boost/iostreams/detail/execute.hpp

   1 /*
   2  * Distributed under the Boost Software License, Version 1.0.(See accompanying
   3  * file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
   4  *
   5  * See http://www.boost.org/libs/iostreams for documentation.
   6
   7  * File:        boost/iostreams/detail/execute.hpp
   8  * Date:        Thu Dec 06 13:21:54 MST 2007
   9  * Copyright:   2007-2008 CodeRage, LLC
  10  * Author:      Jonathan Turkanis
  11  * Contact:     turkanis at coderage dot com
  12
  13  * Defines the overloaded function template
  14  * boost::iostreams::detail::execute_all() and the function template
  15  * boost::iostreams::detail::execute_foreach().
  16  *
  17  * execute_all() invokes a primary operation and performs a sequence of cleanup
  18  * operations, returning the result of the primary operation if no exceptions
  19  * are thrown. If one of the operations throws an exception, performs the
  20  * remaining operations and rethrows the initial exception.
  21  *
  22  * execute_foreach() is a variant of std::foreach which invokes a function
  23  * object for each item in a sequence, catching all execptions and rethrowing
  24  * the first caught exception after the function object has been invoked on each
  25  * item.
  26  */
  27
  28 #ifndef BOOST_IOSTREAMS_DETAIL_EXECUTE_HPP_INCLUDED
  29 #define BOOST_IOSTREAMS_DETAIL_EXECUTE_HPP_INCLUDED
  30
  31 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
  32 # pragma once
  33 #endif
  34
  35 #include <boost/config.hpp>
  36 #include <boost/detail/workaround.hpp>
  37 #include <boost/iostreams/detail/config/limits.hpp>   // MAX_EXECUTE_ARITY
  38 #include <boost/preprocessor/arithmetic/dec.hpp>
  39 #include <boost/preprocessor/cat.hpp>
  40 #include <boost/preprocessor/iteration/local.hpp>
  41 #include <boost/preprocessor/repetition/enum_params.hpp>
  42 #include <boost/preprocessor/repetition/enum_binary_params.hpp>
  43 #include <boost/preprocessor/punctuation/comma_if.hpp>
  44 #include <boost/utility/result_of.hpp>
  45
  46 namespace boost { namespace iostreams { namespace detail {
  47
  48 // Helper for class template execute_traits.
  49 template<typename Result>
  50 struct execute_traits_impl {
  51     typedef Result result_type;
  52     template<typename Op>
  53     static Result execute(Op op) { return op(); }
  54 };
  55
  56 // Specialization for void return. For simplicity, execute() returns int
  57 // for operations returning void. This could be avoided with additional work.
  58 template<>
  59 struct execute_traits_impl<void> {
  60     typedef int result_type;
  61     template<typename Op>
  62     static int execute(Op op) { op(); return 0; }
  63 };
  64
  65 // Deduces the result type of Op and allows uniform treatment of operations
  66 // returning void and non-void.
  67 template< typename Op,
  68           typename Result = // VC6.5 workaround.
  69               #if !defined(BOOST_NO_RESULT_OF) && \
  70                   !BOOST_WORKAROUND(__BORLANDC__, BOOST_TESTED_AT(0x592))
  71                   typename boost::result_of<Op()>::type
  72               #else
  73                   BOOST_DEDUCED_TYPENAME Op::result_type
  74               #endif
  75           >
  76 struct execute_traits
  77     : execute_traits_impl<Result>
  78     { };
  79
  80 // Implementation with no cleanup operations.
  81 template<typename Op>
  82 typename execute_traits<Op>::result_type
  83 execute_all(Op op)
  84 {
  85     return execute_traits<Op>::execute(op);
  86 }
  87
  88 // Implementation with one or more cleanup operations
  89 #define BOOST_PP_LOCAL_MACRO(n) \
  90    template<typename Op, BOOST_PP_ENUM_PARAMS(n, typename C)> \
  91    typename execute_traits<Op>::result_type \
  92    execute_all(Op op, BOOST_PP_ENUM_BINARY_PARAMS(n, C, c)) \
  93    { \
  94        typename execute_traits<Op>::result_type r; \
  95        try { \
  96            r = boost::iostreams::detail::execute_all( \
  97                    op BOOST_PP_COMMA_IF(BOOST_PP_DEC(n)) \
  98                    BOOST_PP_ENUM_PARAMS(BOOST_PP_DEC(n), c) \
  99                ); \
 100        } catch (...) { \
 101            try { \
 102                BOOST_PP_CAT(c, BOOST_PP_DEC(n))(); \
 103            } catch (...) { } \
 104            throw; \
 105        } \
 106        BOOST_PP_CAT(c, BOOST_PP_DEC(n))(); \
 107        return r; \
 108    } \
 109    /**/
 110
 111 #define BOOST_PP_LOCAL_LIMITS (1, BOOST_IOSTREAMS_MAX_EXECUTE_ARITY)
 112 #include BOOST_PP_LOCAL_ITERATE()
 113 #undef BOOST_PP_LOCAL_MACRO
 114
 115 template<class InIt, class Op>
 116 Op execute_foreach(InIt first, InIt last, Op op)
 117 {
 118     if (first == last)
 119         return op;
 120     try {
 121         op(*first);
 122     } catch (...) {
 123         try {
 124             ++first;
 125             boost::iostreams::detail::execute_foreach(first, last, op);
 126         } catch (...) { }
 127         throw;
 128     }
 129     ++first;
 130     return boost::iostreams::detail::execute_foreach(first, last, op);
 131 }
 132
 133 } } } // End namespaces detail, iostreams, boost.
 134
 135 #endif // #ifndef BOOST_IOSTREAMS_DETAIL_EXECUTE_HPP_INCLUDED