Include/object.h

   1 #ifndef Py_OBJECT_H
   2 #define Py_OBJECT_H
   3 #ifdef __cplusplus
   4 extern "C" {
   5 #endif
   6
   7 /***********************************************************
   8 Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
   9 The Netherlands.
  10
  11                         All Rights Reserved
  12
  13 Permission to use, copy, modify, and distribute this software and its
  14 documentation for any purpose and without fee is hereby granted,
  15 provided that the above copyright notice appear in all copies and that
  16 both that copyright notice and this permission notice appear in
  17 supporting documentation, and that the names of Stichting Mathematisch
  18 Centrum or CWI or Corporation for National Research Initiatives or
  19 CNRI not be used in advertising or publicity pertaining to
  20 distribution of the software without specific, written prior
  21 permission.
  22
  23 While CWI is the initial source for this software, a modified version
  24 is made available by the Corporation for National Research Initiatives
  25 (CNRI) at the Internet address ftp://ftp.python.org.
  26
  27 STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
  28 REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
  29 MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
  30 CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
  31 DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  32 PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  33 TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  34 PERFORMANCE OF THIS SOFTWARE.
  35
  36 ******************************************************************/
  37
  38 /* Object and type object interface */
  39
  40 /*
  41 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
  42
  43 Objects are structures allocated on the heap.  Special rules apply to
  44 the use of objects to ensure they are properly garbage-collected.
  45 Objects are never allocated statically or on the stack; they must be
  46 accessed through special macros and functions only.  (Type objects are
  47 exceptions to the first rule; the standard types are represented by
  48 statically initialized type objects.)
  49
  50 An object has a 'reference count' that is increased or decreased when a
  51 pointer to the object is copied or deleted; when the reference count
  52 reaches zero there are no references to the object left and it can be
  53 removed from the heap.
  54
  55 An object has a 'type' that determines what it represents and what kind
  56 of data it contains.  An object's type is fixed when it is created.
  57 Types themselves are represented as objects; an object contains a
  58 pointer to the corresponding type object.  The type itself has a type
  59 pointer pointing to the object representing the type 'type', which
  60 contains a pointer to itself!).
  61
  62 Objects do not float around in memory; once allocated an object keeps
  63 the same size and address.  Objects that must hold variable-size data
  64 can contain pointers to variable-size parts of the object.  Not all
  65 objects of the same type have the same size; but the size cannot change
  66 after allocation.  (These restrictions are made so a reference to an
  67 object can be simply a pointer -- moving an object would require
  68 updating all the pointers, and changing an object's size would require
  69 moving it if there was another object right next to it.)
  70
  71 Objects are always accessed through pointers of the type 'PyObject *'.
  72 The type 'PyObject' is a structure that only contains the reference count
  73 and the type pointer.  The actual memory allocated for an object
  74 contains other data that can only be accessed after casting the pointer
  75 to a pointer to a longer structure type.  This longer type must start
  76 with the reference count and type fields; the macro PyObject_HEAD should be
  77 used for this (to accomodate for future changes).  The implementation
  78 of a particular object type can cast the object pointer to the proper
  79 type and back.
  80
  81 A standard interface exists for objects that contain an array of items
  82 whose size is determined when the object is allocated.
  83
  84 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
  85 */
  86
  87 #ifdef Py_DEBUG
  88
  89 /* Turn on heavy reference debugging */
  90 #define Py_TRACE_REFS
  91
  92 /* Turn on reference counting */
  93 #define Py_REF_DEBUG
  94
  95 #endif /* Py_DEBUG */
  96
  97 #ifdef Py_TRACE_REFS
  98 #define PyObject_HEAD \
  99         struct _object *_ob_next, *_ob_prev; \
 100         int ob_refcnt; \
 101         struct _typeobject *ob_type;
 102 #define PyObject_HEAD_INIT(type) 0, 0, 1, type,
 103 #else /* !Py_TRACE_REFS */
 104 #define PyObject_HEAD \
 105         int ob_refcnt; \
 106         struct _typeobject *ob_type;
 107 #define PyObject_HEAD_INIT(type) 1, type,
 108 #endif /* !Py_TRACE_REFS */
 109
 110 #define PyObject_VAR_HEAD \
 111         PyObject_HEAD \
 112         int ob_size; /* Number of items in variable part */
 113
 114 typedef struct _object {
 115         PyObject_HEAD
 116 } PyObject;
 117
 118 typedef struct {
 119         PyObject_VAR_HEAD
 120 } PyVarObject;
 121
 122
 123 /*
 124 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
 125
 126 Type objects contain a string containing the type name (to help somewhat
 127 in debugging), the allocation parameters (see newobj() and newvarobj()),
 128 and methods for accessing objects of the type.  Methods are optional,a
 129 nil pointer meaning that particular kind of access is not available for
 130 this type.  The Py_DECREF() macro uses the tp_dealloc method without
 131 checking for a nil pointer; it should always be implemented except if
 132 the implementation can guarantee that the reference count will never
 133 reach zero (e.g., for type objects).
