support setting bytes for stdin

[tiziano88]

Motivation

It is quite common to have to provide a pre-determined stdin value to a Wasm module, without having to expose a full file system to it.

Proposed solution

leverage this function:

https://docs.wasmtime.dev/c-api/wasi_8h.html#a525abd98ade58887a969b796ea05468e

would require modifying

wasmer-go/wasmer/packaged/include/wasmer.h

Lines 705 to 707 in ca60a45

	#if defined(WASMER_WASI_ENABLED)
	void wasi_config_inherit_stdin(struct wasi_config_t *config);
	#endif

and

wasmer-go/wasmer/wasi.go

Lines 196 to 202 in ca60a45

	// InheritStdin configures the WASI module to inherit the stdin from
	// the host.
	func (self *WasiStateBuilder) InheritStdin() *WasiStateBuilder {
	C.wasi_config_inherit_stdin(self.inner())
	return self
	}

Alternatives

The best alternative at the moment is passing the value as argument on the command line, but that's not great for large and / or binary values.

[jaime-amate]

I'm currently facing the same issue on my project. It would be quite handy having somehow a setStdIn function.

Could you explain on more further details about the workaround to pass input data to the wasi module execution?

[tiziano88]

For the time being I just serialize the data as a string (base64 if necessary) and pass it as the first command line argument to the Wasm module, which then reads it as argv[1]

[jaime-amate]

Thanks for the explanation, I think this wouldn't even work in my use case :(

I'm trying to embed a .wasm module compiled by Javy and according to this issue, it doesn't currently expose APIs to read environment variables or command line arguments.

[tiziano88]

Right, in that case fixing this issue wouldn't help you, since this is specific to WASI, which AFAICT you are not using. I think your best bet is to declare a custom function for the Wasm module to read the data into its own memory