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