Library import 16 (#2433)

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1 files changed, 242 insertions, 0 deletions

diff --git a/contrib/tools/python3/Lib/_threading_local.py b/contrib/tools/python3/Lib/_threading_local.py
new file mode 100644
index 0000000000..b006d76c4e
--- /dev/null
+++ b/contrib/tools/python3/Lib/_threading_local.py
@@ -0,0 +1,242 @@
+"""Thread-local objects.
+
+(Note that this module provides a Python version of the threading.local
+ class.  Depending on the version of Python you're using, there may be a
+ faster one available.  You should always import the `local` class from
+ `threading`.)
+
+Thread-local objects support the management of thread-local data.
+If you have data that you want to be local to a thread, simply create
+a thread-local object and use its attributes:
+
+  >>> mydata = local()
+  >>> mydata.number = 42
+  >>> mydata.number
+  42
+
+You can also access the local-object's dictionary:
+
+  >>> mydata.__dict__
+  {'number': 42}
+  >>> mydata.__dict__.setdefault('widgets', [])
+  []
+  >>> mydata.widgets
+  []
+
+What's important about thread-local objects is that their data are
+local to a thread. If we access the data in a different thread:
+
+  >>> log = []
+  >>> def f():
+  ...     items = sorted(mydata.__dict__.items())
+  ...     log.append(items)
+  ...     mydata.number = 11
+  ...     log.append(mydata.number)
+
+  >>> import threading
+  >>> thread = threading.Thread(target=f)
+  >>> thread.start()
+  >>> thread.join()
+  >>> log
+  [[], 11]
+
+we get different data.  Furthermore, changes made in the other thread
+don't affect data seen in this thread:
+
+  >>> mydata.number
+  42
+
+Of course, values you get from a local object, including a __dict__
+attribute, are for whatever thread was current at the time the
+attribute was read.  For that reason, you generally don't want to save
+these values across threads, as they apply only to the thread they
+came from.
+
+You can create custom local objects by subclassing the local class:
+
+  >>> class MyLocal(local):
+  ...     number = 2
+  ...     def __init__(self, /, **kw):
+  ...         self.__dict__.update(kw)
+  ...     def squared(self):
+  ...         return self.number ** 2
+
+This can be useful to support default values, methods and
+initialization.  Note that if you define an __init__ method, it will be
+called each time the local object is used in a separate thread.  This
+is necessary to initialize each thread's dictionary.
+
+Now if we create a local object:
+
+  >>> mydata = MyLocal(color='red')
+
+Now we have a default number:
+
+  >>> mydata.number
+  2
+
+an initial color:
+
+  >>> mydata.color
+  'red'
+  >>> del mydata.color
+
+And a method that operates on the data:
+
+  >>> mydata.squared()
+  4
+
+As before, we can access the data in a separate thread:
+
+  >>> log = []
+  >>> thread = threading.Thread(target=f)
+  >>> thread.start()
+  >>> thread.join()
+  >>> log
+  [[('color', 'red')], 11]
+
+without affecting this thread's data:
+
+  >>> mydata.number
+  2
+  >>> mydata.color
+  Traceback (most recent call last):
+  ...
+  AttributeError: 'MyLocal' object has no attribute 'color'
+
+Note that subclasses can define slots, but they are not thread
+local. They are shared across threads:
+
+  >>> class MyLocal(local):
+  ...     __slots__ = 'number'
+
+  >>> mydata = MyLocal()
+  >>> mydata.number = 42
+  >>> mydata.color = 'red'
+
+So, the separate thread:
+
+  >>> thread = threading.Thread(target=f)
+  >>> thread.start()
+  >>> thread.join()
+
+affects what we see:
+
+  >>> mydata.number
+  11
+
+>>> del mydata
+"""
+
+from weakref import ref
+from contextlib import contextmanager
+
+__all__ = ["local"]
+
+# We need to use objects from the threading module, but the threading
+# module may also want to use our `local` class, if support for locals
+# isn't compiled in to the `thread` module.  This creates potential problems
+# with circular imports.  For that reason, we don't import `threading`
+# until the bottom of this file (a hack sufficient to worm around the
+# potential problems).  Note that all platforms on CPython do have support
+# for locals in the `thread` module, and there is no circular import problem
+# then, so problems introduced by fiddling the order of imports here won't
+# manifest.
+
+class _localimpl:
+    """A class managing thread-local dicts"""
+    __slots__ = 'key', 'dicts', 'localargs', 'locallock', '__weakref__'
+
+    def __init__(self):
+        # The key used in the Thread objects' attribute dicts.
+        # We keep it a string for speed but make it unlikely to clash with
+        # a "real" attribute.
+        self.key = '_threading_local._localimpl.' + str(id(self))
+        # { id(Thread) -> (ref(Thread), thread-local dict) }
+        self.dicts = {}
+
+    def get_dict(self):
+        """Return the dict for the current thread. Raises KeyError if none
+        defined."""
+        thread = current_thread()
+        return self.dicts[id(thread)][1]
+
+    def create_dict(self):
+        """Create a new dict for the current thread, and return it."""
+        localdict = {}
+        key = self.key
+        thread = current_thread()
+        idt = id(thread)
+        def local_deleted(_, key=key):
+            # When the localimpl is deleted, remove the thread attribute.
+            thread = wrthread()
+            if thread is not None:
+                del thread.__dict__[key]
+        def thread_deleted(_, idt=idt):
+            # When the thread is deleted, remove the local dict.
+            # Note that this is suboptimal if the thread object gets
+            # caught in a reference loop. We would like to be called
+            # as soon as the OS-level thread ends instead.
+            local = wrlocal()
+            if local is not None:
+                dct = local.dicts.pop(idt)
+        wrlocal = ref(self, local_deleted)
+        wrthread = ref(thread, thread_deleted)
+        thread.__dict__[key] = wrlocal
+        self.dicts[idt] = wrthread, localdict
+        return localdict
+
+
+@contextmanager
+def _patch(self):
+    impl = object.__getattribute__(self, '_local__impl')
+    try:
+        dct = impl.get_dict()
+    except KeyError:
+        dct = impl.create_dict()
+        args, kw = impl.localargs
+        self.__init__(*args, **kw)
+    with impl.locallock:
+        object.__setattr__(self, '__dict__', dct)
+        yield
+
+
+class local:
+    __slots__ = '_local__impl', '__dict__'
+
+    def __new__(cls, /, *args, **kw):
+        if (args or kw) and (cls.__init__ is object.__init__):
+            raise TypeError("Initialization arguments are not supported")
+        self = object.__new__(cls)
+        impl = _localimpl()
+        impl.localargs = (args, kw)
+        impl.locallock = RLock()
+        object.__setattr__(self, '_local__impl', impl)
+        # We need to create the thread dict in anticipation of
+        # __init__ being called, to make sure we don't call it
+        # again ourselves.
+        impl.create_dict()
+        return self
+
+    def __getattribute__(self, name):
+        with _patch(self):
+            return object.__getattribute__(self, name)
+
+    def __setattr__(self, name, value):
+        if name == '__dict__':
+            raise AttributeError(
+                "%r object attribute '__dict__' is read-only"
+                % self.__class__.__name__)
+        with _patch(self):
+            return object.__setattr__(self, name, value)
+
+    def __delattr__(self, name):
+        if name == '__dict__':
+            raise AttributeError(
+                "%r object attribute '__dict__' is read-only"
+                % self.__class__.__name__)
+        with _patch(self):
+            return object.__delattr__(self, name)
+
+
+from threading import current_thread, RLock