Bug 1142999 - Add an EnumeratedRange class to iterate EnumeratedArrays. r=nfroyd

mfbt/EnumeratedRange.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 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 "mozilla/IntegerRange.h"
+#include "mozilla/IntegerTypeTraits.h"
+
+namespace mozilla {
+
+namespace detail {
+
+template<typename IntTypeT, typename EnumTypeT>
+class EnumeratedIterator
+{
+public:
+  typedef const EnumTypeT ValueType;
+  typedef typename MakeSigned<IntTypeT>::Type DifferenceType;
+
+  template<typename EnumType>
+  explicit EnumeratedIterator(EnumType aCurrent)
+    : mCurrent(aCurrent) { }
+
+  template<typename IntType, typename EnumType>
+  EnumeratedIterator(const EnumeratedIterator<IntType, EnumType>& aOther)
+    : mCurrent(aOther.mCurrent) { }
+
+  // Since operator* is required to return a reference, we return
+  // a reference to our member here.
+  const 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;
+  }
+
+  EnumeratedIterator operator+(DifferenceType aN) const
+  {
+    return EnumeratedIterator(EnumTypeT(IntTypeT(mCurrent) + aN));
+  }
+  EnumeratedIterator operator-(DifferenceType aN) const
+  {
+    return EnumeratedIterator(EnumTypeT(IntTypeT(mCurrent) - aN));
+  }
+  EnumeratedIterator& operator+=(DifferenceType aN)
+  {
+    mCurrent = EnumTypeT(IntTypeT(mCurrent) + aN);
+    return *this;
+  }
+  EnumeratedIterator& operator-=(DifferenceType aN)
+  {
+    mCurrent = EnumTypeT(IntTypeT(mCurrent) - aN);
+    return *this;
+  }
+
+  /* Comparison operators */
+
+  template<typename IntType, typename EnumType>
+  friend bool operator==(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                         const EnumeratedIterator<IntType, EnumType>& aIter2);
+  template<typename IntType, typename EnumType>
+  friend bool operator!=(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                         const EnumeratedIterator<IntType, EnumType>& aIter2);
+  template<typename IntType, typename EnumType>
+  friend bool operator<(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                        const EnumeratedIterator<IntType, EnumType>& aIter2);
+  template<typename IntType, typename EnumType>
+  friend bool operator<=(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                         const EnumeratedIterator<IntType, EnumType>& aIter2);
+  template<typename IntType, typename EnumType>
+  friend bool operator>(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                        const EnumeratedIterator<IntType, EnumType>& aIter2);
+  template<typename IntType, typename EnumType>
+  friend bool operator>=(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                         const EnumeratedIterator<IntType, EnumType>& aIter2);
+
+private:
+  EnumTypeT mCurrent;
+};
+
+template<typename IntType, typename EnumType>
+bool operator==(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                const EnumeratedIterator<IntType, EnumType>& aIter2)
+{
+  return aIter1.mCurrent == aIter2.mCurrent;
+}
+
+template<typename IntType, typename EnumType>
+bool operator!=(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                const EnumeratedIterator<IntType, EnumType>& aIter2)
+{
+  return aIter1.mCurrent != aIter2.mCurrent;
+}
+
+template<typename IntType, typename EnumType>
+bool operator<(const EnumeratedIterator<IntType, EnumType>& aIter1,
+               const EnumeratedIterator<IntType, EnumType>& aIter2)
+{
+  return aIter1.mCurrent < aIter2.mCurrent;
+}
+
+template<typename IntType, typename EnumType>
+bool operator<=(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                const EnumeratedIterator<IntType, EnumType>& aIter2)
+{
+  return aIter1.mCurrent <= aIter2.mCurrent;
+}
+
+template<typename IntType, typename EnumType>
+bool operator>(const EnumeratedIterator<IntType, EnumType>& aIter1,
+               const EnumeratedIterator<IntType, EnumType>& aIter2)
+{
+  return aIter1.mCurrent > aIter2.mCurrent;
+}
+
+template<typename IntType, typename EnumType>
+bool operator>=(const EnumeratedIterator<IntType, EnumType>& aIter1,
+                const EnumeratedIterator<IntType, EnumType>& aIter2)
+{
+  return aIter1.mCurrent >= aIter2.mCurrent;
+}
+
+template<typename IntTypeT, typename EnumTypeT>
+class EnumeratedRange
+{
+public:
+  typedef EnumeratedIterator<IntTypeT, EnumTypeT> iterator;
+  typedef EnumeratedIterator<IntTypeT, EnumTypeT> const_iterator;
+  typedef ReverseIterator<iterator> reverse_iterator;
+  typedef ReverseIterator<const_iterator> const_reverse_iterator;
+
+  template<typename EnumType>
+  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 IntType, typename EnumType>
+inline detail::EnumeratedRange<IntType, EnumType>
+MakeEnumeratedRange(EnumType aBegin, EnumType aEnd)
+{
+  typedef typename MakeUnsigned<IntType>::Type UnsignedType;
+  static_assert(sizeof(IntType) >= sizeof(EnumType),
+                "IntType should be at least as big as EnumType!");
+  MOZ_ASSERT(aBegin <= aEnd, "Cannot generate invalid, unbounded range!");
+  MOZ_ASSERT_IF(aBegin < EnumType(0), IsSigned<IntType>::value);
+  MOZ_ASSERT_IF(aBegin >= EnumType(0) && IsSigned<IntType>::value,
+                UnsignedType(aEnd) <= UnsignedType(MaxValue<IntType>::value));
+  return detail::EnumeratedRange<IntType, 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 IntType, typename EnumType>
+inline detail::EnumeratedRange<IntType, EnumType>
+MakeEnumeratedRange(EnumType aEnd)
+{
+  return MakeEnumeratedRange<IntType>(EnumType(0), aEnd);
+}
+
+#ifdef __GNUC__
+#  pragma GCC diagnostic pop
+#endif
+
+} // namespace mozilla
+
+#endif // mozilla_EnumeratedRange_h
+

mfbt/IntegerRange.h

@@ -33,10 +33,10 @@ public:
     : mCurrent(aOther.mCurrent) { }
 
   // Since operator* is required to return a reference, we return
-  // the reference of our member here.
+  // a reference to our member here.
   const IntTypeT& operator*() const { return mCurrent; }
 
-  /* Increments and descrements operators */
+  /* Increment and decrement operators */
 
   IntegerIterator& operator++() { ++mCurrent; return *this; }
   IntegerIterator& operator--() { --mCurrent; return *this; }

mfbt/moz.build

@@ -32,6 +32,7 @@ EXPORTS.mozilla = [
     'double-conversion/utils.h',
     'Endian.h',
     'EnumeratedArray.h',
+    'EnumeratedRange.h',
     'EnumSet.h',
     'FloatingPoint.h',
     'GuardObjects.h',