Metered concurrency: Difference between revisions

 

The interface for the counting semaphore is defined in an Ada package specification:

protected type Counting_Semaphore(Max : Positive) is

entry Acquire;

Lock_Count : Natural := 0;

end Counting_Semaphore;

The ''Acquire'' entry has a condition associated with it. A task can only execute the ''Acquire'' entry when ''Lock_Count'' is less than ''Max''. This is the key to making this structure behave as a counting semaphore. This condition, and all the other aspects of ''Counting_Semaphore'' are contained in the package body.

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end Counting_Semaphore;

We now need a set of tasks to properly call an instance of ''Counting_Semaphore''.

with Ada.Text_Io; use Ada.Text_Io;