Control.Concurrent.Counter.Lifted.ST

Counters that support some atomic operations. Safe to use from multiple threads and likely faster than using IORef or TVar for the same operation (terms and conditions apply).

Documentation

data Counter s

Memory location that supports select few atomic operations.

Isomorphic to STRef s Int.

Instances

Eq (Counter s)

Pointer equality

Defined in Control.Concurrent.Counter.Lifted.ST

Methods

(==) :: Counter s -> Counter s -> Bool

(/=) :: Counter s -> Counter s -> Bool

Create

new :: Int -> ST s (Counter s)

Create new counter with initial value.

Read/write

get :: Counter s -> ST s Int

Atomically read the counter's value.

set :: Counter s -> Int -> ST s ()

Atomically assign new value to the counter.

cas

Arguments

:: Counter s

-> Int

Expected old value

-> Int

New value

-> ST s Int

Atomic compare and swap, i.e. write the new value if the current value matches the provided old value. Returns the value of the element before the operation

Arithmetic operations

add :: Counter s -> Int -> ST s Int

Atomically add an amount to the counter and return its old value.

sub :: Counter s -> Int -> ST s Int

Atomically subtract an amount from the counter and return its old value.

Bitwise operations

and :: Counter s -> Int -> ST s Int

Atomically combine old value with a new one via bitwise and. Returns old counter value.

or :: Counter s -> Int -> ST s Int

Atomically combine old value with a new one via bitwise or. Returns old counter value.

xor :: Counter s -> Int -> ST s Int

Atomically combine old value with a new one via bitwise xor. Returns old counter value.

nand :: Counter s -> Int -> ST s Int

Atomically combine old value with a new one via bitwise nand. Returns old counter value.