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 not be used in advertising or publicity pertaining to
  19 distribution of the software without specific, written prior permission.
  20
  21 STICHTING MATHEMATISCH CENTRUM DISCLAIMS ALL WARRANTIES WITH REGARD TO
  22 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
  23 FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH CENTRUM BE LIABLE
  24 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  25 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  26 ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
  27 OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  28
  29 ******************************************************************/
  30
  31 #ifndef DEBUG
  32 #define NDEBUG
  33 #endif
  34
  35 /* Object and type object interface */
  36
  37 /*
  38 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
  39
  40 Objects are structures allocated on the heap.  Special rules apply to
  41 the use of objects to ensure they are properly garbage-collected.
  42 Objects are never allocated statically or on the stack; they must be
  43 accessed through special macros and functions only.  (Type objects are
  44 exceptions to the first rule; the standard types are represented by
  45 statically initialized type objects.)
  46
  47 An object has a 'reference count' that is increased or decreased when a
  48 pointer to the object is copied or deleted; when the reference count
  49 reaches zero there are no references to the object left and it can be
  50 removed from the heap.
  51
  52 An object has a 'type' that determines what it represents and what kind
  53 of data it contains.  An object's type is fixed when it is created.
  54 Types themselves are represented as objects; an object contains a
  55 pointer to the corresponding type object.  The type itself has a type
  56 pointer pointing to the object representing the type 'type', which
  57 contains a pointer to itself!).
  58
  59 Objects do not float around in memory; once allocated an object keeps
  60 the same size and address.  Objects that must hold variable-size data
  61 can contain pointers to variable-size parts of the object.  Not all
  62 objects of the same type have the same size; but the size cannot change
  63 after allocation.  (These restrictions are made so a reference to an
  64 object can be simply a pointer -- moving an object would require
  65 updating all the pointers, and changing an object's size would require
  66 moving it if there was another object right next to it.)
  67
  68 Objects are always accessed through pointers of the type 'PyObject *'.
  69 The type 'PyObject' is a structure that only contains the reference count
  70 and the type pointer.  The actual memory allocated for an object
  71 contains other data that can only be accessed after casting the pointer
  72 to a pointer to a longer structure type.  This longer type must start
  73 with the reference count and type fields; the macro PyObject_HEAD should be
  74 used for this (to accomodate for future changes).  The implementation
  75 of a particular object type can cast the object pointer to the proper
  76 type and back.
  77
  78 A standard interface exists for objects that contain an array of items
  79 whose size is determined when the object is allocated.
  80
  81 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
  82 */
  83
  84 #ifndef NDEBUG
  85
  86 /* Turn on heavy reference debugging */
  87 #define Py_TRACE_REFS
  88
  89 /* Turn on reference counting */
  90 #define Py_REF_DEBUG
  91
  92 #endif /* NDEBUG */
  93
  94 #ifdef Py_TRACE_REFS
  95 #define PyObject_HEAD \
  96         struct _object *_ob_next, *_ob_prev; \
  97         int ob_refcnt; \
  98         struct _typeobject *ob_type;
  99 #define PyObject_HEAD_INIT(type) 0, 0, 1, type,
 100 #else
 101 #define PyObject_HEAD \
 102         int ob_refcnt; \
 103         struct _typeobject *ob_type;
 104 #define PyObject_HEAD_INIT(type) 1, type,
 105 #endif
 106
 107 #define PyObject_VAR_HEAD \
 108         PyObject_HEAD \
 109         int ob_size; /* Number of items in variable part */
 110
 111 typedef struct _object {
 112         PyObject_HEAD
 113 } PyObject;
 114
 115 typedef struct {
 116         PyObject_VAR_HEAD
 117 } varobject;
 118
 119
 120 /*
 121 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
 122
 123 Type objects contain a string containing the type name (to help somewhat
 124 in debugging), the allocation parameters (see newobj() and newvarobj()),
 125 and methods for accessing objects of the type.  Methods are optional,a
 126 nil pointer meaning that particular kind of access is not available for
 127 this type.  The Py_DECREF() macro uses the tp_dealloc method without
 128 checking for a nil pointer; it should always be implemented except if
 129 the implementation can guarantee that the reference count will never
 130 reach zero (e.g., for type objects).
 131
 132 NB: the methods for certain type groups are now contained in separate
 133 method blocks.
