ashtonmeuser
commented
1 year ago Edit: I got a little carried away so here's a TL;DR: To interact with Wasm module memory from GDScript, use the stream property of an instantiated module which adheres to the Godot's StreamPeer interface.
This is a pretty deep topic. Godot Wasm doesn't specify an API on top of strictly basic Wasm32 (in a Rust context, wasm32-unknonwn-unknown). That means that the only types that can be natively exchanged between GDScript and the Wasm module are i32, i64, f32, and f64. If libSQL supports strings and byte arrays as well, they're doing some custom reading/writing of module memory and, in the case of strings, marshalling of the data. In short, you can either use functions with simple int/float value types or memory operations that leave you with the burden of (un)marshalling.
I decided to not reinvent the wheel for (un)marshalling data. Godot's StreamPeer interface is used to read and write from and to Wasm module memory. So to write a byte array, you can use put_data via wasm.stream.seek(MODULE_MEMORY_POINTER).put_data(MY_PACKED_BYTE_ARRAY). How you determine the memory address to which to write is left up the user. That said, there's plenty of this in the visualization example. If all you need to exchange dictionaries is a byte array, this is the easiest way to do it. To exchange a string, you could use put_string and read the UTF8 on the module side (note the first eight bytes represent string length). There's a little string exchange in the basic example that uses just the UTF8 bytes (without length header).
In the visualization example, I use an imported function that's called from the Wasm module and takes a pointer to the image buffer and a byte length as arguments. Another solution would be to use a global exported by the Wasm module to store the memory offset of the variable that will store your data on the Wasm side. For all examples, I'm using AssemblyScript, which is a super easy way to dive into Wasm if you're familiar with JS/TS. The Wasm code for the visualization example is here.
Like I said, this is a pretty deep topic. How you would exchange a dictionary is totally dependent on the data stored within that dictionary. You could use StreamPeer's put_var method to write literally any arbitrary GDScript value to memory. However, to use this in the Wasm module, you'd have to unmarshall that value the same way Godot does.
To give me a little more context, what language are you using to create a Wasm module? I definitely recommend checking out the examples if you haven't already!
fire
What is the proper way to interact with godot-wasm data transfer?
libsql's wasm implementation does int(8,16,32,64), float(32,64), string and byte array. I only saw int32_t and float32_t in godot-wasm. Godot can have int64_t and float64_t.
I want some sort of array type. A dictionary can be implemented with a byte array.