Objects/genobject.c

   1 /* Generator object implementation */
   2
   3 #include "Python.h"
   4 #include "frameobject.h"
   5 #include "genobject.h"
   6 #include "ceval.h"
   7 #include "structmember.h"
   8 #include "opcode.h"
   9
  10 static int
  11 gen_traverse(PyGenObject *gen, visitproc visit, void *arg)
  12 {
  13     Py_VISIT((PyObject *)gen->gi_frame);
  14     Py_VISIT(gen->gi_code);
  15     return 0;
  16 }
  17
  18 static void
  19 gen_dealloc(PyGenObject *gen)
  20 {
  21     PyObject *self = (PyObject *) gen;
  22
  23     _PyObject_GC_UNTRACK(gen);
  24
  25     if (gen->gi_weakreflist != NULL)
  26         PyObject_ClearWeakRefs(self);
  27
  28     _PyObject_GC_TRACK(self);
  29
  30     if (gen->gi_frame != NULL && gen->gi_frame->f_stacktop != NULL) {
  31         /* Generator is paused, so we need to close */
  32         Py_TYPE(gen)->tp_del(self);
  33         if (self->ob_refcnt > 0)
  34             return;                     /* resurrected.  :( */
  35     }
  36
  37     _PyObject_GC_UNTRACK(self);
  38     Py_CLEAR(gen->gi_frame);
  39     Py_CLEAR(gen->gi_code);
  40     PyObject_GC_Del(gen);
  41 }
  42
  43
  44 static PyObject *
  45 gen_send_ex(PyGenObject *gen, PyObject *arg, int exc)
  46 {
  47     PyThreadState *tstate = PyThreadState_GET();
  48     PyFrameObject *f = gen->gi_frame;
  49     PyObject *result;
  50
  51     if (gen->gi_running) {
  52         PyErr_SetString(PyExc_ValueError,
  53                         "generator already executing");
  54         return NULL;
  55     }
  56     if (f==NULL || f->f_stacktop == NULL) {
  57         /* Only set exception if called from send() */
  58         if (arg && !exc)
  59             PyErr_SetNone(PyExc_StopIteration);
  60         return NULL;
  61     }
  62
  63     if (f->f_lasti == -1) {
  64         if (arg && arg != Py_None) {
  65             PyErr_SetString(PyExc_TypeError,
  66                             "can't send non-None value to a "
  67                             "just-started generator");
  68             return NULL;
  69         }
  70     } else {
  71         /* Push arg onto the frame's value stack */
  72         result = arg ? arg : Py_None;
  73         Py_INCREF(result);
  74         *(f->f_stacktop++) = result;
  75     }
  76
  77     /* Generators always return to their most recent caller, not
  78      * necessarily their creator. */
  79     Py_XINCREF(tstate->frame);
  80     assert(f->f_back == NULL);
  81     f->f_back = tstate->frame;
  82
  83     gen->gi_running = 1;
  84     result = PyEval_EvalFrameEx(f, exc);
  85     gen->gi_running = 0;
  86
  87     /* Don't keep the reference to f_back any longer than necessary.  It
  88      * may keep a chain of frames alive or it could create a reference
  89      * cycle. */
  90     assert(f->f_back == tstate->frame);
  91     Py_CLEAR(f->f_back);
  92
  93     /* If the generator just returned (as opposed to yielding), signal
  94      * that the generator is exhausted. */
  95     if (result == Py_None && f->f_stacktop == NULL) {
  96         Py_DECREF(result);
  97         result = NULL;
  98         /* Set exception if not called by gen_iternext() */
  99         if (arg)
 100             PyErr_SetNone(PyExc_StopIteration);
