Data.Atomics.Counter.IORef

This version uses a boxed IORef representation, but it can be somewhat cheaper than the Refence version because it uses raw CAS rather than full atomicModifyIORef.

Documentation

newtype AtomicCounter

Constructors

AtomicCounter (IORef Int)

type CTicket = Ticket Int

newCounter :: Int -> IO AtomicCounter

Create a new counter initialized to the given value.

incrCounter :: Int -> AtomicCounter -> IO Int

Try repeatedly until we successfully increment the counter by a given amount. Returns the original value of the counter (pre-increment).

readCounterForCAS :: AtomicCounter -> IO CTicket

Just like the Data.Atomics CAS interface, this routine returns an opaque ticket that can be used in CAS operations.

peekCTicket :: CTicket -> Int

Opaque tickets cannot be constructed, but they can be destructed into values.

readCounter :: AtomicCounter -> IO Int

Equivalent to readCounterForCAS followed by peekCTicket.

writeCounter :: AtomicCounter -> Int -> IO ()

Make a non-atomic write to the counter. No memory-barrier.

casCounter :: AtomicCounter -> CTicket -> Int -> IO (Bool, CTicket)

Compare and swap for the counter ADT.