Add import D function usage example

README.md

@@ -35,16 +35,58 @@ const string wat_sum_module =
 auto engine = new Engine();
 auto store = new Store(engine);
 auto module_ = Module.from(store, wat_sum_module);
+assert(engine.valid && store.valid && module_.valid, "Could not load module!");
+
 auto instance = new Instance(store, module_);
-auto sumFunc = Function.from(instance.exports[0]);
+assert(instance.valid, "Could not instantiate module!");
 
-assert(engine.valid && store.valid && module_.valid && instance.valid && sumFunc.valid, "Could not instantiate module!");
+assert(instance.exports[0].name == "sum");
+auto sumFunc = Function.from(instance.exports[0]);
+assert(sumFunc.valid, "Could not load exported 'sum' function!");
 
 Value[] results;
 assert(sumFunc.call([new Value(3), new Value(4)], results), "Error calling the `sum` function!");
 assert(results.length == 1 && results[0].value.of.i32 == 7);
 ```
 
+### Import a D Function into a WebAssembly Module
+
+```d
+const string wat_callback_module =
+  "(module" ~
+  "  (func $print (import \"\" \"print\") (param i32) (result i32))" ~
+  "  (func (export \"run\") (param $x i32) (param $y i32) (result i32)" ~
+  "    (call $print (i32.add (local.get $x) (local.get $y)))" ~
+  "  )" ~
+  ")";
+
+auto engine = new Engine();
+auto store = new Store(engine);
+auto module_ = Module.from(store, wat_callback_module);
+assert(module_.valid, "Error compiling module!");
+
+auto print = (Module module_, int value) => {
+  return value;
+}();
+auto imports = [new Function(store, module_, print.toDelegate).asExtern];
+auto instance = module_.instantiate(imports);
+assert(instance.valid, "Could not instantiate module!");
+
+auto runFunc = Function.from(instance.exports[0]);
+assert(instance.exports[0].name == "run" && runFunc.valid, "Failed to get the `run` function!");
+
+auto three = new Value(3);
+auto four = new Value(4);
+Value[] results;
+assert(runFunc.call([three, four], results), "Error calling the `run` function!");
+assert(results.length == 1 && results[0].value.of.i32 == 7);
+
+destroy(three);
+destroy(four);
+destroy(instance);
+destroy(module_);
+```
+
 ## License
 
 [MIT Licence](https://opensource.org/licenses/MIT)

views/index.html

@@ -84,7 +84,7 @@ <h2 id="Usage">Usage</h2>
 }
 </pre>
 <p>See the official <a href="https://github.com/wasmerio/wasmer/tree/master/lib/c-api#readme">Wasmer Runtime C API</a> documentation.</p>
-<h3>Run a WebAssembly Module</h3>
+<h3 id="run">Run a WebAssembly Module</h3>
 <p>
   Sum function in a WebAssembly <a href="https://webassembly.github.io/spec/core/text/index.html">text format</a> module:
 </p>
@@ -101,14 +101,54 @@ <h3>Run a WebAssembly Module</h3>
 auto engine = new Engine();
 auto store = new Store(engine);
 auto module_ = Module.from(store, wat_sum_module);
+assert(engine.valid && store.valid && module_.valid, "Could not load module!");
+
 auto instance = new Instance(store, module_);
-auto sumFunc = Function.from(instance.exports[0]);
+assert(instance.valid, "Could not instantiate module!");
 
-assert(engine.valid && store.valid && module_.valid && instance.valid && sumFunc.valid, "Could not instantiate module!");
+assert(instance.exports[0].name == "sum");
+auto sumFunc = Function.from(instance.exports[0]);
+assert(sumFunc.valid, "Could not load exported 'sum' function!");
 
 Value[] results;
 assert(sumFunc.call([new Value(3), new Value(4)], results), "Error calling the `sum` function!");
 assert(results.length == 1 && results[0].value.of.i32 == 7);
 </pre>
+<h3 id="import-d-function">Import a D Function into a WebAssembly Module</h3>
+<pre class="c">
+const string wat_callback_module =
+  "(module" ~
+  "  (func $print (import \"\" \"print\") (param i32) (result i32))" ~
+  "  (func (export \"run\") (param $x i32) (param $y i32) (result i32)" ~
+  "    (call $print (i32.add (local.get $x) (local.get $y)))" ~
+  "  )" ~
+  ")";
+
+auto engine = new Engine();
+auto store = new Store(engine);
+auto module_ = Module.from(store, wat_callback_module);
+assert(module_.valid, "Error compiling module!");
+
+auto print = (Module module_, int value) => {
+  return value;
+}();
+auto imports = [new Function(store, module_, print.toDelegate).asExtern];
+auto instance = module_.instantiate(imports);
+assert(instance.valid, "Could not instantiate module!");
+
+auto runFunc = Function.from(instance.exports[0]);
+assert(instance.exports[0].name == "run" && runFunc.valid, "Failed to get the `run` function!");
+
+auto three = new Value(3);
+auto four = new Value(4);
+Value[] results;
+assert(runFunc.call([three, four], results), "Error calling the `run` function!");
+assert(results.length == 1 && results[0].value.of.i32 == 7);
+
+destroy(three);
+destroy(four);
+destroy(instance);
+destroy(module_);
+</pre>
 <!-- <h2>Acknowledgements</h2> -->
 <h2>Modules</h2>