129 lines
4.4 KiB
C++
129 lines
4.4 KiB
C++
// Copyright ⓒ 2018-2021 ThePhD.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// See https://github.com/ThePhD/out_ptr/blob/master/docs/out_ptr.adoc for documentation.
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#include <ztd/out_ptr.hpp>
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#include <boost/core/empty_value.hpp>
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#include <boost/smart_ptr/local_shared_ptr.hpp>
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#include <avformat.h>
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// a shared pointer
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// that we need to make sure is
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// not used with inout_ptr
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// because ownership is not unique or releasable!
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template <typename T>
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struct my_company_shared_ptr : public ztd::local_shared_ptr<T> {};
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// type to allow us to use static assert
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// that is not eagerly evaluated
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template <typename>
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struct dependent_type_false : std::true_type {};
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// this customization point is the more powerful version
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namespace ztd { namespace out_ptr {
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template <typename T, typename Pointer, typename... Args>
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class inout_ptr_t<my_company_shared_ptr<T>, Pointer, Args...> {
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static_assert(dependent_type_false<T>::value,
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"you cannot release from a shared pointer "
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"there is no way to release the resource from all "
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"the shared pointers!");
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};
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// require all out_ptr calls to need
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// a deleter argument to make it
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// safer to use
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template <typename T, typename D, typename Pointer, typename... Args>
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class out_ptr_t<my_company_shared_ptr<T, D>, Pointer, Args...> : std::tuple<Args...> {
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private:
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using Smart = my_company_shared_ptr<T>;
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using source_pointer = pointer_of_or_t<Smart, Pointer>;
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using ArgsTuple = std::tuple<Args...>;
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using Base = ArgsTuple;
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static_assert(sizeof...(Args) > 0, "you forgot to pass a deleter: it will (most likely) be reset to the wrong one!");
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Smart* m_smart_ptr;
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Pointer m_target_ptr;
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public:
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out_ptr_t(Smart& s, Args... args) noexcept
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: Base(std::forward<Args>(args)...), m_smart_ptr(std::addressof(s)), m_old_ptr(s.get()), m_target_ptr() {
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}
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out_ptr_t(out_ptr_t&& right) noexcept
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: Base(std::move(right)), m_smart_ptr(right.m_smart_ptr), m_old_ptr(right.m_old_ptr), m_target_ptr(right.m_target_ptr) {
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right.m_old_ptr = nullptr;
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}
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out_ptr_t& operator=(out_ptr_t&& right) noexcept {
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Base::operator =(std::move(right));
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this->m_smart_ptr = std::move(right.m_smart_ptr);
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this->m_target_ptr = std::move(right.m_target_ptr);
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right.m_smart_ptr = nullptr;
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return *this;
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}
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operator Pointer*() const noexcept {
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return const_cast<Pointer*>(this->m_target_ptr);
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}
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~out_ptr_t() noexcept {
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reset(ztd::out_ptr::op_detail::make_index_sequence<std::tuple_size<std::tuple<Args...>>::value>());
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}
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private:
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template <std::size_t I0, std::size_t... I>
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void reset(ztd::out_ptr::op_detail::index_sequence<I0, I...>) {
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if (this->m_smart_ptr != nullptr) {
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Base&& base = static_cast<Base&&>(*this);
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this->m_smart_ptr->reset(static_cast<source_pointer>(this->m_target_ptr, std::get<I0>(std::move(base)), std::get<I>(std::move(base))...));
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}
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}
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};
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}} // namespace ztd::out_ptr
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struct av_format_context_deleter {
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void operator()(AVFormatContext* c) noexcept {
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avformat_close_input(&c);
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avformat_free_context(c);
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}
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};
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using av_format_context_ptr = my_company_shared_ptr<AVFormatContext>;
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int main(int, char* argv[]) {
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using zop = ztd::out_ptr;
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av_format_context_ptr context(avformat_alloc_context());
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// cannot use it with inout_ptr
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//if (0 != avformat_open_input(pop::out_ptr(raw_context, av_format_context_deleter{}), argv[0], nullptr, nullptr)) { ... }
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// cannot use it wihout a deleter
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//if (0 != avformat_open_input(pop::out_ptr(raw_context, av_format_context_deleter{}), argv[0], nullptr, nullptr)) { ... }
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// this is the only way to use it properly!
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if (0 != avformat_open_input(pop::out_ptr(raw_context, av_format_context_deleter{}), argv[0], nullptr, nullptr)) {
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std::stringstream ss;
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ss << "ffmpeg_image_loader could not open file '"
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<< path << "'";
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throw FFmpegInputException(ss.str().c_str());
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}
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return 0;
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}
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