boost/python/with_custodian_and_ward.hpp

   1 // Copyright David Abrahams 2002.
   2 // Distributed under the Boost Software License, Version 1.0. (See
   3 // accompanying file LICENSE_1_0.txt or copy at
   4 // http://www.boost.org/LICENSE_1_0.txt)
   5 #ifndef WITH_CUSTODIAN_AND_WARD_DWA2002131_HPP
   6 # define WITH_CUSTODIAN_AND_WARD_DWA2002131_HPP
   7
   8 # include <boost/python/detail/prefix.hpp>
   9
  10 # include <boost/python/default_call_policies.hpp>
  11 # include <boost/python/object/life_support.hpp>
  12 # include <algorithm>
  13
  14 namespace boost { namespace python {
  15
  16 namespace detail
  17 {
  18   template <std::size_t N>
  19   struct get_prev
  20   {
  21       template <class ArgumentPackage>
  22       static PyObject* execute(ArgumentPackage const& args, PyObject* = 0)
  23       {
  24           int const pre_n = static_cast<int>(N) - 1; // separate line is gcc-2.96 workaround
  25           return detail::get(mpl::int_<pre_n>(), args);
  26       }
  27   };
  28   template <>
  29   struct get_prev<0>
  30   {
  31       template <class ArgumentPackage>
  32       static PyObject* execute(ArgumentPackage const&, PyObject* zeroth)
  33       {
  34           return zeroth;
  35       }
  36   };
  37 }
  38 template <
  39     std::size_t custodian
  40   , std::size_t ward
  41   , class BasePolicy_ = default_call_policies
  42 >
  43 struct with_custodian_and_ward : BasePolicy_
  44 {
  45     BOOST_STATIC_ASSERT(custodian != ward);
  46     BOOST_STATIC_ASSERT(custodian > 0);
  47     BOOST_STATIC_ASSERT(ward > 0);
  48
  49     template <class ArgumentPackage>
  50     static bool precall(ArgumentPackage const& args_)
  51     {
  52         unsigned arity_ = detail::arity(args_);
  53         if (custodian > arity_ || ward > arity_)
  54         {
  55             PyErr_SetString(
  56                 PyExc_IndexError
  57               , "boost::python::with_custodian_and_ward: argument index out of range"
  58             );
  59             return false;
  60         }
  61
  62         PyObject* patient = detail::get_prev<ward>::execute(args_);
  63         PyObject* nurse = detail::get_prev<custodian>::execute(args_);
  64
  65         PyObject* life_support = python::objects::make_nurse_and_patient(nurse, patient);
  66         if (life_support == 0)
  67             return false;
  68
  69         bool result = BasePolicy_::precall(args_);
  70
  71         if (!result) {
  72             Py_DECREF(life_support);
  73         }
  74
  75         return result;
  76     }
  77 };
  78
  79 template <std::size_t custodian, std::size_t ward, class BasePolicy_ = default_call_policies>
  80 struct with_custodian_and_ward_postcall : BasePolicy_
  81 {
  82     BOOST_STATIC_ASSERT(custodian != ward);
  83
  84     template <class ArgumentPackage>
  85     static PyObject* postcall(ArgumentPackage const& args_, PyObject* result)
  86     {
  87         std::size_t arity_ = detail::arity(args_);
  88 #if BOOST_WORKAROUND(BOOST_MSVC, < 1300)
  89         if ( custodian > arity_ || ward > arity_ )
  90 #else
  91         // check if either custodian or ward exceeds the arity
  92         // (this weird formulation avoids "always false" warnings
  93         // for arity_ = 0)
  94         if ( (std::max)(custodian, ward) > arity_ )
  95 #endif
  96         {
  97             PyErr_SetString(
  98                 PyExc_IndexError
  99               , "boost::python::with_custodian_and_ward_postcall: argument index out of range"
 100             );
 101             return 0;
 102         }
 103
 104         PyObject* patient = detail::get_prev<ward>::execute(args_, result);
 105         PyObject* nurse = detail::get_prev<custodian>::execute(args_, result);
 106
 107         if (nurse == 0) return 0;
 108
 109         result = BasePolicy_::postcall(args_, result);
 110         if (result == 0)
 111             return 0;
 112
 113         if (python::objects::make_nurse_and_patient(nurse, patient) == 0)
 114         {
 115             Py_XDECREF(result);
 116             return 0;
 117         }
 118         return result;
 119     }
 120 };
 121
 122
 123 }} // namespace boost::python
 124
 125 #endif // WITH_CUSTODIAN_AND_WARD_DWA2002131_HPP