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 
13 namespace cppgc {
14 namespace internal {
15 
16 // The class is needed in the header to allow for fast access to HeapHandle in
17 // the write barrier.
18 class BasePageHandle {
19  public:
FromPayload(void* payload)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   }
FromPayload(const void* payload)26   static V8_INLINE const BasePageHandle* FromPayload(const void* payload) {
27     return FromPayload(const_cast<void*>(payload));
28   }
29 
heap_handle()30   HeapHandle& heap_handle() { return heap_handle_; }
heap_handle() const31   const HeapHandle& heap_handle() const { return heap_handle_; }
32 
33  protected:
BasePageHandle(HeapHandle& heap_handle)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