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| -rw-r--r-- | mfbt/EnumeratedRange.h | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/mfbt/EnumeratedRange.h b/mfbt/EnumeratedRange.h new file mode 100644 index 0000000000..74d9592392 --- /dev/null +++ b/mfbt/EnumeratedRange.h @@ -0,0 +1,206 @@ +/* -*- 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/. */ + +/* Iterator over contiguous enum values */ + +/* + * Implements generator functions that create a range to iterate over the values + * of a scoped or unscoped enum. Unlike IntegerRange, which can only function on + * the underlying integral type, the elements of the generated sequence will + * have the type of the enum in question. + * + * Note that the enum values should be contiguous in the iterated range; + * unfortunately there exists no way for EnumeratedRange to enforce this + * either dynamically or at compile time. + */ + +#ifndef mozilla_EnumeratedRange_h +#define mozilla_EnumeratedRange_h + +#include <limits> +#include <type_traits> + +#include "mozilla/Assertions.h" +#include "mozilla/ReverseIterator.h" + +namespace mozilla { + +namespace detail { + +template <typename EnumTypeT> +class EnumeratedIterator { + public: + typedef typename std::underlying_type<EnumTypeT>::type IntTypeT; + + template <typename EnumType> + constexpr explicit EnumeratedIterator(EnumType aCurrent) + : mCurrent(aCurrent) {} + + template <typename EnumType> + explicit EnumeratedIterator(const EnumeratedIterator<EnumType>& aOther) + : mCurrent(aOther.mCurrent) {} + + EnumTypeT operator*() const { return mCurrent; } + + /* Increment and decrement operators */ + + EnumeratedIterator& operator++() { + mCurrent = EnumTypeT(IntTypeT(mCurrent) + IntTypeT(1)); + return *this; + } + EnumeratedIterator& operator--() { + mCurrent = EnumTypeT(IntTypeT(mCurrent) - IntTypeT(1)); + return *this; + } + EnumeratedIterator operator++(int) { + auto ret = *this; + mCurrent = EnumTypeT(IntTypeT(mCurrent) + IntTypeT(1)); + return ret; + } + EnumeratedIterator operator--(int) { + auto ret = *this; + mCurrent = EnumTypeT(IntTypeT(mCurrent) - IntTypeT(1)); + return ret; + } + + /* Comparison operators */ + + template <typename EnumType> + friend bool operator==(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2); + template <typename EnumType> + friend bool operator!=(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2); + template <typename EnumType> + friend bool operator<(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2); + template <typename EnumType> + friend bool operator<=(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2); + template <typename EnumType> + friend bool operator>(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2); + template <typename EnumType> + friend bool operator>=(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2); + + private: + EnumTypeT mCurrent; +}; + +template <typename EnumType> +bool operator==(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2) { + return aIter1.mCurrent == aIter2.mCurrent; +} + +template <typename EnumType> +bool operator!=(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2) { + return aIter1.mCurrent != aIter2.mCurrent; +} + +template <typename EnumType> +bool operator<(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2) { + return aIter1.mCurrent < aIter2.mCurrent; +} + +template <typename EnumType> +bool operator<=(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2) { + return aIter1.mCurrent <= aIter2.mCurrent; +} + +template <typename EnumType> +bool operator>(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2) { + return aIter1.mCurrent > aIter2.mCurrent; +} + +template <typename EnumType> +bool operator>=(const EnumeratedIterator<EnumType>& aIter1, + const EnumeratedIterator<EnumType>& aIter2) { + return aIter1.mCurrent >= aIter2.mCurrent; +} + +template <typename EnumTypeT> +class EnumeratedRange { + public: + typedef EnumeratedIterator<EnumTypeT> iterator; + typedef EnumeratedIterator<EnumTypeT> const_iterator; + typedef ReverseIterator<iterator> reverse_iterator; + typedef ReverseIterator<const_iterator> const_reverse_iterator; + + template <typename EnumType> + constexpr EnumeratedRange(EnumType aBegin, EnumType aEnd) + : mBegin(aBegin), mEnd(aEnd) {} + + iterator begin() const { return iterator(mBegin); } + const_iterator cbegin() const { return begin(); } + iterator end() const { return iterator(mEnd); } + const_iterator cend() const { return end(); } + reverse_iterator rbegin() const { return reverse_iterator(mEnd); } + const_reverse_iterator crbegin() const { return rbegin(); } + reverse_iterator rend() const { return reverse_iterator(mBegin); } + const_reverse_iterator crend() const { return rend(); } + + private: + EnumTypeT mBegin; + EnumTypeT mEnd; +}; + +} // namespace detail + +#ifdef __GNUC__ +// Enums can have an unsigned underlying type, which makes some of the +// comparisons below always true or always false. Temporarily disable +// -Wtype-limits to avoid breaking -Werror builds. +# pragma GCC diagnostic push +# pragma GCC diagnostic ignored "-Wtype-limits" +#endif + +// Create a range to iterate from aBegin to aEnd, exclusive. +template <typename EnumType> +constexpr detail::EnumeratedRange<EnumType> MakeEnumeratedRange(EnumType aBegin, + EnumType aEnd) { + MOZ_ASSERT(aBegin <= aEnd, "Cannot generate invalid, unbounded range!"); + return detail::EnumeratedRange<EnumType>(aBegin, aEnd); +} + +// Create a range to iterate from EnumType(0) to aEnd, exclusive. EnumType(0) +// should exist, but note that there is no way for us to ensure that it does! +template <typename EnumType> +constexpr detail::EnumeratedRange<EnumType> MakeEnumeratedRange(EnumType aEnd) { + return MakeEnumeratedRange(EnumType(0), aEnd); +} + +// Create a range to iterate from aBegin to aEnd, inclusive. +// +// NOTE: This internally constructs a value that is one past `aEnd`, so the +// enumeration needs to either have a fixed underlying type, or `aEnd + 1` must +// be inside the range of the enumeration, in order to not be undefined +// behavior. +// +// See bug 1614512. +template <typename EnumType> +constexpr detail::EnumeratedRange<EnumType> MakeInclusiveEnumeratedRange( + EnumType aBegin, EnumType aEnd) { + using EnumUnderlyingType = typename std::underlying_type_t<EnumType>; + const auto end = static_cast<EnumUnderlyingType>(aEnd); + + MOZ_ASSERT(end != std::numeric_limits<EnumUnderlyingType>::max(), + "aEnd shouldn't overflow!"); + return MakeEnumeratedRange(aBegin, static_cast<EnumType>(end + 1)); +} + +#ifdef __GNUC__ +# pragma GCC diagnostic pop +#endif + +} // namespace mozilla + +#endif // mozilla_EnumeratedRange_h |