genobject.c revision 4c20bc40d73a7f4a977475e4fa02f7c8a43d796a 
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
10static int
11gen_traverse(PyGenObject *gen, visitproc visit, void *arg)
12{
13	Py_VISIT((PyObject *)gen->gi_frame);
14	return 0;
15}
16
17static void
18gen_dealloc(PyGenObject *gen)
19{
20	PyObject *self = (PyObject *) gen;
21
22	_PyObject_GC_UNTRACK(gen);
23
24	if (gen->gi_weakreflist != NULL)
25		PyObject_ClearWeakRefs(self);
26
27	_PyObject_GC_TRACK(self);
28
29	if (gen->gi_frame != NULL && gen->gi_frame->f_stacktop != NULL) {
30		/* Generator is paused, so we need to close */
31		Py_Type(gen)->tp_del(self);
32		if (self->ob_refcnt > 0)
33			return;		/* resurrected.  :( */
34	}
35
36	_PyObject_GC_UNTRACK(self);
37	Py_CLEAR(gen->gi_frame);
38	PyObject_GC_Del(gen);
39}
40
41
42static PyObject *
43gen_send_ex(PyGenObject *gen, PyObject *arg, int exc)
44{
45	PyThreadState *tstate = PyThreadState_GET();
46	PyFrameObject *f = gen->gi_frame;
47	PyObject *result;
48
49	if (gen->gi_running) {
50		PyErr_SetString(PyExc_ValueError,
51				"generator already executing");
52		return NULL;
53	}
54	if (f==NULL || f->f_stacktop == NULL) {
55		/* Only set exception if called from send() */
56		if (arg && !exc)
57			PyErr_SetNone(PyExc_StopIteration);
58		return NULL;
59	}
60
61	if (f->f_lasti == -1) {
62		if (arg && arg != Py_None) {
63			PyErr_SetString(PyExc_TypeError,
64					"can't send non-None value to a "
65					"just-started generator");
66			return NULL;
67		}
68	} else {
69		/* Push arg onto the frame's value stack */
70		result = arg ? arg : Py_None;
71	        Py_INCREF(result);
72	        *(f->f_stacktop++) = result;
73	}
74
75	/* Generators always return to their most recent caller, not
76	 * necessarily their creator. */
77	Py_XINCREF(tstate->frame);
78	assert(f->f_back == NULL);
79	f->f_back = tstate->frame;
80
81	gen->gi_running = 1;
82	result = PyEval_EvalFrameEx(f, exc);
83	gen->gi_running = 0;
84
85	/* Don't keep the reference to f_back any longer than necessary.  It
86	 * may keep a chain of frames alive or it could create a reference
87	 * cycle. */
88	assert(f->f_back == tstate->frame);
89	Py_CLEAR(f->f_back);
90
91	/* If the generator just returned (as opposed to yielding), signal
92	 * that the generator is exhausted. */
93	if (result == Py_None && f->f_stacktop == NULL) {
94		Py_DECREF(result);
95		result = NULL;
96		/* Set exception if not called by gen_iternext() */
97		if (arg)
98			PyErr_SetNone(PyExc_StopIteration);
99	}
100
101	if (!result || f->f_stacktop == NULL) {
102		/* generator can't be rerun, so release the frame */
103		Py_DECREF(f);
104		gen->gi_frame = NULL;
105	}
106
107	return result;
108}
109
110PyDoc_STRVAR(send_doc,
111"send(arg) -> send 'arg' into generator,\n\
112return next yielded value or raise StopIteration.");
113
114static PyObject *
115gen_send(PyGenObject *gen, PyObject *arg)
116{
117	return gen_send_ex(gen, arg, 0);
118}
119
120PyDoc_STRVAR(close_doc,
121"close(arg) -> raise GeneratorExit inside generator.");
122
123static PyObject *
124gen_close(PyGenObject *gen, PyObject *args)
125{
126	PyObject *retval;
127	PyErr_SetNone(PyExc_GeneratorExit);
128	retval = gen_send_ex(gen, Py_None, 1);
129	if (retval) {
130		Py_DECREF(retval);
131		PyErr_SetString(PyExc_RuntimeError,
132				"generator ignored GeneratorExit");
133		return NULL;
134	}
135	if (PyErr_ExceptionMatches(PyExc_StopIteration)
136	    || PyErr_ExceptionMatches(PyExc_GeneratorExit))
137	{
138		PyErr_Clear();	/* ignore these errors */
139		Py_INCREF(Py_None);
140		return Py_None;
141	}
142	return NULL;
143}
144
145static void
146gen_del(PyObject *self)
147{
148        PyObject *res;
149        PyObject *error_type, *error_value, *error_traceback;
150	PyGenObject *gen = (PyGenObject *)self;
151
152	if (gen->gi_frame == NULL || gen->gi_frame->f_stacktop == NULL)
153		/* Generator isn't paused, so no need to close */
154		return;
155
156        /* Temporarily resurrect the object. */
157        assert(self->ob_refcnt == 0);
158        self->ob_refcnt = 1;
159
160        /* Save the current exception, if any. */
161        PyErr_Fetch(&error_type, &error_value, &error_traceback);
162
163	res = gen_close(gen, NULL);
164
165	if (res == NULL)
166		PyErr_WriteUnraisable(self);
167	else
168		Py_DECREF(res);
169
170        /* Restore the saved exception. */
171        PyErr_Restore(error_type, error_value, error_traceback);
172
173        /* Undo the temporary resurrection; can't use DECREF here, it would
174         * cause a recursive call.
