WebAssembly (Wasm) is a binary instruction format for a stack-based virtual machine that fills a critical gap in the web platform's capabilities. It doesn't replace JavaScript, but it does give developers a performant, low-level compilation target for their web applications. It also supports languages other than JavaScript, like C++, allowing them to run on the web at near-native speed.

If we see the web as your operating system, Wasm literally extends the capabilities of web browsers and adds an extra layer to web apps, which translates to a better end-user experience. If you've ever used Google Maps or Facebook on your browser, you've already used WebAssembly. Facebook for example, uses Wasm for its SQL client library in the browser.

Coding in Wasm's native language can be low-level and challenging. However, C++, one of the most efficient and widely-used languages, especially for high-performance tasks, can be compiled into WebAssembly, extending its web applications reach and making Wasm accessible to a wider audience.

Since our ideal user is a basketball fan, consider Wasm as the point guard of your web applications, facilitating communication between the frontend, backend, and other parts, strategizing to make the best use of resources, and increasing your applications' speed.

Let's start this Wasm journey with a simple 'Hello' program on C++. Don't worry; this code won't be executed. It's just a simple illustration for now.

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#include <iostream>

using namespace std;

int main() {

​

  // Just to illustrate, this program won't do much

  cout << "Welcome to WebAssembly!";

  return 0;

​

}

C++ is a powerful language that has been used in the programming world for decades, majorly for system programming, game development, and embedded systems, due to its flexibility and performance benefits. When it comes to WebAssembly (WASM), C++ plays a significant role for a number of reasons.

Firstly, C++ has mature toolchains like Emscripten that can compile C++ code into WASM modules, making it an attractive interoperable option. This is particularly useful as shipping complex algorithms and data structures in native code to the browser, thereby saving resources on both the server and the client-side.

Secondly, compiling C++ into WASM allows developers to leverage the low-level features of C++ and the performance benefits that come along with them. Web applications compiled from C++ to WASM can run at near-native speed, providing a great boost in performance.

Moreover, there is a large body of existing C++ code, libraries, and frameworks available that can be brought to the web platform through WASM. For instance, physics engines used in games or simulation, advanced data processing or image manipulation libraries that have been time-proven and optimized can leveraged in the web context.

A simple parallel can be drawn here in terms of web application performance and basketball. Much like a seasoned player like Kobe Bryant adds a huge performance boost to a team with his experience and technical skills, C++ when compiled to WASM delivers superior performance benefits to web applications.

As a senior engineer, mastering the process of compiling C++ to WebAssembly can help you bring high-performance applications to the web, opening up a broad range of possibilities.

As a seasoned programmer, you must know that C++ is a general-purpose programming language with significant influence on other languages like C, C#, Objective-C, Java, and even newer ones like Rust and Swift. But for WebAssembly, the synergy between C++ and Wasm is amplified due to the former's maturity, performance benefits, and substantial codebase.

C++ is an extension of the C language, but it's unique in its support for Object-Oriented Programming (OOP) and Generic Programming. These features, especially OOP, allow for better code reusability and make your code more intuitive and easy to follow.

Let's delve into some basic concepts of C++, that you must be familiar with:

• Variables and Basic Data Types: C++ supports various data types, including but not limited to, integers (int), floating-point numbers (float, double), and characters (char), along with the familiar operations for manipulating these data types.

• Control Flow: Akin to most programming languages, C++ offers constructs for control flow maneuvres, such as if, else, while, for, and so on.

• Functions: Functions in C++ help us encapsulate and reuse code. They follow a binomial structure that includes a return type, name, parameters, and body.

• Object-Oriented Programming: C++ supports OOP through classes. Classes are blueprints using which you can create objects. Classes have data members (attributes) and member functions (behavior). The concept of encapsulation, inheritance, and polymorphism are key principles in C++ OOP.

• C++ Standard Template Library (STL): STL is a powerful library in C++ that provides generic templates for various common algorithms and data structures, which aids in fast development involving complex data manipulations.

