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AlignedTArray.h (3928B)

      1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
      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 AlignedTArray_h__
      8 #define AlignedTArray_h__
      9 
     10 #include "nsTArray.h"
     11 
     12 /**
     13 * E: element type, must be a POD type.
     14 * N: N bytes alignment for the first element, defaults to 32
     15 * S: S bytes of inline storage
     16 */
     17 template <typename E, int S, int N = 32>
     18 class AlignedAutoTArray : private AutoTArray<E, S + N> {
     19  static_assert((N & (N - 1)) == 0, "N must be power of 2");
     20  typedef AutoTArray<E, S + N> base_type;
     21 
     22 public:
     23  typedef E value_type;
     24  typedef typename base_type::size_type size_type;
     25  typedef typename base_type::index_type index_type;
     26 
     27  AlignedAutoTArray() = default;
     28  explicit AlignedAutoTArray(size_type capacity)
     29      : base_type(capacity + sExtra) {}
     30  value_type* Elements() { return getAligned(base_type::Elements()); }
     31  const value_type* Elements() const {
     32    return getAligned(base_type::Elements());
     33  }
     34  value_type& operator[](index_type i) { return Elements()[i]; }
     35  const value_type& operator[](index_type i) const { return Elements()[i]; }
     36 
     37  void SetLength(size_type newLen) { base_type::SetLength(newLen + sExtra); }
     38 
     39  [[nodiscard]] bool SetLength(size_type newLen, const mozilla::fallible_t&) {
     40    return base_type::SetLength(newLen + sExtra, mozilla::fallible);
     41  }
     42 
     43  size_type Length() const {
     44    return base_type::Length() <= sExtra ? 0 : base_type::Length() - sExtra;
     45  }
     46 
     47  using base_type::ShallowSizeOfExcludingThis;
     48  using base_type::ShallowSizeOfIncludingThis;
     49 
     50 private:
     51  AlignedAutoTArray(const AlignedAutoTArray& other) = delete;
     52  void operator=(const AlignedAutoTArray& other) = delete;
     53 
     54  static const size_type sPadding = N <= alignof(E) ? 0 : N - alignof(E);
     55  static const size_type sExtra = (sPadding + sizeof(E) - 1) / sizeof(E);
     56 
     57  template <typename U>
     58  static U* getAligned(U* p) {
     59    return reinterpret_cast<U*>(((uintptr_t)p + N - 1) & ~(N - 1));
     60  }
     61 };
     62 
     63 /**
     64 * E: element type, must be a POD type.
     65 * N: N bytes alignment for the first element, defaults to 32
     66 */
     67 template <typename E, int N = 32>
     68 class AlignedTArray : private nsTArray_Impl<E, nsTArrayInfallibleAllocator> {
     69  static_assert((N & (N - 1)) == 0, "N must be power of 2");
     70  typedef nsTArray_Impl<E, nsTArrayInfallibleAllocator> base_type;
     71 
     72 public:
     73  typedef E value_type;
     74  typedef typename base_type::size_type size_type;
     75  typedef typename base_type::index_type index_type;
     76 
     77  AlignedTArray() = default;
     78  explicit AlignedTArray(size_type capacity) : base_type(capacity + sExtra) {}
     79  value_type* Elements() { return getAligned(base_type::Elements()); }
     80  const value_type* Elements() const {
     81    return getAligned(base_type::Elements());
     82  }
     83  value_type& operator[](index_type i) { return Elements()[i]; }
     84  const value_type& operator[](index_type i) const { return Elements()[i]; }
     85 
     86  void SetLength(size_type newLen) { base_type::SetLength(newLen + sExtra); }
     87 
     88  [[nodiscard]] bool SetLength(size_type newLen, const mozilla::fallible_t&) {
     89    return base_type::SetLength(newLen + sExtra, mozilla::fallible);
     90  }
     91 
     92  size_type Length() const {
     93    return base_type::Length() <= sExtra ? 0 : base_type::Length() - sExtra;
     94  }
     95 
     96  using base_type::ShallowSizeOfExcludingThis;
     97  using base_type::ShallowSizeOfIncludingThis;
     98 
     99 private:
    100  AlignedTArray(const AlignedTArray& other) = delete;
    101  void operator=(const AlignedTArray& other) = delete;
    102 
    103  static const size_type sPadding = N <= alignof(E) ? 0 : N - alignof(E);
    104  static const size_type sExtra = (sPadding + sizeof(E) - 1) / sizeof(E);
    105 
    106  template <typename U>
    107  static U* getAligned(U* p) {
    108    return reinterpret_cast<U*>(((uintptr_t)p + N - 1) & ~(N - 1));
    109  }
    110 };
    111 
    112 #endif  // AlignedTArray_h__