utf_ostream_operators.h (2145B)
1 // Copyright 2023 The Chromium Authors 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_STRINGS_UTF_OSTREAM_OPERATORS_H_ 6 #define BASE_STRINGS_UTF_OSTREAM_OPERATORS_H_ 7 8 #include <iosfwd> 9 #include <string> 10 #include <string_view> 11 12 #include "base/base_export.h" 13 14 // Note that "The behavior of a C++ program is undefined if it adds declarations 15 // or definitions to namespace std or to a namespace within namespace std unless 16 // otherwise specified." --C++11[namespace.std] 17 // 18 // We've checked that this particular definition has the intended behavior on 19 // our implementations, but it's prone to breaking in the future, and please 20 // don't imitate this in your own definitions without checking with some 21 // standard library experts. 22 namespace std { 23 // These functions are provided as a convenience for logging, which is where we 24 // use streams (it is against Google style to use streams in other places). It 25 // is designed to allow you to emit non-ASCII Unicode strings to the log file, 26 // which is normally ASCII. It is relatively slow, so try not to use it for 27 // common cases. Non-ASCII characters will be converted to UTF-8 by these 28 // operators. 29 // 30 // The `std::basic_string<T>` overloads are necessary to allow logging types 31 // which are implicitly convertible to `std::basic_string<T>`. Simply taking 32 // `std::basic_string_view<T>` would not work because C++ only allows one 33 // implicit conversion. 34 BASE_EXPORT std::ostream& operator<<(std::ostream& out, const wchar_t* wstr); 35 BASE_EXPORT std::ostream& operator<<(std::ostream& out, std::wstring_view wstr); 36 BASE_EXPORT std::ostream& operator<<(std::ostream& out, 37 const std::wstring& wstr); 38 39 BASE_EXPORT std::ostream& operator<<(std::ostream& out, const char16_t* str16); 40 BASE_EXPORT std::ostream& operator<<(std::ostream& out, 41 std::u16string_view str16); 42 BASE_EXPORT std::ostream& operator<<(std::ostream& out, 43 const std::u16string& str16); 44 } // namespace std 45 46 #endif // BASE_STRINGS_UTF_OSTREAM_OPERATORS_H_