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: unexpected(T value)24 LIBC_INLINE constexpr explicit unexpected(T value) : value(value) {} error()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: expected(T exp)38 LIBC_INLINE constexpr expected(T exp) : exp(exp), is_expected(true) {} expected(unexpected<E> unexp)39 LIBC_INLINE constexpr expected(unexpected<E> unexp) 40 : unexp(unexp.error()), is_expected(false) {} 41 has_value()42 LIBC_INLINE constexpr bool has_value() const { return is_expected; } 43 value()44 LIBC_INLINE constexpr T &value() { return exp; } error()45 LIBC_INLINE constexpr E &error() { return unexp; } value()46 LIBC_INLINE constexpr const T &value() const { return exp; } error()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