summaryrefslogtreecommitdiffstats
path: root/Objects/genobject.c
blob: 016bfa297522c8fe71f0d2085b407124dffb0817 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
/* Generator object implementation */

#include "Python.h"
#include "frameobject.h"
#include "structmember.h"
#include "opcode.h"

static PyObject *gen_close(PyGenObject *gen, PyObject *args);

static int
gen_traverse(PyGenObject *gen, visitproc visit, void *arg)
{
    Py_VISIT((PyObject *)gen->gi_frame);
    Py_VISIT(gen->gi_code);
    return 0;
}

static void
gen_dealloc(PyGenObject *gen)
{
    PyObject *self = (PyObject *) gen;

    _PyObject_GC_UNTRACK(gen);

    if (gen->gi_weakreflist != NULL)
        PyObject_ClearWeakRefs(self);

    _PyObject_GC_TRACK(self);

    if (gen->gi_frame != NULL && gen->gi_frame->f_stacktop != NULL) {
        /* Generator is paused, so we need to close */
        Py_TYPE(gen)->tp_del(self);
        if (self->ob_refcnt > 0)
            return;                     /* resurrected.  :( */
    }

    _PyObject_GC_UNTRACK(self);
    Py_CLEAR(gen->gi_frame);
    Py_CLEAR(gen->gi_code);
    PyObject_GC_Del(gen);
}


static PyObject *
gen_send_ex(PyGenObject *gen, PyObject *arg, int exc)
{
    PyThreadState *tstate = PyThreadState_GET();
    PyFrameObject *f = gen->gi_frame;
    PyObject *result;

    if (gen->gi_running) {
        PyErr_SetString(PyExc_ValueError,
                        "generator already executing");
        return NULL;
    }
    if (f == NULL || f->f_stacktop == NULL) {
        /* Only set exception if called from send() */
        if (arg && !exc)
            PyErr_SetNone(PyExc_StopIteration);
        return NULL;
    }

    if (f->f_lasti == -1) {
        if (arg && arg != Py_None) {
            PyErr_SetString(PyExc_TypeError,
                            "can't send non-None value to a "
                            "just-started generator");
            return NULL;
        }
    } else {
        /* Push arg onto the frame's value stack */
        result = arg ? arg : Py_None;
        Py_INCREF(result);
        *(f->f_stacktop++) = result;
    }

    /* Generators always return to their most recent caller, not
     * necessarily their creator. */
    Py_XINCREF(tstate->frame);
    assert(f->f_back == NULL);
    f->f_back = tstate->frame;

    gen->gi_running = 1;
    result = PyEval_EvalFrameEx(f, exc);
    gen->gi_running = 0;

    /* Don't keep the reference to f_back any longer than necessary.  It
     * may keep a chain of frames alive or it could create a reference
     * cycle. */
    assert(f->f_back == tstate->frame);
    Py_CLEAR(f->f_back);

    /* If the generator just returned (as opposed to yielding), signal
     * that the generator is exhausted. */
    if (result && f->f_stacktop == NULL) {
        if (result == Py_None) {
            /* Delay exception instantiation if we can */
            PyErr_SetNone(PyExc_StopIteration);
        } else {
            PyObject *e = PyObject_CallFunctionObjArgs(
                               PyExc_StopIteration, result, NULL);
            if (e != NULL) {
                PyErr_SetObject(PyExc_StopIteration, e);
                Py_DECREF(e);
            }
        }
        Py_CLEAR(result);
    }

    if (!result || f->f_stacktop == NULL) {
        /* generator can't be rerun, so release the frame */
        /* first clean reference cycle through stored exception traceback */
        PyObject *t, *v, *tb;
        t = f->f_exc_type;
        v = f->f_exc_value;
        tb = f->f_exc_traceback;
        f->f_exc_type = NULL;
        f->f_exc_value = NULL;
        f->f_exc_traceback = NULL;
        Py_XDECREF(t);
        Py_XDECREF(v);
        Py_XDECREF(tb);
        gen->gi_frame = NULL;
        Py_DECREF(f);
    }

    return result;
}

PyDoc_STRVAR(send_doc,
"send(arg) -> send 'arg' into generator,\n\
return next yielded value or raise StopIteration.");

PyObject *
_PyGen_Send(PyGenObject *gen, PyObject *arg)
{
    return gen_send_ex(gen, arg, 0);
}

PyDoc_STRVAR(close_doc,
"close() -> raise GeneratorExit inside generator.");

