Hide keyboard shortcuts

Hot-keys on this page

r m x p   toggle line displays

j k   next/prev highlighted chunk

0   (zero) top of page

1   (one) first highlighted chunk

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

# -*- coding: utf-8 -*- 

# Copyright 2017 Christoph Reiter 

# 

# This library is free software; you can redistribute it and/or 

# modify it under the terms of the GNU Lesser General Public 

# License as published by the Free Software Foundation; either 

# version 2.1 of the License, or (at your option) any later version. 

# 

# This library is distributed in the hope that it will be useful, 

# but WITHOUT ANY WARRANTY; without even the implied warranty of 

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 

# Lesser General Public License for more details. 

# 

# You should have received a copy of the GNU Lesser General Public 

# License along with this library; if not, see <http://www.gnu.org/licenses/>. 

 

from __future__ import print_function 

 

import os 

import sys 

import socket 

import signal 

import ctypes 

import threading 

from contextlib import closing, contextmanager 

 

 

def ensure_socket_not_inheritable(sock): 

"""Ensures that the socket is not inherited by child processes 

 

Raises: 

EnvironmentError 

NotImplementedError: With Python <3.4 on Windows 

""" 

 

if hasattr(sock, "set_inheritable"): 

sock.set_inheritable(False) 

else: 

try: 

import fcntl 

except ImportError: 

raise NotImplementedError( 

"Not implemented for older Python on Windows") 

else: 

fd = sock.fileno() 

flags = fcntl.fcntl(fd, fcntl.F_GETFD) 

fcntl.fcntl(fd, fcntl.F_SETFD, flags | fcntl.FD_CLOEXEC) 

 

 

_wakeup_fd_is_active = False 

"""Since we can't check if set_wakeup_fd() is already used for nested event 

loops without introducing a race condition we keep track of it globally. 

""" 

 

 

@contextmanager 

def wakeup_on_signal(): 

"""A decorator for functions which create a glib event loop to keep 

Python signal handlers working while the event loop is idling. 

 

In case an OS signal is received will wake the default event loop up 

shortly so that any registered Python signal handlers registered through 

signal.signal() can run. 

 

Works on Windows but needs Python 3.5+. 

 

In case the wrapped function is not called from the main thread it will be 

called as is and it will not wake up the default loop for signals. 

""" 

 

global _wakeup_fd_is_active 

 

if _wakeup_fd_is_active: 

yield 

return 

 

from gi.repository import GLib 

 

# On Windows only Python 3.5+ supports passing sockets to set_wakeup_fd 

set_wakeup_fd_supports_socket = ( 

os.name != "nt" or sys.version_info[:2] >= (3, 5)) 

# On Windows only Python 3 has an implementation of socketpair() 

has_socketpair = hasattr(socket, "socketpair") 

 

if not has_socketpair or not set_wakeup_fd_supports_socket: 

yield 

return 

 

read_socket, write_socket = socket.socketpair() 

with closing(read_socket), closing(write_socket): 

 

for sock in [read_socket, write_socket]: 

sock.setblocking(False) 

ensure_socket_not_inheritable(sock) 

 

try: 

orig_fd = signal.set_wakeup_fd(write_socket.fileno()) 

except ValueError: 

# Raised in case this is not the main thread -> give up. 

yield 

return 

else: 

_wakeup_fd_is_active = True 

 

def signal_notify(source, condition): 

if condition & GLib.IO_IN: 

try: 

return bool(read_socket.recv(1)) 

except EnvironmentError as e: 

print(e) 

return False 

return True 

else: 

return False 

 

try: 

if os.name == "nt": 

channel = GLib.IOChannel.win32_new_socket( 

read_socket.fileno()) 

else: 

channel = GLib.IOChannel.unix_new(read_socket.fileno()) 

 

source_id = GLib.io_add_watch( 

channel, 

GLib.PRIORITY_DEFAULT, 

(GLib.IOCondition.IN | GLib.IOCondition.HUP | 

GLib.IOCondition.NVAL | GLib.IOCondition.ERR), 

signal_notify) 

try: 

yield 

finally: 

