*
* Author: S. Piccardi Dec. 2002
*
- * $Id: Mutex.c,v 1.2 2002/12/03 22:30:11 piccardi Exp $
+ * $Id: Mutex.c,v 1.7 2003/05/02 09:55:14 piccardi Exp $
*
*****************************************************************************/
#include <sys/sem.h> /* IPC semaphore declarations */
*/
int MutexFind(key_t ipc_key)
{
- return semget(ipc_key,1,0);
+ return semget(ipc_key, 1, 0);
}
/*
* Function MutexRead: read the current value of the mutex/semaphore
{
return semop(sem_id, &sem_ulock, 1);
}
+/*
+ * Function MutexRemove: remove a mutex/semaphore
+ *
+ * Input: a semaphore id #
+ * Return: return code of semctl
+ */
+int MutexRemove(int sem_id)
+{
+ return semctl(sem_id, 0, IPC_RMID);
+}
+/*****************************************************************************
+ *
+ * File locking mutex
+ *
+ * Create a mutex usinf file locking. Use file locking to lock a file
+ * as a mutex request, and unlock it as a mutex release.
+ *
+ * Author: S. Piccardi Dec. 2002
+ *
+ *****************************************************************************/
+/*
+ * Function CreateMutex: Create a mutex using file locking.
+ *
+ * Open a new lock file (creating it if not existent, and giving error
+ * otherwise). Is a simple wrapper for open.
+ *
+ * Input: a filename
+ * Output: a file descriptor (>0 OK, -1 KO)
+ */
+int CreateMutex(const char *path_name)
+{
+ return open(path_name, O_EXCL|O_CREAT);
+}
+/*
+ * Function UnlockMutex: unlock a file.
+ *
+ * Open a lock file (failing if not existent). Is a simple wrapper for
+ * open.
+ *
+ * Input: a filename
+ * Output: a return code (>0 OK, -1 KO)
+ */
+int FindMutex(const char *path_name)
+{
+ return open(path_name, O_RDWR);
+}
+/*
+ * Function LockMutex: lock mutex using file locking.
+ *
+ * Input: a mutex (i.e. a file descriptor)
+ * Output: a return code (0 OK, -1 KO)
+ */
+int LockMutex(int fd)
+{
+ struct flock lock; /* file lock structure */
+ /* first open the file (creating it if not existent) */
+ /* set flock structure */
+ lock.l_type = F_WRLCK; /* set type: read or write */
+ lock.l_whence = SEEK_SET; /* start from the beginning of the file */
+ lock.l_start = 0; /* set the start of the locked region */
+ lock.l_len = 0; /* set the length of the locked region */
+ /* do locking */
+ return fcntl(fd, F_SETLKW, &lock);
+}
+/*
+ * Function UnlockMutex: unlock a file.
+ *
+ * Input: a mutex (i.e. a file descriptor)
+ * Output: a return code (0 OK, -1 KO)
+ */
+int UnlockMutex(int fd)
+{
+ struct flock lock; /* file lock structure */
+ /* set flock structure */
+ lock.l_type = F_UNLCK; /* set type: unlock */
+ lock.l_whence = SEEK_SET; /* start from the beginning of the file */
+ lock.l_start = 0; /* set the start of the locked region */
+ lock.l_len = 0; /* set the length of the locked region */
+ /* do locking */
+ return fcntl(fd, F_SETLK, &lock);
+}
+/*
+ * Function RemoveMutex: remove a mutex (unlinking the lock file).
+ *
+ * Just remove the lock file.
+ *
+ * Input: a filename
+ * Output: a return code (0 OK, -1 KO)
+ */
+int RemoveMutex(const char *path_name)
+{
+ return unlink(path_name);
+}
+/*
+ * Function ReadMutex: read a mutex status.
+ *
+ * Read the status for a mutex.
+ *
+ * Input: a mutex (i.e. a file descriptor)
+ * Output: the lock type (F_UNLCK, F_RDLCK or F_WRLCK, or -1 if KO)
+ */
+int ReadMutex(int fd)
+{
+ int res;
+ struct flock lock; /* file lock structure */
+ /* set flock structure */
+ lock.l_type = F_WRLCK; /* set type: unlock */
+ lock.l_whence = SEEK_SET; /* start from the beginning of the file */
+ lock.l_start = 0; /* set the start of the locked region */
+ lock.l_len = 0; /* set the length of the locked region */
+ /* do locking */
+ if ( (res = fcntl(fd, F_GETLK, &lock)) ) {
+ return res;
+ }
+ return lock.l_type;
+}