"""Drop-in replacement for the thread module.
Meant to be used as a brain-dead substitute so that threaded code does
not need to be rewritten for when the thread module is not present.
Suggested usage is::
try:
import _thread
except ImportError:
import _dummy_thread as _thread
"""
# Exports only things specified by thread documentation;
# skipping obsolete synonyms allocate(), start_new(), exit_thread().
__all__ = ['error', 'start_new_thread', 'exit', 'get_ident', 'allocate_lock',
'interrupt_main', 'LockType', 'RLock']
# A dummy value
TIMEOUT_MAX = 2**31
# NOTE: this module can be imported early in the extension building process,
# and so top level imports of other modules should be avoided. Instead, all
# imports are done when needed on a function-by-function basis. Since threads
# are disabled, the import lock should not be an issue anyway (??).
error = RuntimeError
def start_new_thread(function, args, kwargs={}):
"""Dummy implementation of _thread.start_new_thread().
Compatibility is maintained by making sure that ``args`` is a
tuple and ``kwargs`` is a dictionary. If an exception is raised
and it is SystemExit (which can be done by _thread.exit()) it is
caught and nothing is done; all other exceptions are printed out
by using traceback.print_exc().
If the executed function calls interrupt_main the KeyboardInterrupt will be
raised when the function returns.
"""
if type(args) != type(tuple()):
raise TypeError("2nd arg must be a tuple")
if type(kwargs) != type(dict()):
raise TypeError("3rd arg must be a dict")
global _main
_main = False
try:
function(*args, **kwargs)
except SystemExit:
pass
except:
import traceback
traceback.print_exc()
_main = True
global _interrupt
if _interrupt:
_interrupt = False
raise KeyboardInterrupt
def exit():
"""Dummy implementation of _thread.exit()."""
raise SystemExit
def get_ident():
"""Dummy implementation of _thread.get_ident().
Since this module should only be used when _threadmodule is not
available, it is safe to assume that the current process is the
only thread. Thus a constant can be safely returned.
"""
return 1
def allocate_lock():
"""Dummy implementation of _thread.allocate_lock()."""
return LockType()
def stack_size(size=None):
"""Dummy implementation of _thread.stack_size()."""
if size is not None:
raise error("setting thread stack size not supported")
return 0
def _set_sentinel():
"""Dummy implementation of _thread._set_sentinel()."""
return LockType()
class LockType(object):
"""Class implementing dummy implementation of _thread.LockType.
Compatibility is maintained by maintaining self.locked_status
which is a boolean that stores the state of the lock. Pickling of
the lock, though, should not be done since if the _thread module is
then used with an unpickled ``lock()`` from here problems could
occur from this class not having atomic methods.
"""
def __init__(self):
self.locked_status = False
def acquire(self, waitflag=None, timeout=-1):
"""Dummy implementation of acquire().
For blocking calls, self.locked_status is automatically set to
True and returned appropriately based on value of
``waitflag``. If it is non-blocking, then the value is
actually checked and not set if it is already acquired. This
is all done so that threading.Condition's assert statements
aren't triggered and throw a little fit.
"""
if waitflag is None or waitflag:
self.locked_status = True
return True
else:
if not self.locked_status:
self.locked_status = True
return True
else:
if timeout > 0:
import time
time.sleep(timeout)
return False
__enter__ = acquire
def __exit__(self, typ, val, tb):
self.release()
def release(self):
"""Release the dummy lock."""
# XXX Perhaps shouldn't actually bother to test? Could lead
# to problems for complex, threaded code.
if not self.locked_status:
raise error
self.locked_status = False
return True
def locked(self):
return self.locked_status
def __repr__(self):
return "<%s %s.%s object at %s>" % (
"locked" if self.locked_status else "unlocked",
self.__class__.__module__,
self.__class__.__qualname__,
hex(id(self))
)
class RLock(LockType):
"""Dummy implementation of threading._RLock.
Re-entrant lock can be aquired multiple times and needs to be released
just as many times. This dummy implemention does not check wheter the
current thread actually owns the lock, but does accounting on the call
counts.
"""
def __init__(self):
super().__init__()
self._levels = 0
def acquire(self, waitflag=None, timeout=-1):
"""Aquire the lock, can be called multiple times in succession.
"""
locked = super().acquire(waitflag, timeout)
if locked:
self._levels += 1
return locked
def release(self):
"""Release needs to be called once for every call to acquire().
"""
if self._levels == 0:
raise error
if self._levels == 1:
super().release()
self._levels -= 1
# Used to signal that interrupt_main was called in a "thread"
_interrupt = False
# True when not executing in a "thread"
_main = True
def interrupt_main():
"""Set _interrupt flag to True to have start_new_thread raise
KeyboardInterrupt upon exiting."""
if _main:
raise KeyboardInterrupt
else:
global _interrupt
_interrupt = True