 101     }
 102
 103     if (!result || f->f_stacktop == NULL) {
 104         /* generator can't be rerun, so release the frame */
 105         Py_DECREF(f);
 106         gen->gi_frame = NULL;
 107     }
 108
 109     return result;
 110 }
 111
 112 PyDoc_STRVAR(send_doc,
 113 "send(arg) -> send 'arg' into generator,\n\
 114 return next yielded value or raise StopIteration.");
 115
 116 static PyObject *
 117 gen_send(PyGenObject *gen, PyObject *arg)
 118 {
 119     return gen_send_ex(gen, arg, 0);
 120 }
 121
 122 PyDoc_STRVAR(close_doc,
 123 "close(arg) -> raise GeneratorExit inside generator.");
 124
 125 static PyObject *
 126 gen_close(PyGenObject *gen, PyObject *args)
 127 {
 128     PyObject *retval;
 129     PyErr_SetNone(PyExc_GeneratorExit);
 130     retval = gen_send_ex(gen, Py_None, 1);
 131     if (retval) {
 132         Py_DECREF(retval);
 133         PyErr_SetString(PyExc_RuntimeError,
 134                         "generator ignored GeneratorExit");
 135         return NULL;
 136     }
 137     if (PyErr_ExceptionMatches(PyExc_StopIteration)
 138         || PyErr_ExceptionMatches(PyExc_GeneratorExit))
 139     {
 140         PyErr_Clear();          /* ignore these errors */
 141         Py_INCREF(Py_None);
 142         return Py_None;
 143     }
 144     return NULL;
 145 }
 146
 147 static void
 148 gen_del(PyObject *self)
 149 {
 150     PyObject *res;
 151     PyObject *error_type, *error_value, *error_traceback;
 152     PyGenObject *gen = (PyGenObject *)self;
 153
 154     if (gen->gi_frame == NULL || gen->gi_frame->f_stacktop == NULL)
 155         /* Generator isn't paused, so no need to close */
 156         return;
 157
 158     /* Temporarily resurrect the object. */
 159     assert(self->ob_refcnt == 0);
 160     self->ob_refcnt = 1;
 161
 162     /* Save the current exception, if any. */
 163     PyErr_Fetch(&error_type, &error_value, &error_traceback);
 164
 165     res = gen_close(gen, NULL);
 166
 167     if (res == NULL)
 168         PyErr_WriteUnraisable(self);
 169     else
 170         Py_DECREF(res);
 171
 172     /* Restore the saved exception. */
 173     PyErr_Restore(error_type, error_value, error_traceback);
 174
 175     /* Undo the temporary resurrection; can't use DECREF here, it would
 176      * cause a recursive call.
 177      */
 178     assert(self->ob_refcnt > 0);
 179     if (--self->ob_refcnt == 0)
 180         return; /* this is the normal path out */
 181
 182     /* close() resurrected it!  Make it look like the original Py_DECREF
 183      * never happened.
 184      */
 185     {
 186         Py_ssize_t refcnt = self->ob_refcnt;
 187         _Py_NewReference(self);
 188         self->ob_refcnt = refcnt;
 189     }
 190     assert(PyType_IS_GC(self->ob_type) &&
 191            _Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
 192
 193     /* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
 194      * we need to undo that. */
 195     _Py_DEC_REFTOTAL;
 196     /* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
 197      * chain, so no more to do there.
 198      * If COUNT_ALLOCS, the original decref bumped tp_frees, and
 199      * _Py_NewReference bumped tp_allocs:  both of those need to be
 200      * undone.
