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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/. */
/* Iterator over ranges of integers */
#ifndef mozilla_IntegerRange_h
#define mozilla_IntegerRange_h
#include "mozilla/Assertions.h"
#include "mozilla/ReverseIterator.h"
#include <iterator>
#include <type_traits>
namespace mozilla {
namespace detail {
template <typename IntTypeT>
class IntegerIterator {
public:
// It is disputable whether these type definitions are correct, since
// operator* doesn't return a reference at all. Also, the iterator_category
// can be at most std::input_iterator_tag (rather than
// std::bidrectional_iterator_tag, as it might seem), because it is a stashing
// iterator. See also, e.g.,
// https://stackoverflow.com/questions/50909701/what-should-be-iterator-category-for-a-stashing-iterator
using value_type = const IntTypeT;
using pointer = const value_type*;
using reference = const value_type&;
using difference_type = std::make_signed_t<IntTypeT>;
using iterator_category = std::input_iterator_tag;
template <typename IntType>
explicit IntegerIterator(IntType aCurrent) : mCurrent(aCurrent) {}
template <typename IntType>
explicit IntegerIterator(const IntegerIterator<IntType>& aOther)
: mCurrent(aOther.mCurrent) {}
// This intentionally returns a value rather than a reference, to make
// mozilla::ReverseIterator work with it. Still, std::reverse_iterator cannot
// be used with IntegerIterator because it still is a "stashing iterator". See
// Bug 1175485.
IntTypeT operator*() const { return mCurrent; }
/* Increment and decrement operators */
IntegerIterator& operator++() {
++mCurrent;
return *this;
}
IntegerIterator& operator--() {
--mCurrent;
return *this;
}
IntegerIterator operator++(int) {
auto ret = *this;
++mCurrent;
return ret;
}
IntegerIterator operator--(int) {
auto ret = *this;
--mCurrent;
return ret;
}
/* Comparison operators */
template <typename IntType1, typename IntType2>
friend bool operator==(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2);
template <typename IntType1, typename IntType2>
friend bool operator!=(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2);
template <typename IntType1, typename IntType2>
friend bool operator<(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2);
template <typename IntType1, typename IntType2>
friend bool operator<=(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2);
template <typename IntType1, typename IntType2>
friend bool operator>(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2);
template <typename IntType1, typename IntType2>
friend bool operator>=(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2);
private:
IntTypeT mCurrent;
};
template <typename IntType1, typename IntType2>
bool operator==(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2) {
return aIter1.mCurrent == aIter2.mCurrent;
}
template <typename IntType1, typename IntType2>
bool operator!=(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2) {
return aIter1.mCurrent != aIter2.mCurrent;
}
template <typename IntType1, typename IntType2>
bool operator<(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2) {
return aIter1.mCurrent < aIter2.mCurrent;
}
template <typename IntType1, typename IntType2>
bool operator<=(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2) {
return aIter1.mCurrent <= aIter2.mCurrent;
}
template <typename IntType1, typename IntType2>
bool operator>(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2) {
return aIter1.mCurrent > aIter2.mCurrent;
}
template <typename IntType1, typename IntType2>
bool operator>=(const IntegerIterator<IntType1>& aIter1,
const IntegerIterator<IntType2>& aIter2) {
return aIter1.mCurrent >= aIter2.mCurrent;
}
template <typename IntTypeT>
class IntegerRange {
public:
typedef IntegerIterator<IntTypeT> iterator;
typedef IntegerIterator<IntTypeT> const_iterator;
typedef ReverseIterator<IntegerIterator<IntTypeT>> reverse_iterator;
typedef ReverseIterator<IntegerIterator<IntTypeT>> const_reverse_iterator;
template <typename IntType>
explicit IntegerRange(IntType aEnd) : mBegin(0), mEnd(aEnd) {}
template <typename IntType1, typename IntType2>
IntegerRange(IntType1 aBegin, IntType2 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(iterator(mEnd)); }
const_reverse_iterator crbegin() const { return rbegin(); }
reverse_iterator rend() const { return reverse_iterator(iterator(mBegin)); }
const_reverse_iterator crend() const { return rend(); }
private:
IntTypeT mBegin;
IntTypeT mEnd;
};
template <typename T, bool = std::is_unsigned_v<T>>
struct GeqZero {
static bool isNonNegative(T t) { return t >= 0; }
};
template <typename T>
struct GeqZero<T, true> {
static bool isNonNegative(T t) { return true; }
};
} // namespace detail
template <typename IntType>
detail::IntegerRange<IntType> IntegerRange(IntType aEnd) {
static_assert(std::is_integral_v<IntType>, "value must be integral");
MOZ_ASSERT(detail::GeqZero<IntType>::isNonNegative(aEnd),
"Should never have negative value here");
return detail::IntegerRange<IntType>(aEnd);
}
template <typename IntType1, typename IntType2>
detail::IntegerRange<IntType2> IntegerRange(IntType1 aBegin, IntType2 aEnd) {
static_assert(std::is_integral_v<IntType1> && std::is_integral_v<IntType2>,
"values must both be integral");
static_assert(std::is_signed_v<IntType1> == std::is_signed_v<IntType2>,
"signed/unsigned mismatch");
MOZ_ASSERT(aEnd >= aBegin, "End value should be larger than begin value");
return detail::IntegerRange<IntType2>(aBegin, aEnd);
}
} // namespace mozilla
#endif // mozilla_IntegerRange_h
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