SHA1 digest (Electron)

In this example we're going to create an app that calculates the SHA-1 digests of files. With the help of Zig, naturally.

Creating the app

First, we'll create the basic skeleton:

npm init electron-app@latest sha1
cd sha1
mkdir zig
npm install --save node-zigar

We tinker with the HTML page slightly, bringing in a script file for the renderer:

<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="Content-Security-Policy" content="default-src 'self'; script-src 'self'" />
    <title>SHA-1 digest</title>
    <link rel="stylesheet" href="index.css" />
  </head>
  <body>
    <h2 id="heading">Use file menu to open a file</h2>
  </body>
  <script src="./renderer.js"></script>
</html>

renderer.js exposes a function that update the text of the heading element:

const heading = document.getElementById('heading')

window.electronAPI.onShowHash((value) => {
  heading.textContent = value;
});

We then add the following bridging code to preload.js so the function is accessible from the app's main process:

const { contextBridge, ipcRenderer } = require('electron')

contextBridge.exposeInMainWorld('electronAPI', {
  onShowHash: (callback) => ipcRenderer.on('show-hash', (_event, value) => callback(value)),
});

Consult Electron's documentation if you're unfamiliar with its process model.

At the top of index.js, we add dialog and Menu to the require statement:

const { app, dialog, BrowserWindow, Menu } = require('electron');

Further down, we add the following code at end of the function createWindow:

  // Open the DevTools.
  // mainWindow.webContents.openDevTools();

  const onOpenlick = async () => {
    const { canceled, filePaths } = await dialog.showOpenDialog({ properties: [ 'openFile' ]});
    if (!canceled) {
      const [ path ] = filePaths;
      mainWindow.webContents.send('show-hash', path);
    }
  };
  const isMac = process.platform === 'darwin'
  const menuTemplate = [
    (isMac) ? {
      label: app.name,
      submenu: [
        { role: 'quit' }
      ]
    } : null,
    {
      label: '&File',
      submenu: [
        { label: '&Open', click: onOpenlick },
        { type: 'separator' },
        isMac ? { role: 'close' } : { role: 'quit' }
      ]
    },
  ].filter(Boolean);
  const menu = Menu.buildFromTemplate(menuTemplate)
  Menu.setApplicationMenu(menu);

Initially, our UI code merely display the path to the selected file. After verifying that it works as expected, we add our Zig code, sha1.zig:

const std = @import("std");

pub fn sha1(bytes: []const u8) [std.crypto.hash.Sha1.digest_length * 2]u8 {
    var digest: [std.crypto.hash.Sha1.digest_length]u8 = undefined;
    std.crypto.hash.Sha1.hash(bytes, &digest, .{});
    return std.fmt.bytesToHex(digest, .lower);
}

At the top of index.js, we add require statements that activate Zig support and import the function:

require('node-zigar/cjs');
const { sha1 } = require('../src/sha1.zig');

We also need a function for reading the contents of a file:

const { readFile } = require('fs/promises');

We then modify onOpenClick so it performs the intended function:

  const onOpenlick = async () => {
    const { canceled, filePaths } = await dialog.showOpenDialog({ properties: [ 'openFile' ]});
    if (!canceled) {
      const [ path ] = filePaths;
      const data = await readFile(path);
      const hash = sha1(data).string;
      mainWindow.webContents.send('show-hash', hash);
    }
  };

The Zig function sha1 returns []const u8, a type that can be a text string but isn't treated automatically as such. To get the text we access its string property.

Configuring app for deployment

We're going to follow the same steps as described in the hello world tutorial. First, we'll alter the require statement so it references a node-zigar module instead of a Zig file:

const { sha1 } = require('../lib/sha1.zigar');

Then we add node-zigar.config.json to the app's root directory:

{
  "optimize": "ReleaseSmall",
  "sourceFiles": {
    "lib/sha1.zigar": "zig/sha1.zig"
  },
  "targets": [
    { "platform": "win32", "arch": "x64" },
    { "platform": "win32", "arch": "arm64" },
    { "platform": "win32", "arch": "ia32" },
    { "platform": "linux", "arch": "x64" },
    { "platform": "linux", "arch": "arm64" },
    { "platform": "darwin", "arch": "x64" },
    { "platform": "darwin", "arch": "arm64" }
  ]
}

We build the library files:

npx node-zigar build

And make necessary changes to forge.config.js:

const { FusesPlugin } = require('@electron-forge/plugin-fuses');
const { FuseV1Options, FuseVersion } = require('@electron/fuses');

module.exports = {
  packagerConfig: {
    asar: {
      unpack: '*.{dll,dylib,so}',
    },
    ignore: [ 
      /\/(zig|zig-cache|zigar-cache)(\/|$)/, 
      /\/node-zigar\.config\.json$/,
    ],    
  },
  rebuildConfig: {},
  makers: [
    {
      name: '@electron-forge/maker-squirrel',
      config: {},
    },
    {
      name: '@electron-forge/maker-zip',
      platforms: ['darwin'],
    },
    {
      name: '@electron-forge/maker-deb',
      config: {},
    },
    {
      name: '@electron-forge/maker-rpm',
      config: {},
    },
  ],
  plugins: [
    {
      name: '@electron-forge/plugin-auto-unpack-natives',
      config: {},
    },
    // Fuses are used to enable/disable various Electron functionality
    // at package time, before code signing the application
    new FusesPlugin({
      version: FuseVersion.V1,
      [FuseV1Options.RunAsNode]: false,
      [FuseV1Options.EnableCookieEncryption]: true,
      [FuseV1Options.EnableNodeOptionsEnvironmentVariable]: false,
      [FuseV1Options.EnableNodeCliInspectArguments]: false,
      [FuseV1Options.EnableEmbeddedAsarIntegrityValidation]: true,
      [FuseV1Options.OnlyLoadAppFromAsar]: true,
    }),
  ],
};

We're now ready to create the installation packages:

npm run make -- --platform linux --arch x64,arm64
npm run make -- --platform windows --arch x64,ia32,arm64
npm run make -- --platform darwin --arch x64,arm64

The packages will be in the out/make directory:

📁 out
  📁 make
    📁 deb
      📁 arm64
        📦 sha1_1.0.0_arm64.deb
      📁 x64
        📦 sha1_1.0.0_amd64.deb
    📁 rpm
      📁 arm64
        📦 sha1-1.0.0-1.arm64.rpm
      📁 x64
        📦 sha1-1.0.0-1.x86_64.rpm
    📁 squirrel.windows
      📁 arm64
        📦 sha1-1.0.0-full.nupkg
        📦 sha1-1.0.0 Setup.exe
        📄 RELEASES
      📁 ia32
        📦 sha1-1.0.0-full.nupkg
        📦 sha1-1.0.0 Setup.exe
        📄 RELEASES
      📁 x64
        📦 sha1-1.0.0-full.nupkg
        📦 sha1-1.0.0 Setup.exe
        📄 RELEASES
    📁 zip
      📁 darwin
        📁 arm64
          📦 sha1-darwin-arm64-1.0.0.zip
        📁 x64
          📦 sha1-darwin-x64-1.0.0.zip

The app running in Windows 10:

Windows 10