Is there a way to execute a cheerp-wasm program without using the 'path' module for loading?

Question

Is there a way to execute a cheerp-wasm program without using the 'path' module for loading?

One interesting feature of Cheerp is its cheerp-wasm target, which compiles C++ into both a .js file and its corresponding .wasm file. Essentially, the .js file acts as a loader for the WebAssembly code.

This particular loader🔗 uses require("path") to bring in essential filesystem functionalities needed to load the .wasm file as a module. Unfortunately, the environment where my code operates (Screeps) does not support this "path" module.

[8:39:54 AM][shard3]Error: Unknown module 'path'
                        at Object.requireFn (<runtime>:31712:23)
                        at fetchBuffer (main:10:5)
                        at main:30:1
                        at main:42:3
                        at Object.exports.evalCode (<runtime>:15584:76)
                        at Object.requireFn (<runtime>:31730:28)
                        at Object.exports.run (<runtime>:31673:60)

Given that the Cheerp loader relies on functionality that I can't access, how can I properly load my wasm code?

Although Cheerp presents various flags that can be configured, none seem relevant to my current predicament.

Is there a way to direct Cheerp to simply call

bytecode = require("mycode.wasm")

and utilize that? Could Cheerp potentially incorporate the wasm directly as bytecode within the .js itself? Or should I consider developing my own custom loader instead?

javascript c++screeps cheerp

Answer 1

Answer №1

Cheerp utilizes various methods to retrieve the wasm file depending on the environment.

The supported environments include: browser, node.js, d8, and js.

For the node environment, it assumes the presence of a path module for accessing the wasm from the filesystem.

If this module is not available in your current environment, there may be an issue.

We are working towards providing more flexibility for passing the wasm file in the future, but it poses a challenge to do so in a universal manner.

In the meantime, I can offer a temporary solution.

Here is the code segment responsible for fetching the wasm:

function fetchBuffer(p){
    var b=null,f='function';
    if(typeof fetch===f) {
        b=fetch(p).then(r=>r.arrayBuffer());
    } else if(typeof require===f) {
        p=require('path').join(__dirname, p);
        b=new Promise((y,n)=>{
            require('fs').readFile(p,(e,d)=>{
                if(e) n(e);
                else y(d);
            });
        });
    } else {
        b=new Promise((y,n)=>{
            y(read(p,'binary'));
        });
    }
    return b;
}

This function first attempts to use the fetch method if it's available.

If you're encountering issues due to its undefined status in your environment, you can define it manually before the cheerp code and implement it by using your own require("mycode.wasm").

Below is an example implementation (not tested):

function fetch(path) {
  return new Promise((y,n)=> {
    let ret = {
      arrayBuffer: () => {
        return require("mycode.wasm");
      }
    };
    y(ret);

  });
}

Answer 2

Cheerp utilizes various methods to retrieve the wasm file depending on the environment.

The supported environments include: browser, node.js, d8, and js.

For the node environment, it assumes the presence of a path module for accessing the wasm from the filesystem.

If this module is not available in your current environment, there may be an issue.

We are working towards providing more flexibility for passing the wasm file in the future, but it poses a challenge to do so in a universal manner.

In the meantime, I can offer a temporary solution.

Here is the code segment responsible for fetching the wasm:

function fetchBuffer(p){
    var b=null,f='function';
    if(typeof fetch===f) {
        b=fetch(p).then(r=>r.arrayBuffer());
    } else if(typeof require===f) {
        p=require('path').join(__dirname, p);
        b=new Promise((y,n)=>{
            require('fs').readFile(p,(e,d)=>{
                if(e) n(e);
                else y(d);
            });
        });
    } else {
        b=new Promise((y,n)=>{
            y(read(p,'binary'));
        });
    }
    return b;
}

This function first attempts to use the fetch method if it's available.

If you're encountering issues due to its undefined status in your environment, you can define it manually before the cheerp code and implement it by using your own require("mycode.wasm").

Below is an example implementation (not tested):

function fetch(path) {
  return new Promise((y,n)=> {
    let ret = {
      arrayBuffer: () => {
        return require("mycode.wasm");
      }
    };
    y(ret);

  });
}

Is there a way to execute a cheerp-wasm program without using the 'path' module for loading?

Answer №1

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