Pass a JavaScript array as argument to a WebAssembly function

Question

I would like to test WebAssembly for doing some complex array calculations.

So I\'ve written a simple C++ function adding two int arrays containing 3 e

Answer 1

So thanks to other similar questions :

Pass array to C function with emscripten

How to handle passing/returning array pointers to emscripten compiled code?

And API docs :

https://kripken.github.io/emscripten-site/docs/api_reference/preamble.js.html#getValue

I have figured it out. To examplify how to pass an array to wasm function / get an array back, I have implemented a simple array copy in C++ :

#include 

extern "C" {

int* copy_array(int* in_array, int length) {
  int out_array[length];
  for (int i=0; i

Which you can compile like this :

emcc wasm_dsp.cpp -s WASM=1 -s "MODULARIZE=1" -s "EXPORT_NAME='WasmDsp'" -s "BINARYEN_METHOD='native-wasm'" -s "EXPORTED_FUNCTIONS=['_copy_array']" -o build/wasm_dsp.js

And run in the browser like this :

Note the arrayToPtr and ptrToArray functions here ... they are the ones doing the work of passing / returning array.