gr_threading_23.py

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"""Thread module emulating a subset of Java's threading model."""

# This started life as the threading.py module of Python 2.3
# It's been patched to fix a problem with join, where a KeyboardInterrupt
# caused a lock to be left in the acquired state.

import sys as _sys

try:
    import thread
except ImportError:
    del _sys.modules[__name__]
    raise

from StringIO import StringIO as _StringIO
from time import time as _time, sleep as _sleep
from traceback import print_exc as _print_exc

# Rename some stuff so "from threading import *" is safe
__all__ = ['activeCount', 'Condition', 'currentThread', 'enumerate', 'Event',
           'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Thread',
           'Timer', 'setprofile', 'settrace']

_start_new_thread = thread.start_new_thread
_allocate_lock = thread.allocate_lock
_get_ident = thread.get_ident
ThreadError = thread.error
del thread


# Debug support (adapted from ihooks.py).
# All the major classes here derive from _Verbose.  We force that to
# be a new-style class so that all the major classes here are new-style.
# This helps debugging (type(instance) is more revealing for instances
# of new-style classes).

_VERBOSE = False

if __debug__:

    class _Verbose(object):

        def __init__(self, verbose=None):
            if verbose is None:
                verbose = _VERBOSE
            self.__verbose = verbose

        def _note(self, format, *args):
            if self.__verbose:
                format = format % args
                format = "%s: %s\n" % (
                    currentThread().getName(), format)
                _sys.stderr.write(format)

else:
    # Disable this when using "python -O"
    class _Verbose(object):
        def __init__(self, verbose=None):
            pass
        def _note(self, *args):
            pass

# Support for profile and trace hooks

_profile_hook = None
_trace_hook = None

def setprofile(func):
    global _profile_hook
    _profile_hook = func

def settrace(func):
    global _trace_hook
    _trace_hook = func

# Synchronization classes

Lock = _allocate_lock

def RLock(*args, **kwargs):
    return _RLock(*args, **kwargs)

class _RLock(_Verbose):

    def __init__(self, verbose=None):
        _Verbose.__init__(self, verbose)
        self.__block = _allocate_lock()
        self.__owner = None
        self.__count = 0

    def __repr__(self):
        return "<%s(%s, %d)>" % (
                self.__class__.__name__,
                self.__owner and self.__owner.getName(),
                self.__count)

    def acquire(self, blocking=1):
        me = currentThread()
        if self.__owner is me:
            self.__count = self.__count + 1
            if __debug__:
                self._note("%s.acquire(%s): recursive success", self, blocking)
            return 1
        rc = self.__block.acquire(blocking)
        if rc:
            self.__owner = me
            self.__count = 1
            if __debug__:
                self._note("%s.acquire(%s): initial succes", self, blocking)
        else:
            if __debug__:
                self._note("%s.acquire(%s): failure", self, blocking)
        return rc

    def release(self):
        me = currentThread()
        assert self.__owner is me, "release() of un-acquire()d lock"
        self.__count = count = self.__count - 1
        if not count:
            self.__owner = None
            self.__block.release()
            if __debug__:
                self._note("%s.release(): final release", self)
        else:
            if __debug__:
                self._note("%s.release(): non-final release", self)

    # Internal methods used by condition variables

    def _acquire_restore(self, (count, owner)):
        self.__block.acquire()
        self.__count = count
        self.__owner = owner
        if __debug__:
            self._note("%s._acquire_restore()", self)

    def _release_save(self):
        if __debug__:
            self._note("%s._release_save()", self)
        count = self.__count
        self.__count = 0
        owner = self.__owner
        self.__owner = None
        self.__block.release()
        return (count, owner)

    def _is_owned(self):
        return self.__owner is currentThread()


def Condition(*args, **kwargs):
    return _Condition(*args, **kwargs)

class _Condition(_Verbose):

    def __init__(self, lock=None, verbose=None):
        _Verbose.__init__(self, verbose)
        if lock is None:
            lock = RLock()
        self.__lock = lock
        # Export the lock's acquire() and release() methods
        self.acquire = lock.acquire
        self.release = lock.release
        # If the lock defines _release_save() and/or _acquire_restore(),
        # these override the default implementations (which just call
        # release() and acquire() on the lock).  Ditto for _is_owned().
        try:
            self._release_save = lock._release_save
        except AttributeError:
            pass
        try:
            self._acquire_restore = lock._acquire_restore
        except AttributeError:
            pass
        try:
            self._is_owned = lock._is_owned
        except AttributeError:
            pass
        self.__waiters = []

    def __repr__(self):
        return "<Condition(%s, %d)>" % (self.__lock, len(self.__waiters))

    def _release_save(self):
        self.__lock.release()           # No state to save

    def _acquire_restore(self, x):
        self.__lock.acquire()           # Ignore saved state

