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|
{-# LANGUAGE NumericUnderscores #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE NoImplicitPrelude #-}
-- | An EDSL to make working with concurrent in-process code a bit easier
-- to read.
--
-- This module is expected to be imported qualified as `Go`. Inspired by
-- Golang and Clojure's core.async.
--
-- \$example
-- : out go
module Control.Concurrent.Go
( -- * Running and forking
fork,
-- * Channels
Channel,
Mult,
chan,
read,
write,
mult,
tap,
-- * internal
sleep,
test,
main,
)
where
import Alpha
import qualified Biz.Cli as Cli
import Biz.Test ((@?=))
import qualified Biz.Test as Test
import qualified Control.Concurrent as Concurrent
import qualified Control.Concurrent.Chan.Unagi.Bounded as Chan
import qualified Data.Aeson as Aeson
import qualified System.IO.Unsafe as Unsafe
main :: IO ()
main =
Cli.main
<| Cli.Plan
{ Cli.help = help,
Cli.move = \_ -> pure (),
Cli.test = test,
Cli.tidy = pure
}
where
help =
[Cli.docopt|
go
Usage:
go test
|]
-- | A standard channel.
data Channel a = Channel
{ _in :: !(Chan.InChan a),
_out :: !(Chan.OutChan a),
_size :: !Int
}
instance Aeson.ToJSON (Channel a) where
toJSON c = Aeson.String ("#<channel " <> len c <> ">" :: Text)
where
len = show <. Unsafe.unsafePerformIO <. Chan.estimatedLength <. _in
-- | Starts a background process.
fork :: IO () -> IO Concurrent.ThreadId
fork = Concurrent.forkIO
-- | Make a new channel.
chan :: Int -> IO (Channel a)
chan n = do
(i, o) <- Chan.newChan n
pure <| Channel i o n
-- | A channel for broadcasting to multiple consumers. See 'mult'.
type Mult a = Chan.OutChan a
-- | Duplicates a channel, but then anything written to the source will
-- be available to both. This is like Clojure's `core.async/mult`
mult :: Channel a -> IO (Mult a)
mult = Chan.dupChan <. _in
-- | Read a value from a 'Mult'. This is like Clojure's `core.async/tap`.
--
-- You can use this to read from a channel in a background process, e.g.:
--
-- >>> c <- Go.chan
-- >>> Go.fork <. forever <| Go.mult c +> Go.tap +> print
tap :: Mult a -> IO a
tap = Chan.readChan
-- | Take from a channel. Blocks until a value is received.
read :: Channel a -> IO a
read = Chan.readChan <. _out
-- | Write to a channel. Blocks if the channel is full.
write :: Channel a -> a -> IO Bool
write = Chan.tryWriteChan <. _in
-- | Sleep for some number of milliseconds
sleep :: Int -> IO ()
sleep n = threadDelay <| n * 1_000
-- <|example
--
-- A simple example from ghci:
--
-- >>> import qualified Control.Concurrent.Go as Go
-- >>> c <- Go.chan :: IO (Go.Channel Text)
-- >>> Go.write c "test"
-- >>> Go.read c
-- "test"
--
-- An example with tap and mult:
--
-- >>> c <- Go.chan :: IO (Go.Channel Text)
-- >>> Go.write c "hi"
-- >>> Go.read c
-- "hi"
-- m <- Go.mult
-- >>> Go.fork <| forever (Go.tap m +> \t -> print ("one: " <> t))
-- ThreadId 810
-- >>> Go.fork <| forever (Go.tap m +> \t -> print ("two: " <> t))
-- ThreadId 825
-- >>> Go.write c "test"
-- "two: t"eosnte":
-- test"
--
-- The text is garbled because the actions are happening concurrently and
-- trying to serialize to write the output, but you get the idea.
--
test :: Test.Tree
test =
Test.group
"Control.Concurrent.Go"
[ Test.unit "simple example" <| do
c <- chan 1 :: IO (Channel Text)
recv <- mult c
_ <- fork (forever (tap recv +> pure))
ret <- write c "simple example"
True @?= ret,
Test.unit "simple MVar counter" <| do
counter <- newEmptyMVar
putMVar counter (0 :: Integer)
modifyMVar_ counter (pure <. (+ 1))
modifyMVar_ counter (pure <. (+ 1))
modifyMVar_ counter (pure <. (+ 1))
r <- takeMVar counter
r @?= 3
{- Why don't these work?
Test.unit "subscription counter" <| do
counter <- newEmptyMVar :: IO (MVar Integer)
putMVar counter 0
let dec = modifyMVar_ counter (\x -> pure <| x -1)
let inc = modifyMVar_ counter (pure <. (+ 1))
c <- chan 10 :: IO (Channel Bool)
c1 <- mult c
_ <- fork (forever (tap c1 +> bool dec inc))
_ <- write c True
_ <- write c True
_ <- write c True
threadDelay 1
r1 <- takeMVar counter
r1 @?= 3,
Test.unit "SPMC" <| do
out1 <- newEmptyMVar
out2 <- newEmptyMVar
putMVar out1 "init"
putMVar out2 "init"
c <- chan 10 :: IO (Channel Text)
c1 <- mult c
c2 <- mult c
_ <- fork <| forever (tap c1 +> swapMVar out1 >> pure ())
_ <- fork <| forever (tap c2 +> swapMVar out2 >> pure ())
_ <- write c "test1"
_ <- write c "test2"
threadDelay 1
r1 <- takeMVar out1
r2 <- takeMVar out2
r1 @?= r2
r1 @?= "test2",
Test.unit "Unagi SPMC" <| do
out1 <- newEmptyMVar
out2 <- newEmptyMVar
putMVar out1 "init"
putMVar out2 "init"
(i, _) <- Chan.newChan 10 :: IO (Chan.InChan Text, Chan.OutChan Text)
o1 <- Chan.dupChan i
o2 <- Chan.dupChan i
_ <- forkIO <| forever (Chan.readChan o1 +> swapMVar out1 >> pure ())
_ <- forkIO <| forever (Chan.readChan o2 +> swapMVar out2 >> pure ())
_ <- Chan.writeChan i "test1"
_ <- Chan.writeChan i "test2"
threadDelay 1
r1 <- takeMVar out1
r2 <- takeMVar out2
r1 @?= r2
r1 @?= "test2"
-}
]
|
