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
|
"""
The Stackless module allows you to do multitasking without using threads.
The essential objects are tasklets and channels.
Please refer to their documentation.
"""
import _continuation
class TaskletExit(Exception):
pass
CoroutineExit = TaskletExit
def _coroutine_getcurrent():
"Returns the current coroutine (i.e. the one which called this function)."
try:
return _tls.current_coroutine
except AttributeError:
# first call in this thread: current == main
return _coroutine_getmain()
def _coroutine_getmain():
try:
return _tls.main_coroutine
except AttributeError:
# create the main coroutine for this thread
continulet = _continuation.continulet
main = coroutine()
main._frame = continulet.__new__(continulet)
main._is_started = -1
_tls.current_coroutine = _tls.main_coroutine = main
return _tls.main_coroutine
class coroutine(object):
_is_started = 0 # 0=no, 1=yes, -1=main
def __init__(self):
self._frame = None
def bind(self, func, *argl, **argd):
"""coro.bind(f, *argl, **argd) -> None.
binds function f to coro. f will be called with
arguments *argl, **argd
"""
if self.is_alive:
raise ValueError("cannot bind a bound coroutine")
def run(c):
_tls.current_coroutine = self
self._is_started = 1
return func(*argl, **argd)
self._is_started = 0
self._frame = _continuation.continulet(run)
def switch(self):
"""coro.switch() -> returnvalue
switches to coroutine coro. If the bound function
f finishes, the returnvalue is that of f, otherwise
None is returned
"""
current = _coroutine_getcurrent()
try:
current._frame.switch(to=self._frame)
finally:
_tls.current_coroutine = current
def kill(self):
"""coro.kill() : kill coroutine coro"""
current = _coroutine_getcurrent()
try:
current._frame.throw(CoroutineExit, to=self._frame)
finally:
_tls.current_coroutine = current
@property
def is_alive(self):
return self._is_started < 0 or (
self._frame is not None and self._frame.is_pending())
@property
def is_zombie(self):
return self._is_started > 0 and not self._frame.is_pending()
getcurrent = staticmethod(_coroutine_getcurrent)
def __reduce__(self):
if self._is_started < 0:
return _coroutine_getmain, ()
else:
return type(self), (), self.__dict__
try:
from threading import local as _local
except ImportError:
class _local(object): # assume no threads
pass
_tls = _local()
# ____________________________________________________________
from collections import deque
import operator
__all__ = 'run getcurrent getmain schedule tasklet channel coroutine'.split()
_global_task_id = 0
_squeue = None
_main_tasklet = None
_main_coroutine = None
_last_task = None
_channel_callback = None
_schedule_callback = None
def _scheduler_remove(value):
try:
del _squeue[operator.indexOf(_squeue, value)]
except ValueError:
pass
def _scheduler_append(value, normal=True):
if normal:
_squeue.append(value)
else:
_squeue.rotate(-1)
_squeue.appendleft(value)
_squeue.rotate(1)
def _scheduler_contains(value):
try:
operator.indexOf(_squeue, value)
return True
except ValueError:
return False
def _scheduler_switch(current, next):
global _last_task
prev = _last_task
if (_schedule_callback is not None and
prev is not next):
_schedule_callback(prev, next)
_last_task = next
assert not next.blocked
if next is not current:
next.switch()
return current
def set_schedule_callback(callback):
global _schedule_callback
_schedule_callback = callback
def set_channel_callback(callback):
global _channel_callback
_channel_callback = callback
def getruncount():
return len(_squeue)
class bomb(object):
def __init__(self, exp_type=None, exp_value=None, exp_traceback=None):
self.type = exp_type
self.value = exp_value
self.traceback = exp_traceback
def raise_(self):
raise self.type, self.value, self.traceback
#
#
class channel(object):
"""
A channel object is used for communication between tasklets.
By sending on a channel, a tasklet that is waiting to receive
is resumed. If there is no waiting receiver, the sender is suspended.
By receiving from a channel, a tasklet that is waiting to send
is resumed. If there is no waiting sender, the receiver is suspended.
