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Easier WebAssembly with twr-wasm
Documentation and Examples

Version 2.5.0

twr-wasm is a simple, lightweight and easy to use library for building C/C++ WebAssembly code directly with clang. Run C/C++ code in a web browser. Legacy code, libraries, full applications, or single functions can be integrated with JavaScript and TypeScript. twr-wam solves some common use cases with less work than the more feature rich emscripten.

Key Features:

  • build .wasm modules using C/C++ using clang directly (no wrapper)
  • from JavaScript load .wasm modules, call C/C++ functions, and access wasm memory

  • comprehensive console support for stdin, stdio, and stderr.

    • in C/C++, print and get characters to/from <div> tags in your HTML page
    • in C/C++, print and get characters to/from a <canvas> based "terminal"
    • localization support, UTF-8, and windows-1252 support

  • the optional TypeScript class twrWasmModuleAsync can be used to:

    • integrate a C/C++ Read-Eval-Print Loop (REPL) with JavaScript
    • integrate a C/C++ CLI or Shell with JavaScript
    • In JavaScript await on blocking/synchronous C/C++ functions.

  • 2D drawing API for C/C++ compatible with JavaScript Canvas

  • audio playback APIs for C/C++
  • create your own C/C++ APIs using TypeScript by extending class twrLibrary
  • standard C library optimized for WebAssembly
  • libc++ built for WebAssembly
  • comprehensive examples and documentation
  • TypeScript and JavaScript support

Live WebAssembly Examples and Source

Name View Live Link Source Link
Bouncing Balls (C++) View bouncing balls Source for balls
Pong (C++) Pong Source
Input/Output with <div> View square demo Source
I/O to terminal with <canvas> View demo Source
CLI using libc++ and <canvas>) View console Source

Hello World

Here is the simplest twr-wasm example.

helloworld.c
#include <stdio.h>

void hello() {
    printf("hello, world!\n");
}
index.html
<head>
   <title>Hello World</title>
</head>
<body>
   <div id="twr_iodiv"></div>

   <script type="module">
      import {twrWasmModule} from "twr-wasm";

      const mod = new twrWasmModule();
      await mod.loadWasm("./helloworld.wasm");
      await mod.callC(["hello"]);
   </script>
</body>

On Github

https://github.com/twiddlingbits/twr-wasm

Why?

The Wasm Runtime Limitations section explains why a library like twr-wasm is needed to use WebAssembly.

Limitations

  • libc++ not built with exceptions enabled
  • some standard C library functions are not 100% implemented
  • Designed to work with a browser. Not tested with or designed to work with node.js
  • Not all of compile-rt is ported (but most bits you need are)

Post Feedback

Please post feedback (it worked for you, didn't work, requests, questions, etc) at https://github.com/twiddlingbits/twr-wasm/