/*

 * Copyright (c) Meta Platforms, Inc. and affiliates.

 *

 * This source code is licensed under the MIT license found in the

 * LICENSE file in the root directory of this source tree.

 */

#ifndef HERMES_VM_HEAPRUNTIME_H

#define HERMES_VM_HEAPRUNTIME_H

#include "hermes/VM/StorageProvider.h"

namespace hermes {

namespace vm {

/// Helper class to create a runtime object instantiated on the heap and manage

/// its lifetime via an aliased shared_ptr. It can be used with any

/// StorageProvider, and will consume the entirety of the next available segment

/// from the provider.

template <typename RT>

class HeapRuntime {

 public:

  ~HeapRuntime() {

    runtime_->~RT();

    sp_->deleteStorage(runtime_);

  }

  /// Allocate a segment and create an aliased shared_ptr that points to the

  /// start of the segment, but manages the lifetime of a HeapRuntime<RT>. The

  /// caller must instantiate an RT in the returned storage, and its destructor

  /// will automatically be called when the HeapRuntime is destroyed.

  static std::shared_ptr<RT> create(std::shared_ptr<StorageProvider> sp) {

    auto hrt = std::shared_ptr<HeapRuntime>(new HeapRuntime(std::move(sp)));

    return std::shared_ptr<RT>(hrt, hrt->runtime_);

  }

 private:

  HeapRuntime(std::shared_ptr<StorageProvider> sp) : sp_{std::move(sp)} {

    auto ptrOrError = sp_->newStorage("hermes-rt");

    if (!ptrOrError)

      hermes_fatal("Cannot initialize Runtime storage.", ptrOrError.getError());

    static_assert(sizeof(RT) < AlignedStorage::size(), "Segments too small.");

    runtime_ = static_cast<RT *>(*ptrOrError);

  }

  std::shared_ptr<StorageProvider> sp_;

  RT *runtime_;

};

} // namespace vm

} // namespace hermes

#endif // HERMES_VM_HEAPRUNTIME_H