 134 */
 135
 136 typedef PyObject * (*unaryfunc) Py_PROTO((PyObject *));
 137 typedef PyObject * (*binaryfunc) Py_PROTO((PyObject *, PyObject *));
 138 typedef PyObject * (*ternaryfunc) Py_PROTO((PyObject *, PyObject *, PyObject *));
 139 typedef int (*inquiry) Py_PROTO((PyObject *));
 140 typedef int (*coercion) Py_PROTO((PyObject **, PyObject **));
 141 typedef PyObject *(*intargfunc) Py_PROTO((PyObject *, int));
 142 typedef PyObject *(*intintargfunc) Py_PROTO((PyObject *, int, int));
 143 typedef int(*intobjargproc) Py_PROTO((PyObject *, int, PyObject *));
 144 typedef int(*intintobjargproc) Py_PROTO((PyObject *, int, int, PyObject *));
 145 typedef int(*objobjargproc) Py_PROTO((PyObject *, PyObject *, PyObject *));
 146
 147 typedef struct {
 148         binaryfunc nb_add;
 149         binaryfunc nb_subtract;
 150         binaryfunc nb_multiply;
 151         binaryfunc nb_divide;
 152         binaryfunc nb_remainder;
 153         binaryfunc nb_divmod;
 154         ternaryfunc nb_power;
 155         unaryfunc nb_negative;
 156         unaryfunc nb_positive;
 157         unaryfunc nb_absolute;
 158         inquiry nb_nonzero;
 159         unaryfunc nb_invert;
 160         binaryfunc nb_lshift;
 161         binaryfunc nb_rshift;
 162         binaryfunc nb_and;
 163         binaryfunc nb_xor;
 164         binaryfunc nb_or;
 165         coercion nb_coerce;
 166         unaryfunc nb_int;
 167         unaryfunc nb_long;
 168         unaryfunc nb_float;
 169         unaryfunc nb_oct;
 170         unaryfunc nb_hex;
 171 } PyNumberMethods;
 172
 173 typedef struct {
 174         inquiry sq_length;
 175         binaryfunc sq_concat;
 176         intargfunc sq_repeat;
 177         intargfunc sq_item;
 178         intintargfunc sq_slice;
 179         intobjargproc sq_ass_item;
 180         intintobjargproc sq_ass_slice;
 181 } PySequenceMethods;
 182
 183 typedef struct {
 184         inquiry mp_length;
 185         binaryfunc mp_subscript;
 186         objobjargproc mp_ass_subscript;
 187 } PyMappingMethods;
 188
 189 typedef void (*destructor) Py_PROTO((PyObject *));
 190 typedef int (*printfunc) Py_PROTO((PyObject *, FILE *, int));
 191 typedef PyObject *(*getattrfunc) Py_PROTO((PyObject *, char *));
 192 typedef int (*setattrfunc) Py_PROTO((PyObject *, char *, PyObject *));
 193 typedef int (*cmpfunc) Py_PROTO((PyObject *, PyObject *));
 194 typedef PyObject *(*reprfunc) Py_PROTO((PyObject *));
 195 typedef long (*hashfunc) Py_PROTO((PyObject *));
 196
 197 typedef struct _typeobject {
 198         PyObject_VAR_HEAD
 199         char *tp_name; /* For printing */
 200         int tp_basicsize, tp_itemsize; /* For allocation */
 201
 202         /* Methods to implement standard operations */
 203
 204         destructor tp_dealloc;
 205         printfunc tp_print;
 206         getattrfunc tp_getattr;
 207         setattrfunc tp_setattr;
 208         cmpfunc tp_compare;
 209         reprfunc tp_repr;
 210
 211         /* Method suites for standard classes */
 212
 213         PyNumberMethods *tp_as_number;
 214         PySequenceMethods *tp_as_sequence;
 215         PyMappingMethods *tp_as_mapping;
 216
 217         /* More standard operations (at end for binary compatibility) */
 218
 219         hashfunc tp_hash;
 220         binaryfunc tp_call;
 221         reprfunc tp_str;
 222
 223         /* Space for future expansion */
 224         long tp_xxx1;
 225         long tp_xxx2;
 226         long tp_xxx3;
 227         long tp_xxx4;
 228
 229         char *tp_doc; /* Documentation string */
 230
 231 #ifdef COUNT_ALLOCS
 232         /* these must be last */
 233         int tp_alloc;
 234         int tp_free;
 235         int tp_maxalloc;
 236         struct _typeobject *tp_next;
 237 #endif
 238 } PyTypeObject;
 239
 240 extern DL_IMPORT(PyTypeObject) PyType_Type; /* The type of type objects */
 241
 242 #define PyType_Check(op) ((op)->ob_type == &PyType_Type)
 243
 244 /* Generic operations on objects */
 245 extern int PyObject_Print Py_PROTO((PyObject *, FILE *, int));
 246 extern PyObject * PyObject_Repr Py_PROTO((PyObject *));
 247 extern PyObject * PyObject_Str Py_PROTO((PyObject *));
 248 extern int PyObject_Compare Py_PROTO((PyObject *, PyObject *));
