| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | // ====================================================================== | ||
| 2 | // \title Optional.hpp | ||
| 3 | // \author celskeggs | ||
| 4 | // \brief hpp file for Optional type | ||
| 5 | // | ||
| 6 | // \description | ||
| 7 | // A lightweight optional type for C++14 environments where | ||
| 8 | // std::optional (C++17) is not available. | ||
| 9 | // | ||
| 10 | // \copyright | ||
| 11 | // Copyright (C) 2025-2026 California Institute of Technology. | ||
| 12 | // ALL RIGHTS RESERVED. United States Government Sponsorship | ||
| 13 | // acknowledged. | ||
| 14 | // | ||
| 15 | // ====================================================================== | ||
| 16 | |||
| 17 | #ifndef Fw_Optional_HPP | ||
| 18 | #define Fw_Optional_HPP | ||
| 19 | |||
| 20 | #include <Fw/Types/Assert.hpp> | ||
| 21 | #include <type_traits> | ||
| 22 | |||
| 23 | namespace Fw { | ||
| 24 | |||
| 25 | //! \brief Sentinel type representing the absence of a value in an Optional | ||
| 26 | struct None_t { | ||
| 27 | constexpr explicit None_t() {} | ||
| 28 | }; | ||
| 29 | |||
| 30 | //! \brief Global constant representing an absent/empty optional value | ||
| 31 | constexpr None_t NONE = None_t(); | ||
| 32 | |||
| 33 | //! \class Optional | ||
| 34 | //! \brief A type-safe container for an optional value | ||
| 35 | //! | ||
| 36 | //! Provides a C++14-compatible alternative to std::optional. | ||
| 37 | //! Only supports trivially copyable types (no non-trivial constructors, | ||
| 38 | //! destructors, or copy/move operators). | ||
| 39 | //! | ||
| 40 | //! \tparam T The type of the contained value. Must be trivially copyable. | ||
| 41 | //! | ||
| 42 | template <typename T> | ||
| 43 | class Optional { | ||
| 44 | static_assert(std::is_trivially_copyable<T>::value, "Fw::Optional only supports trivially copyable types"); | ||
| 45 | |||
| 46 | T m_val; | ||
| 47 | bool m_engaged; | ||
| 48 | |||
| 49 | public: | ||
| 50 | // ---------------------------------------------------------------------- | ||
| 51 | // Construction | ||
| 52 | // ---------------------------------------------------------------------- | ||
| 53 | |||
| 54 | //! Construct an empty Optional | ||
| 55 | 2 | constexpr Optional() : m_val(), m_engaged(false) {} | |
| 56 | |||
| 57 | //! Construct an empty Optional from NONE sentinel | ||
| 58 | constexpr Optional(const None_t& a) : Optional() { (void)a; } | ||
| 59 | |||
| 60 | //! Construct an Optional containing a value | ||
| 61 | 1 | constexpr Optional(const T& t) : m_val(t), m_engaged(true) {} | |
| 62 | |||
| 63 | //! Copy constructor | ||
| 64 | 2 | Optional(const Optional& other) : Optional() { | |
| 65 |
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2 | if (other.has_value()) { |
| 66 | 1 | *this = other.value(); | |
| 67 | } | ||
| 68 | 2 | } | |
| 69 | |||
| 70 | //! Destructor (trivial — T must be trivially copyable) | ||
| 71 | ~Optional() = default; | ||
| 72 | |||
| 73 | // ---------------------------------------------------------------------- | ||
| 74 | // Observers | ||
| 75 | // ---------------------------------------------------------------------- | ||
| 76 | |||
| 77 | //! Check whether the Optional contains a value | ||
| 78 | //! \return true if a value is present | ||
| 79 |
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40 | bool has_value() const { return m_engaged; } |
| 80 | |||
| 81 | //! Access the contained value | ||
| 82 | //! \pre has_value() must be true | ||
