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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
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* An iterator that acts like another iterator, but iterating in
* the negative direction. (Note that not all iterators can iterate
* in the negative direction.) */
#ifndef mozilla_ReverseIterator_h
#define mozilla_ReverseIterator_h
#include <utility>
#include "mozilla/Attributes.h"
namespace mozilla {
// This should only be used in cases where std::reverse_iterator cannot be used,
// because the underlying iterator is not a proper bidirectional iterator, but
// rather, e.g., a stashing iterator such as IntegerIterator. It is less
// efficient than std::reverse_iterator for proper bidirectional iterators.
template <typename IteratorT>
class ReverseIterator {
public:
using value_type = typename IteratorT::value_type;
using pointer = typename IteratorT::pointer;
using reference = typename IteratorT::reference;
using difference_type = typename IteratorT::difference_type;
using iterator_category = typename IteratorT::iterator_category;
explicit ReverseIterator(IteratorT aIter) : mCurrent(std::move(aIter)) {}
// The return type is not reference, but rather the return type of
// Iterator::operator*(), which might be value_type, to allow this to work
// with stashing iterators such as IntegerIterator, see also Bug 1175485.
decltype(*std::declval<IteratorT>()) operator*() const {
IteratorT tmp = mCurrent;
return *--tmp;
}
/* Difference operator */
difference_type operator-(const ReverseIterator& aOther) const {
return aOther.mCurrent - mCurrent;
}
/* Increments and decrements operators */
ReverseIterator& operator++() {
--mCurrent;
return *this;
}
ReverseIterator& operator--() {
++mCurrent;
return *this;
}
ReverseIterator operator++(int) {
auto ret = *this;
mCurrent--;
return ret;
}
ReverseIterator operator--(int) {
auto ret = *this;
mCurrent++;
return ret;
}
/* Comparison operators */
template <typename Iterator1, typename Iterator2>
friend bool operator==(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2);
template <typename Iterator1, typename Iterator2>
friend bool operator!=(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2);
template <typename Iterator1, typename Iterator2>
friend bool operator<(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2);
template <typename Iterator1, typename Iterator2>
friend bool operator<=(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2);
template <typename Iterator1, typename Iterator2>
friend bool operator>(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2);
template <typename Iterator1, typename Iterator2>
friend bool operator>=(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2);
private:
IteratorT mCurrent;
};
template <typename Iterator1, typename Iterator2>
bool operator==(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2) {
return aIter1.mCurrent == aIter2.mCurrent;
}
template <typename Iterator1, typename Iterator2>
bool operator!=(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2) {
return aIter1.mCurrent != aIter2.mCurrent;
}
template <typename Iterator1, typename Iterator2>
bool operator<(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2) {
return aIter1.mCurrent > aIter2.mCurrent;
}
template <typename Iterator1, typename Iterator2>
bool operator<=(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2) {
return aIter1.mCurrent >= aIter2.mCurrent;
}
template <typename Iterator1, typename Iterator2>
bool operator>(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2) {
return aIter1.mCurrent < aIter2.mCurrent;
}
template <typename Iterator1, typename Iterator2>
bool operator>=(const ReverseIterator<Iterator1>& aIter1,
const ReverseIterator<Iterator2>& aIter2) {
return aIter1.mCurrent <= aIter2.mCurrent;
}
namespace detail {
template <typename IteratorT,
typename ReverseIteratorT = ReverseIterator<IteratorT>>
class IteratorRange {
public:
typedef IteratorT iterator;
typedef IteratorT const_iterator;
typedef ReverseIteratorT reverse_iterator;
typedef ReverseIteratorT const_reverse_iterator;
IteratorRange(IteratorT aIterBegin, IteratorT aIterEnd)
: mIterBegin(std::move(aIterBegin)), mIterEnd(std::move(aIterEnd)) {}
iterator begin() const { return mIterBegin; }
const_iterator cbegin() const { return begin(); }
iterator end() const { return mIterEnd; }
const_iterator cend() const { return end(); }
reverse_iterator rbegin() const { return reverse_iterator(mIterEnd); }
const_reverse_iterator crbegin() const { return rbegin(); }
reverse_iterator rend() const { return reverse_iterator(mIterBegin); }
const_reverse_iterator crend() const { return rend(); }
IteratorT mIterBegin;
IteratorT mIterEnd;
};
} // namespace detail
template <typename Range>
detail::IteratorRange<typename Range::reverse_iterator> Reversed(
Range& aRange) {
return {aRange.rbegin(), aRange.rend()};
}
template <typename Range>
detail::IteratorRange<typename Range::const_reverse_iterator> Reversed(
const Range& aRange) {
return {aRange.rbegin(), aRange.rend()};
}
} // namespace mozilla
#endif // mozilla_ReverseIterator_h
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