v1
This takes a Javascript typed array (Float32Array), asks a C++ piece of code to process it and we can access it again from Javascript in it's modified version.
Example taken from: http://kapadia.github.io/emscripten/2013/09/13/emscripten-pointers-and-pointers.html
| #include <math.h> | |
| // otherwise C++ function names are mangled | |
| extern "C" { | |
| int float_multiply_array(float factor, float *arr, int length) { | |
| for (int i = 0; i < length; i++) { | |
| arr[i] = factor * arr[i]; | |
| } | |
| return 0; | |
| } | |
| } |
| <!doctype html> | |
| <html lang="en-us"> | |
| <head> | |
| <meta charset="utf-8"> | |
| <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> | |
| <title>Emscripten-Generated Code</title> | |
| <script type="text/javascript" src="arrayFunction.js"></script> | |
| </head> | |
| <body> | |
| <script> | |
| // Import function from Emscripten generated file | |
| float_multiply_array = Module.cwrap( | |
| 'float_multiply_array', 'number', ['number', 'number', 'number'] | |
| ); | |
| // Create example data to test float_multiply_array | |
| var data = new Float32Array([1, 2, 3, 4, 5]); | |
| // Get data byte size, allocate memory on Emscripten heap, and get pointer | |
| var nDataBytes = data.length * data.BYTES_PER_ELEMENT; | |
| var dataPtr = Module._malloc(nDataBytes); | |
| // Copy data to Emscripten heap (directly accessed from Module.HEAPU8) | |
| var dataHeap = new Uint8Array(Module.HEAPU8.buffer, dataPtr, nDataBytes); | |
| dataHeap.set(new Uint8Array(data.buffer)); | |
| // Call function and get result | |
| float_multiply_array(20, dataHeap.byteOffset, data.length); | |
| var result = new Float32Array(dataHeap.buffer, dataHeap.byteOffset, data.length); | |
| // Free memory | |
| Module._free(dataHeap.byteOffset); | |
| console.log( result ); | |
| </script> | |
| </body> | |
| </html> |
| emcc -O3 arrayFunction.cpp -o arrayFunction.js -s EXPORTED_FUNCTIONS="['_float_multiply_array']" |