Chapter 8

ch08/README.md

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+## Chapter 7 : WebAssembly in the Server
+
+This chapter exists the browser for Node.js and Deno. While I didn't
+want to create overly complicated examples for the book itself, I will
+have additional examples eventually in this repository as well.
+
+The first example is the traditional way to extend Node.js with Add On
+code. This is in the directory `node-addon`. If you enter that directory, you
+can build the example with:
+
+```
+> node-gyp configure build
+> node test.js
+This should be eight: 8
+```
+
+In the `node` directory, there is the simple example that adds two
+numbers together. If you include the `main()`, you can run it with:
+
+```
+> emcc add.c
+> node a.out.js
+The sum of 2 and 3 is: 5
+```
+
+Node.js has experimental support for loading WebAssembly modules as
+ES6 modules. If you remove the `main()` from `add.c` and do the
+following, you should be able to see this on recent versions of
+Node.js:
+
+```
+> emcc add.c
+> node --experimental-modules --experimental-wasm-modules index.mjs
+The sum of 6 and 2 is: 8
+```
+
+In the `deno` directory, there are some examples that work with this
+exciting new environment.
+
+```
+> deno run --allow-read main.ts
+2 + 3 =  5
+```
+
+or
+
+```
+> deno run --allow-read --allow-net main-serve.ts
+HTTP webserver running.  Access it at:  http://localhost:9000/
+```
+
+or
+
+```
+> deno run --allow-read --allow-write --allow-net db-serve.ts
+HTTP webserver running.  Access it at:  http://localhost:9000/
+```

ch08/deno/db-serve.ts

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+import { DB } from "https://deno.land/x/sqlite/mod.ts";
+import { serve } from "https://deno.land/[email protected]/http/server.ts";
+
+// Create the Database. This requires write access!
+
+const db = new DB("pl.db");
+db.query(
+    "DROP TABLE IF EXISTS languages",
+);
+
+db.query(
+   "CREATE TABLE languages (id INTEGER PRIMARY KEY AUTOINCREMENT, name TEXT)",
+);
+
+const names = ["C", "C++", "Rust", "TypeScript"]
+
+// Populate the database
+
+for (const name of names) {
+  db.query("INSERT INTO languages (name) VALUES (?)", [name]);
+}
+
+// Close out the connection
+
+db.close();
+
+const server = serve({ hostname: "0.0.0.0", port: 9000 });
+console.log(`HTTP webserver running.  Access it at:  http://localhost:9000/`);
+
+for await (const request of server) {
+    // Re-open the Database
+
+    const db = new DB("pl.db");
+    let bodyContent = "Programming Languages that work with WebAssembly:\n\n";
+
+    for(const [name] of db.query("SELECT name FROM languages")) {
+	bodyContent += name + "\n";
+    }
+
+    bodyContent += "\n";
+    request.respond({ status: 200, body: bodyContent });
+
+    // Close the Database
+    db.close();
+}

ch08/deno/main-serve.ts

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+import { serve } from "https://deno.land/[email protected]/http/server.ts";
+
+const wasmCode = await Deno.readFile("./a.out.wasm");
+const wasmModule = new WebAssembly.Module(wasmCode);
+const wasmInstance = new WebAssembly.Instance(wasmModule);
+const add = wasmInstance.exports.add as CallableFunction
+
+const server = serve({ hostname: "0.0.0.0", port: 9000 });
+console.log(`HTTP webserver running.  Access it at:  http://localhost:9000/`);
+
+for await (const request of server) {
+  let bodyContent = "2 + 3 = " + add(2,3);
+  request.respond({ status: 200, body: bodyContent });
+}
+
+

ch08/deno/main.ts

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+const wasmCode = await Deno.readFile("./a.out.wasm");
+const wasmModule = new WebAssembly.Module(wasmCode);
+const wasmInstance = new WebAssembly.Instance(wasmModule);
+const add = wasmInstance.exports.add as CallableFunction
+
+console.log("2 + 3 =  " + add(2,3));

ch08/node-addon/addon.cc

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+// addon.cc
+#include <node.h>
+
+namespace demo {
+
+using v8::Exception;
+using v8::FunctionCallbackInfo;
+using v8::Isolate;
+using v8::Local;
+using v8::Number;
+using v8::Object;
+using v8::String;
+using v8::Value;
+
+// This is the implementation of the "add" method
+// Input arguments are passed using the
+// const FunctionCallbackInfo<Value>& args struct
+void Add(const FunctionCallbackInfo<Value>& args) {
+  Isolate* isolate = args.GetIsolate();
+
+  // Check the number of arguments passed.
+  if (args.Length() < 2) {
+    // Throw an Error that is passed back to JavaScript
+    isolate->ThrowException(Exception::TypeError(
+        String::NewFromUtf8(isolate,
+                            "Wrong number of arguments").ToLocalChecked()));
+    return;
+  }
+
+  // Check the argument types
+  if (!args[0]->IsNumber() || !args[1]->IsNumber()) {
+    isolate->ThrowException(Exception::TypeError(
+        String::NewFromUtf8(isolate,
+                            "Wrong arguments").ToLocalChecked()));
+    return;
+  }
+
+  // Perform the operation
+  double value =
+      args[0].As<Number>()->Value() + args[1].As<Number>()->Value();
+  Local<Number> num = Number::New(isolate, value);
+
+  // Set the return value (using the passed in
+  // FunctionCallbackInfo<Value>&)
+  args.GetReturnValue().Set(num);
+}
+
+void Init(Local<Object> exports) {
+  NODE_SET_METHOD(exports, "add", Add);
+}
+
+NODE_MODULE(NODE_GYP_MODULE_NAME, Init)
+
+}  // namespace demo

ch08/node-addon/binding.gyp

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+{
+  "targets": [
+    {
+      "target_name": "addon",
+      "sources": [ "addon.cc" ]
+    }
+  ]
+}

ch08/node-addon/test.js

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+// test.js
+const addon = require('./build/Release/addon');
+
+console.log('This should be eight:', addon.add(3, 5));