1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/mfbt/ArrayUtils.h Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,111 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* vim: set ts=8 sts=2 et sw=2 tw=80: */
1.6 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.7 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.8 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.9 +
1.10 +/*
1.11 + * Implements various helper functions related to arrays.
1.12 + */
1.13 +
1.14 +#ifndef mozilla_ArrayUtils_h
1.15 +#define mozilla_ArrayUtils_h
1.16 +
1.17 +#include "mozilla/Assertions.h"
1.18 +#include "mozilla/Attributes.h"
1.19 +
1.20 +#include <stddef.h>
1.21 +
1.22 +#ifdef __cplusplus
1.23 +
1.24 +#include "mozilla/Array.h"
1.25 +
1.26 +namespace mozilla {
1.27 +
1.28 +/*
1.29 + * Safely subtract two pointers when it is known that end >= begin. This avoids
1.30 + * the common compiler bug that if (size_t(end) - size_t(begin)) has the MSB
1.31 + * set, the unsigned subtraction followed by right shift will produce -1, or
1.32 + * size_t(-1), instead of the real difference.
1.33 + */
1.34 +template<class T>
1.35 +MOZ_ALWAYS_INLINE size_t
1.36 +PointerRangeSize(T* begin, T* end)
1.37 +{
1.38 + MOZ_ASSERT(end >= begin);
1.39 + return (size_t(end) - size_t(begin)) / sizeof(T);
1.40 +}
1.41 +
1.42 +/*
1.43 + * Compute the length of an array with constant length. (Use of this method
1.44 + * with a non-array pointer will not compile.)
1.45 + *
1.46 + * Beware of the implicit trailing '\0' when using this with string constants.
1.47 + */
1.48 +template<typename T, size_t N>
1.49 +MOZ_CONSTEXPR size_t
1.50 +ArrayLength(T (&arr)[N])
1.51 +{
1.52 + return N;
1.53 +}
1.54 +
1.55 +template<typename T, size_t N>
1.56 +MOZ_CONSTEXPR size_t
1.57 +ArrayLength(const Array<T, N>& arr)
1.58 +{
1.59 + return N;
1.60 +}
1.61 +
1.62 +/*
1.63 + * Compute the address one past the last element of a constant-length array.
1.64 + *
1.65 + * Beware of the implicit trailing '\0' when using this with string constants.
1.66 + */
1.67 +template<typename T, size_t N>
1.68 +MOZ_CONSTEXPR T*
1.69 +ArrayEnd(T (&arr)[N])
1.70 +{
1.71 + return arr + ArrayLength(arr);
1.72 +}
1.73 +
1.74 +template<typename T, size_t N>
1.75 +MOZ_CONSTEXPR T*
1.76 +ArrayEnd(Array<T, N>& arr)
1.77 +{
1.78 + return &arr[0] + ArrayLength(arr);
1.79 +}
1.80 +
1.81 +template<typename T, size_t N>
1.82 +MOZ_CONSTEXPR const T*
1.83 +ArrayEnd(const Array<T, N>& arr)
1.84 +{
1.85 + return &arr[0] + ArrayLength(arr);
1.86 +}
1.87 +
1.88 +namespace detail {
1.89 +
1.90 +/*
1.91 + * Helper for the MOZ_ARRAY_LENGTH() macro to make the length a typesafe
1.92 + * compile-time constant even on compilers lacking constexpr support.
1.93 + */
1.94 +template <typename T, size_t N>
1.95 +char (&ArrayLengthHelper(T (&array)[N]))[N];
1.96 +
1.97 +} /* namespace detail */
1.98 +
1.99 +} /* namespace mozilla */
1.100 +
1.101 +#endif /* __cplusplus */
1.102 +
1.103 +/*
1.104 + * MOZ_ARRAY_LENGTH() is an alternative to mozilla::ArrayLength() for C files
1.105 + * that can't use C++ template functions and for static_assert() calls that
1.106 + * can't call ArrayLength() when it is not a C++11 constexpr function.
1.107 + */
1.108 +#ifdef __cplusplus
1.109 +# define MOZ_ARRAY_LENGTH(array) sizeof(mozilla::detail::ArrayLengthHelper(array))
1.110 +#else
1.111 +# define MOZ_ARRAY_LENGTH(array) (sizeof(array)/sizeof((array)[0]))
1.112 +#endif
1.113 +
1.114 +#endif /* mozilla_ArrayUtils_h */
