91 lines
2.9 KiB
C++
91 lines
2.9 KiB
C++
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/* Copyright 2006-2014 Joaquin M Lopez Munoz.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See http://www.boost.org/libs/flyweight for library home page.
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*/
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#ifndef BOOST_FLYWEIGHT_DETAIL_PERFECT_FWD_HPP
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#define BOOST_FLYWEIGHT_DETAIL_PERFECT_FWD_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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/* C++03-compatible implementation of perfect forwarding.
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* Usage:
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*
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* # define NAME ...
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* # define BODY(args) {...BOOST_FLYWEIGHT_FORWARD(args)...}
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* BOOST_FLYWEIGHT_PERFECT_FWD(name,body)
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*
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* where NAME includes the return type and qualifiers (if any) and BODY(args)
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* is expected to fo the forwarding through BOOST_FLYWEIGHT_FORWARD(args).
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*
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* In compilers capable of perfect forwarding, the real thing is provided
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* (just one variadic args overload is generated). Otherwise the machinery
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* generates n+1 overloads, if rvalue refs are supported, or else 2^(n+1)-1
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* overloads accepting any combination of lvalue refs and const lvalue refs,
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* up to BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS args.
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*
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* BOOST_FLYWEIGHT_PERFECT_FWD_WITH_ARGS(name,body) is a variation omitting the
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* overloads with zero args --when perfect forwarding is available, this second
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* macro is exactly the same as the original.
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*/
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#include <boost/config.hpp> /* keep it first to prevent nasty warns in MSVC */
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#include <boost/preprocessor/cat.hpp>
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#include <boost/preprocessor/repetition/enum.hpp>
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#include <boost/preprocessor/repetition/enum_params.hpp>
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#include <boost/preprocessor/seq/seq.hpp>
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#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
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#include <utility>
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#endif
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#define BOOST_FLYWEIGHT_FORWARD_FORWARD_AUX(z,n,_) \
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std::forward<BOOST_PP_CAT(T,n)>(BOOST_PP_CAT(t,n))
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#define BOOST_FLYWEIGHT_FORWARD_FORWARD(n) \
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BOOST_PP_ENUM(n,BOOST_FLYWEIGHT_FORWARD_FORWARD_AUX,~)
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#define BOOST_FLYWEIGHT_FORWARD_ENUM(n) BOOST_PP_ENUM_PARAMS(n,t)
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#define BOOST_FLYWEIGHT_FORWARD_PASS(arg) arg
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#define BOOST_FLYWEIGHT_FORWARD(args)\
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BOOST_PP_CAT(BOOST_FLYWEIGHT_FORWARD_,BOOST_PP_SEQ_HEAD(args))( \
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BOOST_PP_SEQ_HEAD(BOOST_PP_SEQ_TAIL(args)))
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#if defined(BOOST_NO_CXX11_RVALUE_REFERENCES)||\
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defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)
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#if !defined(BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS)
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#define BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS 5
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#endif
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#if BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS<0
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#error BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS must be >=0
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#endif
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#if BOOST_FLYWEIGHT_LIMIT_PERFECT_FWD_ARGS<=5
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#include <boost/flyweight/detail/pp_perfect_fwd.hpp>
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#else
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#include <boost/flyweight/detail/dyn_perfect_fwd.hpp>
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#endif
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#else
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/* real perfect forwarding */
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#define BOOST_FLYWEIGHT_PERFECT_FWD(name,body) \
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template<typename... Args>name(Args&&... args) \
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body((PASS)(std::forward<Args>(args)...))
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#define BOOST_FLYWEIGHT_PERFECT_FWD_WITH_ARGS \
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BOOST_FLYWEIGHT_PERFECT_FWD
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#endif
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#endif
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