convert String ^ in char *

[nicolas.hilaire]

hi all,

i'm using this code to convert a String ^ in char *


String ^str = "string .net";
IntPtr p =
System::Runtime::InteropServices::Marshal::StringToHGlobalAnsi(str);
LPCSTR str2 = reinterpret_cast<LPCSTR>(static_cast<void *>(p));
System::Runtime::InteropServices::Marshal::FreeHGlobal(p);


I would like to make safe code, so i would like to use safe_cast
instead of reinterpret_cast or static_cast.

I tryed, but i can't achieve making something to work.

Do you have an idea ?

Thanks in advance for your help


Nicolas H.

 

[Jochen Kalmbach [MVP]]

Hi nicolas!

i'm using this code to convert a String ^ in char *

I use the following struct and code:

struct StringConvA
{
char *szAnsi;
StringConvA(System::String* s)
:
szAnsi(static_cast<char*>(System::Runtime::InteropServices::Marshal::String­ToHGlobalAnsi(s).ToPointer()))

{}
~StringConvA()
{


System::Runtime::InteropServices::Marshal::FreeHGlobal(IntPtr(szAnsi));
}
operator LPCSTR() const
{
return szAnsi;
}
};


struct StringConvW
{
wchar_t *szUnicode;
StringConvW(System::String* s)
:
szUnicode(static_cast<wchar_t*>(System::Runtime::InteropServices::Marshal::­StringToHGlobalUni(s).ToPointer()))

{}
~StringConvW()
{

System::Runtime::InteropServices::Marshal::FreeHGlobal(IntPtr(szUnicode));
}
operator LPCWSTR() const
{
return szUnicode;
}
};


#ifdef _UNICODE
#define StringConvT StringConvW
#else
#define StringConvT StringConvA
#endif

int _tmain()
{
String *s = S"abc";
std::string ansi = StringConvA(s);
std::wstring unicode = StringConvW(s);
_tprintf(_T("%s"), (LPCTSTR) StringConvT(s));
}



--
Greetings
Jochen

My blog about Win32 and .NET
http://blog.kalmbachnet.de/

 

[nicolas.hilaire]

thanks for your answer Jochen

Your method looks like mine, using static_cast.

I would rather user safe_cast, but this should not be possible ...


Regards,
Nicolas

 

[Marcus Heege]

What would the safe_cast give you?

If you compile with /clr:safe, you can not use pointers at all. If you use
/clrure or /clr, and encapsulate the ugly cast in a separate class that
also provides cleanup of the native data, you should be fine.

Marcus

 

[Vadym Stetsyak]

Hello, Jochen!

The same can also be accomplished, using
pin_ptr class and PtrToStringChars(...) inline func.

String^ managedString;
pin_ptr<const TCHAR> srvNameUnmanged;
srvNameUnmanged = PtrToStringChars(managedString);

--
Regards, Vadym Stetsyak
www: http://vadmyst.blogspot.com

 

[nicolas.hilaire]

What would the safe_cast give you?

If you compile with /clr:safe, you can not use pointers at all. If you use
/clrure or /clr, and encapsulate the ugly cast in a separate class that
also provides cleanup of the native data, you should be fine.

Marcus

Yes, you're right Marcus, that's the good question
No need to make it safe or to get error messages exceptions

Thanks for your help

Nicolas H.

 

[Jochen Kalmbach [MVP]]

Hello, Jochen!

The same can also be accomplished, using
pin_ptr class and PtrToStringChars(...) inline func.

String^ managedString;
pin_ptr<const TCHAR> srvNameUnmanged;
srvNameUnmanged = PtrToStringChars(managedString);

Yes, at least for the W-Version... for the A-Version you need to use
such a construct...

--
Greetings
Jochen

My blog about Win32 and .NET
http://blog.kalmbachnet.de/

 

[Vadym Stetsyak]

JKM> Yes, at least for the W-Version... for the A-Version you need to use
JKM> such a construct...

Agree, this constuct is valid only for W, since String^ are always unicodes...

--
Regards, Vadym Stetsyak
www: http://vadmyst.blogspot.com