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79 lines
2.1 KiB
C++
79 lines
2.1 KiB
C++
/* File locking.
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Copyright (C) 2023-2026 Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING3. If not see
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<http://www.gnu.org/licenses/>. */
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#ifndef LOCKFILE_H
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#define LOCKFILE_H
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/* Used to synchronize across multiple processes. */
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class lockfile {
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public:
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/* Default constructor. */
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lockfile (): fd (-1)
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{}
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/* Intended constructor for use. Filename should not be used for anything
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other than locking to prevent unintentional unlock. */
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lockfile (std::string filename): lockfile ()
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{
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this->filename = std::move (filename);
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}
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lockfile (lockfile const& o): lockfile (o.filename)
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{}
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void operator=(lockfile o)
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{
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unlock ();
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this->filename = o.filename;
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this->fd = o.fd;
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o.fd = -1;
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}
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/* Unique write lock. No other lock can be held on this lockfile.
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Blocking call. */
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int lock_write ();
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/* Unique write lock. No other lock can be held on this lockfile.
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Only locks if this filelock is not locked by any other process.
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Return whether locking was successful. */
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int try_lock_write ();
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/* Shared read lock. Only read lock can be held concurrently.
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If write lock is already held by this process, it will be
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changed to read lock.
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Blocking call. */
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int lock_read ();
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/* Unlock all previously placed locks. */
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void unlock ();
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/* Returns whether any lock is held. */
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bool
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locked ()
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{
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return fd < 0;
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}
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/* Are lockfiles supported? */
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static bool lockfile_supported ();
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private:
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std::string filename;
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int fd;
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};
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#endif
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