kripken/hello_world.c

## readme.markdown

      
    Raw
  

              readme.markdown
            
          
    Standalone WebAssembly Example

Build hello_world.c using
emcc hello_world.c -Os -s WASM=1 -s SIDE_MODULE=1 -o hello_world.wasm

(make sure to use latest Emscripten incoming). That creates a
WebAssembly dynamic libraryhello_world.wasm. You can then run
hello_world.html in your browser, which loads and uses it.
More details: https://github.com/kripken/emscripten/wiki/WebAssembly-Standalone

  
## hello_world.c
int doubler(int x) {
  return 2 * x;
}

## hello_world.html
<html>
<head>
  <script>
    // Check for wasm support.
    if (!('WebAssembly' in window)) {
      alert('you need a browser with wasm support enabled :(');
    }

    // Loads a WebAssembly dynamic library, returns a promise.
    // imports is an optional imports object
    function loadWebAssembly(filename, imports) {
      // Fetch the file and compile it
      return fetch(filename)
        .then(response => response.arrayBuffer())
        .then(buffer => WebAssembly.compile(buffer))
        .then(module => {
          // Create the imports for the module, including the
          // standard dynamic library imports
          imports = imports || {};
          imports.env = imports.env || {};
          imports.env.memoryBase = imports.env.memoryBase || 0;
          imports.env.tableBase = imports.env.tableBase || 0;
          if (!imports.env.memory) {
            imports.env.memory = new WebAssembly.Memory({ initial: 256 });
          }
          if (!imports.env.table) {
            imports.env.table = new WebAssembly.Table({ initial: 0, element: 'anyfunc' });
          }
          // Create the instance.
          return new WebAssembly.Instance(module, imports);
        });
    }

    // Main part of this example, loads the module and uses it.
    loadWebAssembly('hello_world.wasm')
      .then(instance => {
        var exports = instance.exports; // the exports of that instance
        var doubler = exports._doubler; // the "doubler" function (note "_" prefix)
        // now we are ready, set up the button so the user can run the code
        var button = document.getElementById('run');
        button.value = 'Call a method in the WebAssembly module';
        button.addEventListener('click', function() {
          var input = 21;
          alert(input + ' doubled is ' + doubler(input));
        }, false);
      }
    );
  </script>
</head>
<body>
  <input type="button" id="run" value="(waiting for WebAssembly)"/>
</body>
</html>
	<html>
	<head>
	<script>
	// Check for wasm support.
	if (!('WebAssembly' in window)) {
	alert('you need a browser with wasm support enabled :(');
	}

	// Loads a WebAssembly dynamic library, returns a promise.
	// imports is an optional imports object
	function loadWebAssembly(filename, imports) {
	// Fetch the file and compile it
	return fetch(filename)
	.then(response => response.arrayBuffer())
	.then(buffer => WebAssembly.compile(buffer))
	.then(module => {
	// Create the imports for the module, including the
	// standard dynamic library imports
	imports = imports \|\| {};
	imports.env = imports.env \|\| {};
	imports.env.memoryBase = imports.env.memoryBase \|\| 0;
	imports.env.tableBase = imports.env.tableBase \|\| 0;
	if (!imports.env.memory) {
	imports.env.memory = new WebAssembly.Memory({ initial: 256 });
	}
	if (!imports.env.table) {
	imports.env.table = new WebAssembly.Table({ initial: 0, element: 'anyfunc' });
	}
	// Create the instance.
	return new WebAssembly.Instance(module, imports);
	});
	}

	// Main part of this example, loads the module and uses it.
	loadWebAssembly('hello_world.wasm')
	.then(instance => {
	var exports = instance.exports; // the exports of that instance
	var doubler = exports._doubler; // the "doubler" function (note "_" prefix)
	// now we are ready, set up the button so the user can run the code
	var button = document.getElementById('run');
	button.value = 'Call a method in the WebAssembly module';
	button.addEventListener('click', function() {
	var input = 21;
	alert(input + ' doubled is ' + doubler(input));
	}, false);
	}
	);
	</script>
	</head>
	<body>
	<input type="button" id="run" value="(waiting for WebAssembly)"/>
	</body>
	</html>