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-- | This module defines a type for mutable, integer-valued gauges.
-- Gauges are variable values and can be used to track e.g. the
-- current number of concurrent connections. All operations on gauges
-- are thread-safe.
module System.Metrics.Gauge
(
Gauge
, new
, read
, inc
, dec
, add
, subtract
, set
) where
import qualified Data.Atomic as Atomic
import Data.Int (Int64)
import Prelude hiding (subtract, read)
-- | A mutable, integer-valued gauge.
newtype Gauge = C { unC :: Atomic.Atomic }
-- | Create a new, zero initialized, gauge.
new :: IO Gauge
new = C `fmap` Atomic.new 0
-- | Get the current value of the gauge.
read :: Gauge -> IO Int64
read = Atomic.read . unC
-- | Increase the gauge by one.
inc :: Gauge -> IO ()
inc gauge = add gauge 1
-- | Decrease the gauge by one.
dec :: Gauge -> IO ()
dec gauge = subtract gauge 1
-- | Increase the gauge by the given amount.
add :: Gauge -> Int64 -> IO ()
add gauge = Atomic.add (unC gauge)
-- | Decrease the gauge by the given amount.
subtract :: Gauge -> Int64 -> IO ()
subtract gauge = Atomic.subtract (unC gauge)
-- | Set the gauge to the given value.
set :: Gauge -> Int64 -> IO ()
set gauge = Atomic.write (unC gauge)
|
