90 lines
1.6 KiB
C++
90 lines
1.6 KiB
C++
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/* One of many ways to emulate flock() on top of real (good) POSIX locks.
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*
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* This flock() emulation is based upon source taken from the Red Hat
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* implementation used in their imap-2002d SRPM.
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*
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* $RH: flock.c,v 1.2 2000/08/23 17:07:00 nalin Exp $
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*/
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/* flock.c
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Copyright 2003 Red Hat, Inc.
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This file is part of Cygwin.
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This software is a copyrighted work licensed under the terms of the
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Cygwin license. Please consult the file "CYGWIN_LICENSE" for
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details. */
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#include <sys/file.h>
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#include <sys/types.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <unistd.h>
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int
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flock (int fd, int operation)
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{
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int i, cmd;
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struct flock l = { 0, 0, 0, 0, 0 };
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if (operation & LOCK_NB)
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{
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cmd = F_SETLK;
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}
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else
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{
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cmd = F_SETLKW;
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}
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l.l_whence = SEEK_SET;
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switch (operation & (~LOCK_NB))
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{
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case LOCK_EX:
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l.l_type = F_WRLCK;
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i = fcntl (fd, cmd, &l);
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if (i == -1)
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{
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if ((errno == EAGAIN) || (errno == EACCES))
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{
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errno = EWOULDBLOCK;
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}
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}
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break;
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case LOCK_SH:
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l.l_type = F_RDLCK;
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i = fcntl (fd, cmd, &l);
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if (i == -1)
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{
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if ((errno == EAGAIN) || (errno == EACCES))
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{
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errno = EWOULDBLOCK;
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}
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}
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break;
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case LOCK_UN:
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l.l_type = F_UNLCK;
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i = fcntl (fd, cmd, &l);
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if (i == -1)
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{
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if ((errno == EAGAIN) || (errno == EACCES))
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{
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errno = EWOULDBLOCK;
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}
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}
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break;
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default:
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i = -1;
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errno = EINVAL;
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break;
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}
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return i;
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}
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#ifdef FLOCK_EMULATE_IS_MAIN
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int
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main (int argc, char **argv)
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{
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int fd = open (argv[1], O_WRONLY);
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flock (fd, LOCK_EX);
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return 0;
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}
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#endif
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