Emscripten- retrieving array values set by c function with Module.cwrap

Question

We have a "little c" library compiled to javascript via emscripten. Many functions in the c library modify arrays that are passed in. It is not obvious what the mechanism is to access those arrays from the javascript level.

Using Module.cwrap and calling a function that is correctly exported (eg EXPORTED_FUNCTIONS="['_myFunc'] ) is straightforward, but the only access to variables calculated on the c side appears to be in the return from this function. If we return a pointer to an array from the c side, it is not obvious how to access the array from the javascript side.

If we indicate that Module.cwrap has a returnType of array how would the c function called return an array?

Answer 1

There is a description here . Basically you need to know the memory layout of your type (I assume you are using c-style arrays), which should be tight packed values.

And then use the described functions on the JS side.