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
|
# -*- test-case-name: tubes.test.test_kit -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.
"""
Toolkit to alleviate some of the duplication in constructing your own IFount
and IDrain implementations.
"""
from zope.interface import implementer
from .itube import AlreadyUnpaused, IPause
@implementer(IPause)
class _Pause(object):
"""
Implementation of L{IPause} for L{Pauser}.
"""
def __init__(self, pauser):
"""
Construct a L{_Pause} from a L{Pauser}.
@param pauser: the L{Pauser} that created this L{_Pause}.
"""
self._friendPauser = pauser
self._alive = True
def unpause(self):
"""
Unpause this L{_Pause}, potentially invoking the C{actuallyResume}
callback from its L{Pauser}.
"""
if self._alive:
self._alive = False
self._friendPauser._pauses -= 1
if self._friendPauser._pauses == 0:
self._friendPauser._actuallyResume()
else:
raise AlreadyUnpaused()
class Pauser(object):
"""
Multiple parties may be interested in suppressing some ongoing concurrent
activity, each for their own purposes.
A L{Pauser} maintains the state associated with each of these independent
pauses, providing an object for each one, making it straightforward for you
to implement a high-level pause and resume API suitable for use from
multiple clients, in terms of low-level state change operations.
"""
def __init__(self, actuallyPause, actuallyResume):
"""
@param actuallyPause: a callable to be invoked when the underlying
system ought to transition from paused to unpaused.
@type actuallyPause: 0-argument callable
@param actuallyResume: a callable to be invoked when the underlying
system ought to transition from unpaused to paused.
@type actuallyPause: 0-argument callable
"""
self._actuallyPause = actuallyPause
self._actuallyResume = actuallyResume
self._pauses = 0
def pause(self):
"""
Pause something, getting an L{IPause} provider which can be used to
unpause it.
@return: a pause which will invoke the C{actuallyResume} callback if
it's the last one to be unpaused.
@rtype: L{IPause}
"""
self._pauses += 1
if self._pauses == 1:
self._actuallyPause()
return _Pause(self)
def __repr__(self):
return (
"<Pauser pauses={!r} actuallyPause={!r} actuallyResume={!r}>"
.format(self._pauses, self._actuallyPause, self._actuallyResume)
)
def beginFlowingTo(fount, drain):
"""
To correctly implement fount.flowTo you need to do certain things; do those
things here.
@param fount: The fount implementing flowTo.
@param drain: The drain flowTo was called with.
@return: the next fount in the chain.
"""
oldDrain = fount.drain
fount.drain = drain
if (
(oldDrain is not None) and (oldDrain is not drain) and
(oldDrain.fount is fount)
):
oldDrain.flowingFrom(None)
if drain is None:
return
return drain.flowingFrom(fount)
def beginFlowingFrom(drain, fount):
"""
To correctly implement drain.flowingFrom you need to do certian things; do
those things here.
@param drain: The drain implementing flowingFrom.
@param fount: The fount flowingFrom was called with.
@return: L{None}
"""
if fount is not None:
outType = fount.outputType
inType = drain.inputType
if outType is not None and inType is not None:
if not inType.isOrExtends(outType):
raise TypeError(
("the output of {fount}, {outType}, is not compatible "
"with the required input type of {drain}, {inType}")
.format(inType=inType, outType=outType,
fount=fount, drain=drain))
oldFount = drain.fount
drain.fount = fount
if (
(oldFount is not None) and (oldFount is not fount) and
(oldFount.drain is drain)
):
oldFount.flowTo(None)
@implementer(IPause)
class NoPause(object):
"""
A null implementation of L{IPause} that does nothing.
"""
def unpause(self):
"""
No-op.
"""
class OncePause(object):
"""
Pause a pauser once, unpause it if necessary.
"""
def __init__(self, pauser):
"""
Create a L{OncePause} with the given L{Pauser}.
"""
self._pauser = pauser
self._currentlyPaused = False
def __repr__(self):
return "<OncePause pauser={!r} paused={!r}>".format(
self._pauser, self._currentlyPaused
)
def pauseOnce(self):
"""
If this L{OncePause} is not currently paused, pause its pauser.
"""
if not self._currentlyPaused:
self._currentlyPaused = True
self._pause = self._pauser.pause()
def maybeUnpause(self):
"""
If this L{OncePause} is currently paused, unpause it.
"""
if self._currentlyPaused:
self._currentlyPaused = False
self._pause.unpause()
|