 201      */
 202 #ifdef COUNT_ALLOCS
 203     --self->ob_type->tp_frees;
 204     --self->ob_type->tp_allocs;
 205 #endif
 206 }
 207
 208
 209
 210 PyDoc_STRVAR(throw_doc,
 211 "throw(typ[,val[,tb]]) -> raise exception in generator,\n\
 212 return next yielded value or raise StopIteration.");
 213
 214 static PyObject *
 215 gen_throw(PyGenObject *gen, PyObject *args)
 216 {
 217     PyObject *typ;
 218     PyObject *tb = NULL;
 219     PyObject *val = NULL;
 220
 221     if (!PyArg_UnpackTuple(args, "throw", 1, 3, &typ, &val, &tb))
 222         return NULL;
 223
 224     /* First, check the traceback argument, replacing None with
 225        NULL. */
 226     if (tb == Py_None)
 227         tb = NULL;
 228     else if (tb != NULL && !PyTraceBack_Check(tb)) {
 229         PyErr_SetString(PyExc_TypeError,
 230             "throw() third argument must be a traceback object");
 231         return NULL;
 232     }
 233
 234     Py_INCREF(typ);
 235     Py_XINCREF(val);
 236     Py_XINCREF(tb);
 237
 238     if (PyExceptionClass_Check(typ)) {
 239         PyErr_NormalizeException(&typ, &val, &tb);
 240     }
 241
 242     else if (PyExceptionInstance_Check(typ)) {
 243         /* Raising an instance.  The value should be a dummy. */
 244         if (val && val != Py_None) {
 245             PyErr_SetString(PyExc_TypeError,
 246               "instance exception may not have a separate value");
 247             goto failed_throw;
 248         }
 249         else {
 250             /* Normalize to raise <class>, <instance> */
 251             Py_XDECREF(val);
 252             val = typ;
 253             typ = PyExceptionInstance_Class(typ);
 254             Py_INCREF(typ);
 255         }
 256     }
 257     else {
 258         /* Not something you can raise.  throw() fails. */
 259         PyErr_Format(PyExc_TypeError,
 260                      "exceptions must be classes, or instances, not %s",
 261                      typ->ob_type->tp_name);
 262             goto failed_throw;
 263     }
 264
 265     PyErr_Restore(typ, val, tb);
 266     return gen_send_ex(gen, Py_None, 1);
 267
 268 failed_throw:
 269     /* Didn't use our arguments, so restore their original refcounts */
 270     Py_DECREF(typ);
 271     Py_XDECREF(val);
 272     Py_XDECREF(tb);
 273     return NULL;
 274 }
 275
 276
 277 static PyObject *
 278 gen_iternext(PyGenObject *gen)
 279 {
 280     return gen_send_ex(gen, NULL, 0);
 281 }
 282
 283
 284 static PyObject *
 285 gen_repr(PyGenObject *gen)
 286 {
 287     char *code_name;
 288     code_name = PyString_AsString(((PyCodeObject *)gen->gi_code)->co_name);
 289     if (code_name == NULL)
 290         return NULL;
 291     return PyString_FromFormat("<generator object %.200s at %p>",
 292                                code_name, gen);
 293 }
 294
 295
 296 static PyObject *
 297 gen_get_name(PyGenObject *gen)
 298 {
 299     PyObject *name = ((PyCodeObject *)gen->gi_code)->co_name;
 300     Py_INCREF(name);
 301     return name;
 302 }
 303
 304
 305 PyDoc_STRVAR(gen__name__doc__,
 306 "Return the name of the generator's associated code object.");
 307
 308 static PyGetSetDef gen_getsetlist[] = {
 309     {"__name__", (getter)gen_get_name, NULL, gen__name__doc__},
 310     {NULL}
 311 };
 312
 313
 314 static PyMemberDef gen_memberlist[] = {
 315     {"gi_frame",        T_OBJECT, offsetof(PyGenObject, gi_frame),      RO},
 316     {"gi_running",      T_INT,    offsetof(PyGenObject, gi_running),    RO},
 317     {"gi_code",     T_OBJECT, offsetof(PyGenObject, gi_code),  RO},
 318     {NULL}      /* Sentinel */
 319 };
 320
 321 static PyMethodDef gen_methods[] = {
 322     {"send",(PyCFunction)gen_send, METH_O, send_doc},
 323     {"throw",(PyCFunction)gen_throw, METH_VARARGS, throw_doc},
 324     {"close",(PyCFunction)gen_close, METH_NOARGS, close_doc},
 325     {NULL, NULL}        /* Sentinel */
 326 };
 327
 328 PyTypeObject PyGen_Type = {
 329     PyVarObject_HEAD_INIT(&PyType_Type, 0)
 330     "generator",                                /* tp_name */
 331     sizeof(PyGenObject),                        /* tp_basicsize */
