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/* -*- 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
/* 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.
//
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));
}
template <typename EnumType>
constexpr auto MakeInclusiveEnumeratedRange(EnumType aEnd) {
return MakeInclusiveEnumeratedRange(EnumType{0}, aEnd);
}
#ifdef __GNUC__
# pragma GCC diagnostic pop
#endif
} // namespace mozilla
#endif // mozilla_EnumeratedRange_h