Move document sidebar entries extraction to document.View
This way other modules can benefit from the same logic. Also make use
of the sidebar.getSidebarMenu method so that getMenusForScope is no
longer specific to full menu's.
Patch by: Sverre Rabbelier
"""
Synchronization primitives:
- reader-writer lock (preference to writers)
(Contributed to Django by eugene@lazutkin.com)
"""
try:
import threading
except ImportError:
import dummy_threading as threading
class RWLock:
"""
Classic implementation of reader-writer lock with preference to writers.
Readers can access a resource simultaneously.
Writers get an exclusive access.
API is self-descriptive:
reader_enters()
reader_leaves()
writer_enters()
writer_leaves()
"""
def __init__(self):
self.mutex = threading.RLock()
self.can_read = threading.Semaphore(0)
self.can_write = threading.Semaphore(0)
self.active_readers = 0
self.active_writers = 0
self.waiting_readers = 0
self.waiting_writers = 0
def reader_enters(self):
self.mutex.acquire()
try:
if self.active_writers == 0 and self.waiting_writers == 0:
self.active_readers += 1
self.can_read.release()
else:
self.waiting_readers += 1
finally:
self.mutex.release()
self.can_read.acquire()
def reader_leaves(self):
self.mutex.acquire()
try:
self.active_readers -= 1
if self.active_readers == 0 and self.waiting_writers != 0:
self.active_writers += 1
self.waiting_writers -= 1
self.can_write.release()
finally:
self.mutex.release()
def writer_enters(self):
self.mutex.acquire()
try:
if self.active_writers == 0 and self.waiting_writers == 0 and self.active_readers == 0:
self.active_writers += 1
self.can_write.release()
else:
self.waiting_writers += 1
finally:
self.mutex.release()
self.can_write.acquire()
def writer_leaves(self):
self.mutex.acquire()
try:
self.active_writers -= 1
if self.waiting_writers != 0:
self.active_writers += 1
self.waiting_writers -= 1
self.can_write.release()
elif self.waiting_readers != 0:
t = self.waiting_readers
self.waiting_readers = 0
self.active_readers += t
while t > 0:
self.can_read.release()
t -= 1
finally:
self.mutex.release()