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Diffstat (limited to 'libical/src/libical/locking.c')
-rw-r--r-- | libical/src/libical/locking.c | 143 |
1 files changed, 0 insertions, 143 deletions
diff --git a/libical/src/libical/locking.c b/libical/src/libical/locking.c deleted file mode 100644 index 0376bc2bec..0000000000 --- a/libical/src/libical/locking.c +++ /dev/null @@ -1,143 +0,0 @@ - -/* - I Stole this from: - http://www.cis.temple.edu/~ingargio/old/cis307s96/readings/rwlockexample.html - - CIS 307: An example using Read/Write File Locks - [fcntl.h], [fcntl.c], [fcntlmain.c] - -In Stevens "Advanced Programming in the Unix Environment" we see ways to use -the Unix service fcntl to lock portions of a file for reading and writing in -the manner stated in the Reader and Writer problem [any number of readers at -a time, but writers must operate alone]. Here we have three files that adapt -and use the code from Stevens: - -*fcntl.h: Specification of the locking functions. -*fcntl.c: Implementation of the locking functions. -*fcntlmain.c: Driver that does a simple test of the locking functions. - -WARNING: A file lock request which is blocked can be interrupted by a -signal. In this case the lock operation returns EINTR. Thus we may think we -got a lock when we really don't. A solution is to block signals when -locking. Another solution is to test the value returned by the lock -operation and relock if the value is EINTR. Another solution, which we adopt -here, is to do nothing about it. - -/* fcntl.c -- Defines mutexes in terms of read/write locks on files. - * (code is mostly from Stevens: Advanced Programming in the - * Unix environment. See from page 367 on. - * filerwlock, filerwlockCreate, filerwlockDelete, - * filerwreadlock, filerwlongreadlock, filerwlongunlock, - * filerwlockUnlock - */ - -#include <sys/types.h> -#include <sys/stat.h> -#include <fcntl.h> -#include <unistd.h> - -int lock_reg(int, int, int, off_t, int, off_t); - -#define read_lock(fd, offset, whence, len) \ - lock_reg(fd, F_SETLK, F_RDLCK, offset, whence, len) - -#define readw_lock(fd, offset, whence, len) \ - lock_reg(fd, F_SETLKW, F_RDLCK, offset, whence, len) - -#define write_lock(fd, offset, whence, len) \ - lock_reg(fd, F_SETLK, F_WRLCK, offset, whence, len) - -#define writew_lock(fd, offset, whence, len) \ - lock_reg(fd, F_SETLKW, F_WRLCK, offset, whence, len) - -#define un_lock(fd, offset, whence, len) \ - lock_reg(fd, F_SETLK, F_UNLCK, offset, whence, len) - -pid_t lock_test(int, int , off_t , int , off_t ); - -#define is_readlock(fd, offset, whence, len) \ - lock_test(fd, F_RDLCK, offset, whence, len) - -#define is_writelock(fd, offset, whence, len) \ - lock_test(fd, F_WRLCK, offset, whence, len) - -int lock_reg(int fd, int cmd, int type, off_t offset, int whence, off_t len) -{ - struct flock lock; - lock.l_type = type; /* F_RDLCK, F_WRLCK, F_UNLCK */ - lock.l_start = offset; /* byte offset relative to l_whence */ - lock.l_whence = whence; /* SEEK_SET, SEEK_CUR, SEEK_END */ - lock.l_len = len; /* #bytes (0 means to EOF) */ - return (fcntl(fd, cmd, &lock)); -} - -pid_t lock_test(int fd, int type, off_t offset, int whence, off_t len) -{ - struct flock lock; - lock.l_type = type; /* F_RDLCK or F_WRLCK */ - lock.l_start = offset; /* byte offset relative to l_whence */ - lock.l_whence = whence; /* SEEK_SET, SEEK_CUR, SEEK_END */ - lock.l_len = len; /* #bytes (0 means to EOF) */ - if (fcntl(fd,F_GETLK,&lock) < 0){ - perror("fcntl"); exit(1);} - if (lock.l_type == F_UNLCK) - return (0); /* false, region is not locked by another process */ - return (lock.l_pid); /* true, return pid of lock owner */ -} - -typedef struct { - int fd; - int n;} filerwlock; - -/* Create N read/write locks and returns the id of this cluster of locks. */ -filerwlock * filerwlockCreate(char *filename, int n) { - filerwlock *fl = (filerwlock *)malloc(sizeof(filerwlock)); - if (((fl->fd) = open(filename, O_RDWR | O_CREAT | O_TRUNC, S_IWUSR)) < 0) { - perror("open"); - exit(1);} - fl->n = n; - return fl; - } - -/* Delete the cluster of read/write locks associated with fl. */ -int filerwlockDelete(filerwlock *fl) { - if (close(fl->fd) < 0) { - perror("close"); - exit(1);} - return free(fl); - } - -/* Given the read/write lock cluster fl, lock its ith element */ -int filerwreadlock(filerwlock *fl, int i) { - if ((i < 0) | (i >= fl->n)) { - printf("filerwlockLock needs i in range 0 .. %d\n", (fl->n)-1); - exit(0);} - readw_lock(fl->fd, i, SEEK_SET, 1); - } - -int filerwwritelock(filerwlock *fl, int i) { - if ((i < 0) | (i >= fl->n)) { - printf("filerwlockLock needs i in range 0 .. %d\n", (fl->n)-1); - exit(0);} - writew_lock(fl->fd, i, SEEK_SET, 1); - } - -/* Given the lock cluster fl, unlock its ith element */ -int filerwunlock(filerwlock *fl, int i){ - - if ((i < 0) | (i >= fl->n)) { - printf("filerwlockUnlock needs i in range 0 .. %d\n", (fl->n)-1); - exit(0);} - un_lock(fl->fd, i, SEEK_SET, 1); - } - -/* Given the lock cluster fl, it read locks all its elements */ -int filerwlongreadlock(filerwlock *fl) { - readw_lock(fl->fd, 0, SEEK_SET, fl->n); -} - -/* Given the lock cluster fl, it unlocks all its elements */ -int filerwlongunlock(filerwlock *fl) { - un_lock(fl->fd, 0, SEEK_SET, fl->n); -} - |