This is not as fast as C#, and I stronly suspect it's because of the C# String to Rust FFI passing

[jrouaix]

To sum up what is done when an already parsed expression is call from C# :

• only if the identifier exists in the expression, the identifier / value pair is send through FFI
• dotnet converts string to CStr when calling the native method https://github.com/jrouaix/csharp-expr-rs/blob/e08669247aa5d6a4bae410174615a83fc6ccae3b/src-csharp/csharp-expr-rs/Native.cs#L19
• then when the Rust side wants to use the string it's converting back the CStr to Rust String https://github.com/jrouaix/csharp-expr-rs/blob/e08669247aa5d6a4bae410174615a83fc6ccae3b/src/lib.rs#L498

It's really a pitty !

Is there a way to send a string usable directly from Rust, or to send a raw dotnet pointer to the String an allow Rust to go digging the value right into C# managed memory ... I need help here ...

[jrouaix]

Some benchmark : see how a single use of a big sized string mess down all the adventage of the Rust lib ?

[jrouaix]

Seems possible to get a string from C# .net without having .net do to conversation ... this way I could lazy decode the string on demand ...

[jrouaix]

suggested from : https://twitter.com/ryan_levick/status/1214523004903968768