[Original] 2 conversion between char* and wchar_t*

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There are several ways to convert between multibyte (char*) and wide character (wchar_t*), which are introduced one by one in the order from general to special.

1. C library functions

1.1 Key functions

(1) setlocale()  
function: configure the localization information
header file: <locale.h>

Function prototype:

char *setlocale (int category, const char * locale);

Function parameters: 
category: Indicates the setting of a localized content, and can take the following values: 
LC_ALL All options including the following require
LC_COLLATE to configure string comparison
C_CTYPE to configure character categories and conversions, such as all-caps strtoupper()
LC_MONETARY to configure financial Currency
LC_NUMERIC Configure the number of digits after the decimal point
LC_TIME Configure the time and date format, used with strftime()

locale: indicates the local domain code
Return value: if it is NULL, it will return the current locale name (usually C); if it is not empty, it will be set according to category and locale, if successful, it will return the new locale name (regional name) , or NULL on failure.

(2) wcstombs_s()  
function: convert wide character encoding string into multi-byte encoding string 
header file:  <stdlib.h> 

Function prototype:

errno_t __cdecl wcstombs_s(size_t * _PtNumOfCharConverted, char * _Dst, size_t _DstSizeInBytes, const wchar_t * _Src, size_t _MaxCountInBytes);

Function parameters: 
PtNumOfCharConverted: Point to the length of the converted string plus terminator (unit byte)
Dst: Point to the first address of the converted string
DstSizeInBytes: The maximum byte space of the destination address (unit byte) 
_Src: Source wide character String start address
_MaxCountInBytes: The maximum number of bytes that can be stored in the multi-byte string buffer, used to trim the converted string
Return value : 0 is returned if successful, and a failure code if it fails

(3) mbstowcs_s ()  
function function: convert multi-byte encoded string into wide character encoded string 
header file: <stdlib.h> 

Function prototype:

errno_t __cdecl mbstowcs_s(size_t * _PtNumOfCharConverted, wchar_t * _DstBuf, size_t _SizeInWords, const char * _SrcBuf, size_t _MaxCount );

Parameter description: 
PtNumOfCharConverted: Points to the length of the converted string plus a terminator (unit wchar_t)
_DstBuf: Points to the first address of the converted string
_SizeInWords: The maximum character space size of the destination address (unit wchar_t)
_SrcBuf: Source multi-byte characters String start address
_MaxCount: The maximum number of characters that can be stored in the wide string buffer, which is used to trim the converted wide string

Return value: 0 is returned on success, and a failure code is returned on failure

1.2 Conversion example

The example is implemented in C++, in order to use string and wstring as parameters or return values, internally still convert string to char*, and convert wstring to wchar_t*

If you need the C version, you only need to intercept the mutual conversion part of char* and wchar_t* inside the function.

#include <iostream>
#include <locale.h>
#include <string>
using namespace std;

string ws2s(const wstring& ws){
    size_t convertedChars=0;
    string curLocale=setlocale(LC_ALL,NULL); //curLocale="C"
    setlocale(LC_ALL,"chs");
    const wchar_t* wcs = ws.c_str();
    size_t dByteNum=sizeof(wchar_t)*ws.size()+1;
    cout<<"ws.size():"<<ws.size()<<endl;            //5

    char* dest=new char[dByteNum];
    wcstombs_s(&convertedChars,dest,dByteNum,wcs,_TRUNCATE);
    cout<<"convertedChars:"<<convertedChars<<endl; //8
    string result=dest;
    delete [] dest;
    setlocale(LC_ALL,curLocale.c_str());
    return result;
}

wstring s2ws(const string& s)

{
    size_t convertedChars=0;
    string curLocale=setlocale(LC_ALL,NULL);   //curLocale="C"
    setlocale(LC_ALL,"chs");
    const char* source=s.c_str();
    size_t charNum=sizeof(char)*s.size()+1;
    cout<<"s.size():"<<s.size()<<endl;   //7

    wchar_t* dest=new wchar_t[charNum];
    mbstowcs_s(&convertedChars,dest,charNum,source,_TRUNCATE);
    cout<<"s2ws_convertedChars:"<<convertedChars<<endl; //6
    wstring result=dest;
    delete [] dest;
    setlocale(LC_ALL,curLocale.c_str());
    return result;
}

int main() {

     wchar_t *pwstr = L"123ABC Hello";

    string obj=ws2s(pwstr);
    cout<<obj<<endl; //Output 123ABC Hello

    char *pstr = "123ABC Hello";

    wstring objw = s2ws(pstr);
    setlocale(LC_ALL, "chs"); //In order to make wcout output Chinese
    //or wcout.imbue(locale("chs"));
    wcout<<objw<<endl; //Output 123ABC Hello

}

2.Windows API

3. Windows ATL function