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[.net] char*

Started by Greg K Nov 15, 2004 at 9:13 PM 2 replies 450+ views

Original Post

Nov 15, 2004 at 9:13 PM

I am trying to pass a pointer to a char* to an unmanaged c++ dll function. The function allocates a string (ASCII) and sets the parameter to point to it. It is the callers responsibility to free that string. How do I do this in c#? bool myFunc( char** myNewString ) { *myNewString = new char[32]; return true; }

TheBluMage

Nov 16, 2004 at 12:56 AM

I'd have to know what you're going to use this buffer for to give you a more specific answer, but with out any marshalling conversions thrown in it should be something like this to import it:

using System.Runtime.InteropServices; public class MyDllClass { [DllImport("mydll.dll")] public extern unsafe static bool myFunc(ref byte* buffer); }

And make sure you have the unsafe compiler option on. Sorry, I can't get much more specific unless I know how you're going to use the buffer.

Greg K

Author

Greg K

Nov 16, 2004 at 12:59 AM

I am using it as a string

TheBluMage

Nov 16, 2004 at 3:21 AM

So, this DLL function is passing a string back to the caller? Okay, If that's the case, you can import it like this:

[DllImport("yourdllname.dll")] public static extern bool myFunc([MarshalAs(UnmanagedType.LPStr)] out string str);

Then call it like this:

string str; myFunc(out str); //Now str is assigned the data from the buffer

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