Add BaseForm class to soc.views.helper.forms module (work in progress). This changes the way as_table function displays the form (for more information have a look into doc string). BaseForm is going to be used for all forms in Melange in future. Right now it's still missing custom form errors labels and "required" text in 3rd column, but that's added as TODO and I'm working on it.
Patch by: Pawel Solyga
Review by: to-be-reviewed
"""
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()