 134
 135 NB: the methods for certain type groups are now contained in separate
 136 method blocks.
 137 */
 138
 139 typedef PyObject * (*unaryfunc) Py_PROTO((PyObject *));
 140 typedef PyObject * (*binaryfunc) Py_PROTO((PyObject *, PyObject *));
 141 typedef PyObject * (*ternaryfunc) Py_PROTO((PyObject *, PyObject *, PyObject *));
 142 typedef int (*inquiry) Py_PROTO((PyObject *));
 143 typedef int (*coercion) Py_PROTO((PyObject **, PyObject **));
 144 typedef PyObject *(*intargfunc) Py_PROTO((PyObject *, int));
 145 typedef PyObject *(*intintargfunc) Py_PROTO((PyObject *, int, int));
 146 typedef int(*intobjargproc) Py_PROTO((PyObject *, int, PyObject *));
 147 typedef int(*intintobjargproc) Py_PROTO((PyObject *, int, int, PyObject *));
 148 typedef int(*objobjargproc) Py_PROTO((PyObject *, PyObject *, PyObject *));
 149 typedef int (*getreadbufferproc) Py_PROTO((PyObject *, int, void **));
 150 typedef int (*getwritebufferproc) Py_PROTO((PyObject *, int, void **));
 151 typedef int (*getsegcountproc) Py_PROTO((PyObject *, int *));
 152 typedef int (*getcharbufferproc) Py_PROTO((PyObject *, int, const char **));
 153
 154 typedef struct {
 155         binaryfunc nb_add;
 156         binaryfunc nb_subtract;
 157         binaryfunc nb_multiply;
 158         binaryfunc nb_divide;
 159         binaryfunc nb_remainder;
 160         binaryfunc nb_divmod;
 161         ternaryfunc nb_power;
 162         unaryfunc nb_negative;
 163         unaryfunc nb_positive;
 164         unaryfunc nb_absolute;
 165         inquiry nb_nonzero;
 166         unaryfunc nb_invert;
 167         binaryfunc nb_lshift;
 168         binaryfunc nb_rshift;
 169         binaryfunc nb_and;
 170         binaryfunc nb_xor;
 171         binaryfunc nb_or;
 172         coercion nb_coerce;
 173         unaryfunc nb_int;
 174         unaryfunc nb_long;
 175         unaryfunc nb_float;
 176         unaryfunc nb_oct;
 177         unaryfunc nb_hex;
 178 } PyNumberMethods;
 179
 180 typedef struct {
 181         inquiry sq_length;
 182         binaryfunc sq_concat;
 183         intargfunc sq_repeat;
 184         intargfunc sq_item;
 185         intintargfunc sq_slice;
 186         intobjargproc sq_ass_item;
 187         intintobjargproc sq_ass_slice;
 188 } PySequenceMethods;
 189
 190 typedef struct {
 191         inquiry mp_length;
 192         binaryfunc mp_subscript;
 193         objobjargproc mp_ass_subscript;
 194 } PyMappingMethods;
 195
 196 typedef struct {
 197         getreadbufferproc bf_getreadbuffer;
 198         getwritebufferproc bf_getwritebuffer;
 199         getsegcountproc bf_getsegcount;
 200         getcharbufferproc bf_getcharbuffer;
 201 } PyBufferProcs;
 202
 203
 204 typedef void (*destructor) Py_PROTO((PyObject *));
 205 typedef int (*printfunc) Py_PROTO((PyObject *, FILE *, int));
 206 typedef PyObject *(*getattrfunc) Py_PROTO((PyObject *, char *));
 207 typedef PyObject *(*getattrofunc) Py_PROTO((PyObject *, PyObject *));
 208 typedef int (*setattrfunc) Py_PROTO((PyObject *, char *, PyObject *));
 209 typedef int (*setattrofunc) Py_PROTO((PyObject *, PyObject *, PyObject *));
 210 typedef int (*cmpfunc) Py_PROTO((PyObject *, PyObject *));
 211 typedef PyObject *(*reprfunc) Py_PROTO((PyObject *));
 212 typedef long (*hashfunc) Py_PROTO((PyObject *));
 213
 214 typedef struct _typeobject {
 215         PyObject_VAR_HEAD
 216         char *tp_name; /* For printing */
 217         int tp_basicsize, tp_itemsize; /* For allocation */
 218
 219         /* Methods to implement standard operations */
 220
 221         destructor tp_dealloc;
 222         printfunc tp_print;
 223         getattrfunc tp_getattr;
