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Semaphores

Semaphores for inter process locking and resource counting

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Semaphores

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Semaphores for inter process locking and resource counting. POSIX named semaphores and SysV semaphores are supported. Tested on Linux and MacOS.

Posix Named Semaphores

Creation and deletion

# create a semaphore (or attach to an existing one)
sem = NamedSemaphore("/testsem") 

# close / detach
close(sem)

# delete
delete!(sem)

# create (exclusive)
sem = NamedSemaphore("/testsem", true, true)

Operations

# get current value (Not supported on OSX)
count(sem)

# lock / decrement value / reserve resource (blocking call)
lock(sem)
@test count(sem) == 0

# try to lock / decrement / reserve (non blocking, returns true on success)
trylock(sem)

# unlock / increment value / return resource (blocking call)
unlock(sem)

SysV Semaphores

Creation and deletion

# create an array of 2 semaphores
tok = Semaphores.ftok(pwd(), 0)
sem = Semaphores.semcreate(tok, 2)

# delete
Semaphores.semrm(sem)

Operations

# set values of semaphores
a = Cushort[0,0]
Semaphores.semset(sem, a)
Semaphores.semget(sem, a)
@test sum(a) == 0

# atomic operations on semaphore sets
o = [Semaphores.SemBuf(0,1),Semaphores.SemBuf(1,1)]
Semaphores.semop(sem, o)

Resource Counter (based on SysV Semaphores)

Counting single resources

# create a resoruce counter for a single resource
rescounter = ResourceCounter(pwd())

# set counter value
reset(rescounter, 1)
@test count(rescounter,0) == 1

# change value by amount
change(rescounter, 2)
@test count(rescounter,0) == 3

Counting multiple resources

# create a resource counter for 2 resources
rescounter = ResourceCounter((pwd(),2), 2)

# set counter values
reset(rescounter, [1,2])
@test count(rescounter,0) == 1
@test count(rescounter,1) == 2

# change values by amount
change(rescounter, -1, 0)
@test count(rescounter,0) == 0
@test count(rescounter,1) == 2

First Commit

10/31/2017

Last Touched

over 2 years ago

Commits

8 commits

Requires:

Used By: