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v8/include/cppgc/internal/caged-heap.h

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+// 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_CAGED_HEAP_H_
+#define INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_H_
+
+#include <climits>
+#include <cstddef>
+
+#include "cppgc/internal/api-constants.h"
+#include "cppgc/internal/base-page-handle.h"
+#include "v8config.h"  // NOLINT(build/include_directory)
+
+#if defined(CPPGC_CAGED_HEAP)
+
+namespace cppgc {
+namespace internal {
+
+class V8_EXPORT CagedHeapBase {
+ public:
+  V8_INLINE static uintptr_t OffsetFromAddress(const void* address) {
+    return reinterpret_cast<uintptr_t>(address) &
+           (api_constants::kCagedHeapReservationAlignment - 1);
+  }
+
+  V8_INLINE static bool IsWithinCage(const void* address) {
+    CPPGC_DCHECK(g_heap_base_);
+    return (reinterpret_cast<uintptr_t>(address) &
+            ~(api_constants::kCagedHeapReservationAlignment - 1)) ==
+           g_heap_base_;
+  }
+
+  V8_INLINE static bool AreWithinCage(const void* addr1, const void* addr2) {
+#if defined(CPPGC_2GB_CAGE)
+    static constexpr size_t kHalfWordShift = sizeof(uint32_t) * CHAR_BIT - 1;
+#else   //! defined(CPPGC_2GB_CAGE)
+    static constexpr size_t kHalfWordShift = sizeof(uint32_t) * CHAR_BIT;
+#endif  //! defined(CPPGC_2GB_CAGE)
+    static_assert((static_cast<size_t>(1) << kHalfWordShift) ==
+                  api_constants::kCagedHeapReservationSize);
+    CPPGC_DCHECK(g_heap_base_);
+    return !(((reinterpret_cast<uintptr_t>(addr1) ^ g_heap_base_) |
+              (reinterpret_cast<uintptr_t>(addr2) ^ g_heap_base_)) >>
+             kHalfWordShift);
+  }
+
+  V8_INLINE static uintptr_t GetBase() { return g_heap_base_; }
+
+ private:
+  friend class CagedHeap;
+
+  static uintptr_t g_heap_base_;
+};
+
+}  // namespace internal
+}  // namespace cppgc
+
+#endif  // defined(CPPGC_CAGED_HEAP)
+
+#endif  // INCLUDE_CPPGC_INTERNAL_CAGED_HEAP_H_