summaryrefslogtreecommitdiffstats
path: root/mfbt/IntegerRange.h
diff options
context:
space:
mode:
Diffstat (limited to 'mfbt/IntegerRange.h')
-rw-r--r--mfbt/IntegerRange.h192
1 files changed, 192 insertions, 0 deletions
diff --git a/mfbt/IntegerRange.h b/mfbt/IntegerRange.h
new file mode 100644
index 0000000000..4415031454
--- /dev/null
+++ b/mfbt/IntegerRange.h
@@ -0,0 +1,192 @@
+/* -*- 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