C declarations in C#, continued

[Ted Sung]

Hi,

I finally got this C function to be called correctly from C#.

char * version_chk( const char *)

I needed to do the following:

[DllImport( "test.dll",
CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr version_chk(
[MarshalAs(UnmanagedType.LPStr)]
string version );

string sTestVersion = "3.0f_p2";
IntPtr test = version_chk( sTestVersion );
// how do we figure out the length?
string sReturnVersion = Marshal.PtrToStringAnsi(test,7);
Console.WriteLine( "version is " + sReturnVersion ) ;

The key was the CallingConvention!

Now that I have the IntPtr, test, available, I'm trying to understand
how I can know the length instead of having to hardcode it.

Any ideas?

Thanks,

Ted

[Ben Rush]

Can you marshal in strlen()?

"Ted Sung" <te**@intex.com> wrote in message
news:86**************************@posting.google.c om...

Hi,

I finally got this C function to be called correctly from C#.

char * version_chk( const char *)

I needed to do the following:

[DllImport( "test.dll",
CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr version_chk(
[MarshalAs(UnmanagedType.LPStr)]
string version );

string sTestVersion = "3.0f_p2";
IntPtr test = version_chk( sTestVersion );
// how do we figure out the length?
string sReturnVersion = Marshal.PtrToStringAnsi(test,7);
Console.WriteLine( "version is " + sReturnVersion ) ;

The key was the CallingConvention!

Now that I have the IntPtr, test, available, I'm trying to understand
how I can know the length instead of having to hardcode it.

Any ideas?

Thanks,

Ted

[Mattias Sjögren]

Now that I have the IntPtr, test, available, I'm trying to understand
how I can know the length instead of having to hardcode it.

Any ideas?

If the string is zero terminated, you can simply use the
PtrToStringAnsi overload that doesn't take a length parameter. It will
read the string up to the null terminator.

Mattias

--
Mattias Sjögren [MVP] mattias @ mvps.org
http://www.msjogren.net/dotnet/ | http://www.dotnetinterop.com
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