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Support etl::inplace_function
Provide similar api to std::function. Store a callable inside the inplace_function object's member field in a type-erasure way. The member field, i.e. storage or buffer, has a compile-time fixed size. The size is specify either by the macro ETL_INPLACE_FUNCTION_DEFAULT_CAPACITY or a non-type template parameter. The implementation is inspired by: 1. SG14 inplace_function 2. folly::Function 3. function2
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‎include/etl/file_error_numbers.h

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#define ETL_BASE64_FILE_ID "72"
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#define ETL_SINGLETON_BASE_FILE_ID "73"
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#define ETL_UNALIGNED_TYPE_FILE_ID "74"
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#define ETL_INPLACE_FUNCTION_FILE_ID "75"
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#endif

‎include/etl/inplace_function.h

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///\file
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/******************************************************************************
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The MIT License(MIT)
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Embedded Template Library.
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https://github.com/ETLCPP/etl
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https://www.etlcpp.com
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Copyright(c) 2025 BMW AG
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files(the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions :
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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******************************************************************************/
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#ifndef ETL_INPLACE_FUNCTION_INCLUDED
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#define ETL_INPLACE_FUNCTION_INCLUDED
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#include "platform.h"
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#if ETL_USING_CPP11
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#include "private/inplace_function_cpp11.h"
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#endif
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#endif

