text: // Copyright 2021 the V8 project authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef INCLUDE_CPPGC_EXPLICIT_MANAGEMENT_H_
  #define INCLUDE_CPPGC_EXPLICIT_MANAGEMENT_H_
  
  #include <cstddef>
  
  #include "cppgc/allocation.h"
  #include "cppgc/internal/logging.h"
  #include "cppgc/type-traits.h"
  
  namespace cppgc {
  
  class HeapHandle;
  
  namespace internal {
  
  V8_EXPORT void FreeUnreferencedObject(HeapHandle&, void*);
  V8_EXPORT bool Resize(void*, size_t);
  
  }  // namespace internal
  
  namespace subtle {
  
  /**
   * Informs the garbage collector that `object` can be immediately reclaimed. The
   * destructor may not be invoked immediately but only on next garbage
   * collection.
   *
   * It is up to the embedder to guarantee that no other object holds a reference
   * to `object` after calling `FreeUnreferencedObject()`. In case such a
   * reference exists, it's use results in a use-after-free.
   *
   * To aid in using the API, `FreeUnreferencedObject()` may be called from
   * destructors on objects that would be reclaimed in the same garbage collection
   * cycle.
   *
   * \param heap_handle The corresponding heap.
   * \param object Reference to an object that is of type `GarbageCollected` and
   *   should be immediately reclaimed.
   */
  template <typename T>
  void FreeUnreferencedObject(HeapHandle& heap_handle, T& object) {
    static_assert(IsGarbageCollectedTypeV<T>,
                  "Object must be of type GarbageCollected.");
    internal::FreeUnreferencedObject(heap_handle, &object);
  }
  
  /**
   * Tries to resize `object` of type `T` with additional bytes on top of
   * sizeof(T). Resizing is only useful with trailing inlined storage, see e.g.
   * `MakeGarbageCollected(AllocationHandle&, AdditionalBytes)`.
   *
   * `Resize()` performs growing or shrinking as needed and may skip the operation
   * for internal reasons, see return value.
   *
   * It is up to the embedder to guarantee that in case of shrinking a larger
   * object down, the reclaimed area is not used anymore. Any subsequent use
   * results in a use-after-free.
   *
   * The `object` must be live when calling `Resize()`.
   *
   * \param object Reference to an object that is of type `GarbageCollected` and
   *   should be resized.
   * \param additional_bytes Bytes in addition to sizeof(T) that the object should
   *   provide.
   * \returns true when the operation was successful and the result can be relied
   *   on, and false otherwise.
   */
  template <typename T>
  bool Resize(T& object, AdditionalBytes additional_bytes) {
    static_assert(IsGarbageCollectedTypeV<T>,
                  "Object must be of type GarbageCollected.");
    return internal::Resize(&object, sizeof(T) + additional_bytes.value);
  }
  
  }  // namespace subtle
  }  // namespace cppgc
  
  #endif  // INCLUDE_CPPGC_EXPLICIT_MANAGEMENT_H_
  