Help passing multibyte unicode characters as string parameters to clr methods.

[weliwita]

I'm trying to find the root cause of the issue I created in this repo(agracio/edge-js#50).
I was trying to repro the issue with following steps.

1. Copied and ran the sample https://github.com/dotnet/samples/tree/master/core/hosting successfully.
2. Added the following method to my core app.

public static void Run(string s)
	{
        var x = "a";
        var y = "å";
        var z = s;
        Console.WriteLine(x);
        Console.WriteLine(y);
        Console.WriteLine(z);
    }

3. Calling the Run method from native code.

typedef void (STDMETHODCALLTYPE RunMethodFp)(char* args);
void *pfnDelegate = NULL;
    hr = runtimeHost->CreateDelegate(
   	  domainId,
   	  L"Core",	// Target managed assembly
   	  L"Test",				// Target managed type
   	  L"Run",									// Target entry point (static method)
   	  (INT_PTR*)&pfnDelegate);
    if (FAILED(hr))
    {
   	  printf("ERROR - Failed to create delegate.\nError code:%x\n", hr);
   	  return -1;
    }
char* param= "å";
((RunMethodFp*)pfnDelegate)(param);

4. I got A¥ for the z parameter. (c3 00 a5 00).

5. I tried the following combinations without luck.

• following code would just print Ã (c3 00 00 00)

 typedef void (STDMETHODCALLTYPE RunMethodFp)(LPWSTR args);
LPWSTR param= L"å";

• following code would just print Ã (c3 00 00 00)

 typedef void (STDMETHODCALLTYPE RunMethodFp)(BSTR args);
BSTR param= SysAllocString(L"å"); 

• Tried to encode with active code point and pass as char* didn't work either.

bool acp_encode(const std::wstring &str, std::vector<char>* out)
{
	out->clear();
	size_t size = ::WideCharToMultiByte(CP_ACP, 0, str.c_str(), -1, nullptr, 0, nullptr, nullptr);
    if (size == 0)
    {
        return false;
    }
    out->resize(size, '\0');
    return WideCharToMultiByte(CP_ACP, 0, str.c_str(), -1, out->data(), out->size(), nullptr, nullptr) != 0;
}

Can you please point me to a sample on how to achieve this conversion?

[weliwita]

I found the answer here http://yizhang82.me/hosting-coreclr. But I would like to have a little more detailed explanation(docs) on how the default marshaling applied cross-platform.

[weliwita]

Adding [MarshalAs(UnmanagedType.LPUTF8Str)] to the managed method argument resolved initial issue. But still, I'm not able to pass a structure with UTF8 strings.

typedef struct bootstrapperContext
{
	const char* runtimeDirectory;
	const char* applicationDirectory;
	const char* dependencyManifestFile;
} BootstrapperContext;

BootstrapperContext context;
context.runtimeDirectory = "";
context.applicationDirectory="å";
context.dependencyManifestFile="";

The CLR side.

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
public struct EdgeBootstrapperContext
{
    [MarshalAs(UnmanagedType.LPUTF8Str)]
    public string RuntimeDirectory;

    [MarshalAs(UnmanagedType.LPUTF8Str)]
    public string ApplicationDirectory;

    [MarshalAs(UnmanagedType.LPUTF8Str)]
    public string DependencyManifestFile;
}

public static void Run2(EdgeBootstrapperContext c)
{
        var z = c.ApplicationDirectory;
        Console.WriteLine(z);
}

Please suggest proper attributes or point me to some documentation where the marshaling behavior is defined.

[AaronRobinsonMSFT]

@weliwita Please see the new Native interoperability documentation that @jkoritzinsky has written. The marshalling of strings is non-trivial due to the intersection of platform and "default" encoding. If there is something missing in our new documentation please create an issue and tag @jkoritzinsky and me. Thanks!