C# - look for native library in nuget conventional locations

[dkackman]

.NET's package manage, NuGet, will install native libraries in a standard location, denoted by it's Runtime Identifier. This is the most common way for a .net package to be deployed.

This change modifies the C# POC code to look in those locations when loading the native library in the blst static constructor, making it easier to author NuGet packages that include the blst native libraries.

[dot-asm]

Doc says that its behaviour changed in .NET 8. Would it be appropriate to compile it conditionally? As in #if NET8_0_OR_GREATER that is. And mimic the new behaviour in #else? Or maybe one can simply mimic it without referring the RuntimeIdentifier? Also, does it make sense to preserve the original lookup? I mean it could check if the library exists in several locations...

[dkackman]

Doc says that its behaviour changed in .NET 8. Would it be appropriate to compile it conditionally? As in #if NET8_0_OR_GREATER that is. And mimic the new behaviour in #else? Or maybe one can simply mimic it without referring the RuntimeIdentifier? Also, does it make sense to preserve the original lookup? I mean it could check if the library exists in several locations...

How about like this:

var dir = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location) ?? ".";
var arch = RuntimeInformation.ProcessArchitecture switch
{
    Architecture.X64 => "x64",
    Architecture.Arm64 => "arm64",
    _ => "unsupported"
};
var os = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "win"
            : RuntimeInformation.IsOSPlatform(OSPlatform.OSX) ? "osx"
            : "linux";
var name = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ? "blst.dll"
            : RuntimeInformation.IsOSPlatform(OSPlatform.OSX) ? "libblst.dll.dylib"
            : "libblst.dll.so";

// first look for the file in the standard locations for a nuget installed native lib
// which will be something like "win-x64", "linux-x64", "linux-arm64", "osx-x64"
dll = Path.Combine(dir, "runtimes", $"{os}-{arch}", "native", name);

// if that's not found look using a simple default
if (!File.Exists(dll))
    dll = Path.Combine(dir, arch, name);

// if not there we'll try the current directory
if (!File.Exists(dll))
    dll = Path.Combine(Environment.CurrentDirectory, name);

if (File.Exists(dll))
{
    AssemblyLoadContext.Default.ResolvingUnmanagedDll += (asm, needs) =>
        (needs == "blst.dll" ? NativeLibrary.Load(dll) : IntPtr.Zero);
}

[dot-asm]

How about like this:

Cool, that's basically what I meant :-) But please add a remark that $"{os}-{arch}" mimics RuntimeIdentifier from NET 8.

Couple of questions. Is there feature availability conflict between the $"{x}" interpolation and #if NET5_0_OR_GREATER? It doesn't seem to be, because interpolation was added in C# 6, which predates NET 5. Does it sound right to you? Second question is if it makes sense to expand the os selection with OSPlatform.FreeBSD. I mean it's documented at least in NET 5, so why not...

[dot-asm]

Oh! And execute run.me and update even supranational.blst.cs.

[dkackman]

How about like this:

Cool, that's basically what I meant :-) But please add a remark that $"{os}-{arch}" mimics RuntimeIdentifier from NET 8.

Couple of questions. Is there feature availability conflict between the $"{x}" interpolation and #if NET5_0_OR_GREATER? It doesn't seem to be, because interpolation was added in C# 6, which predates NET 5. Does it sound right to you? Second question is if it makes sense to expand the os selection with OSPlatform.FreeBSD. I mean it's documented at least in NET 5, so why not...

makes sense to me. I'll put the conditional compilation back in so for net 8 forward at least this can pick up new permutations without change.

libblst.dll.so the expected file name on FreeBSD?

[dot-asm]

I'll put the conditional compilation back in so for net 8 forward at least this can pick up new permutations without change.

I meant a commentary would be sufficient, but feel free to add #if NET8_0_OR_GREATER.

libblst.dll.so the expected file name on FreeBSD?

Yes.

[Out for today.]

[dkackman]

Feedback merged.

FYI using it over here which is a library modeled on how chia implemented it: https://github.com/dkackman/chia-dotnet-bls/tree/blst

[dot-asm]

Thanks!