| 83 | //! \return Mutable reference to the contained value | ||
| 84 | 26 | T& value() { | |
| 85 | 26 | FW_ASSERT(m_engaged); | |
| 86 | 26 | return m_val; | |
| 87 | } | ||
| 88 | |||
| 89 | //! Access the contained value (const) | ||
| 90 | //! \pre has_value() must be true | ||
| 91 | //! \return Const reference to the contained value | ||
| 92 | 3 | const T& value() const { | |
| 93 | 3 | FW_ASSERT(m_engaged); | |
| 94 | 3 | return m_val; | |
| 95 | } | ||
| 96 | |||
| 97 | //! Access the value or return a default | ||
| 98 | //! \return The contained value if present, otherwise the provided default | ||
| 99 |
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2 | T value_or(const T& default_value) const { return m_engaged ? m_val : default_value; } |
| 100 | |||
| 101 | // ---------------------------------------------------------------------- | ||
| 102 | // Modifiers | ||
| 103 | // ---------------------------------------------------------------------- | ||
| 104 | |||
| 105 | //! Reset the Optional to an empty state | ||
| 106 | 3 | void reset() { m_engaged = false; } | |
| 107 | |||
| 108 | // ---------------------------------------------------------------------- | ||
| 109 | // Assignment operators | ||
| 110 | // ---------------------------------------------------------------------- | ||
| 111 | |||
| 112 | //! Assign a value into the Optional | ||
| 113 | 12 | Optional& operator=(const T& t) { | |
| 114 | 12 | m_engaged = true; | |
| 115 | 12 | m_val = t; | |
| 116 | 12 | return *this; | |
| 117 | } | ||
| 118 | |||
| 119 | //! Reset the Optional via NONE assignment | ||
| 120 | 1 | Optional& operator=(const None_t& a) { | |
| 121 | (void)a; | ||
| 122 | 1 | reset(); | |
| 123 | 1 | return *this; | |
| 124 | } | ||
| 125 | |||
| 126 | //! Copy assignment operator | ||
| 127 | 2 | Optional& operator=(const Optional& other) { | |
| 128 |
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2 | if (other.has_value()) { |
| 129 | 1 | *this = other.value(); | |
| 130 | } else { | ||
| 131 | 1 | reset(); | |
| 132 | } | ||
| 133 | 2 | return *this; | |
| 134 | } | ||
| 135 | |||
| 136 | // ---------------------------------------------------------------------- | ||
| 137 | // Comparison operators | ||
| 138 | // ---------------------------------------------------------------------- | ||
| 139 | |||
| 140 | //! Compare with NONE sentinel | ||
| 141 | 3 | bool operator==(const None_t& a) const { | |
| 142 | (void)a; | ||
| 143 |
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3 | return !m_engaged; |
| 144 | } | ||
| 145 | |||
| 146 | //! Compare with NONE sentinel (inequality) | ||
| 147 | 2 | bool operator!=(const None_t& a) const { | |
| 148 | (void)a; | ||
| 149 |
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2 | return m_engaged; |
| 150 | } | ||
| 151 | |||
| 152 | //! Equality comparison with another Optional | ||
| 153 | 4 | bool operator==(const Optional& other) const { | |
| 154 |
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4 | if (m_engaged != other.m_engaged) { |
| 155 | 1 | return false; | |
| 156 | } | ||
| 157 |
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3 | if (!m_engaged) { |
| 158 | 1 | return true; | |
| 159 | } | ||
| 160 | 2 | return m_val == other.m_val; | |
| 161 | } | ||
| 162 | |||
| 163 | //! Inequality comparison with another Optional | ||
| 164 | 2 | bool operator!=(const Optional& other) const { return !(*this == other); } | |
| 165 | }; | ||
| 166 | |||
| 167 | } // namespace Fw | ||
| 168 | |||
| 169 | #endif | ||
| 170 |