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glibc/io/lockf.c
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/* Copyright (C) 1994,1996,1997,1998,2000,2003 Free Software Foundation, Inc. | |
This file is part of the GNU C Library. | |
The GNU C Library is free software; you can redistribute it and/or | |
modify it under the terms of the GNU Lesser General Public | |
License as published by the Free Software Foundation; either | |
version 2.1 of the License, or (at your option) any later version. | |
The GNU C Library 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 | |
Lesser General Public License for more details. | |
You should have received a copy of the GNU Lesser General Public | |
License along with the GNU C Library; if not, write to the Free | |
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | |
02111-1307 USA. */ | |
#include <sys/types.h> | |
#include <unistd.h> | |
#include <fcntl.h> | |
#include <errno.h> | |
#include <string.h> | |
/* lockf is a simplified interface to fcntl's locking facilities. */ | |
int | |
lockf (int fd, int cmd, off_t len) | |
{ | |
struct flock fl; | |
memset ((char *) &fl, '\0', sizeof (fl)); | |
/* lockf is always relative to the current file position. */ | |
fl.l_whence = SEEK_CUR; | |
fl.l_start = 0; | |
fl.l_len = len; | |
switch (cmd) | |
{ | |
case F_TEST: | |
/* Test the lock: return 0 if FD is unlocked or locked by this process; | |
return -1, set errno to EACCES, if another process holds the lock. */ | |
fl.l_type = F_RDLCK; | |
if (__fcntl (fd, F_GETLK, &fl) < 0) | |
return -1; | |
if (fl.l_type == F_UNLCK || fl.l_pid == __getpid ()) | |
return 0; | |
__set_errno (EACCES); | |
return -1; | |
case F_ULOCK: | |
fl.l_type = F_UNLCK; | |
cmd = F_SETLK; | |
break; | |
case F_LOCK: | |
fl.l_type = F_WRLCK; | |
cmd = F_SETLKW; | |
break; | |
case F_TLOCK: | |
fl.l_type = F_WRLCK; | |
cmd = F_SETLK; | |
break; | |
default: | |
__set_errno (EINVAL); | |
return -1; | |
} | |
/* lockf() is a cancellation point but so is fcntl() if F_SETLKW is | |
used. Therefore we don't have to care about cancellation here, | |
the fcntl() function will take care of it. */ | |
return __fcntl (fd, cmd, &fl); | |
} |