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74 lines
2.1 KiB
C
74 lines
2.1 KiB
C
/* Copyright (C) 1994,1996,1997,1998,2000,2003 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <sys/types.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <errno.h>
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#include <string.h>
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/* lockf is a simplified interface to fcntl's locking facilities. */
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int
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lockf (int fd, int cmd, off_t len)
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{
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struct flock fl;
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memset ((char *) &fl, '\0', sizeof (fl));
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/* lockf is always relative to the current file position. */
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fl.l_whence = SEEK_CUR;
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fl.l_start = 0;
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fl.l_len = len;
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switch (cmd)
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{
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case F_TEST:
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/* Test the lock: return 0 if FD is unlocked or locked by this process;
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return -1, set errno to EACCES, if another process holds the lock. */
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fl.l_type = F_RDLCK;
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if (__fcntl (fd, F_GETLK, &fl) < 0)
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return -1;
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if (fl.l_type == F_UNLCK || fl.l_pid == __getpid ())
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return 0;
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__set_errno (EACCES);
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return -1;
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case F_ULOCK:
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fl.l_type = F_UNLCK;
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cmd = F_SETLK;
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break;
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case F_LOCK:
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fl.l_type = F_WRLCK;
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cmd = F_SETLKW;
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break;
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case F_TLOCK:
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fl.l_type = F_WRLCK;
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cmd = F_SETLK;
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break;
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default:
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__set_errno (EINVAL);
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return -1;
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}
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/* lockf() is a cancellation point but so is fcntl() if F_SETLKW is
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used. Therefore we don't have to care about cancellation here,
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the fcntl() function will take care of it. */
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return __fcntl (fd, cmd, &fl);
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}
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