How can I load .wasm files stored in a subdirectory?

user_2305095 0
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I am trying out a simple example to call a C function compiled to .wasm with JavaScript.

This is the counter.c file:

#include <emscripten.h>

int counter = 100;

EMSCRIPTEN_KEEPALIVE
int count() {  
    counter += 1;
    return counter;
}

I compiled it using emcc counter.c -s WASM=1 -o counter.js.

My main.js JavaScript file:

Module['onRuntimeInitialized'] = onRuntimeInitialized;
const count = Module.cwrap('count ', 'number');

function onRuntimeInitialized() {
    console.log(count());
}

My index.html file only loads both .js files in the body, nothing else:

<script type="text/javascript" src="counter.js"></script>
<script type="text/javascript" src="main.js"></script>

It works fine / prints 101 to the console, but when I move the counter.c file to a wasm subdirectory, recompile it with emscripten and update the script tag to src="wasm/counter.js", the counter.js script tries to load counter.wasm from the root directory instead of the wasm subdirectory and I get the error:

counter.js:190 failed to asynchronously prepare wasm: failed to load wasm binary file at 'counter.wasm'

I did some research, but I didn't find any way to tell emscripten to let the generated .js file load the .wasm from the same subdirectory.

emscripten webassembly javascript
2 Answers

If you look at the generated 'loader' file that emscripten creates, it has an integrateWasmJS function as follows:

function integrateWasmJS(Module) {
  var method = Module['wasmJSMethod'] || 'native-wasm';
  Module['wasmJSMethod'] = method;

  var wasmTextFile = Module['wasmTextFile'] || 'hello.wast';
  var wasmBinaryFile = Module['wasmBinaryFile'] || 'hello.wasm';
  var asmjsCodeFile = Module['asmjsCodeFile'] || 'hello.temp.asm.js';

  ...
}

You can see that the wasmBinaryFile indicates the location of the binary. If it is not set it provides a default.

It looks like you should be able to override this in your main.js file as follows:

Module['wasmBinaryFile'] = 'wasm/counter.wasm';
user_2499330
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