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C++ - Convert a wString to char *
I am trying to write a C++ library (dll) that will be called by the WebI reporting tool.
The parameters passed from WebI are of type wString.
I need to pass these to another function that takes char * as the parameters.
How do I convert a wString to a char *?
mlmcc
The parameters passed from WebI are of type wString.
I need to pass these to another function that takes char * as the parameters.
How do I convert a wString to a char *?
mlmcc
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There are two issues. Firstly, wString (not a standard type, so most likely a typedef or custom class) is almost certainly a wide char type string (based on wchar_t). This will need to be narrowed to a char. Your second problem is one of encoding. What is the encoding format of the original string? Uft16? What encoding format does your function expect? Utf8? ANSI? There isn't enough info in the question to provide a real answer.
Assuming that you are on windows (since you mentioned 'DLL') and taking in mind what evilrix wrote about character sets, 'WideCharToMultiByte()' (https://msdn.microsoft.com/en-us/library/windows/desktop/dd374130%28v=vs.85%29.aspx) should be the most flexible way to approach that, since its parameters allow to control that. Scroll down for an example or check the section 'String Handling' in http://www.codeproject.com/Articles/633/Introduction-to-COM-What-It-Is-and-How-to-Use-It
We tried the 'WideCharToMultiByte but couldn't make it work.
This does seem to work
This does seem to work
std::wstring valPar0(param0);
const wchar_t *str = valPar0.c_str();
size_t size = wcslen(str)*2 + 2;
char * StartPoint= new char[size];
size_t c_size;
wcstombs_s(&c_size, StartPoint, size, str, size);
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That's a bit odd, since 'wcstombs_s()' is a wrapper around 'WideCharToMultiByte()' providing the most common parameters. Or, as in the Codeproject article, using
is equivalent to
// Assuming we already have a Unicode string wszSomeString...
char szANSIString [MAX_PATH];
WideCharToMultiByte ( CP_ACP, // ANSI code page
WC_COMPOSITECHECK, // Check for accented characters
wszSomeString, // Source Unicode string
-1, // -1 means string is zero-terminated
szANSIString, // Destination char string
sizeof(szANSIString), // Size of buffer
NULL, // No default character
NULL ); // Don't care about this flag
is equivalent to
wcstombs ( szANSIString, wszSomeString, sizeof(szANSIString) );
Maybe... I'd just consider using the 1st way if you would encounter different encodings in the future. Maybe you'd just roll your own conversion layer that then can host either 'wcstombs*()' or 'WideCharToMultiByte()', depending on your future requirement. Just Something like 'MyProjectUtils::ConvertoA
Hopefully this is a one time thing for a special requirement. I am a report writer who happens to be able to write code. The last serious programming I did was in 2001 in VB6.
mlmcc
mlmcc
a little remark apart from this question:
if using visual c++ compiler for the dll you may consider to passing std::wstring to the dll and handle the strings in the dll. most report libraries for windows can handle wide strings (utf16/ms unicode) same as (or even better than) ansi strings. also if you want to return strings from dll, you could avoid a reverse conversion (with possible issues, for example if utf-8 characters are involved).
Sara
if using visual c++ compiler for the dll you may consider to passing std::wstring to the dll and handle the strings in the dll. most report libraries for windows can handle wide strings (utf16/ms unicode) same as (or even better than) ansi strings. also if you want to return strings from dll, you could avoid a reverse conversion (with possible issues, for example if utf-8 characters are involved).
Sara
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