--- /dev/null
+/* Mutex.c
+ *
+ * Copyright (C) 2002 Simone Piccardi
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+/*****************************************************************************
+ *
+ * File Mutex.c: define a set of functions for mutex manipulation
+ *
+ * Author: S. Piccardi Dec. 2002
+ *
+ * $Id: Mutex.c,v 1.7 2003/05/02 09:55:14 piccardi Exp $
+ *
+ *****************************************************************************/
+#include <sys/sem.h> /* IPC semaphore declarations */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <signal.h> /* signal handling declarations */
+
+#include "Gapil.h"
+/*
+ * Function MutexCreate: create a mutex/semaphore
+ *
+ * First call create a semaphore, using the given key.
+ * We want only one semaphore so we set second argument to 1; third
+ * parameter is the flag argument, and is set to create a semaphore
+ * with R/W privilege for the user.
+ * Second call initialize the semaphore to 1 (unlocked)
+ *
+ * Input: an IPC key value (to create an unique semaphore)
+ * Return: the semaphore id# or -1 on error
+ */
+int MutexCreate(key_t ipc_key)
+{
+ const union semun semunion={1}; /* semaphore union structure */
+ int sem_id, ret;
+ sem_id = semget(ipc_key, 1, IPC_CREAT|0666); /* get semaphore ID */
+ if (sem_id == -1) { /* if error return code */
+ return sem_id;
+ }
+ ret = semctl(sem_id, 0, SETVAL, semunion); /* init semaphore */
+ if (ret == -1) {
+ return ret;
+ }
+ return sem_id;
+}
+/*
+ * Function MutexFind: get the semaphore/mutex Id given the IPC key value
+ *
+ * Input: an IPC key value
+ */
+int MutexFind(key_t ipc_key)
+{
+ return semget(ipc_key, 1, 0);
+}
+/*
+ * Function MutexRead: read the current value of the mutex/semaphore
+ *
+ * Input: a semaphore id #
+ * Return: the semaphore value
+ */
+int MutexRead(int sem_id)
+{
+ return semctl(sem_id, 0, GETVAL);
+}
+/*
+ * Define sembuf structures to lock and unlock the semaphore
+ * (used to implement a mutex)
+ */
+struct sembuf sem_lock={ /* to lock semaphore */
+ 0, /* semaphore number (only one so 0) */
+ -1, /* operation (-1 to use resource) */
+ SEM_UNDO}; /* flag (set for undo at exit) */
+struct sembuf sem_ulock={ /* to unlock semaphore */
+ 0, /* semaphore number (only one so 0) */
+ 1, /* operation (1 to release resource) */
+ SEM_UNDO}; /* flag (in this case 0) */
+/*
+ * Function MutexLock: to lock a mutex/semaphore
+ *
+ * Input: a semaphore id #
+ * Output: semop return code (0 OK, -1 KO)
+ */
+int MutexLock(int sem_id)
+{
+ return semop(sem_id, &sem_lock, 1);
+}
+/*
+ * Function MutexUnlock: to unlock a mutex/semaphore
+ *
+ * Input: a semaphore id #
+ * Return: semop return code (0 OK, -1 KO)
+ */
+int MutexUnlock(int sem_id)
+{
+ 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;
+}
projects / gapil.git / blobdiff