_README.md

This gist is part of my article “Emscripten’s embind”.

Build it with

$ emcc -s EXTRA_EXPORTED_RUNTIME_METHODS='["cwrap"]' -O3 nobind.cpp

or

$ docker run --rm -v $(pwd):/src trzeci/emscripten emcc -s EXTRA_EXPORTED_RUNTIME_METHODS='["cwrap"]' -O3 nobind.cpp

---

License Apache-2.0

nobind.cpp

/**
 * Copyright 2018 Google Inc. All Rights Reserved.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *     http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <emscripten.h>
#include <stdint.h>
#include <stdlib.h>
#include <string>

extern "C"
EMSCRIPTEN_KEEPALIVE
double add(double a, double b) {
 return a + b;
}

extern "C"
EMSCRIPTEN_KEEPALIVE
const char* exclaim(char* message) {
  std::string *input = new std::string(message);
  return (*input + "!").c_str();
}

extern "C"
EMSCRIPTEN_KEEPALIVE
int mymalloc(int size) {
  return (int)malloc(size);
}

extern "C"
EMSCRIPTEN_KEEPALIVE
void myfree(int p) {
  free((void *)p);
}

nobind.html

<script src="/a.out.js"></script>
<script>
  Module.onRuntimeInitialized = _ => {
    const api = {
      add: Module.cwrap('add', 'number', ['number', 'number']),
      exclaim: Module.cwrap('exclaim', 'number', ['number']),
      malloc: Module.cwrap('mymalloc', 'number', ['number']),
      free: Module.cwrap('myfree', '', ['number'])
    };

    function add(a, b) {
      return api.add(a, b);
    }

    function exclaim(str) {
      const utf8 = new TextEncoder('utf-8').encode(str);
      const p = api.malloc(utf8.byteLength);
      Module.HEAP8.set(utf8, p);
      const p2 = api.exclaim(p);
      const resultView = new Uint8Array(Module.HEAP8.buffer, p2, utf8.byteLength + 1);
      return new TextDecoder('utf-8').decode(resultView);
    }
    console.log(add(22, 20));
    console.log(exclaim('Hello World'));
  };
</script>

@surma Why async?

@beaufortfrancois Habit. Removed it.

@surma Thank you for sharing the example. Your blogs related to WebAssembly are useful and knowledgeable.

Related to this example, I have one doubt.
In file nobind.html, and in function exclaim(str), memory pointed by p and p2 should be freed after the usage. Otherwise, there will be memory leak. Is that correct ?