How to insert wchar_t type string to PostgreSQL

Hello all,

I am programming in Windows environment. Previously, we are using MBCs
(http://msdn.microsoft.com/en-us/library/5z097dxa%28VS.71%29.aspx),in order to support language other than English. 

The following function still can be used, as long as we are setting the database to correct encoding. For example, if
wewant to support china mainland, we will be using "GBK" as encoding. 

PGresult *PQexec(PGconn *conn, const char *query);

But once we compile using unicode, we are no longer using char * typed string. Instead, we are using wchar_t * typed
string.

But, I do not find any function as follow in libpq library.

PGresult *PQexec(PGconn *conn, const wchar_t *query);

May I know, how I can store wchar_t * typed string into PostgreSQl, using C library?

Thanks and Regards
Yan Cheng CHEOK