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/* File locking.
Copyright (C) 2023-2025 Free Software Foundation, Inc.
This file is part of GCC.
GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#ifndef LOCKFILE_H
#define LOCKFILE_H
/* Used to synchronize across multiple processes. */
class lockfile {
public:
/* Default constructor. */
lockfile (): fd (-1)
{}
/* Intended constructor for use. Filename should not be used for anything
other than locking to prevent unintentional unlock. */
lockfile (std::string filename): lockfile ()
{
this->filename = std::move (filename);
}
lockfile (lockfile const& o): lockfile (o.filename)
{}
void operator=(lockfile o)
{
unlock ();
this->filename = o.filename;
this->fd = o.fd;
o.fd = -1;
}
/* Unique write lock. No other lock can be held on this lockfile.
Blocking call. */
int lock_write ();
/* Unique write lock. No other lock can be held on this lockfile.
Only locks if this filelock is not locked by any other process.
Return whether locking was successful. */
int try_lock_write ();
/* Shared read lock. Only read lock can be held concurrently.
If write lock is already held by this process, it will be
changed to read lock.
Blocking call. */
int lock_read ();
/* Unlock all previously placed locks. */
void unlock ();
/* Returns whether any lock is held. */
bool
locked ()
{
return fd < 0;
}
/* Are lockfiles supported? */
static bool lockfile_supported ();
private:
std::string filename;
int fd;
};
#endif
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