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// Copyright 2017 The Crashpad Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef CRASHPAD_UTIL_MISC_FROM_POINTER_CAST_H_
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#define CRASHPAD_UTIL_MISC_FROM_POINTER_CAST_H_
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#include <stdint.h>
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#include <cstddef>
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#include <type_traits>
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#include "base/numerics/safe_conversions.h"
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namespace crashpad {
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#if DOXYGEN
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//! \brief Casts from a pointer type to an integer.
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//!
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//! Compared to `reinterpret_cast<>()`, FromPointerCast<>() defines whether a
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//! pointer type is sign-extended or zero-extended. Casts to signed integral
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//! types are sign-extended. Casts to unsigned integral types are zero-extended.
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//!
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//! Use FromPointerCast<>() instead of `reinterpret_cast<>()` when casting a
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//! pointer to an integral type that may not be the same width as a pointer.
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//! There is no need to prefer FromPointerCast<>() when casting to an integral
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//! type that’s definitely the same width as a pointer, such as `uintptr_t` and
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//! `intptr_t`.
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template <typename To, typename From>
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FromPointerCast(From from) {
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return reinterpret_cast<To>(from);
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}
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#else // DOXYGEN
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// Cast std::nullptr_t to any type.
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//
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// In C++14, the nullptr_t check could use std::is_null_pointer<From>::value
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// instead of the is_same<remove_cv<From>::type, nullptr_t>::type construct.
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template <typename To, typename From>
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typename std::enable_if<
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std::is_same<typename std::remove_cv<From>::type, std::nullptr_t>::value,
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To>::type
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FromPointerCast(From) {
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return To();
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}
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// Cast a pointer to any other pointer type.
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template <typename To, typename From>
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typename std::enable_if<std::is_pointer<From>::value &&
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std::is_pointer<To>::value,
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To>::type
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FromPointerCast(From from) {
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return reinterpret_cast<To>(from);
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}
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// Cast a pointer to an integral type. Sign-extend when casting to a signed
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// type, zero-extend when casting to an unsigned type.
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template <typename To, typename From>
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typename std::enable_if<std::is_pointer<From>::value &&
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std::is_integral<To>::value,
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To>::type
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FromPointerCast(From from) {
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const auto intermediate =
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reinterpret_cast<typename std::conditional<std::is_signed<To>::value,
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intptr_t,
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uintptr_t>::type>(from);
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if (sizeof(To) >= sizeof(From)) {
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// If the destination integral type is at least as wide as the source
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// pointer type, use static_cast<>() and just return it.
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return static_cast<To>(intermediate);
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}
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// If the destination integral type is narrower than the source pointer type,
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// use checked_cast<>().
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return base::checked_cast<To>(intermediate);
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}
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#endif // DOXYGEN
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} // namespace crashpad
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#endif // CRASHPAD_UTIL_MISC_FROM_POINTER_CAST_H_
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