1// Copyright 2022 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef INCLUDE_CPPGC_INTERNAL_BASE_PAGE_HANDLE_H_
6#define INCLUDE_CPPGC_INTERNAL_BASE_PAGE_HANDLE_H_
7
8#include "cppgc/heap-handle.h"
9#include "cppgc/internal/api-constants.h"
10#include "cppgc/internal/logging.h"
11#include "v8config.h"  // NOLINT(build/include_directory)
12
13namespace cppgc {
14namespace internal {
15
16// The class is needed in the header to allow for fast access to HeapHandle in
17// the write barrier.
18class BasePageHandle {
19 public:
20  static V8_INLINE BasePageHandle* FromPayload(void* payload) {
21    return reinterpret_cast<BasePageHandle*>(
22        (reinterpret_cast<uintptr_t>(payload) &
23         ~(api_constants::kPageSize - 1)) +
24        api_constants::kGuardPageSize);
25  }
26  static V8_INLINE const BasePageHandle* FromPayload(const void* payload) {
27    return FromPayload(const_cast<void*>(payload));
28  }
29
30  HeapHandle& heap_handle() { return heap_handle_; }
31  const HeapHandle& heap_handle() const { return heap_handle_; }
32
33 protected:
34  explicit BasePageHandle(HeapHandle& heap_handle) : heap_handle_(heap_handle) {
35    CPPGC_DCHECK(reinterpret_cast<uintptr_t>(this) % api_constants::kPageSize ==
36                 api_constants::kGuardPageSize);
37  }
38
39  HeapHandle& heap_handle_;
40};
41
42}  // namespace internal
43}  // namespace cppgc
44
45#endif  // INCLUDE_CPPGC_INTERNAL_BASE_PAGE_HANDLE_H_
46