 332     0,                                          /* tp_itemsize */
 333     /* methods */
 334     (destructor)gen_dealloc,                    /* tp_dealloc */
 335     0,                                          /* tp_print */
 336     0,                                          /* tp_getattr */
 337     0,                                          /* tp_setattr */
 338     0,                                          /* tp_compare */
 339     (reprfunc)gen_repr,                         /* tp_repr */
 340     0,                                          /* tp_as_number */
 341     0,                                          /* tp_as_sequence */
 342     0,                                          /* tp_as_mapping */
 343     0,                                          /* tp_hash */
 344     0,                                          /* tp_call */
 345     0,                                          /* tp_str */
 346     PyObject_GenericGetAttr,                    /* tp_getattro */
 347     0,                                          /* tp_setattro */
 348     0,                                          /* tp_as_buffer */
 349     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
 350     0,                                          /* tp_doc */
 351     (traverseproc)gen_traverse,                 /* tp_traverse */
 352     0,                                          /* tp_clear */
 353     0,                                          /* tp_richcompare */
 354     offsetof(PyGenObject, gi_weakreflist),      /* tp_weaklistoffset */
 355     PyObject_SelfIter,                          /* tp_iter */
 356     (iternextfunc)gen_iternext,                 /* tp_iternext */
 357     gen_methods,                                /* tp_methods */
 358     gen_memberlist,                             /* tp_members */
 359     gen_getsetlist,                             /* tp_getset */
 360     0,                                          /* tp_base */
 361     0,                                          /* tp_dict */
 362
 363     0,                                          /* tp_descr_get */
 364     0,                                          /* tp_descr_set */
 365     0,                                          /* tp_dictoffset */
 366     0,                                          /* tp_init */
 367     0,                                          /* tp_alloc */
 368     0,                                          /* tp_new */
 369     0,                                          /* tp_free */
 370     0,                                          /* tp_is_gc */
 371     0,                                          /* tp_bases */
 372     0,                                          /* tp_mro */
 373     0,                                          /* tp_cache */
 374     0,                                          /* tp_subclasses */
 375     0,                                          /* tp_weaklist */
 376     gen_del,                                    /* tp_del */
 377 };
 378
 379 PyObject *
 380 PyGen_New(PyFrameObject *f)
 381 {
 382     PyGenObject *gen = PyObject_GC_New(PyGenObject, &PyGen_Type);
 383     if (gen == NULL) {
 384         Py_DECREF(f);
 385         return NULL;
 386     }
 387     gen->gi_frame = f;
 388     Py_INCREF(f->f_code);
 389     gen->gi_code = (PyObject *)(f->f_code);
 390     gen->gi_running = 0;
 391     gen->gi_weakreflist = NULL;
 392     _PyObject_GC_TRACK(gen);
 393     return (PyObject *)gen;
 394 }
 395
 396 int
 397 PyGen_NeedsFinalizing(PyGenObject *gen)
 398 {
 399     int i;
 400     PyFrameObject *f = gen->gi_frame;
 401
 402     if (f == NULL || f->f_stacktop == NULL || f->f_iblock <= 0)
 403         return 0; /* no frame or empty blockstack == no finalization */
 404
 405     /* Any block type besides a loop requires cleanup. */
 406     i = f->f_iblock;
 407     while (--i >= 0) {
 408         if (f->f_blockstack[i].b_type != SETUP_LOOP)
 409             return 1;
 410     }
 411
 412     /* No blocks except loops, it's safe to skip finalization. */
 413     return 0;
 414 }