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/* Copyright 2012, Google Inc.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are
* met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above
* copyright notice, this list of conditions and the following
* disclaimer in the documentation and/or other materials provided
* with the distribution.
* * Neither the name of Google Inc. nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef __UTIL_IPC_LOCK_H
#define __UTIL_IPC_LOCK_H
struct ipc_lock {
int is_held; /* internal */
const char *filename; /* provided by the developer */
int fd; /* internal */
};
/* don't use C99 initializers here, so this can be used in C++ code */
#define LOCKFILE_INIT(lockfile) \
{ \
0, /* is_held */ \
lockfile, /* filename */ \
-1, /* fd */ \
}
/*
* acquire_lock: acquire a lock
*
* timeout <0 = no timeout (try forever)
* timeout 0 = do not wait (return immediately)
* timeout >0 = wait up to $timeout milliseconds (subject to kernel scheduling)
*
* return 0 = lock acquired
* return >0 = lock was already held
* return <0 = failed to acquire lock
*/
extern int acquire_lock(struct ipc_lock *lock, int timeout_msecs);
/*
* release_lock: release a lock
*
* returns 0 if lock was released successfully
* returns -1 if lock had not been held before the call
*/
extern int release_lock(struct ipc_lock *lock);
#endif /* __UTIL_IPC_LOCK_H */
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