This Is How To Convert u16string To A wstring In C++

What do we mean by “wide string” in a C++ app? What is a u16string? How can I convert a u16string to a wstring? Let’s answer these questions.

What is a wstring?

Wide strings are the string class for ‘wide’ characters represented by wstring. Alphanumeric characters are stored and displayed in string form. In other words wstring stores alphanumeric text with 2 or 4 byte chars. Wide strings are the instantiation of the basic_string class template that uses wchar_t as the character type. Simply we can define a wstring as below,

What is u16string?

The u16string (std::u16string or std::pmr::u16string) are the string class data types for the 16bit characters defined in the std and std::pmr namespaces. It is a string class for 16-bit characters.

This is an instantiation of the basic_string class template that uses char16_t as the character type, with its default char_traits ad allocator types. In example, the std:string uses one byte (8 bits) while the std::u16string uses two bytes (16bits) per each character of the text string. In basic string definition std::u16string is defined as std::basic_string<char16_t>. Type definition can be shown as below,

Is there a simple example of using wstring and u16string in Modern C++?

Here is a simple C++ example of how to use u16string,

How do I convert u16string to a wstring?

First, we should say that we do not recommend converting the higher byte string to a lower byte string. Currently there is no way to convert u16string to a wstring in modern C++. There is a way to convert them by using std::wstring_convert and std::codecvt_utf16 templates. In some references these both has been deprecated, however there is no good alternative thus they are not removed in most of popular C++ compilers and this means you can use them if you really need to – but do so with caution.

We can use std::wstring_convert class template to convert a u16string to a wstring. The wstring_convert class template converts byte string to wide strings using an individual code conversion facet Codecvt These standard facets suitable for use with the std::wstring_convert. We can use these with,

• std::codecvt_utf8 for the UTF-8/UCS2 and UTF-8/UCS4 conversions
• std::codecvt_utf8_utf16 for the UTF-8/UTF-16 conversions.

Syntax of std::wstring_convert class template (deprecated in C++17),

Syntax of std::codecvt_utf8 class template (deprecated in C++17),

Is there an example of how to convert u16string to a wstring?

Here is a example that converts u16string to a wstring,

This example works in most of C++ compilers including C++ Builder applications.

C++ Builder is the easiest and fastest C and C++ IDE for building simple or professional applications on the Windows, MacOS, iOS & Android operating systems. It is also easy for beginners to learn with its wide range of samples, tutorials, help files, and LSP support for code. RAD Studio’s C++ Builder version comes with the award-winning VCL framework for high-performance native Windows apps and the powerful FireMonkey (FMX) framework for cross-platform UIs.

There is a free C++ Builder Community Edition for students, beginners, and startups; it can be downloaded from here. For professional developers, there are Professional, Architect, or Enterprise versions of C++ Builder and there is a trial version you can download from here.