Attributes:
preference
----------
-1: prefer receiver
0: don't prefer anything
1: prefer sender
Pseudocode that shows in what situation a schedule happens:
def send(arg):
if !receiver:
schedule()
elif schedule_all:
schedule()
else:
if (prefer receiver):
schedule()
else (don't prefer anything, prefer sender):
pass
NOW THE INTERESTING STUFF HAPPENS
def receive():
if !sender:
schedule()
elif schedule_all:
schedule()
else:
if (prefer sender):
schedule()
else (don't prefer anything, prefer receiver):
pass
NOW THE INTERESTING STUFF HAPPENS
schedule_all
------------
True: overwrite preference. This means that the current tasklet always
schedules before returning from send/receive (it always blocks).
(see Stackless/module/channelobject.c)
"""
def __init__(self, label=''):
self.balance = 0
self.closing = False
self.queue = deque()
self.label = label
self.preference = -1
self.schedule_all = False
def __str__(self):
return 'channel[%s](%s,%s)' % (self.label, self.balance, self.queue)
def close(self):
"""
channel.close() -- stops the channel from enlarging its queue.
If the channel is not empty, the flag 'closing' becomes true.
If the channel is empty, the flag 'closed' becomes true.
"""
self.closing = True
@property
def closed(self):
return self.closing and not self.queue
def open(self):
"""
channel.open() -- reopen a channel. See channel.close.
"""
self.closing = False
def _channel_action(self, arg, d):
"""
d == -1 : receive
d == 1 : send
the original CStackless has an argument 'stackl' which is not used
here.
'target' is the peer tasklet to the current one
"""
do_schedule=False
assert abs(d) == 1
source = getcurrent()
source.tempval = arg
while True:
if d > 0:
cando = self.balance < 0
dir = d
else:
cando = self.balance > 0
dir = 0
if cando and self.queue[0]._tasklet_killed:
# issue #2595: the tasklet was killed while waiting.
# drop that tasklet from consideration and try again.
self.balance += d
self.queue.popleft()
else:
# normal path
break
if _channel_callback is not None:
_channel_callback(self, source, dir, not cando)
self.balance += d
if cando:
# communication 1): there is somebody waiting
target = self.queue.popleft()
source.tempval, target.tempval = target.tempval, source.tempval
target.blocked = 0
if self.schedule_all:
# always schedule
_scheduler_append(target)
do_schedule = True
elif self.preference == -d:
_scheduler_append(target, False)
do_schedule = True
else:
_scheduler_append(target)
else:
# communication 2): there is nobody waiting
# if source.block_trap:
# raise RuntimeError("this tasklet does not like to be blocked")
# if self.closing:
# raise StopIteration()
source.blocked = d
self.queue.append(source)
_scheduler_remove(getcurrent())
do_schedule = True
if do_schedule:
schedule()
retval = source.tempval
if isinstance(retval, bomb):
retval.raise_()
return retval
def receive(self):
"""
channel.receive() -- receive a value over the channel.
If no other tasklet is already sending on the channel,
the receiver will be blocked. Otherwise, the receiver will
continue immediately, and the sender is put at the end of
the runnables list.
The above policy can be changed by setting channel flags.
"""
return self._channel_action(None, -1)
def send_exception(self, exp_type, msg):
self.send(bomb(exp_type, exp_type(msg)))
def send_sequence(self, iterable):
for item in iterable:
self.send(item)
def send(self, msg):
"""
channel.send(value) -- send a value over the channel.
If no other tasklet is already receiving on the channel,
the sender will be blocked. Otherwise, the receiver will
be activated immediately, and the sender is put at the end of
the runnables list.
"""
return self._channel_action(msg, 1)
class tasklet(coroutine):
"""
A tasklet object represents a tiny task in a Python thread.
At program start, there is always one running main tasklet.
New tasklets can be created with methods from the stackless
module.
"""
tempval = None
_tasklet_killed = False
def __new__(cls, func=None, label=''):
res = coroutine.__new__(cls)
res.label = label
res._task_id = None
return res
def __init__(self, func=None, label=''):
coroutine.__init__(self)
self._init(func, label)
def _init(self, func=None, label=''):
global _global_task_id
self.func = func
self.alive = False
self.blocked = False
self._task_id = _global_task_id
self.label = label
_global_task_id += 1
def __str__(self):
return '<tasklet[%s, %s]>' % (self.label,self._task_id)
__repr__ = __str__
def __call__(self, *argl, **argd):
return self.setup(*argl, **argd)
def bind(self, func):
"""
Binding a tasklet to a callable object.