 224         setattrfunc tp_setattr;
 225         cmpfunc tp_compare;
 226         reprfunc tp_repr;
 227
 228         /* Method suites for standard classes */
 229
 230         PyNumberMethods *tp_as_number;
 231         PySequenceMethods *tp_as_sequence;
 232         PyMappingMethods *tp_as_mapping;
 233
 234         /* More standard operations (at end for binary compatibility) */
 235
 236         hashfunc tp_hash;
 237         ternaryfunc tp_call;
 238         reprfunc tp_str;
 239         getattrofunc tp_getattro;
 240         setattrofunc tp_setattro;
 241
 242         /* Functions to access object as input/output buffer */
 243         PyBufferProcs *tp_as_buffer;
 244
 245         /* Flags to define presence of optional/expanded features */
 246         long tp_flags;
 247
 248         char *tp_doc; /* Documentation string */
 249
 250         /* More spares */
 251         long tp_xxx5;
 252         long tp_xxx6;
 253         long tp_xxx7;
 254         long tp_xxx8;
 255
 256 #ifdef COUNT_ALLOCS
 257         /* these must be last */
 258         int tp_alloc;
 259         int tp_free;
 260         int tp_maxalloc;
 261         struct _typeobject *tp_next;
 262 #endif
 263 } PyTypeObject;
 264
 265 extern DL_IMPORT(PyTypeObject) PyType_Type; /* The type of type objects */
 266
 267 #define PyType_Check(op) ((op)->ob_type == &PyType_Type)
 268
 269 /* Generic operations on objects */
 270 extern int PyObject_Print Py_PROTO((PyObject *, FILE *, int));
 271 extern PyObject * PyObject_Repr Py_PROTO((PyObject *));
 272 extern PyObject * PyObject_Str Py_PROTO((PyObject *));
 273 extern int PyObject_Compare Py_PROTO((PyObject *, PyObject *));
 274 extern PyObject *PyObject_GetAttrString Py_PROTO((PyObject *, char *));
 275 extern int PyObject_SetAttrString Py_PROTO((PyObject *, char *, PyObject *));
 276 extern int PyObject_HasAttrString Py_PROTO((PyObject *, char *));
 277 extern PyObject *PyObject_GetAttr Py_PROTO((PyObject *, PyObject *));
 278 extern int PyObject_SetAttr Py_PROTO((PyObject *, PyObject *, PyObject *));
 279 extern int PyObject_HasAttr Py_PROTO((PyObject *, PyObject *));
 280 extern long PyObject_Hash Py_PROTO((PyObject *));
 281 extern int PyObject_IsTrue Py_PROTO((PyObject *));
 282 extern int PyObject_Not Py_PROTO((PyObject *));
 283 extern int PyCallable_Check Py_PROTO((PyObject *));
 284 extern int PyNumber_Coerce Py_PROTO((PyObject **, PyObject **));
 285 extern int PyNumber_CoerceEx Py_PROTO((PyObject **, PyObject **));
 286
 287 /* Helpers for printing recursive container types */
 288 extern int Py_ReprEnter Py_PROTO((PyObject *));
 289 extern void Py_ReprLeave Py_PROTO((PyObject *));
 290
 291 /* Flag bits for printing: */
 292 #define Py_PRINT_RAW    1       /* No string quotes etc. */
 293
 294 /*
 295
 296 Type flags (tp_flags)
 297
 298 These flags are used to extend the type structure in a backwards-compatible
 299 fashion. Extensions can use the flags to indicate (and test) when a given
 300 type structure contains a new feature. The Python core will use these when
 301 introducing new functionality between major revisions (to avoid mid-version
 302 changes in the PYTHON_API_VERSION).
 303
 304 Arbitration of the flag bit positions will need to be coordinated among
 305 all extension writers who publically release their extensions (this will
 306 be fewer than you might expect!)..
 307
 308 Python 1.5.2 introduced the bf_getcharbuffer slot into PyBufferProcs.
 309
 310 Type definitions should use Py_TPFLAGS_DEFAULT for their tp_flags value.
 311
 312 Code can use PyType_HasFeature(type_ob, flag_value) to test whether the
 313 given type object has a specified feature.
