106 lines
3.1 KiB
C++
106 lines
3.1 KiB
C++
// Copyright 2019 The MediaPipe Authors.
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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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// MakeCleanup(f) returns an RAII cleanup object that calls 'f' in its
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// destructor. The easiest way to use MakeCleanup is with a lambda argument,
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// capturing the return value in an 'auto' local variable. Most users will not
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// need more sophisticated syntax than that.
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//
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// Example:
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// void func() {}
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// FILE* fp = fopen("data.txt", "r");
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// if (fp == nullptr) return;
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// auto fp_cleaner = mediapipe::MakeCleanup([fp] { fclose(fp); });
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// // No matter what, fclose(fp) will happen.
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// DataObject d;
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// while (ReadDataObject(fp, &d)) {
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// if (d.IsBad()) {
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// LOG(ERROR) << "Bad Data";
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// return;
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// }
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// PushGoodData(d);
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// }
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// }
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#ifndef MEDIAPIPE_DEPS_CLEANUP_H_
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#define MEDIAPIPE_DEPS_CLEANUP_H_
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#include <type_traits>
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#include <utility>
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#include "absl/base/attributes.h"
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namespace mediapipe {
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template <typename F>
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class Cleanup {
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public:
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Cleanup() : released_(true), f_() {}
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template <typename G>
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explicit Cleanup(G&& f) // NOLINT
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: f_(std::forward<G>(f)) {} // NOLINT(build/c++11)
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Cleanup(Cleanup&& src) // NOLINT
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: released_(src.is_released()), f_(src.release()) {}
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// Implicitly move-constructible from any compatible Cleanup<G>.
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// The source will be released as if src.release() were called.
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// A moved-from Cleanup can be safely destroyed or reassigned.
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template <typename G>
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Cleanup(Cleanup<G>&& src) // NOLINT
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: released_(src.is_released()), f_(src.release()) {}
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// Assignment to a Cleanup object behaves like destroying it
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// and making a new one in its place, analogous to unique_ptr
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// semantics.
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Cleanup& operator=(Cleanup&& src) { // NOLINT
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if (!released_) f_();
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released_ = src.released_;
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f_ = src.release();
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return *this;
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}
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~Cleanup() {
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if (!released_) f_();
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}
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// Releases the cleanup function instead of running it.
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// Hint: use c.release()() to run early.
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F release() {
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released_ = true;
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return std::move(f_);
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}
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bool is_released() const { return released_; }
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private:
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static_assert(!std::is_reference<F>::value, "F must not be a reference");
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bool released_ = false;
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F f_;
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};
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template <int&... ExplicitParameterBarrier, typename F,
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typename DecayF = typename std::decay<F>::type>
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ABSL_MUST_USE_RESULT Cleanup<DecayF> MakeCleanup(F&& f) {
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static_assert(sizeof...(ExplicitParameterBarrier) == 0,
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"No explicit template arguments.");
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return Cleanup<DecayF>(std::forward<F>(f));
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}
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} // namespace mediapipe
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#endif // MEDIAPIPE_DEPS_CLEANUP_H_
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