436 lines
11 KiB
C
436 lines
11 KiB
C
/* $NetBSD: sem.c,v 1.9 2019/02/21 21:33:34 christos Exp $ */
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/*-
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* Copyright (c) 2003, 2019 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Jason R. Thorpe.
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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
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* are met:
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* 1. 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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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
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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
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice(s), this list of conditions and the following disclaimer as
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* the first lines of this file unmodified other than the possible
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* addition of one or more copyright notices.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice(s), this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
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* BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
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* OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
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* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: sem.c,v 1.9 2019/02/21 21:33:34 christos Exp $");
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#ifndef __LIBPTHREAD_SOURCE__
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/*
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* There is no longer any difference between the libpthread and the librt
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* versions of sem.c; both are fully kernel-assisted via the _ksem_*()
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* system calls. The only difference is the need to lock some internal
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* data structures in the pthread version, which could be achieved by
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* different means. However, in order to maintain binary compatibility
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* with applications that use POSIX semaphores and linked against only
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* libpthread, we continue to maintain a copy of the implementation here
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* that does not depend on any additional libraries (other than libc).
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*/
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#define sem_init _librt_sem_init
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#define sem_destroy _librt_sem_destroy
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#define sem_open _librt_sem_open
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#define sem_close _librt_sem_close
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#define sem_unlink _librt_sem_unlink
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#define sem_wait _librt_sem_wait
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#define sem_timedwait _librt_sem_timedwait
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#define sem_trywait _librt_sem_trywait
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#define sem_post _librt_sem_post
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#define sem_getvalue _librt_sem_getvalue
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#endif /* ! __LIBPTHREAD_SOURCE__ */
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#undef _LIBC
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#define _LIBC
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#include <sys/types.h>
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#include <sys/ksem.h>
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#include <sys/queue.h>
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#include <stdlib.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdint.h>
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#include <semaphore.h>
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#include <stdarg.h>
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#ifdef __LIBPTHREAD_SOURCE__
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#include "pthread.h"
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#endif /* __LIBPTHREAD_SOURCE__ */
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#define SEM_NAMED 0x4e414d44U /* 'NAMD' */
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#define SEM_MAGIC 0x90af0421U
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#define SEM_MAGIC_NAMED (SEM_MAGIC ^ SEM_NAMED)
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#define SEMID_IS_KSEMID(id) (((uint32_t)(id) & KSEM_MARKER_MASK) \
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== KSEM_PSHARED_MARKER)
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#define SEM_IS_KSEMID(k) SEMID_IS_KSEMID((intptr_t)(k))
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#define SEM_IS_UNNAMED(k) (SEM_IS_KSEMID(k) || \
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(k)->ksem_magic == SEM_MAGIC)
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#define SEM_IS_NAMED(k) (!SEM_IS_UNNAMED(k))
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#define SEM_MAGIC_OK(k) (SEM_IS_KSEMID(k) || \
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(k)->ksem_magic == SEM_MAGIC || \
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(k)->ksem_magic == SEM_MAGIC_NAMED)
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struct _sem_st {
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unsigned int ksem_magic;
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intptr_t ksem_semid;
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/* Used only to de-dup named semaphores. */
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LIST_ENTRY(_sem_st) ksem_list;
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sem_t *ksem_identity;
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};
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static LIST_HEAD(, _sem_st) named_sems = LIST_HEAD_INITIALIZER(&named_sems);
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#ifdef __LIBPTHREAD_SOURCE__
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static pthread_mutex_t named_sems_mtx = PTHREAD_MUTEX_INITIALIZER;
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#define LOCK_NAMED_SEMS() pthread_mutex_lock(&named_sems_mtx)
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#define UNLOCK_NAMED_SEMS() pthread_mutex_unlock(&named_sems_mtx)
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#else /* ! __LIBPTHREAD_SOURCE__ */
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#define LOCK_NAMED_SEMS() __nothing
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#define UNLOCK_NAMED_SEMS() __nothing
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#endif /* __LIBPTHREAD_SOURCE__ */
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#ifndef __LIBPTHREAD_SOURCE__
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#ifdef __weak_alias
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__weak_alias(sem_init,_librt_sem_init)
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__weak_alias(sem_destroy,_librt_sem_destroy)
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__weak_alias(sem_open,_librt_sem_open)
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__weak_alias(sem_close,_librt_sem_close)
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__weak_alias(sem_unlink,_librt_sem_unlink)
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__weak_alias(sem_wait,_librt_sem_wait)
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__weak_alias(sem_timedwait,_librt_sem_timedwait)
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__weak_alias(sem_trywait,_librt_sem_trywait)
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__weak_alias(sem_post,_librt_sem_post)
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__weak_alias(sem_getvalue,_librt_sem_getvalue)
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#else
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#error Weak aliases required to build POSIX semaphore support.
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#endif /* __weak_alias */
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#endif /* __LIBPTHREAD_SOURCE__ */
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static inline intptr_t
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sem_to_semid(sem_t *sem)
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{
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if (SEM_IS_KSEMID(*sem))
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return (intptr_t)*sem;
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return (*sem)->ksem_semid;
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}
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static void
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sem_free(sem_t sem)
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{
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sem->ksem_magic = 0;
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free(sem);
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}
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static int
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sem_alloc(unsigned int value, intptr_t semid, unsigned int magic, sem_t *semp)
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{
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sem_t sem;
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if (value > SEM_VALUE_MAX)
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return EINVAL;
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if ((sem = malloc(sizeof(struct _sem_st))) == NULL)
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return ENOSPC;
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sem->ksem_magic = magic;
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sem->ksem_semid = semid;
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*semp = sem;
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return 0;
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}
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/* ARGSUSED */
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int
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sem_init(sem_t *sem, int pshared, unsigned int value)
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{
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intptr_t semid = pshared ? KSEM_PSHARED : 0;
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int error;
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if (_ksem_init(value, &semid) == -1)
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return -1;
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/*
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* pshared anonymous semaphores are treated a little differently.
