src/utils/ScopedAutoreleasePool.h

// Copyright 2021 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef UTILS_SCOPEDAUTORELEASEPOOL_H_
#define UTILS_SCOPEDAUTORELEASEPOOL_H_

#include "common/Compiler.h"

#include <cstddef>

namespace utils {

    /**
     * ScopedAutoreleasePool is a scoped class which initializes an NSAutoreleasePool on
     * creation, and drains it on destruction. On non-Apple platforms, ScopedAutoreleasePool
     * is a no-op.
     *
     * An autoreleasepool is needed when using protocol objects in Objective-C because Cocoa
     * expects a pool to always be available in each thread. If a pool is not available, then
     * autoreleased objects will never be released and will leak.
     *
     * In long-running blocks of code or loops, it is important to periodically create and drain
     * autorelease pools so that memory is recycled. In Dawn's tests, we have an autoreleasepool
     * per-test. In graphics applications it's advised to create an autoreleasepool around the
     * frame loop. Ex.)
     *   void frame() {
     *     // Any protocol objects will be reclaimed when this object falls out of scope.
     *     utils::ScopedAutoreleasePool pool;
     *
     *     // do rendering ...
     *   }
     */
    class [[nodiscard]] ScopedAutoreleasePool {
      public:
        ScopedAutoreleasePool();
        ~ScopedAutoreleasePool();

        ScopedAutoreleasePool(const ScopedAutoreleasePool&) = delete;
        ScopedAutoreleasePool& operator=(const ScopedAutoreleasePool&) = delete;

        ScopedAutoreleasePool(ScopedAutoreleasePool&&);
        ScopedAutoreleasePool& operator=(ScopedAutoreleasePool&&);

      private:
        void* mPool = nullptr;
    };

}  // namespace utils

#endif  // UTILS_SCOPEDAUTORELEASEPOOL_H_