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