Bug 1126701 - Add IntegerRange for iterating integers. r=waldo

--HG--
extra : source : 2977cf3c5b545826a4ec0cdf245e804574cf7ff9

mfbt/IntegerRange.h

+/* -*- 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/TypeTraits.h"
+#include "mozilla/ReverseIterator.h"
+
+namespace mozilla {
+
+namespace detail {
+
+template<typename IntTypeT>
+class IntegerIterator
+{
+public:
+  typedef const IntTypeT ValueType;
+  typedef typename MakeSigned<IntTypeT>::Type DifferenceType;
+
+  template<typename IntType>
+  explicit IntegerIterator(IntType aCurrent)
+    : mCurrent(aCurrent) { }
+
+  template<typename IntType>
+  IntegerIterator(const IntegerIterator<IntType>& aOther)
+    : mCurrent(aOther.mCurrent) { }
+
+  // Since operator* is required to return a reference, we return
+  // the reference of our member here.
+  const IntTypeT& operator*() const { return mCurrent; }
+
+  /* Increments and descrements 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; }
+
+  IntegerIterator operator+(DifferenceType aN) const
+  {
+    return IntegerIterator(mCurrent + aN);
+  }
+  IntegerIterator operator-(DifferenceType aN) const
+  {
+    return IntegerIterator(mCurrent - aN);
+  }
+  IntegerIterator& operator+=(DifferenceType aN)
+  {
+    mCurrent += aN;
+    return *this;
+  }
+  IntegerIterator& operator-=(DifferenceType aN)
+  {
+    mCurrent -= aN;
+    return *this;
+  }
+
+  /* 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(mEnd); }
+  const_reverse_iterator crbegin() const { return rbegin(); }
+  reverse_iterator rend() const { return reverse_iterator(mBegin); }
+  const_reverse_iterator crend() const { return rend(); }
+
+private:
+  IntTypeT mBegin;
+  IntTypeT mEnd;
+};
+
+template<typename T, bool = IsUnsigned<T>::value>
+struct GeqZero
+{
+  static bool check(T t) {
+    return t >= 0;
+  }
+};
+
+template<typename T>
+struct GeqZero<T, true>
+{
+  static bool check(T t) {
+    return true;
+  }
+};
+
+} // namespace detail
+
+template<typename IntType>
+detail::IntegerRange<IntType>
+MakeRange(IntType aEnd)
+{
+  MOZ_ASSERT(detail::GeqZero<IntType>::check(aEnd),
+             "Should never have negative value here");
+  return detail::IntegerRange<IntType>(aEnd);
+}
+
+template<typename IntType1, typename IntType2>
+detail::IntegerRange<IntType2>
+MakeRange(IntType1 aBegin, IntType2 aEnd)
+{
+  static_assert(IsSigned<IntType1>::value == IsSigned<IntType2>::value,
+                "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

mfbt/moz.build

@@ -37,6 +37,7 @@ EXPORTS.mozilla = [
     'GuardObjects.h',
     'HashFunctions.h',
     'IntegerPrintfMacros.h',
+    'IntegerRange.h',
     'IntegerTypeTraits.h',
     'IteratorTraits.h',
     'JSONWriter.h',