Assemblyscript: for array loop - RuntimeError: memory access out of bounds

[ranbuch]

My index.ts:

export function foo(data: Array<i32>): Array<i32> {
  for (let i = 0; i < 1; i++) {
    data[i];
  }
  return data;
}

compiles fine but throws a runtime error:
RuntimeError: memory access out of bounds

This code works fine:

export function foo(data: Array<i32>): Array<i32> {
  for (let i = 0; i < 1; i++) {
  }
  return data;
}

I'm running it with this javascript code:

let exportedInterface = module.instance.exports;
console.log(exportedInterface.foo([5]));

Obviously this code is doing nothing, I just want to understand how can I access an array cell.

BTW (probably related) the return value is 5 while the expected value is [5]. seems like data is the value of the first cell on the array instead of the array itself.

Any idea on how to pass an array as a parameter?

Thanks.

[MaxGraey]

You can't pass JS array to AS array directly. This WebAssembly limitation. You could use loader

export const ARRAY_I32_ID = idof<Array<i32>>();
export function foo(data: Array<i32>): Array<i32> {
  for (let i = 0; i < 1; i++) {
    data[i];
  }
  return data;
}

const loader = require("assemblyscript/lib/loader");
const myModule = await loader.instantiateStreaming(fetch("optimized.wasm"));
var arrPtr = myModule.__retain(myModule.__allocArray(myModule.ARRAY_I32_ID, [5]));
var resPtr = myModule.foo(arrPtr);
var result = myModule.__getArray(resPtr);
console.log(result);
myModule.__release(arrPtr);

[ranbuch]

@MaxGraey your code doesn't run well:

if ((id >>>= 0) >= count) throw Error("invalid id: " + id);

while id = [5].

I've tried this:

var arrPtr = myModule.__retain(myModule.__allocArray([5, 4, 6, 3]));

but this one is throwing here:

if (!(info & (ARRAYBUFFERVIEW | ARRAY))) throw Error("not an array: " + id + " @ " + info);

Error: not an array: 5,4,6,3 @ 16

My realworld usage will be Uint8ClampedArray from ctx.getImageData().data, will it work?
Do you have any example with images and pixels manipulations or something like that?

Thank you!

[dcodeIO]

__allocArray expects the runtime id of the kind of array to allocate, like so:

// wasm
export const Uint8ClampedArray_ID = idof<Uint8ClampedArray>();

// js
var arrPtr = myModule.__retain(myModule.__allocArray(myModule.Uint8ClampedArray_ID, [5]));
...

See also: https://github.com/AssemblyScript/assemblyscript/tree/master/lib/loader

[MaxGraey]

yes. First argument should be id.

[ranbuch]

Can you maybe share a link to an example with transferring a param and getting the answer back. The loader documentation assumes I already know a great deal about assemblyscript.

I've tried to find reference to the type WasmImports on this repository but turns out it's not an existing interface but it just stands for any?

I couldn't find an example that uses the loader on this repository examples folder.

[stale[bot]]

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