Data.Atomics.Counter.Unboxed

Documentation

data AtomicCounter

type CTicket = Int

newCounter :: Int -> IO AtomicCounter

Create a new counter initialized to the given value.

readCounterForCAS :: AtomicCounter -> IO CTicket

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

readCounter :: AtomicCounter -> IO Int

Equivalent to readCounterForCAS followed by peekCTicket.

peekCTicket :: CTicket -> Int

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

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.

incrCounter :: Int -> AtomicCounter -> IO Int

Increment the counter by a given amount. Returns the value AFTER the increment (in contrast with the behavior of the underlying instruction on architectures like x86.)

Note that UNLIKE with boxed implementations of counters, where increment is based on CAS, this increment is O(1). Fetch-and-add does not require a retry loop like CAS.

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

An alternate version for when you don't care about the old value.