Sending an array from a C pointer to a JS function without copying

Question

I'd like to send a data pointer to a JS function at a very high rate (in order to render it on a canvas). What is the best way to do this with Emscripten, without copying the actual data ?

Is the following correct?

void send(void const * data, unsigned length) {

    EM_ASM({

        var data = new Uint8Array(HEAP8.buffer, $0, $1);
        Module.send();

    }, data, length);

}

The issue is that it requires an Uint8Array allocation at each frame, which will not make the garbage collector very happy... :(

Maël Nison · Accepted Answer · 2015-03-06 21:47:32Z

2

According to the Emscripten GL implementation, it seems that the best way to achieve what I want is TypedArray#subarray. I wonder if it might affect the garbage collection, tho.

void send(void const * data, unsigned length) {

    EM_ASM({

        Module.send(HEAPU8.subarray($0, $0 + $1));

    }, data, length);

}

answered Mar 6, 2015 at 21:47

Maël Nison

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