add multibyte-encoded comment with byte length instead of character l…

…ength

package.json

@@ -3,7 +3,7 @@
   "version": "0.4.16",
   "description": "Javascript implementation of zip for nodejs with support for electron original-fs. Allows user to create or extract zip files both in memory or to/from disk",
   "scripts": {
-    "test": "mocha test/mocha.js test/crc/index.js"
+    "test": "mocha test/mocha.js test/crc/index.js test/multibyte/test.js"
   },
   "keywords": [
     "zip",

test/multibyte/test.js

@@ -0,0 +1,24 @@
+const { expect } = require("chai");
+const Utils = require("../../util");
+const AdmZip = require("../../adm-zip");
+const path = require("path");
+
+describe('adm-zip', () => {
+   it('adds multibyte ZIP comment in UTF-8 with appropriate byte', () => {
+    const zip = new AdmZip();
+    zip.addLocalFile(
+        path.join(__dirname, "./じっぷ/じっぷ.txt")
+    );
+    zip.addZipComment("じっぷ");
+    const willSend = zip.toBuffer();
+    const end = willSend.slice(
+        willSend.lastIndexOf(Utils.Constants.ENDSIG)
+    );
+    const commentLength = end.readInt16LE(Utils.Constants.ENDCOM, 2);
+    expect(commentLength).to.eq(9);
+    const expected = Buffer.from("じっぷ");
+    const actual = end.slice(Utils.Constants.ENDCOM + 2);
+    expect(actual).to.include(expected);
+    expect(expected).to.include(actual);
+   });
+});

test/multibyte/じっぷ/じっぷ.txt

@@ -0,0 +1 @@
+じっぷ

zipFile.js

@@ -133,8 +133,8 @@ module.exports = function (/*String|Buffer*/input, /*Number*/inputType) {
 			return _comment.toString();
 		},
 		set comment(val) {
-			mainHeader.commentLength = val.length;
-			_comment = val;
+			_comment = Utils.toBuffer(val);
+			mainHeader.commentLength = _comment.length;
 		},
 
 		getEntryCount: function() {