// 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_SENTINEL_POINTER_H_
#define INCLUDE_CPPGC_SENTINEL_POINTER_H_
#include <cstdint>
#include "cppgc/internal/api-constants.h"
namespace cppgc {
namespace internal {
// Special tag type used to denote some sentinel member. The semantics of the
// sentinel is defined by the embedder.
struct SentinelPointer {
#if defined(CPPGC_POINTER_COMPRESSION)
static constexpr intptr_t kSentinelValue =
1 << api_constants::kPointerCompressionShift;
#else // !defined(CPPGC_POINTER_COMPRESSION)
static constexpr intptr_t kSentinelValue = 0b10;
#endif // !defined(CPPGC_POINTER_COMPRESSION)
template <typename T>
operator T*() const {
return reinterpret_cast<T*>(kSentinelValue);
}
// Hidden friends.
friend bool operator==(SentinelPointer, SentinelPointer) { return true; }
friend bool operator!=(SentinelPointer, SentinelPointer) { return false; }
};
} // namespace internal
constexpr internal::SentinelPointer kSentinelPointer;
} // namespace cppgc
#endif // INCLUDE_CPPGC_SENTINEL_POINTER_H_