In the following lessons, we're going to use some of these concepts to compile C++ code into WebAssembly. So even though you may be familiar with all of this being a senior engineer, it serves as a good refresher to achieve our end goal - mastering WebAssembly!

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#include <iostream>

using namespace std;

​

// defining a simple function

int add(int x, int y) {

  return x + y;

}

​

int main() {

  int a = 5, b = 3;

  cout << "Sum of a and b is: " << add(a, b) << endl;

  return 0;

}

The process of compiling C++ code to WebAssembly involves several tools. Let's get your development environment set up, to ensure an effective learning journey.

First and foremost, you need a modern web browser that supports the WebAssembly JavaScript APIs. Current versions of Firefox, Chrome, Safari, and Edge will do the trick.

Secondly, you need to have Emscripten installed on your machine. Emscripten is a source-to-source compiler that compiles C and C++ code to WebAssembly or JavaScript. Its significant role in our process is to provide bindings from WebAssembly to the host environment (the web browser).

Here are the steps you can follow to install it:

1. Clone the Emscripten repo from Github

1#include <iostream>
2using namespace std;
3int main() {
4  // This is just a placeholder to indicate the start of installing Emscripten
5  cout << "Cloning Emscripten Repo from Github...";
6}

2. Navigate to the folder in the Terminal and check out the latest stable branch

3. Next, fetch the latest registry of precompiled Emscripten Ports libraries.

1#include <iostream>
2using namespace std;
3int main() {
4  // This is just a placeholder to indicate the end of installing Emscripten
5  cout << "Completed all steps needed for installing Emscripten!";
6}

To verify the success of the installation, try compiling a simple 'Hello, World!' C++ program. You should see the program output in the terminal. With this environment, you're now ready to delve into the world of WebAssembly.

Remember, in case of errors, carefully read the error messages, they often provide clues about what's going wrong. In the worst-case scenario? Google is always your best friend when it comes to troubleshooting.

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#include <iostream>

using namespace std;

int main() {

  // Replace with your c++ logic here

  cout << "Hello, WebAssembly!";

}

Welcome to the world of Emscripten!

Emscripten is a vital tool for WebAssembly. Being an open-source compiler toolchain, Emscripten compiles C++, Rust, or other LLVM-based languages into WebAssembly or JavaScript. In other words, it bridges the gap between high-efficiency languages and the web.

Emscripten is noticeable among other WebAssembly compilers due to its extensive feature set. Besides supporting a majority of C++ features, it also offers seamless integration with JavaScript and the web platform like the DOM, WebGL, and WebAudio APIs.

Emscripten can be visualized as a moving agent that gets your C++ project, transforms it into a format understood by your web browser, and ensures it runs accurately. It's as if we have a translator who can efficiently convert C++ phrases into JavaScript or WebAssembly equivalents.

Moreover, this advanced compiler not only strengthens your applications but also helps you squeeze every bit of performance from your code. Incorporating C++ into your web development stack unlocks unprecedented potential for CPU-intensive scenarios such as game development, image/video processing, or physics simulations.

In addition to being highly beneficial for senior web developers, Emscripten provides an excellent opportunity for C++ developers to venture into web development. It can be a stepping stone for shipping your C++ products straight to the web with relatively minor changes.

If you had any doubts about the significance of Emscripten in the journey from C++ to WebAssembly, we hope they are cleared now. Buckle up, and get ready to dive deeper!

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#include <iostream>

using namespace std;

int main() {

  // Placeholder for Emscripten Image

  cout << "Image: Emscripten SDK";

}

In this screen, we will compile a simple C++ program into WebAssembly using Emscripten. This program is going to output a message Hello, WebAssembly! in the console.

Let's start by writing the C++ code:

1#include <iostream>
2using namespace std;
3
4int main() {
5  cout << "Hello, WebAssembly!";
6  return 0;
7}

We will examine the steps of compiling this C++ program to wasm in detail in the upcoming screens. Understanding this process is crucial as it forms the basis of integrating performance-critical scenarios such as physics simulations or heavy computations into web applications. This undoubtedly opens numerous possibilities for a web developer, particularly those having a decent amount of web development coding experience.

