atomics

func NewCounter ¶

func NewCounter[T uint32 | uint64](maximum T) Counter

NewCounter returns a function that atomically counts to a given maximum upon call.

When the resulting closure is called the function enters a for-loop that atomically loads the value at address &counter. This value is then compared against the given maximum. If the value is greater than or equal to the given maximum this function returns the current value and true to signify completion.

If the value at address &counter at time of the atomic load is less than the given maximum this function attempts to swap the value at address &counter with a value equal to the previous value +1. Upon successfully setting a new value this function returns the new value and false to signify that the counter has not yet reached the given maximum.

The use of compare-and-swap ensures that if the value at address &counter has not yet changed, the function atomically replaces it with the previous value +1. If the compare-and-swap fails and returns false then another agent as modified the value at address &counter. In this case the function rewinds to the beginning of the for-loop for another counter increment attempt.