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83 lines
2.3 KiB
C
83 lines
2.3 KiB
C
/* f_setlk -- locking part of fcntl
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Copyright (C) 2014-2023 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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#include <sys/types.h>
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#include <sys/file.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <errno.h>
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/* XXX
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We need new RPCs to support POSIX.1 fcntl file locking!!
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For the time being we support the whole-file case only,
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with all kinds of WRONG WRONG WRONG semantics,
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by using flock. This is definitely the Wrong Thing,
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but it might be better than nothing (?). */
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int
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__f_setlk (int fd, int type, int whence, __off64_t start, __off64_t len, int wait)
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{
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int cmd = 0;
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switch (type)
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{
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case F_RDLCK: cmd = LOCK_SH; break;
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case F_WRLCK: cmd = LOCK_EX; break;
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case F_UNLCK: cmd = LOCK_UN; break;
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default:
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errno = EINVAL;
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return -1;
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}
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if (cmd != LOCK_UN && wait == 0)
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cmd |= LOCK_NB;
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if (whence == SEEK_CUR)
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{
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/* In case the target position is 0, we can support it below. */
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__off64_t cur = __lseek64 (fd, 0, SEEK_CUR);
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if (cur >= 0)
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{
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start = cur + start;
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whence = SEEK_SET;
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}
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}
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switch (whence)
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{
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case SEEK_SET:
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if (start == 0 && len == 0) /* Whole file request. */
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break;
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/* It seems to be common for applications to lock the first
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byte of the file when they are really doing whole-file locking.
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So, since it's so wrong already, might as well do that too. */
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if (start == 0 && len == 1)
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break;
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/* FALLTHROUGH */
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case SEEK_CUR:
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case SEEK_END:
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errno = ENOTSUP;
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return -1;
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default:
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errno = EINVAL;
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return -1;
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}
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return __flock (fd, cmd);
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}
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