As a senior engineer, you are likely to appreciate how WebAssembly allows us to leverage the advantages of C++, and bring its efficiency to the web.

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#include <iostream>

using namespace std;

​

int main() {

  cout << "Hello, WebAssembly!";

  return 0;

}

Now that we have compiled our C++ code into a WebAssembly module, it's time to understand and interpret the generated Wasm output. Wasm output is a binary code format, different from higher level languages like JavaScript or C++. This compact and portable format leads to quicker applications initialization and improved performance, both crucial for web applications.

After compiling our simple C++ program using Emscripten, the Wasm output will be a .wasm file. This binary file may not be human-readable, but there are tools like Wabt's wasm2wat that allow us to convert it into a more readable format called WebAssembly Text format (wat).

The wasm2wat tool would convert our C++ program's Wasm output into something like the following:

1(module
2(type (;0;) (func))
3(func (;0;) (type 0)
4  (i32.store offset=4
5    (i32.const 0)
6    (i32.const 1024))
7  (call $main)
8  (drop
9    (call $main))
10  return)
11)

This representation starts with a (module ...), indicating that this is a WebAssembly module. It includes a (type (;0;) (func)), defining the type of functions that can be included in this module, and then it defines a function (func ...) with a type 0.

Important to note is that WebAssembly is a stack-based virtual machine. This means that operations are performed by pushing operands onto a stack and popping operands from the top of the stack when fetching results.

This sort of understanding is not only valuable, but required to effectively leverage the benefits of WebAssembly and deal with performance optimization and debugging in real-world scenarios. However, remember you would primarily interact with the Wasm output through JavaScript or an HTML page, making the non-human readability far less of a hindrance in practice.

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#include <iostream>

using namespace std;

​

int main() {

  cout << "Hello, WebAssembly!";

  return 0;

}

We can invoke WebAssembly functions from JavaScript by loading the wasm module and making the function calls in the JavaScript environment. Imagine we've compiled a very simple C++ program (like the one featured in the code block) that prints Hello from WebAssembly!. The wasm module contains our print statement that we want to call from JavaScript.

1WebAssembly.instantiateStreaming(fetch('main.wasm')).then(wasmModule => {
2  wasmModule.instance.exports._Z14print_statementv();
3});

Considering we have our main.wasm file available at the same location as our JS file, we use WebAssembly.instantiateStreaming combined with fetch to load and compile our wasm module directly from the server. After it's ready, we get a WebAssembly.Module object, and we can access its exported functions. In this case, wasmModule.instance.exports._Z14print_statementv() is our Hello from WebAssembly! message.

Note that the C++'s print_statement() translated into _Z14print_statementv(). The translation is a result of name mangling in C++, a way for the compiler to generate unique names for each function.

Remember, using WebAssembly functions from JavaScript is pivotal for a good integration between low-level wasm modules and your high-level JavaScript code. Since WebAssembly isn't designed to manipulate the DOM directly, your JavaScript code acts as a bridge between wasm modules and web APIs.

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#include <iostream>

using namespace std;

int main() {

  cout << "Hello from WebAssembly!";

  return 0;

}

WebAssembly modules are not easy to debug due to their low-level nature. However, Emscripten offers several ways to debug compiled wasm code which can be really beneficial in your web development workflow, especially considering your background in web development.

The first one is Emscripten's debug mode. When compiling your C++ code into wasm, you can use the -g flag to include debugging information in the output. This allows you to see more detailed error messages if something goes wrong.

1emcc -g main.cpp -o main.js

Additionally, modern browsers, like Chrome and Firefox, include outstanding devtools to step through the JavaScript code that interacts with the wasm module, inspect the memory and variables as well as view the wasm text format for easier understanding. They're expected to keep enhancing wasm's debugging capabilities, making life easier for developers.

Do note, however, that wasm debugging support is not yet as mature as JavaScript's. This can occasionally make things tougher, but it's rapidly improving. Your natural debugging instincts from your web developer experience will be invaluable here.