 314
 315 */
 316
 317 /* PyBufferProcs contains bf_getcharbuffer */
 318 #define Py_TPFLAGS_HAVE_GETCHARBUFFER  (1L<<0)
 319
 320 #define Py_TPFLAGS_DEFAULT  (Py_TPFLAGS_HAVE_GETCHARBUFFER)
 321
 322 #define PyType_HasFeature(t,f)  (((t)->tp_flags & (f)) != 0)
 323
 324
 325 /*
 326 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
 327
 328 The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
 329 reference counts.  Py_DECREF calls the object's deallocator function; for
 330 objects that don't contain references to other objects or heap memory
 331 this can be the standard function free().  Both macros can be used
 332 whereever a void expression is allowed.  The argument shouldn't be a
 333 NIL pointer.  The macro _Py_NewReference(op) is used only to initialize
 334 reference counts to 1; it is defined here for convenience.
 335
 336 We assume that the reference count field can never overflow; this can
 337 be proven when the size of the field is the same as the pointer size
 338 but even with a 16-bit reference count field it is pretty unlikely so
 339 we ignore the possibility.  (If you are paranoid, make it a long.)
 340
 341 Type objects should never be deallocated; the type pointer in an object
 342 is not considered to be a reference to the type object, to save
 343 complications in the deallocation function.  (This is actually a
 344 decision that's up to the implementer of each new type so if you want,
 345 you can count such references to the type object.)
 346
 347 *** WARNING*** The Py_DECREF macro must have a side-effect-free argument
 348 since it may evaluate its argument multiple times.  (The alternative
 349 would be to mace it a proper function or assign it to a global temporary
 350 variable first, both of which are slower; and in a multi-threaded
 351 environment the global variable trick is not safe.)
 352 */
 353
 354 #ifdef Py_TRACE_REFS
 355 #ifndef Py_REF_DEBUG
 356 #define Py_REF_DEBUG
 357 #endif
 358 #endif
 359
 360 #ifdef Py_TRACE_REFS
 361 extern void _Py_Dealloc Py_PROTO((PyObject *));
 362 extern void _Py_NewReference Py_PROTO((PyObject *));
 363 extern void _Py_ForgetReference Py_PROTO((PyObject *));
 364 extern void _Py_PrintReferences Py_PROTO((FILE *));
 365 #endif
 366
 367 #ifndef Py_TRACE_REFS
 368 #ifdef COUNT_ALLOCS
 369 #define _Py_Dealloc(op) ((op)->ob_type->tp_free++, (*(op)->ob_type->tp_dealloc)((PyObject *)(op)))
 370 #define _Py_ForgetReference(op) ((op)->ob_type->tp_free++)
 371 #else /* !COUNT_ALLOCS */
 372 #define _Py_Dealloc(op) (*(op)->ob_type->tp_dealloc)((PyObject *)(op))
 373 #define _Py_ForgetReference(op) /*empty*/
 374 #endif /* !COUNT_ALLOCS */
 375 #endif /* !Py_TRACE_REFS */
 376
 377 #ifdef COUNT_ALLOCS
 378 extern void inc_count Py_PROTO((PyTypeObject *));
 379 #endif
 380
 381 #ifdef Py_REF_DEBUG
 382
 383 extern long _Py_RefTotal;
 384
 385 #ifndef Py_TRACE_REFS
 386 #ifdef COUNT_ALLOCS
 387 #define _Py_NewReference(op) (inc_count((op)->ob_type), _Py_RefTotal++, (op)->ob_refcnt = 1)
 388 #else
 389 #define _Py_NewReference(op) (_Py_RefTotal++, (op)->ob_refcnt = 1)
 390 #endif
 391 #endif /* !Py_TRACE_REFS */
 392
 393 #define Py_INCREF(op) (_Py_RefTotal++, (op)->ob_refcnt++)
 394 #define Py_DECREF(op) \
 395         if (--_Py_RefTotal, --(op)->ob_refcnt != 0) \
 396                 ; \
 397         else \
 398                 _Py_Dealloc((PyObject *)(op))
 399 #else /* !Py_REF_DEBUG */
 400
 401 #ifdef COUNT_ALLOCS
 402 #define _Py_NewReference(op) (inc_count((op)->ob_type), (op)->ob_refcnt = 1)
 403 #else
 404 #define _Py_NewReference(op) ((op)->ob_refcnt = 1)
 405 #endif
 406
 407 #define Py_INCREF(op) ((op)->ob_refcnt++)
 408 #define Py_DECREF(op) \
 409         if (--(op)->ob_refcnt != 0) \
 410                 ; \
 411         else \
 412                 _Py_Dealloc((PyObject *)(op))
 413 #endif /* !Py_REF_DEBUG */
 414
 415 /* Macros to use in case the object pointer may be NULL: */
 416
 417 #define Py_XINCREF(op) if ((op) == NULL) ; else Py_INCREF(op)
 418 #define Py_XDECREF(op) if ((op) == NULL) ; else Py_DECREF(op)
 419
 420 /* Definition of NULL, so you don't have to include <stdio.h> */
 421
 422 #ifndef NULL
 423 #define NULL 0
 424 #endif
 425
 426
 427 /*
 428 _Py_NoneStruct is an object of undefined type which can be used in contexts
 429 where NULL (nil) is not suitable (since NULL often means 'error').
