def _syscall_wrapper(func, recalc_timeout, *args, **kwargs):
""" Wrapper function for syscalls that could fail due to EINTR.
All functions should be retried if there is time left in the timeout
in accordance with PEP 475. """
timeout = kwargs.get("timeout", None)
if timeout is None:
expires = None
recalc_timeout = False
else:
timeout = float(timeout)
if timeout < 0.0: # Timeout less than 0 treated as no timeout.
expires = None
else:
expires = monotonic() + timeout
if recalc_timeout and 'timeout' not in kwargs:
raise ValueError(
'Timeout must be in kwargs to be recalculated')
result = _SYSCALL_SENTINEL
while result is _SYSCALL_SENTINEL:
try:
result = func(*args, **kwargs)
# OSError is thrown by select.select
# IOError is thrown by select.epoll.poll
# select.error is thrown by select.poll.poll
# Aren't we thankful for Python 3.x rework for exceptions?
except (OSError, IOError, select.error) as e:
# select.error wasn't a subclass of OSError in the past.
errcode = None
if hasattr(e, 'errno') and e.errno is not None:
errcode = e.errno
elif hasattr(e, 'args'):
errcode = e.args[0]
# Also test for the Windows equivalent of EINTR.
is_interrupt = (errcode == errno.EINTR or (hasattr(errno, 'WSAEINTR') and
errcode == errno.WSAEINTR))
if is_interrupt:
if expires is not None:
current_time = monotonic()
if current_time > expires:
raise OSError(errno.ETIMEDOUT, 'Connection timed out')
if recalc_timeout:
kwargs["timeout"] = expires - current_time
continue
raise
return result
# Choose the best implementation, roughly:
# kqueue == devpoll == epoll > poll > select
# select() also can't accept a FD > FD_SETSIZE (usually around 1024)
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