168 lines
5.7 KiB
Markdown
168 lines
5.7 KiB
Markdown
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# 應用程式打包
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為了減少圍繞著 Windows 上長路徑名稱問題的 [issues](https://github.com/joyent/node/issues/6960) ，稍微地加速 `require` 和隱藏你的原始碼避免不小心被看到，你可以選擇把你的應用程式打包成一個 [asar][asar] 壓縮檔，只需要改變一點點你的原始碼就好。
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## 產生 `asar` 壓縮檔
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一個 [asar][asar] 壓縮檔是一個簡單的類 tar 格式的檔案，它會把幾個檔案串接成一個檔案， Electron 可以不需要解壓縮整個檔案就從中讀取任意檔案。
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把你的應用程式打包成 `asar` 壓縮檔的步驟：
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### 1. 安裝 asar 工具包
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```bash
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$ npm install -g asar
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```
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### 2. 用 `asar pack` 打包
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```bash
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$ asar pack your-app app.asar
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```
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## 使用 `asar` 壓縮檔
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在 Electron 中有兩組 API：Node.js 提供的 Node APIs 和 Chromium 提供的 Web
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APIs，兩組 API 都支援從 `asar` 壓縮檔中讀取檔案。
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### Node API
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因為 Electron 中有一些特別的補釘，像是 `fs.readFile` 和 `require` 這樣的 Node API 會將 `asar` 壓縮檔視為許多虛擬目錄，將裡頭的檔案視為在檔案系統上的一般檔案。
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例如，假設我們有一個 `example.asar` 壓縮檔在 `/path/to` 中:
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```bash
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$ asar list /path/to/example.asar
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/app.js
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/file.txt
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/dir/module.js
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/static/index.html
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/static/main.css
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/static/jquery.min.js
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```
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讀取一個在 `asar` 壓縮檔中的檔案：
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```javascript
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const fs = require('fs');
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fs.readFileSync('/path/to/example.asar/file.txt');
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```
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列出所有在壓縮檔根目錄下的檔案：
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```javascript
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const fs = require('fs');
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fs.readdirSync('/path/to/example.asar');
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```
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使用一個壓縮檔中的模組：
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```javascript
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require('/path/to/example.asar/dir/module.js');
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```
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你也可以利用 `BrowserWindow` 在 `asar` 壓縮檔中呈現一個網頁：
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```javascript
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const BrowserWindow = require('electron').BrowserWindow;
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var win = new BrowserWindow({width: 800, height: 600});
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win.loadURL('file:///path/to/example.asar/static/index.html');
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```
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### Web API
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在一個網頁中，壓縮檔中的檔案都可以透過 `file:` 這個協定被存取，如同 Node API，`asar` 壓縮檔都被視為目錄。
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例如，要透過 `$.get` 取得一個檔案：
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```html
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<script>
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var $ = require('./jquery.min.js');
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$.get('file:///path/to/example.asar/file.txt', function(data) {
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console.log(data);
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});
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</script>
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```
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### 把一個 `asar` 壓縮檔視為一般檔案
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在一些像是驗證 `asar` 壓縮檔檢查碼(checksum)的例子中，我們需要以檔案的方式讀取 `asar` 壓縮檔中的內容，為了達到這個目的，你可以使用內建的
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`original-fs` 模組，它提供了沒有 `asar` 支援的原生 `fs` API:
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```javascript
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var originalFs = require('original-fs');
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originalFs.readFileSync('/path/to/example.asar');
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```
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你也可以設定 `process.noAsar` 為 `true` 來關掉在 `fs` 模組中的 `asar` 支援：
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```javascript
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process.noAsar = true;
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fs.readFileSync('/path/to/example.asar');
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```
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## Node API 上的限制
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儘管我們盡可能的努力嘗試著使 Node API 中的 `asar` 壓縮檔像目錄一樣運作，還是有一些基於 Node API 低階本質的限制存在。
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### 壓縮檔都是唯讀的
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所有壓縮檔都無法被修改，因此所有可以修改檔案的 Node API 都無法與 `asar ` 壓縮檔一起運作。
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### 使用中的目錄無法被設為壓縮檔中的目錄
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儘管 `asar` 壓縮檔被視為目錄，卻並沒有真正的目錄在檔案系統中，所以你永遠無法將使用中的目錄設定成 `asar` 壓縮檔中的目錄，把他們以 `cwd` 選項的方式傳遞，對某些 API 也會造成錯誤。
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### Extra Unpacking on Some APIs
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Most `fs` APIs can read a file or get a file's information from `asar` archives
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without unpacking, but for some APIs that rely on passing the real file path to
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underlying system calls, Electron will extract the needed file into a
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temporary file and pass the path of the temporary file to the APIs to make them
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work. This adds a little overhead for those APIs.
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APIs that requires extra unpacking are:
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* `child_process.execFile`
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* `child_process.execFileSync`
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* `fs.open`
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* `fs.openSync`
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* `process.dlopen` - Used by `require` on native modules
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### Fake Stat Information of `fs.stat`
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The `Stats` object returned by `fs.stat` and its friends on files in `asar`
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archives is generated by guessing, because those files do not exist on the
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filesystem. So you should not trust the `Stats` object except for getting file
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size and checking file type.
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### Executing Binaries Inside `asar` Archive
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There are Node APIs that can execute binaries like `child_process.exec`,
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`child_process.spawn` and `child_process.execFile`, but only `execFile` is
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supported to execute binaries inside `asar` archive.
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This is because `exec` and `spawn` accept `command` instead of `file` as input,
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and `command`s are executed under shell. There is no reliable way to determine
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whether a command uses a file in asar archive, and even if we do, we can not be
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sure whether we can replace the path in command without side effects.
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## Adding Unpacked Files in `asar` Archive
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As stated above, some Node APIs will unpack the file to filesystem when
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calling, apart from the performance issues, it could also lead to false alerts
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of virus scanners.
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To work around this, you can unpack some files creating archives by using the
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`--unpack` option, an example of excluding shared libraries of native modules
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is:
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```bash
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$ asar pack app app.asar --unpack *.node
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```
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After running the command, apart from the `app.asar`, there is also an
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`app.asar.unpacked` folder generated which contains the unpacked files, you
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should copy it together with `app.asar` when shipping it to users.
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[asar]: https://github.com/atom/asar
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