175         */
176        assert(self->ob_refcnt > 0);
177        if (--self->ob_refcnt == 0)
178                return; /* this is the normal path out */
179
180        /* close() resurrected it!  Make it look like the original Py_DECREF
181         * never happened.
182         */
183        {
184                Py_ssize_t refcnt = self->ob_refcnt;
185                _Py_NewReference(self);
186                self->ob_refcnt = refcnt;
187        }
188        assert(PyType_IS_GC(self->ob_type) &&
189               _Py_AS_GC(self)->gc.gc_refs != _PyGC_REFS_UNTRACKED);
190
191        /* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
192         * we need to undo that. */
193        _Py_DEC_REFTOTAL;
194        /* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
195         * chain, so no more to do there.
196         * If COUNT_ALLOCS, the original decref bumped tp_frees, and
197         * _Py_NewReference bumped tp_allocs:  both of those need to be
198         * undone.
199         */
200#ifdef COUNT_ALLOCS
201        --self->ob_type->tp_frees;
202        --self->ob_type->tp_allocs;
203#endif
204}
205
206
207
208PyDoc_STRVAR(throw_doc,
209"throw(typ[,val[,tb]]) -> raise exception in generator,\n\
210return next yielded value or raise StopIteration.");
211
212static PyObject *
213gen_throw(PyGenObject *gen, PyObject *args)
214{
215	PyObject *typ;
216	PyObject *tb = NULL;
217	PyObject *val = NULL;
218
219	if (!PyArg_UnpackTuple(args, "throw", 1, 3, &typ, &val, &tb))
220		return NULL;
221
222	/* First, check the traceback argument, replacing None with
223	   NULL. */
224	if (tb == Py_None)
225		tb = NULL;
226	else if (tb != NULL && !PyTraceBack_Check(tb)) {
227		PyErr_SetString(PyExc_TypeError,
228			"throw() third argument must be a traceback object");
229		return NULL;
230	}
231
232	Py_INCREF(typ);
233	Py_XINCREF(val);
234	Py_XINCREF(tb);
235
236	if (PyExceptionClass_Check(typ)) {
237		PyErr_NormalizeException(&typ, &val, &tb);
238	}
239
240	else if (PyExceptionInstance_Check(typ)) {
241		/* Raising an instance.  The value should be a dummy. */
242		if (val && val != Py_None) {
243			PyErr_SetString(PyExc_TypeError,
244			  "instance exception may not have a separate value");
245			goto failed_throw;
246		}
247		else {
248			/* Normalize to raise <class>, <instance> */
249			Py_XDECREF(val);
250			val = typ;
251			typ = PyExceptionInstance_Class(typ);
252			Py_INCREF(typ);
253		}
254	}
255	else {
256		/* Not something you can raise.  throw() fails. */
257		PyErr_Format(PyExc_TypeError,
258			     "exceptions must be classes, or instances, not %s",
259			     typ->ob_type->tp_name);
260			goto failed_throw;
261	}
262
263	PyErr_Restore(typ, val, tb);
264	return gen_send_ex(gen, Py_None, 1);
265
266failed_throw:
267	/* Didn't use our arguments, so restore their original refcounts */
268	Py_DECREF(typ);
269	Py_XDECREF(val);
270	Py_XDECREF(tb);
271	return NULL;
272}
273
274
275static PyObject *