/*
 *   This helper function is used by gen_close and gen_throw to
 *   close a subiterator being delegated to by yield-from.
 */

static int
gen_close_iter(PyObject *yf)
{
    PyObject *retval = NULL;
    _Py_IDENTIFIER(close);

    if (PyGen_CheckExact(yf)) {
        retval = gen_close((PyGenObject *)yf, NULL);
        if (retval == NULL)
            return -1;
    } else {
        PyObject *meth = _PyObject_GetAttrId(yf, &PyId_close);
        if (meth == NULL) {
            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
                PyErr_WriteUnraisable(yf);
            PyErr_Clear();
        } else {
            retval = PyObject_CallFunction(meth, "");
            Py_DECREF(meth);
            if (retval == NULL)
                return -1;
        }
    }
    Py_XDECREF(retval);
    return 0;
}

static PyObject *
gen_yf(PyGenObject *gen)
{
    PyObject *yf = NULL;
    PyFrameObject *f = gen->gi_frame;

    if (f && f->f_stacktop) {
        PyObject *bytecode = f->f_code->co_code;
        unsigned char *code = (unsigned char *)PyBytes_AS_STRING(bytecode);

        if (code[f->f_lasti + 1] != YIELD_FROM)
            return NULL;
        yf = f->f_stacktop[-1];
        Py_INCREF(yf);
    }

    return yf;
}

static PyObject *
gen_close(PyGenObject *gen, PyObject *args)
{
    PyObject *retval;
    PyObject *yf = gen_yf(gen);
    int err = 0;

    if (yf) {
        gen->gi_running = 1;
        err = gen_close_iter(yf);
        gen->gi_running = 0;
        Py_DECREF(yf);
    }
    if (err == 0)
        PyErr_SetNone(PyExc_GeneratorExit);
    retval = gen_send_ex(gen, Py_None, 1);
    if (retval) {
        Py_DECREF(retval);
        PyErr_SetString(PyExc_RuntimeError,
                        "generator ignored GeneratorExit");
        return NULL;
    }
    if (PyErr_ExceptionMatches(PyExc_StopIteration)
        || PyErr_ExceptionMatches(PyExc_GeneratorExit)) {
        PyErr_Clear();          /* ignore these errors */
        Py_INCREF(Py_None);
        return Py_None;
    }
    return NULL;
}

static void
gen_del(PyObject *self)
{
    PyObject *res;
    PyObject *error_type, *error_value, *error_traceback;
    PyGenObject *gen = (PyGenObject *)self;

    if (gen->gi_frame == NULL || gen->gi_frame->f_stacktop == NULL)
        /* Generator isn't paused, so no need to close */
        return;

    /* Temporarily resurrect the object. */
    assert(self->ob_refcnt == 0);
    self->ob_refcnt = 1;

    /* Save the current exception, if any. */
    PyErr_Fetch(&error_type, &error_value, &error_traceback);

    res = gen_close(gen, NULL);

    if (res == NULL)
        PyErr_WriteUnraisable(self);
    else
        Py_DECREF(res);

    /* Restore the saved exception. */
    PyErr_Restore(error_type, error_value, error_traceback);

    /* Undo the temporary resurrection; can't use DECREF here, it would
     * cause a recursive call.
     */
    assert(self->ob_refcnt > 0);
    if (--self->ob_refcnt == 0)
        return; /* this is the normal path out */

    /* close() resurrected it!  Make it look like the original Py_DECREF
     * never happened.
     */
    {
        Py_ssize_t refcnt = self->ob_refcnt;
        _Py_NewReference(self);
        self->ob_refcnt = refcnt;
    }
    assert(PyType_IS_GC(Py_TYPE(self)) &&
           _Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);

    /* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
     * we need to undo that. */
    _Py_DEC_REFTOTAL;
    /* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
     * chain, so no more to do there.
     * If COUNT_ALLOCS, the original decref bumped tp_frees, and
     * _Py_NewReference bumped tp_allocs:  both of those need to be
     * undone.
     */
#ifdef COUNT_ALLOCS
    --(Py_TYPE(self)->tp_frees);
    --(Py_TYPE(self)->tp_allocs);
#endif
}



