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