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* We don't allocate a sem structure and return a pointer to it.
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* That pointer might live in the shared memory segment that's
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* shared between processes, but the _sem_st that contains the
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* important bits certainly would not be.
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*
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* So, instead, we return the ksem ID given to us by the kernel.
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* The kernel has arranged for the least-significant bit of the
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* ksem ID to always be 1 so as to ensure we can always tell
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* these IDs apart from the pointers that we vend out for other
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* non-pshared semaphores.
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*/
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if (pshared) {
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if (!SEMID_IS_KSEMID(semid)) {
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_ksem_destroy(semid);
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errno = ENOTSUP;
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return -1;
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}
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*sem = (sem_t)semid;
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return 0;
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}
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if ((error = sem_alloc(value, semid, SEM_MAGIC, sem)) != 0) {
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_ksem_destroy(semid);
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errno = error;
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return -1;
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}
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return 0;
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}
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int
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sem_destroy(sem_t *sem)
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{
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int error, save_errno;
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#ifdef ERRORCHECK
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if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
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errno = EINVAL;
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return -1;
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}
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#endif
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if (SEM_IS_KSEMID(*sem)) {
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error = _ksem_destroy((intptr_t)*sem);
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} else {
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if (SEM_IS_NAMED(*sem)) {
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errno = EINVAL;
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return -1;
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}
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error = _ksem_destroy((*sem)->ksem_semid);
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save_errno = errno;
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sem_free(*sem);
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if (error == -1)
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errno = save_errno;
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}
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return error;
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}
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sem_t *
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sem_open(const char *name, int oflag, ...)
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{
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sem_t *sem, s;
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intptr_t semid;
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mode_t mode;
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unsigned int value;
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int error;
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va_list ap;
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mode = 0;
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value = 0;
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if (oflag & O_CREAT) {
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va_start(ap, oflag);
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mode = va_arg(ap, int);
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value = va_arg(ap, unsigned int);
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va_end(ap);
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}
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/*
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* We can be lazy and let the kernel handle the oflag,
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* we'll just merge duplicate IDs into our list.
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*/
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if (_ksem_open(name, oflag, mode, value, &semid) == -1)
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return SEM_FAILED;
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/*
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* Search for a duplicate ID, we must return the same sem_t *
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* if we locate one.
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*/
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LOCK_NAMED_SEMS();
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LIST_FOREACH(s, &named_sems, ksem_list) {
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if (s->ksem_semid == semid) {
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UNLOCK_NAMED_SEMS();
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return s->ksem_identity;
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}
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}
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if ((sem = malloc(sizeof(*sem))) == NULL) {
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error = ENOSPC;
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goto bad;
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}
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if ((error = sem_alloc(value, semid, SEM_MAGIC_NAMED, sem)) != 0)
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goto bad;
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LIST_INSERT_HEAD(&named_sems, *sem, ksem_list);
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UNLOCK_NAMED_SEMS();
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(*sem)->ksem_identity = sem;
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return sem;
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bad:
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UNLOCK_NAMED_SEMS();
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_ksem_close(semid);
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if (sem != NULL) {
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if (*sem != NULL)
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sem_free(*sem);
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free(sem);
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}
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errno = error;
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return SEM_FAILED;
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}
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int
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sem_close(sem_t *sem)
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{
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int error, save_errno;
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#ifdef ERRORCHECK
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if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
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errno = EINVAL;
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return -1;
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}
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#endif
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if (!SEM_IS_NAMED(*sem)) {
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errno = EINVAL;
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return -1;
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}
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LOCK_NAMED_SEMS();
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error = _ksem_close((*sem)->ksem_semid);
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LIST_REMOVE((*sem), ksem_list);
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save_errno = errno;
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UNLOCK_NAMED_SEMS();
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sem_free(*sem);
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free(sem);
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if (error == -1)
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errno = save_errno;
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return error;
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}
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int
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sem_unlink(const char *name)
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{
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return _ksem_unlink(name);
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}
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int
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sem_wait(sem_t *sem)
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{
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#ifdef ERRORCHECK
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if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
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errno = EINVAL;
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return -1;
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}
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#endif
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return _ksem_wait(sem_to_semid(sem));
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}
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int
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sem_timedwait(sem_t *sem, const struct timespec * __restrict abstime)
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{
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#ifdef ERRORCHECK
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if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
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errno = EINVAL;
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return -1;
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}
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#endif
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return _ksem_timedwait(sem_to_semid(sem), abstime);
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}
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int
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sem_trywait(sem_t *sem)
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{
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#ifdef ERRORCHECK
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if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
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errno = EINVAL;
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return -1;
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}
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#endif
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return _ksem_trywait(sem_to_semid(sem));
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}
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int
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sem_post(sem_t *sem)
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{
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#ifdef ERRORCHECK
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if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
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errno = EINVAL;
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return -1;
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}
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#endif
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return _ksem_post(sem_to_semid(sem));
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}
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int
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sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
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{
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#ifdef ERRORCHECK
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if (sem == NULL || *sem == NULL || !SEM_MAGIC_OK(*sem)) {
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errno = EINVAL;
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return -1;
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}
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#endif
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return _ksem_getvalue(sem_to_semid(sem), sval);
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}
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