How to Convert a String (or char) to a wstring (or wchar_t) in C ?

C Convert string (or char) to wstring (or wchar_t)

Problem:

Given a string or char variable, how can we assign its contents to a wstring or wchar_t variable?

Solution:

Assuming the input string is encoded in UTF-8, the standard library (C 11 and newer) includes several techniques for converting between UTF-8 and UTF-16:

#include <locale>
#include <codecvt>
#include <string>

using namespace std;

// Create a converter using the UTF-8/UTF-16 codecvt
wstring_convert<codecvt_utf8_utf16<wchar_t>> converter;

// Convert a narrow (UTF-8) string to a wide (UTF-16) string
wstring wide = converter.from_bytes(narrow);

// Convert a wide (UTF-16) string to a narrow (UTF-8) string
string narrow = converter.to_bytes(wide);

Example (Online Compilable and Runnable):

#include <iostream>
#include <locale>
#include <codecvt>
#include <string>

int main() {
  // Sample input string in UTF-8 (see notes below for real-world scenarios):
  string s = "おはよう";

  // Create a wstring to store the converted string
  wstring ws;

  // Convert the narrow (UTF-8) string to wide (UTF-16)
  std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>> conv;
  ws = conv.from_bytes(s);

  // Print the converted wstring
  wcout << ws << endl;

  return 0;
}

Notes:

1. Ensure that the input string is indeed encoded in UTF-8. Non-UTF-8 encodings will not produce the correct conversion.
2. The codecvt_utf8_utf16 converter assumes little-endian byte order for UTF-16. If your system uses big-endian byte order, consider using codecvt_utf8 instead.

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