wasm

README

Using precise-proofs tree generation with WebAssembly

This page assumes a functional Go 1.11 or newer installation. For troubleshooting, see the https://github.com/golang/go/wiki/InstallTroubleshooting[Install Troubleshooting] page.

The package examples/wasm is a simple demo that can be compiled for use in a web browser. It will generate a tree from some JSON input, calculate the roothash and validate a proof.

Compilation

Set GOOS=js and GOARCH=wasm environment variables to compile for WebAssembly:

$ cd examples/wasm
$ GOOS=js GOARCH=wasm go build -o main.wasm

That will build the package and produce an executable WebAssembly module file named main.wasm. The .wasm file extension will make it easier to serve it over HTTP with the correct Content-Type header later on.

To execute main.wasm in a browser, we'll also need a JavaScript support file, and a HTML page to connect everything together.

Copy the JavaScript support file:

$ cp "$(go env GOROOT)/misc/wasm/wasm_exec.js" ./

If your browser doesn't yet support WebAssembly.instantiateStreaming, you can use a polyfill.

Then serve the three files (index.html, wasm_exec.js, and main.wasm) from a web server. For example, with goexec:

$ goexec 'http.ListenAndServe(":8080", http.FileServer(http.Dir(".")))'

Finally, navigate to http://localhost:8080/index.html, open the JavaScript debug console, and you should see the output. You can modify the program, rebuild main.wasm, and refresh to see new output.