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 "mozilla/Alignment.h"
11 #include "nsTArray.h"
12 
13 /**
14  * E: element type, must be a POD type.
15  * N: N bytes alignment for the first element, defaults to 32
16  * S: S bytes of inline storage
17  */
18 template <typename E, int S, int N = 32>
19 class AlignedAutoTArray : private AutoTArray<E, S + N> {
20   static_assert((N & (N - 1)) == 0, "N must be power of 2");
21   typedef AutoTArray<E, S + N> base_type;
22 
23  public:
24   typedef E elem_type;
25   typedef typename base_type::size_type size_type;
26   typedef typename base_type::index_type index_type;
27 
28   AlignedAutoTArray() = default;
AlignedAutoTArray(size_type capacity)29   explicit AlignedAutoTArray(size_type capacity)
30       : base_type(capacity + sExtra) {}
Elements()31   elem_type* Elements() { return getAligned(base_type::Elements()); }
Elements()32   const elem_type* Elements() const {
33     return getAligned(base_type::Elements());
34   }
35   elem_type& operator[](index_type i) { return Elements()[i]; }
36   const elem_type& operator[](index_type i) const { return Elements()[i]; }
37 
SetLength(size_type newLen)38   void SetLength(size_type newLen) { base_type::SetLength(newLen + sExtra); }
39 
SetLength(size_type newLen,const mozilla::fallible_t &)40   [[nodiscard]] bool SetLength(size_type newLen, const mozilla::fallible_t&) {
41     return base_type::SetLength(newLen + sExtra, mozilla::fallible);
42   }
43 
Length()44   size_type Length() const {
45     return base_type::Length() <= sExtra ? 0 : base_type::Length() - sExtra;
46   }
47 
48   using base_type::ShallowSizeOfExcludingThis;
49   using base_type::ShallowSizeOfIncludingThis;
50 
51  private:
52   AlignedAutoTArray(const AlignedAutoTArray& other) = delete;
53   void operator=(const AlignedAutoTArray& other) = delete;
54 
55   static const size_type sPadding =
56       N <= MOZ_ALIGNOF(E) ? 0 : N - MOZ_ALIGNOF(E);
57   static const size_type sExtra = (sPadding + sizeof(E) - 1) / sizeof(E);
58 
59   template <typename U>
getAligned(U * p)60   static U* getAligned(U* p) {
61     return reinterpret_cast<U*>(((uintptr_t)p + N - 1) & ~(N - 1));
62   }
63 };
64 
65 /**
66  * E: element type, must be a POD type.
67  * N: N bytes alignment for the first element, defaults to 32
68  */
69 template <typename E, int N = 32>
70 class AlignedTArray : private nsTArray_Impl<E, nsTArrayInfallibleAllocator> {
71   static_assert((N & (N - 1)) == 0, "N must be power of 2");
72   typedef nsTArray_Impl<E, nsTArrayInfallibleAllocator> base_type;
73 
74  public:
75   typedef E elem_type;
76   typedef typename base_type::size_type size_type;
77   typedef typename base_type::index_type index_type;
78 
79   AlignedTArray() = default;
AlignedTArray(size_type capacity)80   explicit AlignedTArray(size_type capacity) : base_type(capacity + sExtra) {}
Elements()81   elem_type* Elements() { return getAligned(base_type::Elements()); }
Elements()82   const elem_type* Elements() const {
83     return getAligned(base_type::Elements());
84   }
85   elem_type& operator[](index_type i) { return Elements()[i]; }
86   const elem_type& operator[](index_type i) const { return Elements()[i]; }
87 
SetLength(size_type newLen)88   void SetLength(size_type newLen) { base_type::SetLength(newLen + sExtra); }
89 
SetLength(size_type newLen,const mozilla::fallible_t &)90   [[nodiscard]] bool SetLength(size_type newLen, const mozilla::fallible_t&) {
91     return base_type::SetLength(newLen + sExtra, mozilla::fallible);
92   }
93 
Length()94   size_type Length() const {
95     return base_type::Length() <= sExtra ? 0 : base_type::Length() - sExtra;
96   }
97 
98   using base_type::ShallowSizeOfExcludingThis;
99   using base_type::ShallowSizeOfIncludingThis;
100 
101  private:
102   AlignedTArray(const AlignedTArray& other) = delete;
103   void operator=(const AlignedTArray& other) = delete;
104 
105   static const size_type sPadding =
106       N <= MOZ_ALIGNOF(E) ? 0 : N - MOZ_ALIGNOF(E);
107   static const size_type sExtra = (sPadding + sizeof(E) - 1) / sizeof(E);
108 
109   template <typename U>
getAligned(U * p)110   static U* getAligned(U* p) {
111     return reinterpret_cast<U*>(((uintptr_t)p + N - 1) & ~(N - 1));
112   }
113 };
114 
115 #endif  // AlignedTArray_h__
116