110 lines
4.3 KiB
C++
110 lines
4.3 KiB
C++
// This file is distributed under the BSD License.
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// See "license.txt" for details.
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// Copyright 2009-2012, Jonathan Turner (jonathan@emptycrate.com)
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// Copyright 2009-2016, Jason Turner (jason@emptycrate.com)
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// http://www.chaiscript.com
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#ifndef CHAISCRIPT_BOXED_CAST_HPP_
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#define CHAISCRIPT_BOXED_CAST_HPP_
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#include "../chaiscript_defines.hpp"
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#include "bad_boxed_cast.hpp"
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#include "boxed_cast_helper.hpp"
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#include "boxed_value.hpp"
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#include "type_conversions.hpp"
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#include "type_info.hpp"
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namespace chaiscript {
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class Type_Conversions;
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namespace detail {
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namespace exception {
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class bad_any_cast;
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} // namespace exception
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} // namespace detail
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} // namespace chaiscript
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namespace chaiscript
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{
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/// \brief Function for extracting a value stored in a Boxed_Value object
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/// \tparam Type The type to extract from the Boxed_Value
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/// \param[in] bv The Boxed_Value to extract a typed value from
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/// \returns Type equivalent to the requested type
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/// \throws exception::bad_boxed_cast If the requested conversion is not possible
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///
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/// boxed_cast will attempt to make conversions between value, &, *, std::shared_ptr, std::reference_wrapper,
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/// and std::function (const and non-const) where possible. boxed_cast is used internally during function
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/// dispatch. This means that all of these conversions will be attempted automatically for you during
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/// ChaiScript function calls.
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///
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/// \li non-const values can be extracted as const or non-const
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/// \li const values can be extracted only as const
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/// \li Boxed_Value constructed from pointer or std::reference_wrapper can be extracted as reference,
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/// pointer or value types
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/// \li Boxed_Value constructed from std::shared_ptr or value types can be extracted as reference,
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/// pointer, value, or std::shared_ptr types
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///
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/// Conversions to std::function objects are attempted as well
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///
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/// Example:
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/// \code
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/// // All of the following should succeed
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/// chaiscript::Boxed_Value bv(1);
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/// std::shared_ptr<int> spi = chaiscript::boxed_cast<std::shared_ptr<int> >(bv);
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/// int i = chaiscript::boxed_cast<int>(bv);
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/// int *ip = chaiscript::boxed_cast<int *>(bv);
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/// int &ir = chaiscript::boxed_cast<int &>(bv);
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/// std::shared_ptr<const int> cspi = chaiscript::boxed_cast<std::shared_ptr<const int> >(bv);
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/// const int ci = chaiscript::boxed_cast<const int>(bv);
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/// const int *cip = chaiscript::boxed_cast<const int *>(bv);
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/// const int &cir = chaiscript::boxed_cast<const int &>(bv);
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/// \endcode
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///
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/// std::function conversion example
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/// \code
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/// chaiscript::ChaiScript chai;
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/// Boxed_Value bv = chai.eval("`+`"); // Get the functor for the + operator which is built in
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/// std::function<int (int, int)> f = chaiscript::boxed_cast<std::function<int (int, int)> >(bv);
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/// int i = f(2,3);
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/// assert(i == 5);
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/// \endcode
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template<typename Type>
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typename detail::Cast_Helper<Type>::Result_Type boxed_cast(const Boxed_Value &bv, const Type_Conversions_State *t_conversions = nullptr)
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{
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if (!t_conversions || bv.get_type_info().bare_equal(user_type<Type>()) || (t_conversions && !(*t_conversions)->convertable_type<Type>())) {
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try {
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return detail::Cast_Helper<Type>::cast(bv, t_conversions);
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} catch (const chaiscript::detail::exception::bad_any_cast &) {
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}
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}
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if (t_conversions && (*t_conversions)->convertable_type<Type>())
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{
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try {
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// We will not catch any bad_boxed_dynamic_cast that is thrown, let the user get it
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// either way, we are not responsible if it doesn't work
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return detail::Cast_Helper<Type>::cast((*t_conversions)->boxed_type_conversion<Type>(t_conversions->saves(), bv), t_conversions);
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} catch (...) {
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try {
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// try going the other way
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return detail::Cast_Helper<Type>::cast((*t_conversions)->boxed_type_down_conversion<Type>(t_conversions->saves(), bv), t_conversions);
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} catch (const chaiscript::detail::exception::bad_any_cast &) {
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throw exception::bad_boxed_cast(bv.get_type_info(), typeid(Type));
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}
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}
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} else {
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// If it's not convertable, just throw the error, don't waste the time on the
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// attempted dynamic_cast
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throw exception::bad_boxed_cast(bv.get_type_info(), typeid(Type));
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}
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}
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}
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#endif
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