Class Locker

Placement in the overall structure

Module: guard
Base classes: None
Derived classes: Guard
Time of creation: Task 3
Files: locker.h

Description

The Locker class implements a lock that can be used to protect critical sections. However, the variable only indicates whether the critical section is free. Potentially necessary waiting, and protection for counting functionality, must be implemented elsewhere.

Public methods

Locker (): Constructor that initializes the lock variable (free).
void enter (): This method must be called when entering the critical section.
void retne (): This method must be called when leaving the critical section.
bool avail (): Indicates whether the critical section is free.

Notes

The methods of the class are so short that it is best to inline them.
Doubled enter or retne calls (i.e. entering the critical section from within the critical section or leaving it twice) are clear indications for implementation bugs in the operating system. It may be advisable to print an error message and halt the system in this case.