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|
(.using
[library
[lux "*"
[abstract
[monad {"+" do}]]
[control
[pipe {"+" if>}]
["[0]" io {"+" IO}]
["[0]" try {"+" Try}]
["[0]" exception {"+" exception:}]]
[data
[text
["%" format {"+" format}]]
[collection
["[0]" queue {"+" Queue}]]]
[math
[number
["n" nat]
["i" int]]]
[type
abstract
["[0]" refinement]]]]
[//
["[0]" atom {"+" Atom}]
["[0]" async {"+" Async Resolver}]])
(type: State
(Record
[#max_positions Nat
#open_positions Int
#waiting_list (Queue (Resolver Any))]))
(abstract: .public Semaphore
(Atom State)
(def: most_positions_possible
(.nat (# i.interval top)))
(def: .public (semaphore initial_open_positions)
(-> Nat Semaphore)
(let [max_positions (n.min initial_open_positions
..most_positions_possible)]
(:abstraction (atom.atom [#max_positions max_positions
#open_positions (.int max_positions)
#waiting_list queue.empty]))))
(def: .public (wait! semaphore)
(Ex (_ k) (-> Semaphore (Async Any)))
(let [semaphore (:representation semaphore)
[signal sink] (: [(Async Any) (Resolver Any)]
(async.async []))]
(exec
(io.run!
(with_expansions [<had_open_position?> (as_is (the #open_positions) (i.> -1))]
(do io.monad
[[_ state'] (atom.update! (|>> (revised #open_positions --)
(if> [<had_open_position?>]
[]
[(revised #waiting_list (queue.end sink))]))
semaphore)]
(with_expansions [<go_ahead> (sink [])
<get_in_line> (in false)]
(if (|> state' <had_open_position?>)
<go_ahead>
<get_in_line>)))))
signal)))
(exception: .public (semaphore_is_maxed_out [max_positions Nat])
(exception.report
["Max Positions" (%.nat max_positions)]))
(def: .public (signal! semaphore)
(Ex (_ k) (-> Semaphore (Async (Try Int))))
(let [semaphore (:representation semaphore)]
(async.future
(do [! io.monad]
[[pre post] (atom.update! (function (_ state)
(if (i.= (.int (the #max_positions state))
(the #open_positions state))
state
(|> state
(revised #open_positions ++)
(revised #waiting_list queue.next))))
semaphore)]
(if (same? pre post)
(in (exception.except ..semaphore_is_maxed_out [(the #max_positions pre)]))
(do !
[_ (case (queue.front (the #waiting_list pre))
{.#None}
(in true)
{.#Some sink}
(sink []))]
(in {try.#Success (the #open_positions post)})))))))
)
(abstract: .public Mutex
Semaphore
(def: .public (mutex _)
(-> Any Mutex)
(:abstraction (semaphore 1)))
(def: acquire!
(-> Mutex (Async Any))
(|>> :representation ..wait!))
(def: release!
(-> Mutex (Async Any))
(|>> :representation ..signal!))
(def: .public (synchronize! mutex procedure)
(All (_ a) (-> Mutex (IO (Async a)) (Async a)))
(do async.monad
[_ (..acquire! mutex)
output (io.run! procedure)
_ (..release! mutex)]
(in output)))
)
(def: .public limit
(refinement.refiner (n.> 0)))
(type: .public Limit
(:~ (refinement.type limit)))
(abstract: .public Barrier
(Record
[#limit Limit
#count (Atom Nat)
#start_turnstile Semaphore
#end_turnstile Semaphore])
(def: .public (barrier limit)
(-> Limit Barrier)
(:abstraction [#limit limit
#count (atom.atom 0)
#start_turnstile (..semaphore 0)
#end_turnstile (..semaphore 0)]))
(def: (un_block! times turnstile)
(-> Nat Semaphore (Async Any))
(loop [step 0]
(if (n.< times step)
(do async.monad
[outcome (..signal! turnstile)]
(again (++ step)))
(# async.monad in []))))
(template [<phase> <update> <goal> <turnstile>]
[(def: (<phase> (^:representation barrier))
(-> Barrier (Async Any))
(do async.monad
[.let [limit (refinement.value (the #limit barrier))
goal <goal>
[_ count] (io.run! (atom.update! <update> (the #count barrier)))
reached? (n.= goal count)]]
(if reached?
(..un_block! (-- limit) (the <turnstile> barrier))
(..wait! (the <turnstile> barrier)))))]
[start! ++ limit #start_turnstile]
[end! -- 0 #end_turnstile]
)
(def: .public (block! barrier)
(-> Barrier (Async Any))
(do async.monad
[_ (..start! barrier)]
(..end! barrier)))
)
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