PyDoc_STRVAR(throw_doc,
"throw(typ[,val[,tb]]) -> raise exception in generator,\n\
return next yielded value or raise StopIteration.");

static PyObject *
gen_throw(PyGenObject *gen, PyObject *args)
{
    PyObject *typ;
    PyObject *tb = NULL;
    PyObject *val = NULL;
    PyObject *yf = gen_yf(gen);
    _Py_IDENTIFIER(throw);

    if (!PyArg_UnpackTuple(args, "throw", 1, 3, &typ, &val, &tb))
        return NULL;

    if (yf) {
        PyObject *ret;
        int err;
        if (PyErr_GivenExceptionMatches(typ, PyExc_GeneratorExit)) {
            gen->gi_running = 1;
            err = gen_close_iter(yf);
            gen->gi_running = 0;
            Py_DECREF(yf);
            if (err < 0)
                return gen_send_ex(gen, Py_None, 1);
            goto throw_here;
        }
        if (PyGen_CheckExact(yf)) {
            gen->gi_running = 1;
            ret = gen_throw((PyGenObject *)yf, args);
            gen->gi_running = 0;
        } else {
            PyObject *meth = _PyObject_GetAttrId(yf, &PyId_throw);
            if (meth == NULL) {
                if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
                    Py_DECREF(yf);
                    return NULL;
                }
                PyErr_Clear();
                Py_DECREF(yf);
                goto throw_here;
            }
            gen->gi_running = 1;
            ret = PyObject_CallObject(meth, args);
            gen->gi_running = 0;
            Py_DECREF(meth);
        }
        Py_DECREF(yf);
        if (!ret) {
            PyObject *val;
            /* Pop subiterator from stack */
            ret = *(--gen->gi_frame->f_stacktop);
            assert(ret == yf);
            Py_DECREF(ret);
            /* Termination repetition of YIELD_FROM */
            gen->gi_frame->f_lasti++;
            if (_PyGen_FetchStopIterationValue(&val) == 0) {
                ret = gen_send_ex(gen, val, 0);
                Py_DECREF(val);
            } else {
                ret = gen_send_ex(gen, Py_None, 1);
            }
        }
        return ret;
    }

throw_here:
    /* First, check the traceback argument, replacing None with
       NULL. */
    if (tb == Py_None) {
        tb = NULL;
    }
    else if (tb != NULL && !PyTraceBack_Check(tb)) {
        PyErr_SetString(PyExc_TypeError,
            "throw() third argument must be a traceback object");
        return NULL;
    }

    Py_INCREF(typ);
    Py_XINCREF(val);
    Py_XINCREF(tb);

    if (PyExceptionClass_Check(typ))
        PyErr_NormalizeException(&typ, &val, &tb);

    else if (PyExceptionInstance_Check(typ)) {
        /* Raising an instance.  The value should be a dummy. */
        if (val && val != Py_None) {
            PyErr_SetString(PyExc_TypeError,
              "instance exception may not have a separate value");
            goto failed_throw;
        }
        else {
            /* Normalize to raise <class>, <instance> */
            Py_XDECREF(val);
            val = typ;
            typ = PyExceptionInstance_Class(typ);
            Py_INCREF(typ);

            if (tb == NULL)
                /* Returns NULL if there's no traceback */
                tb = PyException_GetTraceback(val);
        }
    }
    else {
        /* Not something you can raise.  throw() fails. */
        PyErr_Format(PyExc_TypeError,
                     "exceptions must be classes or instances "
                     "deriving from BaseException, not %s",
                     Py_TYPE(typ)->tp_name);
            goto failed_throw;
    }

    PyErr_Restore(typ, val, tb);
    return gen_send_ex(gen, Py_None, 1);

failed_throw:
    /* Didn't use our arguments, so restore their original refcounts */
    Py_DECREF(typ);
    Py_XDECREF(val);
    Py_XDECREF(tb);
    return NULL;
}


static PyObject *
gen_iternext(PyGenObject *gen)
{
    PyObject *val = NULL;
    PyObject *ret;
    ret = gen_send_ex(gen, val, 0);
    Py_XDECREF(val);
    return ret;
}

/*
 *   If StopIteration exception is set, fetches its 'value'
 *   attribute if any, otherwise sets pvalue to None.
 *
 *   Returns 0 if no exception or StopIteration is set.
 *   If any other exception is set, returns -1 and leaves
 *   pvalue unchanged.
 */

int
_PyGen_FetchStopIterationValue(PyObject **pvalue) {
    PyObject *et, *ev, *tb;
    PyObject *value = NULL;

    if (PyErr_ExceptionMatches(PyExc_StopIteration)) {
        PyErr_Fetch(&et, &ev, &tb);
        Py_XDECREF(et);
        Py_XDECREF(tb);
        if (ev) {
            value = ((PyStopIterationObject *)ev)->value;
            Py_INCREF(value);
            Py_DECREF(ev);
        }
    } else if (PyErr_Occurred()) {
        return -1;
    }
    if (value == NULL) {
        value = Py_None;
        Py_INCREF(value);
    }
    *pvalue = value;
    return 0;
}

static PyObject *
gen_repr(PyGenObject *gen)
{
    return PyUnicode_FromFormat("<generator object %S at %p>",
                                ((PyCodeObject *)gen->gi_code)->co_name,
                                gen);
}


static PyObject *
gen_get_name(PyGenObject *gen)
{
    PyObject *name = ((PyCodeObject *)gen->gi_code)->co_name;
    Py_INCREF(name);
    return name;
}


PyDoc_STRVAR(gen__name__doc__,
"Return the name of the generator's associated code object.");

static PyGetSetDef gen_getsetlist[] = {
    {"__name__", (getter)gen_get_name, NULL, gen__name__doc__},
    {NULL}
};


static PyMemberDef gen_memberlist[] = {
    {"gi_frame",        T_OBJECT, offsetof(PyGenObject, gi_frame),      READONLY},
    {"gi_running",      T_BOOL,    offsetof(PyGenObject, gi_running),    READONLY},
    {"gi_code",     T_OBJECT, offsetof(PyGenObject, gi_code),  READONLY},
    {NULL}      /* Sentinel */
};

static PyMethodDef gen_methods[] = {
    {"send",(PyCFunction)_PyGen_Send, METH_O, send_doc},
    {"throw",(PyCFunction)gen_throw, METH_VARARGS, throw_doc},
    {"close",(PyCFunction)gen_close, METH_NOARGS, close_doc},
    {NULL, NULL}        /* Sentinel */
};

PyTypeObject PyGen_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "generator",                                /* tp_name */
    sizeof(PyGenObject),                        /* tp_basicsize */
    0,                                          /* tp_itemsize */
    /* methods */
    (destructor)gen_dealloc,                    /* tp_dealloc */
    0,                                          /* tp_print */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    0,                                          /* tp_reserved */
    (reprfunc)gen_repr,                         /* tp_repr */
    0,                                          /* tp_as_number */
    0,                                          /* tp_as_sequence */
    0,                                          /* tp_as_mapping */
    0,                                          /* tp_hash */
    0,                                          /* tp_call */
    0,                                          /* tp_str */
    PyObject_GenericGetAttr,                    /* tp_getattro */
    0,                                          /* tp_setattro */
    0,                                          /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
    0,                                          /* tp_doc */
    (traverseproc)gen_traverse,                 /* tp_traverse */
    0,                                          /* tp_clear */
    0,                                          /* tp_richcompare */
    offsetof(PyGenObject, gi_weakreflist),      /* tp_weaklistoffset */
    PyObject_SelfIter,                          /* tp_iter */
    (iternextfunc)gen_iternext,                 /* tp_iternext */
    gen_methods,                                /* tp_methods */
    gen_memberlist,                             /* tp_members */
    gen_getsetlist,                             /* tp_getset */
    0,                                          /* tp_base */
    0,                                          /* tp_dict */

    0,                                          /* tp_descr_get */
    0,                                          /* tp_descr_set */
    0,                                          /* tp_dictoffset */
    0,                                          /* tp_init */
    0,                                          /* tp_alloc */
    0,                                          /* tp_new */
    0,                                          /* tp_free */
    0,                                          /* tp_is_gc */
    0,                                          /* tp_bases */
    0,                                          /* tp_mro */
    0,                                          /* tp_cache */
    0,                                          /* tp_subclasses */
    0,                                          /* tp_weaklist */
    gen_del,                                    /* tp_del */
};

PyObject *
PyGen_New(PyFrameObject *f)
{
    PyGenObject *gen = PyObject_GC_New(PyGenObject, &PyGen_Type);
    if (gen == NULL) {
        Py_DECREF(f);
        return NULL;
    }
    gen->gi_frame = f;
    Py_INCREF(f->f_code);
    gen->gi_code = (PyObject *)(f->f_code);
    gen->gi_running = 0;
    gen->gi_weakreflist = NULL;
    _PyObject_GC_TRACK(gen);
    return (PyObject *)gen;
}

int
PyGen_NeedsFinalizing(PyGenObject *gen)
{
    int i;
    PyFrameObject *f = gen->gi_frame;

    if (f == NULL || f->f_stacktop == NULL)
        return 0; /* no frame or empty blockstack == no finalization */

    /* Any block type besides a loop requires cleanup. */
    for (i = 0; i < f->f_iblock; i++)
        if (f->f_blockstack[i].b_type != SETUP_LOOP)
            return 1;

    /* No blocks except loops, it's safe to skip finalization. */
    return 0;
}