    def _is_owned(self):
        # Return True if lock is owned by currentThread.
        # This method is called only if __lock doesn't have _is_owned().
        if self.__lock.acquire(0):
            self.__lock.release()
            return False
        else:
            return True

    def wait(self, timeout=None):
        currentThread() # for side-effect
        assert self._is_owned(), "wait() of un-acquire()d lock"
        waiter = _allocate_lock()
        waiter.acquire()
        self.__waiters.append(waiter)
        saved_state = self._release_save()
        try:    # restore state no matter what (e.g., KeyboardInterrupt)
            if timeout is None:
                waiter.acquire()
                if __debug__:
                    self._note("%s.wait(): got it", self)
            else:
                # Balancing act:  We can't afford a pure busy loop, so we
                # have to sleep; but if we sleep the whole timeout time,
                # we'll be unresponsive.  The scheme here sleeps very
                # little at first, longer as time goes on, but never longer
                # than 20 times per second (or the timeout time remaining).
                endtime = _time() + timeout
                delay = 0.0005 # 500 us -> initial delay of 1 ms
                while True:
                    gotit = waiter.acquire(0)
                    if gotit:
                        break
                    remaining = endtime - _time()
                    if remaining <= 0:
                        break
                    delay = min(delay * 2, remaining, .05)
                    _sleep(delay)
                if not gotit:
                    if __debug__:
                        self._note("%s.wait(%s): timed out", self, timeout)
                    try:
                        self.__waiters.remove(waiter)
                    except ValueError:
                        pass
                else:
                    if __debug__:
                        self._note("%s.wait(%s): got it", self, timeout)
        finally:
            self._acquire_restore(saved_state)

    def notify(self, n=1):
        currentThread() # for side-effect
        assert self._is_owned(), "notify() of un-acquire()d lock"
        __waiters = self.__waiters
        waiters = __waiters[:n]
        if not waiters:
            if __debug__:
                self._note("%s.notify(): no waiters", self)
            return
        self._note("%s.notify(): notifying %d waiter%s", self, n,
                   n!=1 and "s" or "")
        for waiter in waiters:
            waiter.release()
            try:
                __waiters.remove(waiter)
            except ValueError:
                pass

    def notifyAll(self):
        self.notify(len(self.__waiters))


def Semaphore(*args, **kwargs):
    return _Semaphore(*args, **kwargs)

class _Semaphore(_Verbose):

    # After Tim Peters' semaphore class, but not quite the same (no maximum)

    def __init__(self, value=1, verbose=None):
        assert value >= 0, "Semaphore initial value must be >= 0"
        _Verbose.__init__(self, verbose)
        self.__cond = Condition(Lock())
        self.__value = value

    def acquire(self, blocking=1):
        rc = False
        self.__cond.acquire()
        while self.__value == 0:
            if not blocking:
                break
            if __debug__:
                self._note("%s.acquire(%s): blocked waiting, value=%s",
                           self, blocking, self.__value)
            self.__cond.wait()
        else:
            self.__value = self.__value - 1
            if __debug__:
                self._note("%s.acquire: success, value=%s",
                           self, self.__value)
            rc = True
        self.__cond.release()
        return rc

    def release(self):
        self.__cond.acquire()
        self.__value = self.__value + 1
        if __debug__:
            self._note("%s.release: success, value=%s",
                       self, self.__value)
        self.__cond.notify()
        self.__cond.release()


def BoundedSemaphore(*args, **kwargs):
    return _BoundedSemaphore(*args, **kwargs)

class _BoundedSemaphore(_Semaphore):
    """Semaphore that checks that # releases is <= # acquires"""
    def __init__(self, value=1, verbose=None):
        _Semaphore.__init__(self, value, verbose)
        self._initial_value = value

    def release(self):
        if self._Semaphore__value >= self._initial_value:
            raise ValueError, "Semaphore released too many times"
        return _Semaphore.release(self)


def Event(*args, **kwargs):
    return _Event(*args, **kwargs)

class _Event(_Verbose):

    # After Tim Peters' event class (without is_posted())

    def __init__(self, verbose=None):
        _Verbose.__init__(self, verbose)
        self.__cond = Condition(Lock())
        self.__flag = False

    def isSet(self):
        return self.__flag

    def set(self):
        self.__cond.acquire()
        try:
            self.__flag = True
            self.__cond.notifyAll()
        finally:
            self.__cond.release()

    def clear(self):
        self.__cond.acquire()
        try:
            self.__flag = False
        finally:
            self.__cond.release()

    def wait(self, timeout=None):
        self.__cond.acquire()
        try:
            if not self.__flag:
                self.__cond.wait(timeout)
        finally:
            self.__cond.release()

# Helper to generate new thread names
_counter = 0
def _newname(template="Thread-%d"):
    global _counter
    _counter = _counter + 1
    return template % _counter