‎include/etl/private/inplace_function_cpp11.h

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///\file
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/******************************************************************************
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The MIT License(MIT)
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Embedded Template Library.
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https://github.com/ETLCPP/etl
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https://www.etlcpp.com
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Copyright(c) 2025 BMW AG
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files(the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions :
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR rhs
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR rhsWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR rhs DEALINGS IN THE
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SOFTWARE.
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******************************************************************************/
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#ifndef ETL_INPLACE_FUNCTION_CPP11_INCLUDED
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#define ETL_INPLACE_FUNCTION_CPP11_INCLUDED
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#include "../platform.h"
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#include "../error_handler.h"
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#include "../exception.h"
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#include "../type_traits.h"
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#include "../utility.h"
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#ifndef ETL_INPLACE_FUNCTION_DEFAULT_CAPACITY
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#define ETL_INPLACE_FUNCTION_DEFAULT_CAPACITY 32
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#endif
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namespace etl
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{
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template <
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typename Signature,
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size_t Capacity = ETL_INPLACE_FUNCTION_DEFAULT_CAPACITY>
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class inplace_function;
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namespace private_inplace_function
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{
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template <typename>
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struct is_inplace_function : etl::false_type
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{
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};
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template <typename Sig, size_t Cap>
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struct is_inplace_function<inplace_function<Sig, Cap>> : etl::true_type
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{
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};
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} // namespace private_inplace_function
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class inplace_function_exception : public etl::exception
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{
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public:
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inplace_function_exception(string_type reason_, string_type file_name_, numeric_type line_number_)
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: exception(reason_, file_name_, line_number_)
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{
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}
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};
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class bad_inplace_function_call : public inplace_function_exception
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{
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public:
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bad_inplace_function_call(string_type file_name_, numeric_type line_number_)
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: inplace_function_exception(ETL_ERROR_TEXT("inplace_function:call", ETL_INPLACE_FUNCTION_FILE_ID "A"), file_name_, line_number_)
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{
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}
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};
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template <
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typename R,
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typename... Args,
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size_t Capacity>
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class inplace_function<R(Args...), Capacity> ETL_FINAL
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{
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public:
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using capacity = etl::integral_constant<size_t, Capacity>;
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inplace_function() = default;
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template <
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typename T,
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typename C = etl::decay_t<T>,
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typename = etl::enable_if_t<
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!private_inplace_function::is_inplace_function<C>::value && etl::is_invocable_r<R, C&, Args...>::value>>
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inplace_function(T&& closure)
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{
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ETL_STATIC_ASSERT(etl::is_copy_constructible<C>::value,
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"cannot be constructed from non-copyable types");
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ETL_STATIC_ASSERT(sizeof(C) <= Capacity,
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"internal storage too small");
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static const vtable_t vt{etl::type_identity<C>{}};
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vtable_ptr = &vt;
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::new (obj) C{etl::forward<T>(closure)};
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}
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template <size_t Cap>
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inplace_function(const inplace_function<R(Args...), Cap>& rhs)
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: inplace_function(rhs.vtable_ptr, rhs.vtable_ptr->copy_func, rhs.obj)
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{
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ETL_STATIC_ASSERT(Cap <= Capacity,
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"internal storage too small");
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}
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template <size_t Cap>
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inplace_function(inplace_function<R(Args...), Cap>&& rhs) ETL_NOEXCEPT
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: inplace_function(rhs.vtable_ptr, rhs.vtable_ptr->move_func, rhs.obj)
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{
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ETL_STATIC_ASSERT(Cap <= Capacity,
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"internal storage too small");
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rhs.vtable_ptr = &default_vtable;
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}
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inplace_function(const inplace_function& rhs)
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: vtable_ptr{rhs.vtable_ptr}
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{
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vtable_ptr->copy_func(
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obj,
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rhs.obj);
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}
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inplace_function(inplace_function&& rhs) ETL_NOEXCEPT
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: vtable_ptr{rhs.vtable_ptr}
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{
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rhs.vtable_ptr = &default_vtable;
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vtable_ptr->move_func(
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obj,
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rhs.obj);
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}
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inplace_function& operator=(etl::nullptr_t) ETL_NOEXCEPT
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{
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vtable_ptr->dtor_func(&obj);
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vtable_ptr = ETL_NULLPTR;
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return *this;
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}
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inplace_function& operator=(inplace_function rhs) ETL_NOEXCEPT
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{
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vtable_ptr->dtor_func(obj);
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vtable_ptr = rhs.vtable_ptr;
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rhs.vtable_ptr = &default_vtable;
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vtable_ptr->move_func(
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obj,
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rhs.obj);
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return *this;
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}
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~inplace_function()
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{
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vtable_ptr->dtor_func(obj);
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}
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R operator()(Args... args) const
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{
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ETL_ASSERT(vtable_ptr->invoke_func, ETL_ERROR(bad_inplace_function_call));
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return vtable_ptr->invoke_func(
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obj,
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etl::forward<Args>(args)...);
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}
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explicit ETL_CONSTEXPR operator bool() const ETL_NOEXCEPT
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{
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return vtable_ptr != &default_vtable;
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}
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private:
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template <typename, size_t>
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friend class inplace_function;
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struct vtable_t ETL_FINAL
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{
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using invoke_func_t = R (*)(char*, Args&&...);
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using copy_or_move_func_t = void (*)(char*, char*);
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using dtor_func_t = void (*)(char*);
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const invoke_func_t invoke_func{ETL_NULLPTR};
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const copy_or_move_func_t copy_func{[](char*, char*) -> void {}};
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const copy_or_move_func_t move_func{[](char*, char*) -> void {}};
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const dtor_func_t dtor_func{[](char*) -> void {}};
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~vtable_t() = default;
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vtable_t() = default;
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template <typename T>
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explicit ETL_CONSTEXPR vtable_t(etl::type_identity<T>) ETL_NOEXCEPT
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: invoke_func{[](char* pobj, Args&&... args) -> R
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{ return (*reinterpret_cast<T*>(pobj))(
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etl::forward<Args&&>(args)...); }},
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copy_func{[](char* dst_obj, char* src_obj) -> void
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{ ::new (dst_obj) T{*reinterpret_cast<T*>(src_obj)}; }},
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move_func{[](char* dst_obj, char* src_obj) -> void
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{
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::new (dst_obj) T{etl::move(*reinterpret_cast<T*>(src_obj))};
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reinterpret_cast<T*>(src_obj)->~T();
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}},
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dtor_func{[](char* pobj) -> void
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{ reinterpret_cast<T*>(pobj)->~T(); }}
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{
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}
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private:
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vtable_t(const vtable_t&) ETL_DELETE;
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vtable_t(vtable_t&&) ETL_NOEXCEPT ETL_DELETE;
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vtable_t& operator=(const vtable_t&) ETL_DELETE;
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vtable_t& operator=(vtable_t&&) ETL_DELETE;
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};
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static const vtable_t default_vtable;
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const vtable_t* vtable_ptr{&default_vtable};
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mutable char obj[Capacity];
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explicit inplace_function(
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const vtable_t* vtable,
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typename vtable_t::copy_or_move_func_t copy_or_move_func,
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char* obj_ptr)
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: vtable_ptr{vtable}
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{
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copy_or_move_func(obj, obj_ptr);
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}
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};
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template <
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typename R,
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typename... Args,
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size_t Capacity>
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const typename inplace_function<R(Args...), Capacity>::vtable_t
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inplace_function<R(Args...), Capacity>::default_vtable{};
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} // namespace etl
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#endif

‎test/CMakeLists.txt

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test_histogram.cpp
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test_indirect_vector.cpp
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test_indirect_vector_external_buffer.cpp
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test_inplace_function.cpp
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test_instance_count.cpp
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test_integral_limits.cpp
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test_intrusive_forward_list.cpp

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