// Copyright 2022 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_INTERNAL_BASE_PAGE_HANDLE_H_

#define INCLUDE_CPPGC_INTERNAL_BASE_PAGE_HANDLE_H_

#include "cppgc/heap-handle.h"

#include "cppgc/internal/api-constants.h"

#include "cppgc/internal/logging.h"

#include "v8config.h"  // NOLINT(build/include_directory)

namespace cppgc {

namespace internal {

// The class is needed in the header to allow for fast access to HeapHandle in

// the write barrier.

class BasePageHandle {

 public:

  static V8_INLINE BasePageHandle* FromPayload(void* payload) {

    return reinterpret_cast<BasePageHandle*>(

        (reinterpret_cast<uintptr_t>(payload) &

         ~(api_constants::kPageSize - 1)) +

        api_constants::kGuardPageSize);

  }

  static V8_INLINE const BasePageHandle* FromPayload(const void* payload) {

    return FromPayload(const_cast<void*>(payload));

  }

  HeapHandle& heap_handle() { return heap_handle_; }

  const HeapHandle& heap_handle() const { return heap_handle_; }

 protected:

  explicit BasePageHandle(HeapHandle& heap_handle) : heap_handle_(heap_handle) {

    CPPGC_DCHECK(reinterpret_cast<uintptr_t>(this) % api_constants::kPageSize ==

                 api_constants::kGuardPageSize);

  }

  HeapHandle& heap_handle_;

};

}  // namespace internal

}  // namespace cppgc

#endif  // INCLUDE_CPPGC_INTERNAL_BASE_PAGE_HANDLE_H_