1 | // Copyright (C) 2023 The Qt Company Ltd. |
2 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
3 | |
4 | #ifndef QTCORE_QSMALLBYTEARRAY_P_H |
5 | #define QTCORE_QSMALLBYTEARRAY_P_H |
6 | |
7 | #include <QtCore/qbytearrayview.h> |
8 | #include <QtCore/qtconfigmacros.h> |
9 | #include <QtCore/qtypes.h> |
10 | |
11 | #include <array> |
12 | #include <limits> |
13 | |
14 | // |
15 | // W A R N I N G |
16 | // ------------- |
17 | // |
18 | // This file is not part of the Qt API. It exists purely as an |
19 | // implementation detail. This header file may change from version to |
20 | // version without notice, or even be removed. |
21 | // |
22 | // We mean it. |
23 | // |
24 | |
25 | QT_BEGIN_NAMESPACE |
26 | |
27 | // |
28 | // A fixed-max-size version of QByteArray. Since it's fixed-max-size, it's |
29 | // never going to the heap. Can contain a maximum of 256 octets. Never |
30 | // NUL-terminates on its own. |
31 | // |
32 | |
33 | template <size_t N> |
34 | class QSmallByteArray |
35 | { |
36 | std::array<quint8, N> m_data; |
37 | static_assert(N <= (std::numeric_limits<std::uint8_t>::max)()); |
38 | quint8 m_size = 0; |
39 | public: |
40 | QSmallByteArray() = default; |
41 | // all compiler-generated SMFs are ok! |
42 | template <std::size_t M, std::enable_if_t<M < N, bool> = true> // M == N is for copy ctor! |
43 | constexpr QSmallByteArray(const QSmallByteArray<M> &other) noexcept |
44 | { |
45 | assign(other); |
46 | } |
47 | template <std::size_t M, std::enable_if_t<M < N, bool> = true> // M == N is for copy-assignment op! |
48 | constexpr QSmallByteArray &operator=(const QSmallByteArray<M> &other) noexcept |
49 | { |
50 | assign(other); |
51 | return *this; |
52 | } |
53 | |
54 | template <typename Container> // ### underconstrained |
55 | constexpr void assign(const Container &c) |
56 | { |
57 | const size_t otherSize = size_t(std::size(c)); |
58 | Q_ASSERT(otherSize < N); |
59 | memcpy(data(), std::data(c), otherSize); |
60 | m_size = quint8(otherSize); |
61 | } |
62 | |
63 | constexpr quint8 *data() noexcept { return m_data.data(); } |
64 | constexpr const quint8 *data() const noexcept { return m_data.data(); } |
65 | constexpr qsizetype size() const noexcept { return qsizetype{m_size}; } |
66 | constexpr quint8 &operator[](qsizetype n) |
67 | { |
68 | Q_ASSERT(n < size()); |
69 | return data()[n]; |
70 | } |
71 | constexpr const quint8 &operator[](qsizetype n) const |
72 | { |
73 | Q_ASSERT(n < size()); |
74 | return data()[n]; |
75 | } |
76 | constexpr bool isEmpty() const noexcept { return size() == 0; } |
77 | constexpr void clear() noexcept { m_size = 0; } |
78 | constexpr void resizeForOverwrite(qsizetype s) |
79 | { |
80 | Q_ASSERT(s >= 0); |
81 | Q_ASSERT(size_t(s) <= N); |
82 | m_size = std::uint8_t(s); |
83 | } |
84 | constexpr void resize(qsizetype s, quint8 v) |
85 | { |
86 | const auto oldSize = size(); |
87 | resizeForOverwrite(s); |
88 | if (s > oldSize) |
89 | memset(data() + oldSize, v, size() - oldSize); |
90 | } |
91 | constexpr QByteArrayView toByteArrayView() const noexcept |
92 | { return *this; } |
93 | |
94 | constexpr auto begin() noexcept { return data(); } |
95 | constexpr auto begin() const noexcept { return data(); } |
96 | constexpr auto cbegin() const noexcept { return begin(); } |
97 | constexpr auto end() noexcept { return data() + size(); } |
98 | constexpr auto end() const noexcept { return data() + size(); } |
99 | constexpr auto cend() const noexcept { return end(); } |
100 | }; |
101 | |
102 | QT_END_NAMESPACE |
103 | |
104 | #endif // QTCORE_QSMALLBYTEARRAY_P_H |
105 | |