In the code block you see a simple C++ program. Try to change the value of the num variable and debug the program by seeing the output. This may seem simple, but getting the hang of these debugging features will greatly help you as you start working with more complex C++ and WebAssembly modules.

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#include <iostream>

using namespace std;

int main() {

  int num = 10;

  if(num == 5) {

    cout << "Number is 5";

  } else {

    cout << "Number is not 5";

  }

}

WebAssembly is always evolving, with ongoing work to add more advanced features that will make it even more powerful. Some of these features include Threads and SIMD.

Threads: WebAssembly threading support is becoming more widespread among browsers. This means you can utilize multi-core processors in your Wasm modules, similar to how you might use threading in a native C++ application. This can greatly improve the performance of CPU-intensive workloads.

SIMD: SIMD (Single Instruction, Multiple Data) allows one instruction to be performed on multiple data elements simultaneously. This can provide significant performance improvements for certain types of calculations, such as those used in image and audio processing or machine learning.

Here's a code example of using SIMD in WebAssembly. It's a simple program that creates a SIMD vector with four elements and then extracts the second element.

These advanced features can unlock higher level of performance in web applications. However, they are more complex to work with and require a deeper understanding of both C++ and WebAssembly. As a senior engineer, mastering these advanced topics can provide a significant advantage when working on performance-critical web applications.

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#include <emscripten.h>

#include <iostream>

​

using namespace std;

​

int main() {

  unsigned int simdData[4] = {1, 2, 3, 4};

  unsigned int result = emscripten_int32x4_extractLane(simdData, 1);

  cout << "The second element in simdData is: " << result << endl;

  return 0;

}

WebAssembly is already revolutionizing web development, with real-world applications demonstrating its potential across various sectors. Let's go through some of the use case scenarios for Wasm:

1. Gaming: Wasm removes the performance handicap of JavaScript, enabling high-performance games or graphics applications. Major game engines like Unity and Unreal have already ported their runtime to Wasm, allowing developers to run games at near-native speed in the browser.

2. Image and Video Editing: Wasm is ideal for implementing performance-critical tasks such as image manipulation, video editing, or even computer vision tasks. Being able to execute such complex computations at near-native speed directly on the client-side has significant advantages for the user in terms of processing time and data privacy.

3. Cryptography: Cryptographic calculations, like hashing and encryption routines, are computationally expensive and often need to be implemented in a low-level language for optimal performance. Using Wasm, these routines can be directly invoked from JavaScript, providing a fast and secure environment for cryptographic operations.

4. IoT devices: WebAssembly can run in resource-constrained environments, making it ideal for IoT devices. Given its low-level nature, Wasm can directly work with device peripherals providing better control over hardware.

5. Scientific Simulations and Data Visualization: Wasm enables running heavy simulations and data visualization tasks directly in the browser, providing real-time updates and interactive explorations of complex data models.

WebAssembly's scope is not limited to the web. With runtimes like Wasmer or Wasmtime, Wasm modules can be executed outside of the browser environment, making Wasm a compelling choice for cross-platform app development.

In this lesson, we've taken quite the journey from C++ to WebAssembly, diving into the mechanics of compiling and debugging WebAssembly modules, invoking functions from JavaScript, and understanding the intricacies of the Wasm output. We've highlighted the benefits of using C++ as a starting point and touched upon the possibilities opened up by the universal binary format of Wasm.

WebAssembly offers significant performance improvements for web applications, making tasks like gaming, image and video editing, and even cryptography feasible straight in the browser. Besides, its use goes beyond the web, finding applications in IoT devices and cross-platform app development.

We hope this course has sparked your interest in WebAssembly and equipped you with the tools to start developing more efficient web applications. Remember, the only limit to what you can achieve is your imagination!

Continue honing your skills and experimenting with the concepts you've learned. Happy Coding!

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#include <iostream>

using namespace std;

int main() {

  // This is the end of our journey from C++ to Wasm

  cout << "Congratulations on completing the course!";

}