276gen_iternext(PyGenObject *gen)
277{
278	return gen_send_ex(gen, NULL, 0);
279}
280
281
282static PyMemberDef gen_memberlist[] = {
283	{"gi_frame",	T_OBJECT, offsetof(PyGenObject, gi_frame),	RO},
284	{"gi_running",	T_INT,    offsetof(PyGenObject, gi_running),	RO},
285	{NULL}	/* Sentinel */
286};
287
288static PyMethodDef gen_methods[] = {
289	{"send",(PyCFunction)gen_send, METH_O, send_doc},
290	{"throw",(PyCFunction)gen_throw, METH_VARARGS, throw_doc},
291	{"close",(PyCFunction)gen_close, METH_NOARGS, close_doc},
292	{NULL, NULL}	/* Sentinel */
293};
294
295PyTypeObject PyGen_Type = {
296	PyVarObject_HEAD_INIT(&PyType_Type, 0)
297	"generator",				/* tp_name */
298	sizeof(PyGenObject),			/* tp_basicsize */
299	0,					/* tp_itemsize */
300	/* methods */
301	(destructor)gen_dealloc, 		/* tp_dealloc */
302	0,					/* tp_print */
303	0, 					/* tp_getattr */
304	0,					/* tp_setattr */
305	0,					/* tp_compare */
306	0,					/* tp_repr */
307	0,					/* tp_as_number */
308	0,					/* tp_as_sequence */
309	0,					/* tp_as_mapping */
310	0,					/* tp_hash */
311	0,					/* tp_call */
312	0,					/* tp_str */
313	PyObject_GenericGetAttr,		/* tp_getattro */
314	0,					/* tp_setattro */
315	0,					/* tp_as_buffer */
316	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
317 	0,					/* tp_doc */
318 	(traverseproc)gen_traverse,		/* tp_traverse */
319 	0,					/* tp_clear */
320	0,					/* tp_richcompare */
321	offsetof(PyGenObject, gi_weakreflist),	/* tp_weaklistoffset */
322	PyObject_SelfIter,			/* tp_iter */
323	(iternextfunc)gen_iternext,		/* tp_iternext */
324	gen_methods,				/* tp_methods */
325	gen_memberlist,				/* tp_members */
326	0,					/* tp_getset */
327	0,					/* tp_base */
328	0,					/* tp_dict */
329
330	0,					/* tp_descr_get */
331	0,					/* tp_descr_set */
332	0,					/* tp_dictoffset */
333	0,					/* tp_init */
334	0,					/* tp_alloc */
335	0,					/* tp_new */
336	0,					/* tp_free */
337	0,					/* tp_is_gc */
338	0,					/* tp_bases */
339	0,					/* tp_mro */
340	0,					/* tp_cache */
341	0,					/* tp_subclasses */
342	0,					/* tp_weaklist */
343	gen_del,				/* tp_del */
344};
345
346PyObject *
347PyGen_New(PyFrameObject *f)
348{
349	PyGenObject *gen = PyObject_GC_New(PyGenObject, &PyGen_Type);
350	if (gen == NULL) {
351		Py_DECREF(f);
352		return NULL;
353	}
354	gen->gi_frame = f;
355	gen->gi_running = 0;
356	gen->gi_weakreflist = NULL;
357	_PyObject_GC_TRACK(gen);
358	return (PyObject *)gen;
359}
360
361int
362PyGen_NeedsFinalizing(PyGenObject *gen)
363{
364	int i;
365	PyFrameObject *f = gen->gi_frame;
366
367	if (f == NULL || f->f_stacktop == NULL || f->f_iblock <= 0)
368		return 0; /* no frame or empty blockstack == no finalization */
369
370	/* Any block type besides a loop requires cleanup. */
371	i = f->f_iblock;
372	while (--i >= 0) {
373		if (f->f_blockstack[i].b_type != SETUP_LOOP)
374			return 1;
375	}
376
377	/* No blocks except loops, it's safe to skip finalization. */
378	return 0;
379}
380