 430
 431 Don't forget to apply Py_INCREF() when returning this value!!!
 432 */
 433
 434 extern DL_IMPORT(PyObject) _Py_NoneStruct; /* Don't use this directly */
 435
 436 #define Py_None (&_Py_NoneStruct)
 437
 438
 439 /*
 440 A common programming style in Python requires the forward declaration
 441 of static, initialized structures, e.g. for a type object that is used
 442 by the functions whose address must be used in the initializer.
 443 Some compilers (notably SCO ODT 3.0, I seem to remember early AIX as
 444 well) botch this if you use the static keyword for both declarations
 445 (they allocate two objects, and use the first, uninitialized one until
 446 the second declaration is encountered).  Therefore, the forward
 447 declaration should use the 'forwardstatic' keyword.  This expands to
 448 static on most systems, but to extern on a few.  The actual storage
 449 and name will still be static because the second declaration is
 450 static, so no linker visible symbols will be generated.  (Standard C
 451 compilers take offense to the extern forward declaration of a static
 452 object, so I can't just put extern in all cases. :-( )
 453 */
 454
 455 #ifdef BAD_STATIC_FORWARD
 456 #define staticforward extern
 457 #ifdef __SC__
 458 #define statichere
 459 #else
 460 #define statichere static
 461 #endif /* __SC__ */
 462 #else /* !BAD_STATIC_FORWARD */
 463 #define staticforward static
 464 #define statichere static
 465 #endif /* !BAD_STATIC_FORWARD */
 466
 467
 468 /*
 469 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
 470
 471 More conventions
 472 ================
 473
 474 Argument Checking
 475 -----------------
 476
 477 Functions that take objects as arguments normally don't check for nil
 478 arguments, but they do check the type of the argument, and return an
 479 error if the function doesn't apply to the type.
 480
 481 Failure Modes
 482 -------------
 483
 484 Functions may fail for a variety of reasons, including running out of
 485 memory.  This is communicated to the caller in two ways: an error string
 486 is set (see errors.h), and the function result differs: functions that
 487 normally return a pointer return NULL for failure, functions returning
 488 an integer return -1 (which could be a legal return value too!), and
 489 other functions return 0 for success and -1 for failure.
 490 Callers should always check for errors before using the result.
 491
 492 Reference Counts
 493 ----------------
 494
 495 It takes a while to get used to the proper usage of reference counts.
 496
 497 Functions that create an object set the reference count to 1; such new
 498 objects must be stored somewhere or destroyed again with Py_DECREF().
 499 Functions that 'store' objects such as PyTuple_SetItem() and
 500 PyDict_SetItemString()
 501 don't increment the reference count of the object, since the most
 502 frequent use is to store a fresh object.  Functions that 'retrieve'
 503 objects such as PyTuple_GetItem() and PyDict_GetItemString() also
 504 don't increment
 505 the reference count, since most frequently the object is only looked at
 506 quickly.  Thus, to retrieve an object and store it again, the caller
 507 must call Py_INCREF() explicitly.
 508
 509 NOTE: functions that 'consume' a reference count like
 510 PyList_SetItemString() even consume the reference if the object wasn't
 511 stored, to simplify error handling.
 512
 513 It seems attractive to make other functions that take an object as
 514 argument consume a reference count; however this may quickly get
 515 confusing (even the current practice is already confusing).  Consider
 516 it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
 517 times.
 518
 519 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
 520 */
 521
 522 #ifdef __cplusplus
 523 }
 524 #endif
 525 #endif /* !Py_OBJECT_H */