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| 1 | //===-- Holds an expected or unexpected value -------------------*- C++ -*-===// |
|---|---|
| 2 | // |
| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| 4 | // See https://llvm.org/LICENSE.txt for license information. |
| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| 6 | // |
| 7 | //===----------------------------------------------------------------------===// |
| 8 | |
| 9 | #ifndef LLVM_LIBC_SRC___SUPPORT_CPP_EXPECTED_H |
| 10 | #define LLVM_LIBC_SRC___SUPPORT_CPP_EXPECTED_H |
| 11 | |
| 12 | #include "src/__support/macros/attributes.h" |
| 13 | #include "src/__support/macros/config.h" |
| 14 | |
| 15 | namespace LIBC_NAMESPACE_DECL { |
| 16 | namespace cpp { |
| 17 | |
| 18 | // This is used to hold an unexpected value so that a different constructor is |
| 19 | // selected. |
| 20 | template <class T> class unexpected { |
| 21 | T value; |
| 22 | |
| 23 | public: |
| 24 | LIBC_INLINE constexpr explicit unexpected(T value) : value(value) {} |
| 25 | LIBC_INLINE constexpr T error() { return value; } |
| 26 | }; |
| 27 | |
| 28 | template <class T> explicit unexpected(T) -> unexpected<T>; |
| 29 | |
| 30 | template <class T, class E> class expected { |
| 31 | union { |
| 32 | T exp; |
| 33 | E unexp; |
| 34 | }; |
| 35 | bool is_expected; |
| 36 | |
| 37 | public: |
| 38 | LIBC_INLINE constexpr expected(T exp) : exp(exp), is_expected(true) {} |
| 39 | LIBC_INLINE constexpr expected(unexpected<E> unexp) |
| 40 | : unexp(unexp.error()), is_expected(false) {} |
| 41 | |
| 42 | LIBC_INLINE constexpr bool has_value() const { return is_expected; } |
| 43 | |
| 44 | LIBC_INLINE constexpr T &value() { return exp; } |
| 45 | LIBC_INLINE constexpr E &error() { return unexp; } |
| 46 | LIBC_INLINE constexpr const T &value() const { return exp; } |
| 47 | LIBC_INLINE constexpr const E &error() const { return unexp; } |
| 48 | |
| 49 | LIBC_INLINE constexpr operator bool() const { return is_expected; } |
| 50 | |
| 51 | LIBC_INLINE constexpr T &operator*() { return exp; } |
| 52 | LIBC_INLINE constexpr const T &operator*() const { return exp; } |
| 53 | LIBC_INLINE constexpr T *operator->() { return &exp; } |
| 54 | LIBC_INLINE constexpr const T *operator->() const { return &exp; } |
| 55 | }; |
| 56 | |
| 57 | } // namespace cpp |
| 58 | } // namespace LIBC_NAMESPACE_DECL |
| 59 | |
| 60 | #endif // LLVM_LIBC_SRC___SUPPORT_CPP_EXPECTED_H |
| 61 |
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