/* -*- 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. */ #ifndef mozilla_ArrayUtils_h #define mozilla_ArrayUtils_h #include "mozilla/Assertions.h" #include "mozilla/Attributes.h" #include <stddef.h> #ifdef __cplusplus #include "mozilla/Alignment.h" #include "mozilla/Array.h" #include "mozilla/EnumeratedArray.h" #include "mozilla/TypeTraits.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); } /* * Compute the length of an array with constant length. (Use of this method * with a non-array pointer will not compile.) * * Beware of the implicit trailing '\0' when using this with string constants. */ template<typename T, size_t N> constexpr size_t ArrayLength(T (&aArr)[N]) { return N; } template<typename T, size_t N> constexpr size_t ArrayLength(const Array<T, N>& aArr) { return N; } template<typename E, E N, typename T> constexpr size_t ArrayLength(const EnumeratedArray<E, N, T>& aArr) { return size_t(N); } /* * Compute the address one past the last element of a constant-length array. * * Beware of the implicit trailing '\0' when using this with string constants. */ template<typename T, size_t N> constexpr T* ArrayEnd(T (&aArr)[N]) { return aArr + ArrayLength(aArr); } template<typename T, size_t N> constexpr T* ArrayEnd(Array<T, N>& aArr) { return &aArr[0] + ArrayLength(aArr); } template<typename T, size_t N> constexpr const T* ArrayEnd(const Array<T, N>& aArr) { return &aArr[0] + ArrayLength(aArr); } namespace detail { template<typename AlignType, typename Pointee, typename = EnableIf<!IsVoid<AlignType>::value>> struct AlignedChecker { static void test(const Pointee* aPtr) { MOZ_ASSERT((uintptr_t(aPtr) % MOZ_ALIGNOF(AlignType)) == 0, "performing a range-check with a misaligned pointer"); } }; template<typename AlignType, typename Pointee> struct AlignedChecker<AlignType, Pointee> { static void test(const Pointee* aPtr) { } }; } // namespace detail /** * 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 typename EnableIf<IsSame<T, U>::value || IsBaseOf<T, U>::value || IsVoid<T>::value, bool>::Type 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> inline bool IsInRange(const T* aPtr, uintptr_t aBegin, uintptr_t aEnd) { return IsInRange(aPtr, reinterpret_cast<const T*>(aBegin), reinterpret_cast<const T*>(aEnd)); } namespace detail { /* * Helper for the MOZ_ARRAY_LENGTH() macro to make the length a typesafe * compile-time constant even on compilers lacking constexpr support. */ template <typename T, size_t N> char (&ArrayLengthHelper(T (&array)[N]))[N]; } /* namespace detail */ } /* namespace mozilla */ #endif /* __cplusplus */ /* * MOZ_ARRAY_LENGTH() is an alternative to mozilla::ArrayLength() for C files * that can't use C++ template functions and for static_assert() calls that * can't call ArrayLength() when it is not a C++11 constexpr function. */ #ifdef __cplusplus # define MOZ_ARRAY_LENGTH(array) sizeof(mozilla::detail::ArrayLengthHelper(array)) #else # define MOZ_ARRAY_LENGTH(array) (sizeof(array)/sizeof((array)[0])) #endif #endif /* mozilla_ArrayUtils_h */