mfbt/Range.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 #ifndef mozilla_Range_h
   8 #define mozilla_Range_h
   9
  10 #include "mozilla/RangedPtr.h"
  11 #include "mozilla/TypeTraits.h"
  12 #include "mozilla/Span.h"
  13
  14 #include <stddef.h>
  15
  16 namespace mozilla {
  17
  18 // Range<T> is a tuple containing a pointer and a length.
  19 template <typename T>
  20 class Range
  21 {
  22   const RangedPtr<T> mStart;
  23   const RangedPtr<T> mEnd;
  24
  25 public:
  26   Range() : mStart(nullptr, 0), mEnd(nullptr, 0) {}
  27   Range(T* aPtr, size_t aLength)
  28     : mStart(aPtr, aPtr, aPtr + aLength),
  29       mEnd(aPtr + aLength, aPtr, aPtr + aLength)
  30   {}
  31   Range(const RangedPtr<T>& aStart, const RangedPtr<T>& aEnd)
  32     : mStart(aStart.get(), aStart.get(), aEnd.get()),
  33       mEnd(aEnd.get(), aStart.get(), aEnd.get())
  34   {
  35     // Only accept two RangedPtrs within the same range.
  36     aStart.checkIdenticalRange(aEnd);
  37     MOZ_ASSERT(aStart <= aEnd);
  38   }
  39
  40   template<typename U,
  41            class = typename EnableIf<IsConvertible<U (*)[], T (*)[]>::value,
  42                                      int>::Type>
  43   MOZ_IMPLICIT Range(const Range<U>& aOther)
  44     : mStart(aOther.mStart),
  45       mEnd(aOther.mEnd)
  46   {}
  47
  48   MOZ_IMPLICIT Range(Span<T> aSpan)
  49     : Range(aSpan.Elements(), aSpan.Length())
  50   {
  51   }
  52
  53   template<typename U,
  54            class = typename EnableIf<IsConvertible<U (*)[], T (*)[]>::value,
  55                                      int>::Type>
  56   MOZ_IMPLICIT Range(const Span<U>& aSpan)
  57     : Range(aSpan.Elements(), aSpan.Length())
  58   {
  59   }
  60
  61   RangedPtr<T> begin() const { return mStart; }
  62   RangedPtr<T> end() const { return mEnd; }
  63   size_t length() const { return mEnd - mStart; }
  64
  65   T& operator[](size_t aOffset) const { return mStart[aOffset]; }
  66
  67   explicit operator bool() const { return mStart != nullptr; }
  68
  69   operator Span<T>() { return Span<T>(mStart.get(), length()); }
  70
  71   operator Span<const T>() const { return Span<T>(mStart.get(), length()); }
  72 };
  73
  74 template<class T>
  75 Span<T>
  76 MakeSpan(Range<T>& aRange)
  77 {
  78   return aRange;
  79 }
  80
  81 template<class T>
  82 Span<const T>
  83 MakeSpan(const Range<T>& aRange)
  84 {
  85   return aRange;
  86 }
  87
  88 } // namespace mozilla
  89
  90 #endif /* mozilla_Range_h */