Symbol Transformations

Sometimes, the name you want to as a member in your interface doesn’t map to what the name of the actual native symbol is. It’s commonplace in C libraries to have a prefix to functions in order to sort them by class, struct, subsystem, etc - however, typing all that out in C# gets tedious.

To that end, ADL provides two attributes - NativeSymbol and NativeSymbols. The former can be applied to individual methods, and the latter to entire interfaces. Let’s look at how.

Given a C library with functions that looks like this,

__declspec(dllexport) int32_t sym_trans_do_thing(int32_t a, int32_t b)
{
    return a * b;
}

you can do one of two things.

NativeSymbol

Firstly, you can explicitly specify the name of the symbol you want to bind to.

public interface ISymbolTransformationTests
{
	[NativeSymbol("sym_trans_do_thing")]
    int DoThing(int a, int b);
}

NativeSymbols

Alternatively, if you’d like to avoid repeating yourself over a larger number of methods, you can provide hinting information for the entire interface.

[NativeSymbols(Prefix = "sym_trans_", SymbolTransformationMethod = Underscore)]
public interface ISymbolTransformationTests
{
    int DoThing(int a, int b);
}

The prefix is appended to all symbols in the interface, and is then passed through a transformation method to finalize the format of the symbol.

The two attributes can be used in combination, and if a method has a NativeSymbol attribute, its value will be used instead of the method’s name when forming the final symbol name together with the interface attribute.