UtilityFunctions.h

// from http://blogs.msdn.com/b/slippman/archive/2004/06/02/147090.aspx

#include <stdlib.h>
#include <vcclr.h>
#include <string>

using namespace System;
using namespace std;

/*String^ source ia a C++/CLI handle to a string object.  The handle
is like a reference, but since there is automatic optimization and 
garbage collection, the reference does not remain pointed at the 
same address.  The handle keeps track of the object wherever it is.
You can't pass a handle to a native function, so we will use pinning pointers*/

void To_string( String^ source, string &target )
{
	/*a pinning pointer is needed to "pin" the handle to the
	string object so it can be converted to a char array.
	PtrToStringChars returns  an interior pointer.
	If you pass a pointer to a native function, then it must be a 
	pinning pointer; the garbage collector will not be able to 
	update any pointers on the unmanaged stack frame.*/

	const int BUFFER_SIZE = 100;

    pin_ptr<const wchar_t> wch = PtrToStringChars( source );    

	//Make a new char array, or C-String
    char *ch = new char[ BUFFER_SIZE ];

	size_t i;		//number of characters converted

	/*
	errno_t wcstombs_s(   size_t *pReturnValue,   char *mbstr,   
												size_t sizeInBytes,   const wchar_t *wcstr,   size_t count);
 [out] pReturnValue 
The number of characters converted.
[out] mbstr 
The address of a buffer for the resulting converted multibyte character string.
[in]sizeInBytes 
The size in bytes of the mbstr buffer.
[in] wcstr 
Points to the wide character string to be converted.
[in] count 
The maximum number of wide characters to be stored in the mbstr buffer, 
not including the terminating null character, or _TRUNCATE.  */


	/*wcstombs converts wide-character string to multibyte string.
	If wcstombs successfully converts the multibyte string, it returns 0.	
	 If the conversion fails,	it returns an error code*/

  
	errno_t err = wcstombs_s(&i, ch, (size_t)BUFFER_SIZE, wch, (size_t)BUFFER_SIZE );
	if(err == 0)
	{
		target = ch;
	}
	
	//Delete the "new" char array
    delete[] ch;
    
}

/* To convert a std C++ native string to a managed string, we only need 
to convert the string to a char array (.c_str()) and make a new managed 
String reference out of it:

std::string phrase;

String ^ newString = gcnew String(phrase.c_str());*/