GLib.source_remove(source_id) 

finally: 

write_fd = signal.set_wakeup_fd(orig_fd) 

if write_fd != write_socket.fileno(): 

# Someone has called set_wakeup_fd while func() was active, 

# so let's re-revert again. 

signal.set_wakeup_fd(write_fd) 

_wakeup_fd_is_active = False 

 

 

def create_pythonapi(): 

# We need our own instance of ctypes.pythonapi so we don't modify the 

# global shared one. Adapted from the ctypes source. 

if os.name == "nt": 

return ctypes.PyDLL("python dll", None, sys.dllhandle) 

elif sys.platform == "cygwin": 

return ctypes.PyDLL("libpython%d.%d.dll" % sys.version_info[:2]) 

else: 

return ctypes.PyDLL(None) 

 

 

pydll = create_pythonapi() 

PyOS_getsig = pydll.PyOS_getsig 

PyOS_getsig.restype = ctypes.c_void_p 

PyOS_getsig.argtypes = [ctypes.c_int] 

 

# We save the signal pointer so we can detect if glib has changed the 

# signal handler behind Python's back (GLib.unix_signal_add) 

if signal.getsignal(signal.SIGINT) is signal.default_int_handler: 

startup_sigint_ptr = PyOS_getsig(signal.SIGINT) 

else: 

# Something has set the handler before import, we can't get a ptr 

# for the default handler so make sure the pointer will never match. 

startup_sigint_ptr = -1 

 

 

def sigint_handler_is_default(): 

"""Returns if on SIGINT the default Python handler would be called""" 

 

return (signal.getsignal(signal.SIGINT) is signal.default_int_handler and 

PyOS_getsig(signal.SIGINT) == startup_sigint_ptr) 

 

 

@contextmanager 

def sigint_handler_set_and_restore_default(handler): 

"""Context manager for saving/restoring the SIGINT handler default state. 

 

Will only restore the default handler again if the handler is not changed 

while the context is active. 

""" 

 

assert sigint_handler_is_default() 

 

signal.signal(signal.SIGINT, handler) 

sig_ptr = PyOS_getsig(signal.SIGINT) 

try: 

yield 

finally: 

if signal.getsignal(signal.SIGINT) is handler and \ 

PyOS_getsig(signal.SIGINT) == sig_ptr: 

signal.signal(signal.SIGINT, signal.default_int_handler) 

 

 

def is_main_thread(): 

"""Returns True in case the function is called from the main thread""" 

 

return threading.current_thread().name == "MainThread" 

 

 

_callback_stack = [] 

_sigint_called = False 

 

 

@contextmanager 

def register_sigint_fallback(callback): 

"""Installs a SIGINT signal handler in case the default Python one is 

active which calls 'callback' in case the signal occurs. 

 

Only does something if called from the main thread. 

 

In case of nested context managers the signal handler will be only 

installed once and the callbacks will be called in the reverse order 

of their registration. 

 

The old signal handler will be restored in case no signal handler is 

registered while the context is active. 

""" 

 

# To handle multiple levels of event loops we need to call the last 

# callback first, wait until the inner most event loop returns control 

# and only then call the next callback, and so on... until we 

# reach the outer most which manages the signal handler and raises 

# in the end 

 

global _callback_stack, _sigint_called 

 

if not is_main_thread(): 

yield 

return 

 

if not sigint_handler_is_default(): 

if _callback_stack: 

# This is an inner event loop, append our callback 

# to the stack so the parent context can call it. 

_callback_stack.append(callback) 

try: 

yield 

finally: 

cb = _callback_stack.pop() 

if _sigint_called: 

cb() 

else: 

# There is a signal handler set by the user, just do nothing 

yield 

return 

 

_sigint_called = False 

 

def sigint_handler(sig_num, frame): 

global _callback_stack, _sigint_called 

 

if _sigint_called: 

return 

_sigint_called = True 

_callback_stack.pop()() 

 

_callback_stack.append(callback) 

try: 

with sigint_handler_set_and_restore_default(sigint_handler): 

yield 

finally: 

if _sigint_called: 

signal.default_int_handler(signal.SIGINT, None) 

else: 

_callback_stack.pop()