From 3bef51eec2299403467e621ae660cef3f9256ac8 Mon Sep 17 00:00:00 2001 From: Determinant Date: Tue, 17 Nov 2020 18:47:40 -0500 Subject: update frozen deps --- freezed_deps/ecdsa/_rwlock.py | 85 ------------------------------------------- 1 file changed, 85 deletions(-) delete mode 100644 freezed_deps/ecdsa/_rwlock.py (limited to 'freezed_deps/ecdsa/_rwlock.py') diff --git a/freezed_deps/ecdsa/_rwlock.py b/freezed_deps/ecdsa/_rwlock.py deleted file mode 100644 index e4ef78d..0000000 --- a/freezed_deps/ecdsa/_rwlock.py +++ /dev/null @@ -1,85 +0,0 @@ -# Copyright Mateusz Kobos, (c) 2011 -# https://code.activestate.com/recipes/577803-reader-writer-lock-with-priority-for-writers/ -# released under the MIT licence - -import threading - - -__author__ = "Mateusz Kobos" - - -class RWLock: - """ - Read-Write locking primitive - - Synchronization object used in a solution of so-called second - readers-writers problem. In this problem, many readers can simultaneously - access a share, and a writer has an exclusive access to this share. - Additionally, the following constraints should be met: - 1) no reader should be kept waiting if the share is currently opened for - reading unless a writer is also waiting for the share, - 2) no writer should be kept waiting for the share longer than absolutely - necessary. - - The implementation is based on [1, secs. 4.2.2, 4.2.6, 4.2.7] - with a modification -- adding an additional lock (C{self.__readers_queue}) - -- in accordance with [2]. - - Sources: - [1] A.B. Downey: "The little book of semaphores", Version 2.1.5, 2008 - [2] P.J. Courtois, F. Heymans, D.L. Parnas: - "Concurrent Control with 'Readers' and 'Writers'", - Communications of the ACM, 1971 (via [3]) - [3] http://en.wikipedia.org/wiki/Readers-writers_problem - """ - - def __init__(self): - """ - A lock giving an even higher priority to the writer in certain - cases (see [2] for a discussion). - """ - self.__read_switch = _LightSwitch() - self.__write_switch = _LightSwitch() - self.__no_readers = threading.Lock() - self.__no_writers = threading.Lock() - self.__readers_queue = threading.Lock() - - def reader_acquire(self): - self.__readers_queue.acquire() - self.__no_readers.acquire() - self.__read_switch.acquire(self.__no_writers) - self.__no_readers.release() - self.__readers_queue.release() - - def reader_release(self): - self.__read_switch.release(self.__no_writers) - - def writer_acquire(self): - self.__write_switch.acquire(self.__no_readers) - self.__no_writers.acquire() - - def writer_release(self): - self.__no_writers.release() - self.__write_switch.release(self.__no_readers) - - -class _LightSwitch: - """An auxiliary "light switch"-like object. The first thread turns on the - "switch", the last one turns it off (see [1, sec. 4.2.2] for details).""" - def __init__(self): - self.__counter = 0 - self.__mutex = threading.Lock() - - def acquire(self, lock): - self.__mutex.acquire() - self.__counter += 1 - if self.__counter == 1: - lock.acquire() - self.__mutex.release() - - def release(self, lock): - self.__mutex.acquire() - self.__counter -= 1 - if self.__counter == 0: - lock.release() - self.__mutex.release() -- cgit v1.2.3