The callable is usually passed in to the constructor.
In some cases, it makes sense to be able to re-bind a tasklet,
after it has been run, in order to keep its identity.
Note that a tasklet can only be bound when it doesn't have a frame.
"""
if not callable(func):
raise TypeError('tasklet function must be a callable')
self.func = func
def kill(self):
"""
tasklet.kill -- raise a TaskletExit exception for the tasklet.
Note that this is a regular exception that can be caught.
The tasklet is immediately activated.
If the exception passes the toplevel frame of the tasklet,
the tasklet will silently die.
"""
self._tasklet_killed = True
if not self.is_zombie:
# Killing the tasklet by throwing TaskletExit exception.
coroutine.kill(self)
_scheduler_remove(self)
self.alive = False
def setup(self, *argl, **argd):
"""
supply the parameters for the callable
"""
if self.func is None:
raise TypeError('cframe function must be callable')
func = self.func
def _func():
try:
try:
coroutine.switch(back)
func(*argl, **argd)
except TaskletExit:
pass
finally:
_scheduler_remove(self)
self.alive = False
self.func = None
coroutine.bind(self, _func)
back = _coroutine_getcurrent()
coroutine.switch(self)
self.alive = True
_scheduler_append(self)
return self
def run(self):
self.insert()
_scheduler_switch(getcurrent(), self)
def insert(self):
if self.blocked:
raise RuntimeError("You cannot run a blocked tasklet")
if not self.alive:
raise RuntimeError("You cannot run an unbound(dead) tasklet")
_scheduler_append(self)
def remove(self):
if self.blocked:
raise RuntimeError("You cannot remove a blocked tasklet.")
if self is getcurrent():
raise RuntimeError("The current tasklet cannot be removed.")
# not sure if I will revive this " Use t=tasklet().capture()"
_scheduler_remove(self)
def getmain():
"""
getmain() -- return the main tasklet.
"""
return _main_tasklet
def getcurrent():
"""
getcurrent() -- return the currently executing tasklet.
"""
curr = coroutine.getcurrent()
if curr is _main_coroutine:
return _main_tasklet
else:
return curr
_run_calls = []
def run():
"""
run_watchdog(timeout) -- run tasklets until they are all
done, or timeout instructions have passed. Tasklets must
provide cooperative schedule() calls.
If the timeout is met, the function returns.
The calling tasklet is put aside while the tasklets are running.
It is inserted back after the function stops, right before the
tasklet that caused a timeout, if any.
If an exception occours, it will be passed to the main tasklet.
Please note that the 'timeout' feature is not yet implemented
"""
curr = getcurrent()
_run_calls.append(curr)
_scheduler_remove(curr)
try:
schedule()
assert not _squeue
finally:
_scheduler_append(curr)
def schedule_remove(retval=None):
"""
schedule(retval=stackless.current) -- switch to the next runnable tasklet.
The return value for this call is retval, with the current
tasklet as default.
schedule_remove(retval=stackless.current) -- ditto, and remove self.
"""
_scheduler_remove(getcurrent())
r = schedule(retval)
return r
def schedule(retval=None):
"""
schedule(retval=stackless.current) -- switch to the next runnable tasklet.
The return value for this call is retval, with the current
tasklet as default.
schedule_remove(retval=stackless.current) -- ditto, and remove self.
"""
mtask = getmain()
curr = getcurrent()
if retval is None:
retval = curr
while True:
if _squeue:
if _squeue[0] is curr:
# If the current is at the head, skip it.
_squeue.rotate(-1)
task = _squeue[0]
#_squeue.rotate(-1)
elif _run_calls:
task = _run_calls.pop()
else:
raise RuntimeError('No runnable tasklets left.')
_scheduler_switch(curr, task)
if curr is _last_task:
# We are in the tasklet we want to resume at this point.
return retval
def _init():
global _main_tasklet
global _global_task_id
global _squeue
global _last_task
_global_task_id = 0
_main_tasklet = coroutine.getcurrent()
_main_tasklet.__class__ = tasklet # XXX HAAAAAAAAAAAAAAAAAAAAACK
_last_task = _main_tasklet
tasklet._init.im_func(_main_tasklet, label='main')
_squeue = deque()
_scheduler_append(_main_tasklet)
_init()
|