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-- | This module defines a type for mutable, integer-valued counters.
-- Counters are non-negative, monotonically increasing values and can
-- be used to track e.g. the number of requests served since program
-- start. All operations on counters are thread-safe.
module System.Metrics.Counter
(
Counter
, new
, read
, inc
, add
) where
import qualified Data.Atomic as Atomic
import Data.Int (Int64)
import Prelude hiding (read)
-- | A mutable, integer-valued counter.
newtype Counter = C { unC :: Atomic.Atomic }
-- | Create a new, zero initialized, counter.
new :: IO Counter
new = C `fmap` Atomic.new 0
-- | Get the current value of the counter.
read :: Counter -> IO Int64
read = Atomic.read . unC
-- | Increase the counter by one.
inc :: Counter -> IO ()
inc counter = add counter 1
-- | Add the argument to the counter.
add :: Counter -> Int64 -> IO ()
add counter = Atomic.add (unC counter)
|
