Swig C# SetConfigOption converts unicode characters to ASCII

[Mbucari]

What is the bug?

The swig-generated bindings for Gdal.SetConfigOption() and Gdal.GetConfigOption() are incorrectly marshalling values as ANSI strings instead of UTF-8 strings, which appears to be what GDAL is expecting. All non-ansi strings passed to Gdal.SetConfigOption() are converted to ansi. This is the cause of #1647, but it also affects any other config options which are file paths. e.g. GEOTIFF_CSV, GDAL_DATA, and GDAL_CURL_CA_BUNDLE.

For .NET to marshal UTF-8 strings, the marshaller must be explicitly told that strings are UTF-8 using the [MarshalAs(UnmanagedType.LPUTF8Str)] attribute. Here's what those P/Invoke signatures should look like.

[DllImport("gdal_wrap", EntryPoint = "CSharp_OSGeofGDAL_GetConfigOption___")]
[return: MarshalAs(UnmanagedType.LPUTF8Str)]
static extern string GetConfigOption(string pszKey, string pszDefault);

[DllImport("gdal_wrap", EntryPoint = "CSharp_OSGeofGDAL_SetConfigOption___")]
static extern void SetConfigOption(string pszKey, [MarshalAs(UnmanagedType.LPUTF8Str)] string pszValue);

Steps to reproduce the issue

1. Create a new dotnet test project with the MaxRev Gdal package

dotnet new console --name TestGdalConfigOption
cd TestGdalConfigOption
dotnet add package MaxRev.Gdal.Universal

2. Edit the Program.cs file

to the below:

Console.OutputEncoding = System.Text.Encoding.UTF8;
OSGeo.GDAL.Gdal.SetConfigOption("UNICODE_STRING", "Ĥĕļĺō Ŵŏŕľď");
Console.WriteLine($"UNICODE_STRING value is '{OSGeo.GDAL.Gdal.GetConfigOption("UNICODE_STRING", "")}'");

3. Run the program

dotnet run

You'll see the following output:

UNICODE_STRING value is 'Hello World'

Versions and provenance

Windows 11
Gdal version 3.12.1.440 MaxRev Universal Nuget Package

Additional context

No response

[Mbucari]

To see the correct behavior, edit the Program.cs file from "Steps to reproduce the issue" to below, then run.

using OSGeo.GDAL;
using System.Runtime.InteropServices;
using System.Text;

Console.OutputEncoding = Encoding.UTF8;
Gdal.SetConfigOption("UNICODE_STRING", "Ĥĕļĺō Ŵŏŕľď");
Console.WriteLine($"Using Gdal.SetConfigOption, UNICODE_STRING value is '{Gdal.GetConfigOption("UNICODE_STRING", "")}'");

SetConfigOption("UNICODE_STRING", "Ĥĕļĺō Ŵŏŕľď");
Console.WriteLine($"Using custom SetConfigOption method, UNICODE_STRING value is '{GetConfigOption("UNICODE_STRING", "")}'");


[DllImport("gdal_wrap", EntryPoint = "CSharp_OSGeofGDAL_GetConfigOption___")]
[return: MarshalAs(UnmanagedType.LPUTF8Str)]
static extern string GetConfigOption(string pszKey, [MarshalAs(UnmanagedType.LPUTF8Str)] string pszDefault);

[DllImport("gdal_wrap", EntryPoint = "CSharp_OSGeofGDAL_SetConfigOption___")]
static extern void SetConfigOption(string pszKey, [MarshalAs(UnmanagedType.LPUTF8Str)] string pszValue);

The output is:

Using Gdal.SetConfigOption, UNICODE_STRING value is 'Hello World'
Using custom SetConfigOption method, UNICODE_STRING value is 'Ĥĕļĺō Ŵŏŕľď'