1 | // Copyright David Abrahams 2002.
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2 | // Distributed under the Boost Software License, Version 1.0. (See
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3 | // accompanying file LICENSE_1_0.txt or copy at
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4 | // http://www.boost.org/LICENSE_1_0.txt)
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5 | #ifndef LVALUE_FROM_PYTYPE_DWA2002130_HPP
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6 | # define LVALUE_FROM_PYTYPE_DWA2002130_HPP
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7 |
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8 | # include <boost/python/detail/prefix.hpp>
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9 |
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10 | # include <boost/python/type_id.hpp>
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11 | # include <boost/python/converter/registry.hpp>
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12 | # include <boost/python/detail/void_ptr.hpp>
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13 |
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14 | namespace boost { namespace python {
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15 |
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16 | namespace detail
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17 | {
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18 | // Given a pointer-to-function of 1 parameter returning a reference
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19 | // type, return the type_id of the function's return type.
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20 | template <class T, class U>
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21 | inline type_info extractor_type_id(T&(*)(U))
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22 | {
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23 | return type_id<T>();
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24 | }
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25 |
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26 | // A function generator whose static execute() function is an lvalue
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27 | // from_python converter using the given Extractor. U is expected to
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28 | // be the actual type of the PyObject instance from which the result
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29 | // is being extracted.
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30 | template <class Extractor, class U>
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31 | struct normalized_extractor
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32 | {
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33 | static inline void* execute(PyObject* op)
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34 | {
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35 | typedef typename boost::add_reference<U>::type param;
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36 | return &Extractor::execute(
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37 | boost::python::detail::void_ptr_to_reference(
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38 | op, (param(*)())0 )
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39 | );
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40 | }
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41 | };
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42 |
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43 | // Given an Extractor type and a pointer to its execute function,
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44 | // return a new object whose static execute function does the same
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45 | // job but is a conforming lvalue from_python conversion function.
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46 | //
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47 | // usage: normalize<Extractor>(&Extractor::execute)
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48 | template <class Extractor, class T, class U>
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49 | inline normalized_extractor<Extractor,U>
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50 | normalize(T(*)(U), Extractor* = 0)
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51 | {
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52 | return normalized_extractor<Extractor, U>();
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53 | }
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54 | }
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55 |
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56 | // An Extractor which extracts the given member from a Python object
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57 | // whose instances are stored as InstanceType.
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58 | template <class InstanceType, class MemberType, MemberType (InstanceType::*member)>
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59 | struct extract_member
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60 | {
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61 | static MemberType& execute(InstanceType& c)
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62 | {
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63 | (void)c.ob_type; // static assertion
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64 | return c.*member;
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65 | }
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66 | };
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67 |
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68 | // An Extractor which simply extracts the entire python object
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69 | // instance of InstanceType.
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70 | template <class InstanceType>
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71 | struct extract_identity
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72 | {
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73 | static InstanceType& execute(InstanceType& c)
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74 | {
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75 | (void)c.ob_type; // static assertion
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76 | return c;
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77 | }
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78 | };
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79 |
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80 | // Registers a from_python conversion which extracts lvalues using
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81 | // Extractor's static execute function from Python objects whose type
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82 | // object is python_type.
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83 | template <class Extractor, PyTypeObject const* python_type>
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84 | struct lvalue_from_pytype
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85 | {
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86 | lvalue_from_pytype()
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87 | {
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88 | converter::registry::insert(
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89 | &extract, detail::extractor_type_id(&Extractor::execute));
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90 | }
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91 | private:
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92 | static void* extract(PyObject* op)
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93 | {
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94 | return PyObject_TypeCheck(op, const_cast<PyTypeObject*>(python_type))
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95 | ? const_cast<void*>(
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96 | static_cast<void const volatile*>(
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97 | detail::normalize<Extractor>(&Extractor::execute).execute(op)))
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98 | : 0
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99 | ;
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100 | }
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101 | };
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102 |
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103 | }} // namespace boost::python
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104 |
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105 | #endif // LVALUE_FROM_PYTYPE_DWA2002130_HPP
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