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#ifndef BOOST_DETAIL_ATOMIC_COUNT_HPP_INCLUDED
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#define BOOST_DETAIL_ATOMIC_COUNT_HPP_INCLUDED
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// boost/detail/atomic_count.hpp - thread/SMP safe reference counter
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// Copyright (c) 2001, 2002 Peter Dimov and Multi Media Ltd.
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// Permission to copy, use, modify, sell and distribute this software
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// is granted provided this copyright notice appears in all copies.
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// This software is provided "as is" without express or implied
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// warranty, and with no claim as to its suitability for any purpose.
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// typedef <implementation-defined> boost::detail::atomic_count;
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// (n is convertible to long)
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// Effects: Constructs an atomic_count with an initial value of n
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// Returns: (long) the current value of a
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// Effects: Atomically increments the value of a
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// Effects: Atomically decrements the value of a
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// Returns: (long) zero if the new value of a is zero,
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// unspecified non-zero value otherwise (usually the new value)
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// Important note: when --a returns zero, it must act as a
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// read memory barrier (RMB); i.e. the calling thread must
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// have a synchronized view of the memory
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// On Intel IA-32 (x86) memory is always synchronized, so this
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// On many architectures the atomic instructions already act as
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// This property is necessary for proper reference counting, since
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// a thread can update the contents of a shared object, then
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// release its reference, and another thread may immediately
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// release the last reference causing object destruction.
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// The destructor needs to have a synchronized view of the
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// object to perform proper cleanup.
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// Original example by Alexander Terekhov:
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// - a mutable shared object OBJ;
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// - two threads THREAD1 and THREAD2 each holding
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// a private smart_ptr object pointing to that OBJ.
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// t1: THREAD1 updates OBJ (thread-safe via some synchronization)
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// and a few cycles later (after "unlock") destroys smart_ptr;
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// t2: THREAD2 destroys smart_ptr WITHOUT doing any synchronization
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// with respect to shared mutable object OBJ; OBJ destructors
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// are called driven by smart_ptr interface...
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// Note: atomic_count_linux.hpp has been disabled by default; see the
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// comments inside for more info.
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#include <boost/config.hpp>
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#ifndef BOOST_HAS_THREADS
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typedef long atomic_count;
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#elif defined(BOOST_USE_ASM_ATOMIC_H)
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# include <boost/detail/atomic_count_linux.hpp>
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#elif defined(BOOST_AC_USE_PTHREADS)
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# include <boost/detail/atomic_count_pthreads.hpp>
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#elif defined(WIN32) || defined(_WIN32) || defined(__WIN32__)
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# include <boost/detail/atomic_count_win32.hpp>
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#elif defined(__GLIBCPP__)
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# include <boost/detail/atomic_count_gcc.hpp>
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#elif defined(BOOST_HAS_PTHREADS)
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# define BOOST_AC_USE_PTHREADS
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# include <boost/detail/atomic_count_pthreads.hpp>
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// Use #define BOOST_DISABLE_THREADS to avoid the error
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#error Unrecognized threading platform
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#endif // #ifndef BOOST_DETAIL_ATOMIC_COUNT_HPP_INCLUDED