mfbt/IntegerRange.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /* Iterator over ranges of integers */
   8
   9 #ifndef mozilla_IntegerRange_h
  10 #define mozilla_IntegerRange_h
  11
  12 #include "mozilla/Assertions.h"
  13 #include "mozilla/ReverseIterator.h"
  14 #include "mozilla/TypeTraits.h"
  15
  16 namespace mozilla {
  17
  18 namespace detail {
  19
  20 template<typename IntTypeT>
  21 class IntegerIterator
  22 {
  23 public:
  24   template<typename IntType>
  25   explicit IntegerIterator(IntType aCurrent)
  26     : mCurrent(aCurrent) { }
  27
  28   template<typename IntType>
  29   explicit IntegerIterator(const IntegerIterator<IntType>& aOther)
  30     : mCurrent(aOther.mCurrent) { }
  31
  32   IntTypeT operator*() const { return mCurrent; }
  33
  34   /* Increment and decrement operators */
  35
  36   IntegerIterator& operator++() { ++mCurrent; return *this; }
  37   IntegerIterator& operator--() { --mCurrent; return *this; }
  38   IntegerIterator operator++(int) { auto ret = *this; ++mCurrent; return ret; }
  39   IntegerIterator operator--(int) { auto ret = *this; --mCurrent; return ret; }
  40
  41   /* Comparison operators */
  42
  43   template<typename IntType1, typename IntType2>
  44   friend bool operator==(const IntegerIterator<IntType1>& aIter1,
  45                          const IntegerIterator<IntType2>& aIter2);
  46   template<typename IntType1, typename IntType2>
  47   friend bool operator!=(const IntegerIterator<IntType1>& aIter1,
  48                          const IntegerIterator<IntType2>& aIter2);
  49   template<typename IntType1, typename IntType2>
  50   friend bool operator<(const IntegerIterator<IntType1>& aIter1,
  51                         const IntegerIterator<IntType2>& aIter2);
  52   template<typename IntType1, typename IntType2>
  53   friend bool operator<=(const IntegerIterator<IntType1>& aIter1,
  54                          const IntegerIterator<IntType2>& aIter2);
  55   template<typename IntType1, typename IntType2>
  56   friend bool operator>(const IntegerIterator<IntType1>& aIter1,
  57                         const IntegerIterator<IntType2>& aIter2);
  58   template<typename IntType1, typename IntType2>
  59   friend bool operator>=(const IntegerIterator<IntType1>& aIter1,
  60                          const IntegerIterator<IntType2>& aIter2);
  61
  62 private:
  63   IntTypeT mCurrent;
  64 };
  65
  66 template<typename IntType1, typename IntType2>
  67 bool operator==(const IntegerIterator<IntType1>& aIter1,
  68                 const IntegerIterator<IntType2>& aIter2)
  69 {
  70   return aIter1.mCurrent == aIter2.mCurrent;
  71 }
  72
  73 template<typename IntType1, typename IntType2>
  74 bool operator!=(const IntegerIterator<IntType1>& aIter1,
  75                 const IntegerIterator<IntType2>& aIter2)
  76 {
  77   return aIter1.mCurrent != aIter2.mCurrent;
  78 }
  79
  80 template<typename IntType1, typename IntType2>
  81 bool operator<(const IntegerIterator<IntType1>& aIter1,
  82                const IntegerIterator<IntType2>& aIter2)
  83 {
  84   return aIter1.mCurrent < aIter2.mCurrent;
  85 }
  86
  87 template<typename IntType1, typename IntType2>
  88 bool operator<=(const IntegerIterator<IntType1>& aIter1,
  89                 const IntegerIterator<IntType2>& aIter2)
  90 {
  91   return aIter1.mCurrent <= aIter2.mCurrent;
  92 }
  93
  94 template<typename IntType1, typename IntType2>
  95 bool operator>(const IntegerIterator<IntType1>& aIter1,
  96                const IntegerIterator<IntType2>& aIter2)
  97 {
  98   return aIter1.mCurrent > aIter2.mCurrent;
  99 }
 100
 101 template<typename IntType1, typename IntType2>
 102 bool operator>=(const IntegerIterator<IntType1>& aIter1,
 103                 const IntegerIterator<IntType2>& aIter2)
 104 {
 105   return aIter1.mCurrent >= aIter2.mCurrent;
 106 }
 107
 108 template<typename IntTypeT>
 109 class IntegerRange
 110 {
 111 public:
 112   typedef IntegerIterator<IntTypeT> iterator;
 113   typedef IntegerIterator<IntTypeT> const_iterator;
 114   typedef ReverseIterator<IntegerIterator<IntTypeT>> reverse_iterator;
 115   typedef ReverseIterator<IntegerIterator<IntTypeT>> const_reverse_iterator;
 116
 117   template<typename IntType>
 118   explicit IntegerRange(IntType aEnd)
 119     : mBegin(0), mEnd(aEnd) { }
 120
 121   template<typename IntType1, typename IntType2>
 122   IntegerRange(IntType1 aBegin, IntType2 aEnd)
 123     : mBegin(aBegin), mEnd(aEnd) { }
 124
 125   iterator begin() const { return iterator(mBegin); }
 126   const_iterator cbegin() const { return begin(); }
 127   iterator end() const { return iterator(mEnd); }
 128   const_iterator cend() const { return end(); }
 129   reverse_iterator rbegin() const { return reverse_iterator(mEnd); }
 130   const_reverse_iterator crbegin() const { return rbegin(); }
 131   reverse_iterator rend() const { return reverse_iterator(mBegin); }
 132   const_reverse_iterator crend() const { return rend(); }
 133
 134 private:
 135   IntTypeT mBegin;
 136   IntTypeT mEnd;
 137 };
 138
 139 template<typename T, bool = IsUnsigned<T>::value>
 140 struct GeqZero
 141 {
 142   static bool check(T t) {
 143     return t >= 0;
 144   }
 145 };
 146
 147 template<typename T>
 148 struct GeqZero<T, true>
 149 {
 150   static bool check(T t) {
 151     return true;
 152   }
 153 };
 154
 155 } // namespace detail
 156
 157 template<typename IntType>
 158 detail::IntegerRange<IntType>
 159 IntegerRange(IntType aEnd)
 160 {
 161   static_assert(IsIntegral<IntType>::value, "value must be integral");
 162   MOZ_ASSERT(detail::GeqZero<IntType>::check(aEnd),
 163              "Should never have negative value here");
 164   return detail::IntegerRange<IntType>(aEnd);
 165 }
 166
 167 template<typename IntType1, typename IntType2>
 168 detail::IntegerRange<IntType2>
 169 IntegerRange(IntType1 aBegin, IntType2 aEnd)
 170 {
 171   static_assert(IsIntegral<IntType1>::value && IsIntegral<IntType2>::value,
 172                 "values must both be integral");
 173   static_assert(IsSigned<IntType1>::value == IsSigned<IntType2>::value,
 174                 "signed/unsigned mismatch");
 175   MOZ_ASSERT(aEnd >= aBegin, "End value should be larger than begin value");
 176   return detail::IntegerRange<IntType2>(aBegin, aEnd);
 177 }
 178
 179 } // namespace mozilla
 180
 181 #endif // mozilla_IntegerRange_h