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57 lines
1.7 KiB
C
57 lines
1.7 KiB
C
/* Copyright (C) 1992-2020 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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<https://www.gnu.org/licenses/>. */
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/* This file implements the `flock' function in terms of the POSIX.1 `fcntl'
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locking mechanism. In 4BSD, these are two incompatible locking mechanisms,
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perhaps with different semantics? */
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#include <errno.h>
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#include <unistd.h>
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#include <fcntl.h>
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#include <sys/file.h>
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/* Apply or remove an advisory lock, according to OPERATION,
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on the file FD refers to. */
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int
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__flock (int fd, int operation)
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{
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struct flock lbuf;
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switch (operation & ~LOCK_NB)
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{
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case LOCK_SH:
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lbuf.l_type = F_RDLCK;
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break;
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case LOCK_EX:
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lbuf.l_type = F_WRLCK;
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break;
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case LOCK_UN:
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lbuf.l_type = F_UNLCK;
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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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lbuf.l_whence = SEEK_SET;
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lbuf.l_start = lbuf.l_len = 0L; /* Lock the whole file. */
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return __fcntl (fd, (operation & LOCK_NB) ? F_SETLK : F_SETLKW, &lbuf);
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}
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weak_alias (__flock, flock)
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