Version 2.1.1
twr-wasm is a simple, lightweight and easy to use library for building C/C++ WebAssembly code directly with clang. It solves some common use cases with less work than the more feature rich emscripten.
twr-wasm is easy to understand, and has some cool features. You can input and print streaming character i/o to a <div> tag, use a <canvas> element as an ANSI terminal, or use a C/C++ 2D drawing api (that is compatible with JavaScript Canvas APIs) to draw to a <canvas> element. You can run blocking C/C++.
twr-wasm allows you to run C/C++ code in a web browser. Legacy code, libraries, full applications, or single functions can be integrated with JavaScript and TypeScript.
twr-wasm is designed to be used with the standard llvm clang compiler and tools.
twr-wasm was previously named tiny-wasm-runtime.
The full documentation can be found here
- compile and link C/C++ for use with WebAssembly using clang directly
- standard C library, libc++. and purpose built APIs available from C/C++
- TypeScrpt/JavaScript classes to load WASM modules and call C/C++ functions
- localization support, UTF-8, and windows-1252 support
- 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" - in C/C++ use 2D drawing API compatible with JavaScript Canvas
- in C/C++, use the "blocking loop" pattern and integrate with Javascript's asynchronous event loop
| Name | View Live Link | Source Link |
|---|---|---|
| Bouncing Balls (C++) | View bouncing balls | Source for balls |
| Maze (Win32 C Port) | View live maze | Source for maze |
| Input from <div> | View square demo | Source |
| Mini-Terminal | View mini-term demo | Source |
Clone from github, or use npm install twr-wasm. To compile C/C++, install clang and wasm-ld.
For details see https://twiddlingbits.dev/docsite/gettingstarted/installation/
Here is the simplest twr-wasm example.
C code:
#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>
I/O can be directed to or from a <div> or a <canvas> tag. Here is a simple example using a <div> for stdio input and output.
#include <stdio.h>
#include <stdlib.h>
#include "twr-crt.h"
void stdio_div() {
char inbuf[64];
int i;
printf("Square Calculator\n");
while (1) {
printf("Enter an integer: ");
twr_gets(inbuf);
i=atoi(inbuf);
printf("%d squared is %d\n\n",i,i*i);
}
}
With an index.html like the following. This time we are using twrWasmModuleAsync which integrates blocking C code into Javascript. twrWasmModuleAsync can also be used to receive key input from a <div> or <canvas> tag.
<head>
<title>stdio-div example</title>
</head>
<body>
<div id="twr_iodiv" style="background-color:LightGray;color:DarkGreen" tabindex="0">Loading... <br></div>
<script type="module">
import {twrWasmModuleAsync} from "twr-wasm";
let amod;
try {
amod = new twrWasmModuleAsync();
document.getElementById("twr_iodiv").innerHTML ="<br>";
document.getElementById("twr_iodiv").addEventListener("keydown",(ev)=>{amod.keyDownDiv(ev)});
await amod.loadWasm("./stdio-div.wasm");
await amod.callC(["stdio_div"]);
}
catch(ex) {
amod.divLog("unexpected exception");
throw ex;
}
</script>
</body>
The full documentation can be found here