 249 extern PyObject *PyObject_GetAttrString Py_PROTO((PyObject *, char *));
 250 extern int PyObject_HasAttrString Py_PROTO((PyObject *, char *));
 251 extern PyObject *PyObject_GetAttr Py_PROTO((PyObject *, PyObject *));
 252 extern int PyObject_SetAttr Py_PROTO((PyObject *, PyObject *, PyObject *));
 253 extern long PyObject_Hash Py_PROTO((PyObject *));
 254 extern int PyObject_IsTrue Py_PROTO((PyObject *));
 255 extern int PyCallable_Check Py_PROTO((PyObject *));
 256
 257 /* Flag bits for printing: */
 258 #define Py_PRINT_RAW    1       /* No string quotes etc. */
 259
 260 /*
 261 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
 262
 263 The macros Py_INCREF(op) and Py_DECREF(op) are used to increment or decrement
 264 reference counts.  Py_DECREF calls the object's deallocator function; for
 265 objects that don't contain references to other objects or heap memory
 266 this can be the standard function free().  Both macros can be used
 267 whereever a void expression is allowed.  The argument shouldn't be a
 268 NIL pointer.  The macro _Py_NewReference(op) is used only to initialize
 269 reference counts to 1; it is defined here for convenience.
 270
 271 We assume that the reference count field can never overflow; this can
 272 be proven when the size of the field is the same as the pointer size
 273 but even with a 16-bit reference count field it is pretty unlikely so
 274 we ignore the possibility.  (If you are paranoid, make it a long.)
 275
 276 Type objects should never be deallocated; the type pointer in an object
 277 is not considered to be a reference to the type object, to save
 278 complications in the deallocation function.  (This is actually a
 279 decision that's up to the implementer of each new type so if you want,
 280 you can count such references to the type object.)
 281
 282 *** WARNING*** The Py_DECREF macro must have a side-effect-free argument
 283 since it may evaluate its argument multiple times.  (The alternative
 284 would be to mace it a proper function or assign it to a global temporary
 285 variable first, both of which are slower; and in a multi-threaded
 286 environment the global variable trick is not safe.)
 287 */
 288
 289 #ifdef Py_TRACE_REFS
 290 #ifndef Py_REF_DEBUG
 291 #define Py_REF_DEBUG
 292 #endif
 293 #endif
 294
 295 #ifndef Py_TRACE_REFS
 296 #ifdef COUNT_ALLOCS
 297 #define _Py_Dealloc(op) ((op)->ob_type->tp_free++, (*(op)->ob_type->tp_dealloc)((PyObject *)(op)))
 298 #else
 299 #define _Py_Dealloc(op) (*(op)->ob_type->tp_dealloc)((PyObject *)(op))
 300 #endif
 301 #define _Py_ForgetReference(op) /*empty*/
 302 #endif
 303
 304 #ifdef COUNT_ALLOCS
 305 extern void inc_count Py_PROTO((PyTypeObject *));
 306 #endif
 307
 308 #ifdef Py_REF_DEBUG
 309 extern long ref_total;
 310 #ifndef Py_TRACE_REFS
 311 #ifdef COUNT_ALLOCS
 312 #define _Py_NewReference(op) (inc_count((op)->ob_type), ref_total++, (op)->ob_refcnt = 1)
 313 #else
 314 #define _Py_NewReference(op) (ref_total++, (op)->ob_refcnt = 1)
 315 #endif
 316 #endif
 317 #define Py_INCREF(op) (ref_total++, (op)->ob_refcnt++)
 318 #define Py_DECREF(op) \
 319         if (--ref_total, --(op)->ob_refcnt != 0) \
 320                 ; \
 321         else \
 322                 _Py_Dealloc(op)
 323 #else
 324 #ifdef COUNT_ALLOCS
 325 #define _Py_NewReference(op) (inc_count((op)->ob_type), (op)->ob_refcnt = 1)
 326 #else
 327 #define _Py_NewReference(op) ((op)->ob_refcnt = 1)
 328 #endif
 329 #define Py_INCREF(op) ((op)->ob_refcnt++)
 330 #define Py_DECREF(op) \
 331         if (--(op)->ob_refcnt != 0) \
 332                 ; \
 333         else \
 334                 _Py_Dealloc(op)
 335 #endif
 336
 337 /* Macros to use in case the object pointer may be NULL: */
 338
 339 #define Py_XINCREF(op) if ((op) == NULL) ; else Py_INCREF(op)
 340 #define Py_XDECREF(op) if ((op) == NULL) ; else Py_DECREF(op)
 341
 342 /* Definition of NULL, so you don't have to include <stdio.h> */
 343
 344 #ifndef NULL
 345 #define NULL 0
 346 #endif
 347
 348
 349 /*
 350 _Py_NoneStruct is an object of undefined type which can be used in contexts
 351 where NULL (nil) is not suitable (since NULL often means 'error').
