/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* vim: set ts=8 sts=2 et sw=2 tw=80: */ /* This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* * Implements various helper functions related to arrays.
*/
#ifdef __cplusplus # include <algorithm> # include <array> # include <type_traits>
# include "mozilla/Alignment.h"
namespace mozilla {
/* * Safely subtract two pointers when it is known that aEnd >= aBegin, yielding a * size_t result. * * Ordinary pointer subtraction yields a ptrdiff_t result, which, being signed, * has insufficient range to express the distance between pointers at opposite * ends of the address space. Furthermore, most compilers use ptrdiff_t to * represent the intermediate byte address distance, before dividing by * sizeof(T); if that intermediate result overflows, they'll produce results * with the wrong sign even when the correct scaled distance would fit in a * ptrdiff_t.
*/ template <class T>
MOZ_ALWAYS_INLINE size_t PointerRangeSize(T* aBegin, T* aEnd) {
MOZ_ASSERT(aEnd >= aBegin); return (size_t(aEnd) - size_t(aBegin)) / sizeof(T);
}
/** * std::equal has subpar ergonomics.
*/
template <typename T, typename U, size_t N> bool ArrayEqual(const T (&a)[N], const U (&b)[N]) { return std::equal(a, a + N, b);
}
template <typename T, typename U> bool ArrayEqual(const T* const a, const U* const b, const size_t n) { return std::equal(a, a + n, b);
}
namespace detail {
template <typename AlignType, typename Pointee, typename = void> struct AlignedChecker { staticvoid test(const Pointee* aPtr) {
MOZ_ASSERT((uintptr_t(aPtr) % alignof(AlignType)) == 0, "performing a range-check with a misaligned pointer");
}
};
/** * Determines whether |aPtr| points at an object in the range [aBegin, aEnd). * * |aPtr| must have the same alignment as |aBegin| and |aEnd|. This usually * should be achieved by ensuring |aPtr| points at a |U|, not just that it * points at a |T|. * * It is a usage error for any argument to be misaligned. * * It's okay for T* to be void*, and if so U* may also be void*. In the latter * case no argument is required to be aligned (obviously, as void* implies no * particular alignment).
*/ template <typename T, typename U> inline std::enable_if_t<std::is_same_v<T, U> || std::is_base_of<T, U>::value ||
std::is_void_v<T>, bool>
IsInRange(const T* aPtr, const U* aBegin, const U* aEnd) {
MOZ_ASSERT(aBegin <= aEnd);
detail::AlignedChecker<U, T>::test(aPtr);
detail::AlignedChecker<U, U>::test(aBegin);
detail::AlignedChecker<U, U>::test(aEnd); return aBegin <= reinterpret_cast<const U*>(aPtr) && reinterpret_cast<const U*>(aPtr) < aEnd;
}
/** * Convenience version of the above method when the valid range is specified as * uintptr_t values. As above, |aPtr| must be aligned, and |aBegin| and |aEnd| * must be aligned with respect to |T|.
*/ template <typename T> inlinebool IsInRange(const T* aPtr, uintptr_t aBegin, uintptr_t aEnd) { return IsInRange(aPtr, reinterpret_cast<const T*>(aBegin), reinterpret_cast<const T*>(aEnd));
}
} /* namespace mozilla */
#endif/* __cplusplus */
#endif/* mozilla_ArrayUtils_h */
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