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comparison: mfbt/ArrayUtils.h
mfbt/ArrayUtils.h
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
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| -1:000000000000 | 0:9d2ef9a7e3a5 |
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| 1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ | |
| 2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */ | |
| 3 /* This Source Code Form is subject to the terms of the Mozilla Public | |
| 4 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 6 | |
| 7 /* | |
| 8 * Implements various helper functions related to arrays. | |
| 9 */ | |
| 10 | |
| 11 #ifndef mozilla_ArrayUtils_h | |
| 12 #define mozilla_ArrayUtils_h | |
| 13 | |
| 14 #include "mozilla/Assertions.h" | |
| 15 #include "mozilla/Attributes.h" | |
| 16 | |
| 17 #include <stddef.h> | |
| 18 | |
| 19 #ifdef __cplusplus | |
| 20 | |
| 21 #include "mozilla/Array.h" | |
| 22 | |
| 23 namespace mozilla { | |
| 24 | |
| 25 /* | |
| 26 * Safely subtract two pointers when it is known that end >= begin. This avoids | |
| 27 * the common compiler bug that if (size_t(end) - size_t(begin)) has the MSB | |
| 28 * set, the unsigned subtraction followed by right shift will produce -1, or | |
| 29 * size_t(-1), instead of the real difference. | |
| 30 */ | |
| 31 template<class T> | |
| 32 MOZ_ALWAYS_INLINE size_t | |
| 33 PointerRangeSize(T* begin, T* end) | |
| 34 { | |
| 35 MOZ_ASSERT(end >= begin); | |
| 36 return (size_t(end) - size_t(begin)) / sizeof(T); | |
| 37 } | |
| 38 | |
| 39 /* | |
| 40 * Compute the length of an array with constant length. (Use of this method | |
| 41 * with a non-array pointer will not compile.) | |
| 42 * | |
| 43 * Beware of the implicit trailing '\0' when using this with string constants. | |
| 44 */ | |
| 45 template<typename T, size_t N> | |
| 46 MOZ_CONSTEXPR size_t | |
| 47 ArrayLength(T (&arr)[N]) | |
| 48 { | |
| 49 return N; | |
| 50 } | |
| 51 | |
| 52 template<typename T, size_t N> | |
| 53 MOZ_CONSTEXPR size_t | |
| 54 ArrayLength(const Array<T, N>& arr) | |
| 55 { | |
| 56 return N; | |
| 57 } | |
| 58 | |
| 59 /* | |
| 60 * Compute the address one past the last element of a constant-length array. | |
| 61 * | |
| 62 * Beware of the implicit trailing '\0' when using this with string constants. | |
| 63 */ | |
| 64 template<typename T, size_t N> | |
| 65 MOZ_CONSTEXPR T* | |
| 66 ArrayEnd(T (&arr)[N]) | |
| 67 { | |
| 68 return arr + ArrayLength(arr); | |
| 69 } | |
| 70 | |
| 71 template<typename T, size_t N> | |
| 72 MOZ_CONSTEXPR T* | |
| 73 ArrayEnd(Array<T, N>& arr) | |
| 74 { | |
| 75 return &arr[0] + ArrayLength(arr); | |
| 76 } | |
| 77 | |
| 78 template<typename T, size_t N> | |
| 79 MOZ_CONSTEXPR const T* | |
| 80 ArrayEnd(const Array<T, N>& arr) | |
| 81 { | |
| 82 return &arr[0] + ArrayLength(arr); | |
| 83 } | |
| 84 | |
| 85 namespace detail { | |
| 86 | |
| 87 /* | |
| 88 * Helper for the MOZ_ARRAY_LENGTH() macro to make the length a typesafe | |
| 89 * compile-time constant even on compilers lacking constexpr support. | |
| 90 */ | |
| 91 template <typename T, size_t N> | |
| 92 char (&ArrayLengthHelper(T (&array)[N]))[N]; | |
| 93 | |
| 94 } /* namespace detail */ | |
| 95 | |
| 96 } /* namespace mozilla */ | |
| 97 | |
| 98 #endif /* __cplusplus */ | |
| 99 | |
| 100 /* | |
| 101 * MOZ_ARRAY_LENGTH() is an alternative to mozilla::ArrayLength() for C files | |
| 102 * that can't use C++ template functions and for static_assert() calls that | |
| 103 * can't call ArrayLength() when it is not a C++11 constexpr function. | |
| 104 */ | |
| 105 #ifdef __cplusplus | |
| 106 # define MOZ_ARRAY_LENGTH(array) sizeof(mozilla::detail::ArrayLengthHelper(array)) | |
| 107 #else | |
| 108 # define MOZ_ARRAY_LENGTH(array) (sizeof(array)/sizeof((array)[0])) | |
| 109 #endif | |
| 110 | |
| 111 #endif /* mozilla_ArrayUtils_h */ |
