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iso1dict begin
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(# Mutual exclusion -- for use with module sched) c n
() p n
(# A mutex has two pieces of state -- a 'locked' bit and a queue.) c n
(# When the mutex is not locked, the queue is empty.) N
(# Otherwise, the queue contains 0 or more \(function, argument\) pairs) N
(# representing functions \(or methods\) waiting to acquire the lock.) N
(# When the mutex is unlocked while the queue is not empty,) N
(# the first queue entry is removed and its function\(argument\) pair called,) N
(# implying it now has the lock.) N
(#) N
(# Of course, no multi-threading is implied -- hence the funny interface) N
(# for lock, where a function is called once the lock is aquired.) N
(#) N
(class) K
( mutex:) p n
() S 8 T () S
(#) c n
() p 8 T () S
(# Create a new mutex -- initially unlocked) c n
() p 8 T () S
(#) c n
() p 8 T () S
(def) K
( __init__\(self\):) p n
() S 8 T () S 16 T (self.locked = 0) N
() S 8 T () S 16 T (self.queue = []) N
() S 8 T () S
(#) c n
() p 8 T () S
(# Test the locked bit of the mutex) c n
() p 8 T () S
(#) c n
() p 8 T () S
(def) K
( test\(self\):) p n
() S 8 T () S 16 T () S
(return) K
( self.locked) p n
() S 8 T () S
(#) c n
() p 8 T () S
(# Atomic test-and-set -- grab the lock if it is not set,) c n
() p 8 T () S
(# return true if it succeeded) c n
() p 8 T () S
(#) c n
() p 8 T () S
(def) K
( testandset\(self\):) p n
() S 8 T () S 16 T () S
(if) K
( ) p
(not) K
( self.locked:) p n
() S 8 T () S 16 T () S 24 T (self.locked = 1) N
() S 8 T () S 16 T () S 24 T () S
(return) K
( 1) p n
() S 8 T () S 16 T () S
(else) K
(:) p n
() S 8 T () S 16 T () S 24 T () S
(return) K
( 0) p n
() S 8 T () S
(#) c n
() p 8 T () S
(# Lock a mutex, call the function with supplied argument) c n
() p 8 T () S
(# when it is acquired.) c n
() p 8 T () S
(# If the mutex is already locked, place function and argument) c n
() p 8 T () S
(# in the queue.) c n
() p 8 T () S
(#) c n
() p 8 T () S
(def) K
( lock\(self, function, argument\):) p n
() S 8 T () S 16 T (""") S
(Take it.) str
(""") p n
() S 8 T () S 16 T () S
(if) K
( self.testandset\(\):) p n
() S 8 T () S 16 T () S 24 T (function\(argument\)) N
() S 8 T () S 16 T () S
(else) K
(:) p n
() S 8 T () S 16 T () S 24 T (self.queue.append\(\(function, argument\)\)) N
() S 8 T () S
(#) c n
() p 8 T () S
(# Unlock a mutex. If the queue is not empty, call the next) c n
() p 8 T () S
(# function with its argument.) c n
() p 8 T () S
(#) c n
() p 8 T () S
(def) K
( unlock\(self\):) p n
() S 8 T () S 16 T (""") S
(Release.) str
(""") p n
() S 8 T () S 16 T () S
(if) K
( self.queue:) p n
() S 8 T () S 16 T () S 24 T (function, argument = self.queue[0]) N
() S 8 T () S 16 T () S 24 T () S
(del) K
( self.queue[0]) p n
() S 8 T () S 16 T () S 24 T (function\(argument\)) N
() S 8 T () S 16 T () S
(else) K
(:) p n
() S 8 T () S 16 T () S 24 T (self.locked = 0) N
() S 8 T () S
(#) c n
(mutex.py) (right) (1) title
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