
279#define _PyObject_GC_UNTRACK(o) do { \
280	PyGC_Head *g = _Py_AS_GC(o); \
281	assert(g->gc.gc_refs != _PyGC_REFS_UNTRACKED); \
282	g->gc.gc_refs = _PyGC_REFS_UNTRACKED; \
283	g->gc.gc_prev->gc.gc_next = g->gc.gc_next; \
284	g->gc.gc_next->gc.gc_prev = g->gc.gc_prev; \
285	g->gc.gc_next = NULL; \
286    } while (0);
287
288PyAPI_FUNC(PyObject *) _PyObject_GC_Malloc(size_t);
289PyAPI_FUNC(PyObject *) _PyObject_GC_New(PyTypeObject *);
290PyAPI_FUNC(PyVarObject *) _PyObject_GC_NewVar(PyTypeObject *, Py_ssize_t);
291PyAPI_FUNC(void) PyObject_GC_Track(void *);
292PyAPI_FUNC(void) PyObject_GC_UnTrack(void *);
293PyAPI_FUNC(void) PyObject_GC_Del(void *);
294
295#define PyObject_GC_New(type, typeobj) \
296		( (type *) _PyObject_GC_New(typeobj) )
297#define PyObject_GC_NewVar(type, typeobj, n) \
298		( (type *) _PyObject_GC_NewVar((typeobj), (n)) )
299
300
301/* Utility macro to help write tp_traverse functions.
302 * To use this macro, the tp_traverse function must name its arguments
303 * "visit" and "arg".  This is intended to keep tp_traverse functions
304 * looking as much alike as possible.
305 */
306#define Py_VISIT(op)							\
307        do { 								\
308                if (op) {						\
309                        int vret = visit((PyObject *)(op), arg);	\
310                        if (vret)					\
311                                return vret;				\
312                }							\
313        } while (0)
314
315/* This is here for the sake of backwards compatibility.  Extensions that
316 * use the old GC API will still compile but the objects will not be
317 * tracked by the GC. */
318#define PyGC_HEAD_SIZE 0
319#define PyObject_GC_Init(op)
320#define PyObject_GC_Fini(op)
321#define PyObject_AS_GC(op) (op)
322#define PyObject_FROM_GC(op) (op)
323
324
325/* Test if a type supports weak references */
326#define PyType_SUPPORTS_WEAKREFS(t) \
327        (PyType_HasFeature((t), Py_TPFLAGS_HAVE_WEAKREFS) \
328         && ((t)->tp_weaklistoffset > 0))
329
330#define PyObject_GET_WEAKREFS_LISTPTR(o) \
331	((PyObject **) (((char *) (o)) + Py_TYPE(o)->tp_weaklistoffset))
332
333#ifdef __cplusplus
334}
335#endif
336#endif /* !Py_OBJIMPL_H */