72 lines
1.7 KiB
C
72 lines
1.7 KiB
C
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#include "semp.h"
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#include <sys/sem.h>
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/**************************************************************************
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* Authors: Gary Fleming, Amber McCloughan
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* Class: CIS452 - Operating Systems Concepts
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* Professor: Dr. Greg Wolffe
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* Date: 3/14/2019
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*
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* Library of functions for synchronization
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* using semaphores. Includes the classic
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* wait() and signal() functions, as well as
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* functions for initializing and deleting
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* semaphores.
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*
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* @see semp.h for function definitions.
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***************************************************************************/
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/**
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* Initialize a semaphore. The ID for using the other
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* functions is returned by the function.
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*
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* @param value, the value to initialize the semaphore to.
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* @return semId, the ID of the semaphore.
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*/
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int semp_init(int value)
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{
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int semId = semget(IPC_PRIVATE, 1, 00600);
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semctl(semId, 0, SETVAL, value);
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return semId;
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}
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/**
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* Attempts to wait on the semaphore. Subtracts 1 from
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* the internal value of the semaphore.
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*
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* @param semId, the ID of the semaphore.
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* @return 0 if there were no errors.
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*/
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int semp_wait(int semId)
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{
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struct sembuf lock = {0, -1, SEM_UNDO};
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semop(semId, &lock, 1);
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return 0;
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}
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/**
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* Signals the semaphore. Adds 1 to the internal value
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* of the semaphore.
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*
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* @param semId, the ID of the semaphore.
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* @return 0 if there were no errors.
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*/
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int semp_signal(int semId)
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{
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struct sembuf unlock = {0, 1, SEM_UNDO};
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semop(semId, &unlock, 1);
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return 0;
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}
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/**
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* Deletes the semaphore.
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*
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* @param semId, the ID of the semaphore.
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* @return 0 if there were no errors.
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*/
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int semp_destroy(int semId)
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{
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semctl(semId, 0, IPC_RMID);
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return 0;
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}
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