 352
 353 Don't forget to apply Py_INCREF() when returning this value!!!
 354 */
 355
 356 extern DL_IMPORT(PyObject) _Py_NoneStruct; /* Don't use this directly */
 357
 358 #define Py_None (&_Py_NoneStruct)
 359
 360
 361 /*
 362 A common programming style in Python requires the forward declaration
 363 of static, initialized structures, e.g. for a type object that is used
 364 by the functions whose address must be used in the initializer.
 365 Some compilers (notably SCO ODT 3.0, I seem to remember early AIX as
 366 well) botch this if you use the static keyword for both declarations
 367 (they allocate two objects, and use the first, uninitialized one until
 368 the second declaration is encountered).  Therefore, the forward
 369 declaration should use the 'forwardstatic' keyword.  This expands to
 370 static on most systems, but to extern on a few.  The actual storage
 371 and name will still be static because the second declaration is
 372 static, so no linker visible symbols will be generated.  (Standard C
 373 compilers take offense to the extern forward declaration of a static
 374 object, so I can't just put extern in all cases. :-( )
 375 */
 376
 377 #ifdef BAD_STATIC_FORWARD
 378 #define staticforward extern
 379 #ifdef __SC__
 380 #define statichere
 381 #else
 382 #define statichere static
 383 #endif /* __SC__ */
 384 #else /* !BAD_STATIC_FORWARD */
 385 #define staticforward static
 386 #define statichere static
 387 #endif /* !BAD_STATIC_FORWARD */
 388
 389
 390 /*
 391 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
 392
 393 More conventions
 394 ================
 395
 396 Argument Checking
 397 -----------------
 398
 399 Functions that take objects as arguments normally don't check for nil
 400 arguments, but they do check the type of the argument, and return an
 401 error if the function doesn't apply to the type.
 402
 403 Failure Modes
 404 -------------
 405
 406 Functions may fail for a variety of reasons, including running out of
 407 memory.  This is communicated to the caller in two ways: an error string
 408 is set (see errors.h), and the function result differs: functions that
 409 normally return a pointer return NULL for failure, functions returning
 410 an integer return -1 (which could be a legal return value too!), and
 411 other functions return 0 for success and -1 for failure.
 412 Callers should always check for errors before using the result.
 413
 414 Reference Counts
 415 ----------------
 416
 417 It takes a while to get used to the proper usage of reference counts.
 418
 419 Functions that create an object set the reference count to 1; such new
 420 objects must be stored somewhere or destroyed again with Py_DECREF().
 421 Functions that 'store' objects such as PyTuple_SetItem() and
 422 PyDict_SetItemString()
 423 don't increment the reference count of the object, since the most
 424 frequent use is to store a fresh object.  Functions that 'retrieve'
 425 objects such as PyTuple_GetItem() and PyDict_GetItemString() also
 426 don't increment
 427 the reference count, since most frequently the object is only looked at
 428 quickly.  Thus, to retrieve an object and store it again, the caller
 429 must call Py_INCREF() explicitly.
 430
 431 NOTE: functions that 'consume' a reference count like
 432 PyDict_SetItemString() even
 433 consume the reference if the object wasn't stored, to simplify error
 434 handling.
 435
 436 It seems attractive to make other functions that take an object as
 437 argument consume a reference count; however this may quickly get
 438 confusing (even the current practice is already confusing).  Consider
 439 it carefully, it may save lots of calls to Py_INCREF() and Py_DECREF() at
 440 times.
 441
 442 123456789-123456789-123456789-123456789-123456789-123456789-123456789-12
 443 */
 444
 445 #ifdef __cplusplus
 446 }
 447 #endif
 448 #endif /* !Py_OBJECT_H */