layout/style/nsStyleAutoArray.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 nsStyleAutoArray_h_
   8 #define nsStyleAutoArray_h_
   9
  10 #include "nsTArray.h"
  11 #include "mozilla/Assertions.h"
  12
  13 /**
  14  * An array of objects, similar to AutoTArray<T,1> but which is memmovable. It
  15  * always has length >= 1.
  16  */
  17 template <typename T>
  18 class nsStyleAutoArray {
  19  public:
  20   // This constructor places a single element in mFirstElement.
  21   enum WithSingleInitialElement { WITH_SINGLE_INITIAL_ELEMENT };
  22   explicit nsStyleAutoArray(WithSingleInitialElement) {}
  23
  24   nsStyleAutoArray(const nsStyleAutoArray&) = delete;
  25   nsStyleAutoArray& operator=(const nsStyleAutoArray&) = delete;
  26
  27   nsStyleAutoArray(nsStyleAutoArray&&) = default;
  28   nsStyleAutoArray& operator=(nsStyleAutoArray&&) = default;
  29
  30   bool Assign(const nsStyleAutoArray& aOther, mozilla::fallible_t) {
  31     mFirstElement = aOther.mFirstElement;
  32     return mOtherElements.Assign(aOther.mOtherElements, mozilla::fallible);
  33   }
  34
  35   nsStyleAutoArray Clone() const {
  36     nsStyleAutoArray res(WITH_SINGLE_INITIAL_ELEMENT);
  37     res.mFirstElement = mFirstElement;
  38     res.mOtherElements = mOtherElements.Clone();
  39     return res;
  40   }
  41
  42   bool operator==(const nsStyleAutoArray& aOther) const {
  43     return Length() == aOther.Length() &&
  44            mFirstElement == aOther.mFirstElement &&
  45            mOtherElements == aOther.mOtherElements;
  46   }
  47   bool operator!=(const nsStyleAutoArray& aOther) const {
  48     return !(*this == aOther);
  49   }
  50
  51   size_t Length() const { return mOtherElements.Length() + 1; }
  52   const T& operator[](size_t aIndex) const {
  53     return aIndex == 0 ? mFirstElement : mOtherElements[aIndex - 1];
  54   }
  55   T& operator[](size_t aIndex) {
  56     return aIndex == 0 ? mFirstElement : mOtherElements[aIndex - 1];
  57   }
  58
  59   void EnsureLengthAtLeast(size_t aMinLen) {
  60     if (aMinLen > 0) {
  61       mOtherElements.EnsureLengthAtLeast(aMinLen - 1);
  62     }
  63   }
  64
  65   void SetLengthNonZero(size_t aNewLen) {
  66     MOZ_ASSERT(aNewLen > 0);
  67     mOtherElements.SetLength(aNewLen - 1);
  68   }
  69
  70   void TruncateLengthNonZero(size_t aNewLen) {
  71     MOZ_ASSERT(aNewLen > 0);
  72     MOZ_ASSERT(aNewLen <= Length());
  73     mOtherElements.TruncateLength(aNewLen - 1);
  74   }
  75
  76  private:
  77   T mFirstElement;
  78   nsTArray<T> mOtherElements;
  79 };
  80
  81 #endif /* nsStyleAutoArray_h_ */