| // Copyright 2023 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef BASE_STRINGS_TO_STRING_H_ |
| #define BASE_STRINGS_TO_STRING_H_ |
| |
| #include <ios> |
| #include <memory> |
| #include <sstream> |
| #include <string> |
| #include <type_traits> |
| |
| #include "base/template_util.h" |
| #include "base/types/supports_ostream_operator.h" |
| |
| namespace gurl_base { |
| |
| namespace internal { |
| |
| template <typename T> |
| concept SupportsToString = requires(const T& t) { t.ToString(); }; |
| |
| // I/O manipulators are function pointers, but should be sent directly to the |
| // `ostream` instead of being cast to `const void*` like other function |
| // pointers. |
| template <typename T, typename = void> |
| constexpr bool IsIomanip = false; |
| template <typename T> |
| constexpr bool |
| IsIomanip<T&(T&), std::enable_if_t<std::is_base_of_v<std::ios_base, T>>> = |
| true; |
| |
| // Function pointers implicitly convert to `bool`, so use this to avoid printing |
| // function pointers as 1 or 0. |
| template <typename T, typename = void> |
| constexpr bool WillBeIncorrectlyStreamedAsBool = false; |
| template <typename T> |
| constexpr bool WillBeIncorrectlyStreamedAsBool< |
| T, |
| std::enable_if_t<std::is_function_v<std::remove_pointer_t<T>> && |
| !IsIomanip<std::remove_pointer_t<T>>>> = true; |
| |
| // Fallback case when there is no better representation. |
| template <typename T, typename = void> |
| struct ToStringHelper { |
| static void Stringify(const T& v, std::ostringstream& ss) { |
| ss << "[" << sizeof(v) << "-byte object at 0x" << std::addressof(v) << "]"; |
| } |
| }; |
| |
| // Most streamables. |
| template <typename T> |
| struct ToStringHelper<T, |
| std::enable_if_t<SupportsOstreamOperator<const T&> && |
| !WillBeIncorrectlyStreamedAsBool<T>>> { |
| static void Stringify(const T& v, std::ostringstream& ss) { ss << v; } |
| }; |
| |
| // Functions and function pointers. |
| template <typename T> |
| struct ToStringHelper<T, |
| std::enable_if_t<SupportsOstreamOperator<const T&> && |
| WillBeIncorrectlyStreamedAsBool<T>>> { |
| static void Stringify(const T& v, std::ostringstream& ss) { |
| ToStringHelper<const void*>::Stringify(reinterpret_cast<const void*>(v), |
| ss); |
| } |
| }; |
| |
| // Non-streamables that have a `ToString` member. |
| template <typename T> |
| struct ToStringHelper<T, |
| std::enable_if_t<!SupportsOstreamOperator<const T&> && |
| SupportsToString<const T&>>> { |
| static void Stringify(const T& v, std::ostringstream& ss) { |
| // .ToString() may not return a std::string, e.g. blink::WTF::String. |
| ToStringHelper<decltype(v.ToString())>::Stringify(v.ToString(), ss); |
| } |
| }; |
| |
| // Non-streamable enums (i.e. scoped enums where no `operator<<` overload was |
| // declared). |
| template <typename T> |
| struct ToStringHelper< |
| T, |
| std::enable_if_t<!SupportsOstreamOperator<const T&> && std::is_enum_v<T>>> { |
| static void Stringify(const T& v, std::ostringstream& ss) { |
| using UT = typename std::underlying_type_t<T>; |
| ToStringHelper<UT>::Stringify(static_cast<UT>(v), ss); |
| } |
| }; |
| |
| } // namespace internal |
| |
| // Converts any type to a string, preferring defined operator<<() or ToString() |
| // methods if they exist. |
| template <typename... Ts> |
| std::string ToString(const Ts&... values) { |
| std::ostringstream ss; |
| (internal::ToStringHelper<remove_cvref_t<decltype(values)>>::Stringify(values, |
| ss), |
| ...); |
| return ss.str(); |
| } |
| |
| } // namespace base |
| |
| #endif // BASE_STRINGS_TO_STRING_H_ |