michael@0: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
michael@0: /* vim: set ts=8 sts=2 et sw=2 tw=80: */
michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: /*
michael@0:  * Implements various helper functions related to arrays.
michael@0:  */
michael@0: 
michael@0: #ifndef mozilla_ArrayUtils_h
michael@0: #define mozilla_ArrayUtils_h
michael@0: 
michael@0: #include "mozilla/Assertions.h"
michael@0: #include "mozilla/Attributes.h"
michael@0: 
michael@0: #include <stddef.h>
michael@0: 
michael@0: #ifdef __cplusplus
michael@0: 
michael@0: #include "mozilla/Array.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: /*
michael@0:  * Safely subtract two pointers when it is known that end >= begin.  This avoids
michael@0:  * the common compiler bug that if (size_t(end) - size_t(begin)) has the MSB
michael@0:  * set, the unsigned subtraction followed by right shift will produce -1, or
michael@0:  * size_t(-1), instead of the real difference.
michael@0:  */
michael@0: template<class T>
michael@0: MOZ_ALWAYS_INLINE size_t
michael@0: PointerRangeSize(T* begin, T* end)
michael@0: {
michael@0:   MOZ_ASSERT(end >= begin);
michael@0:   return (size_t(end) - size_t(begin)) / sizeof(T);
michael@0: }
michael@0: 
michael@0: /*
michael@0:  * Compute the length of an array with constant length.  (Use of this method
michael@0:  * with a non-array pointer will not compile.)
michael@0:  *
michael@0:  * Beware of the implicit trailing '\0' when using this with string constants.
michael@0:  */
michael@0: template<typename T, size_t N>
michael@0: MOZ_CONSTEXPR size_t
michael@0: ArrayLength(T (&arr)[N])
michael@0: {
michael@0:   return N;
michael@0: }
michael@0: 
michael@0: template<typename T, size_t N>
michael@0: MOZ_CONSTEXPR size_t
michael@0: ArrayLength(const Array<T, N>& arr)
michael@0: {
michael@0:   return N;
michael@0: }
michael@0: 
michael@0: /*
michael@0:  * Compute the address one past the last element of a constant-length array.
michael@0:  *
michael@0:  * Beware of the implicit trailing '\0' when using this with string constants.
michael@0:  */
michael@0: template<typename T, size_t N>
michael@0: MOZ_CONSTEXPR T*
michael@0: ArrayEnd(T (&arr)[N])
michael@0: {
michael@0:   return arr + ArrayLength(arr);
michael@0: }
michael@0: 
michael@0: template<typename T, size_t N>
michael@0: MOZ_CONSTEXPR T*
michael@0: ArrayEnd(Array<T, N>& arr)
michael@0: {
michael@0:   return &arr[0] + ArrayLength(arr);
michael@0: }
michael@0: 
michael@0: template<typename T, size_t N>
michael@0: MOZ_CONSTEXPR const T*
michael@0: ArrayEnd(const Array<T, N>& arr)
michael@0: {
michael@0:   return &arr[0] + ArrayLength(arr);
michael@0: }
michael@0: 
michael@0: namespace detail {
michael@0: 
michael@0: /*
michael@0:  * Helper for the MOZ_ARRAY_LENGTH() macro to make the length a typesafe
michael@0:  * compile-time constant even on compilers lacking constexpr support.
michael@0:  */
michael@0: template <typename T, size_t N>
michael@0: char (&ArrayLengthHelper(T (&array)[N]))[N];
michael@0: 
michael@0: } /* namespace detail */
michael@0: 
michael@0: } /* namespace mozilla */
michael@0: 
michael@0: #endif /* __cplusplus */
michael@0: 
michael@0: /*
michael@0:  * MOZ_ARRAY_LENGTH() is an alternative to mozilla::ArrayLength() for C files
michael@0:  * that can't use C++ template functions and for static_assert() calls that
michael@0:  * can't call ArrayLength() when it is not a C++11 constexpr function.
michael@0:  */
michael@0: #ifdef __cplusplus
michael@0: #  define MOZ_ARRAY_LENGTH(array)   sizeof(mozilla::detail::ArrayLengthHelper(array))
michael@0: #else
michael@0: #  define MOZ_ARRAY_LENGTH(array)   (sizeof(array)/sizeof((array)[0]))
michael@0: #endif
michael@0: 
michael@0: #endif /* mozilla_ArrayUtils_h */