Add deflator helper class for deflating data

Wraps pako's deflate for easier usage.

kasmweb/tests/test.deflator.js

@@ -0,0 +1,80 @@
+/* eslint-disable no-console */
+const expect = chai.expect;
+
+import { inflateInit, inflate } from "../vendor/pako/lib/zlib/inflate.js";
+import ZStream from "../vendor/pako/lib/zlib/zstream.js";
+import Deflator from "../core/deflator.js";
+
+function _inflator(compText, expected) {
+    let strm = new ZStream();
+    let chunkSize = 1024 * 10 * 10;
+    strm.output = new Uint8Array(chunkSize);
+
+    inflateInit(strm, 5);
+
+    if (expected > chunkSize) {
+        chunkSize = expected;
+        strm.output = new Uint8Array(chunkSize);
+    }
+
+    strm.input = compText;
+    strm.avail_in = strm.input.length;
+    strm.next_in = 0;
+
+    strm.next_out = 0;
+    strm.avail_out = expected.length;
+
+    let ret = inflate(strm, 0);
+
+    // Check that return code is not an error
+    expect(ret).to.be.greaterThan(-1);
+
+    return new Uint8Array(strm.output.buffer, 0, strm.next_out);
+}
+
+describe('Deflate data', function () {
+
+    it('should be able to deflate messages', function () {
+        let deflator = new Deflator();
+
+        let text = "123asdf";
+        let preText = new Uint8Array(text.length);
+        for (let i = 0; i < preText.length; i++) {
+            preText[i] = text.charCodeAt(i);
+        }
+
+        let compText = deflator.deflate(preText);
+
+        let inflatedText = _inflator(compText, text.length);
+        expect(inflatedText).to.array.equal(preText);
+
+    });
+
+    it('should be able to deflate large messages', function () {
+        let deflator = new Deflator();
+
+        /* Generate a big string with random characters. Used because
+           repetition of letters might be deflated more effectively than
+           random ones. */
+        let text = "";
+        let characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+        for (let i = 0; i < 300000; i++) {
+            text += characters.charAt(Math.floor(Math.random() * characters.length));
+        }
+
+        let preText = new Uint8Array(text.length);
+        for (let i = 0; i < preText.length; i++) {
+            preText[i] = text.charCodeAt(i);
+        }
+
+        let compText = deflator.deflate(preText);
+
+        //Check that the compressed size is expected size
+        expect(compText.length).to.be.greaterThan((1024 * 10 * 10) * 2);
+
+        let inflatedText = _inflator(compText, text.length);
+
+        expect(inflatedText).to.array.equal(preText);
+
+    });
+});