projects / ceph.git / blame
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|---|---|---|
| 7c673cae FG |
1 | // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com) |
| 2 | // (C) Copyright 2005-2007 Jonathan Turkanis | |
| 3 | // (C) Copyright David Abrahams 2004. | |
| 4 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | |
| 5 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.) | |
| 6 | ||
| 7 | // See http://www.boost.org/libs/iostreams for documentation. | |
| 8 | ||
| 9 | #ifndef BOOST_IOSTREAMS_DETAIL_IS_DEREFERENCEABLE_HPP_INCLUDED | |
| 10 | #define BOOST_IOSTREAMS_DETAIL_IS_DEREFERENCEABLE_HPP_INCLUDED | |
| 11 | ||
| 12 | # include <boost/type_traits/remove_cv.hpp> | |
| 13 | # include <boost/mpl/aux_/lambda_support.hpp> | |
| 14 | # include <boost/mpl/bool.hpp> | |
| 15 | # include <boost/detail/workaround.hpp> | |
| 16 | ||
| 17 | namespace boost { namespace iostreams { namespace detail { | |
| 18 | ||
| 19 | // is_dereferenceable<T> metafunction | |
| 20 | // | |
| 21 | // Requires: Given x of type T&, if the expression *x is well-formed | |
| 22 | // it must have complete type; otherwise, it must neither be ambiguous | |
| 23 | // nor violate access. | |
| 24 | ||
| 25 | // This namespace ensures that ADL doesn't mess things up. | |
| 26 | namespace is_dereferenceable_ | |
| 27 | { | |
| 28 | // a type returned from operator* when no increment is found in the | |
| 29 | // type's own namespace | |
| 30 | struct tag {}; | |
| 31 | ||
| 32 | // any soaks up implicit conversions and makes the following | |
| 33 | // operator* less-preferred than any other such operator that | |
| 34 | // might be found via ADL. | |
| 35 | struct any { template <class T> any(T const&); }; | |
| 36 | ||
| 37 | // This is a last-resort operator* for when none other is found | |
| 38 | tag operator*(any const&); | |
| 39 | ||
| 40 | # if BOOST_WORKAROUND(__MWERKS__, BOOST_TESTED_AT(0x3202)) | |
| 41 | # define BOOST_comma(a,b) (a) | |
| 42 | # else | |
| 43 | // In case an operator++ is found that returns void, we'll use ++x,0 | |
| 44 | tag operator,(tag,int); | |
| 45 | # define BOOST_comma(a,b) (a,b) | |
| 46 | # endif | |
| 47 | ||
| 48 | // two check overloads help us identify which operator++ was picked | |
| 49 | char (& check_increment(tag) )[2]; | |
| 50 | ||
| 51 | template <class T> | |
| 52 | char check_increment(T const&); | |
| 53 | ||
| 54 | template <class T> | |
| 55 | struct impl | |
| 56 | { | |
| 57 | static typename boost::remove_cv<T>::type& x; | |
| 58 | ||
| 59 | BOOST_STATIC_CONSTANT( | |
| 60 | bool | |
| 61 | , value = sizeof(is_dereferenceable_::check_increment(BOOST_comma(*x,0))) == 1 | |
| 62 | ); | |
| 63 | }; | |
| 64 | } | |
| 65 | ||
| 66 | # undef BOOST_comma | |
| 67 | ||
| 68 | template<typename T> | |
| 69 | struct is_dereferenceable | |
| 70 | : public ::boost::integral_constant<bool, is_dereferenceable_::impl<T>::value > | |
| 71 | { | |
| 72 | BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_dereferenceable,(T)) | |
| 73 | }; | |
| 74 | ||
| 75 | } } | |
| 76 | ||
| 77 | ||
| 78 | } // End namespaces detail, iostreams, boost. | |
| 79 | ||
| 80 | #endif // BOOST_IOSTREAMS_DETAIL_IS_DEREFERENCEABLE_HPP_INCLUDED |