Add workaround for faulty MP3ext padding

MP3ext V3.3.17 places a non-compliant padding string at the end of the ID3v2 header.
To get around this problem the program stops reading frames as soon as the padding is detected to avoid overflow reading.

Fixes #58

Author: aadsm

src/ID3v2FrameReader.js

@@ -227,6 +227,17 @@ class ID3v2FrameReader {
       if (tags && tags.indexOf(frameId) === -1) {
         continue;
       }
+      // Workaround: MP3ext V3.3.17 places a non-compliant padding string at
+      // the end of the ID3v2 header. A string like "MP3ext V3.3.19(ansi)"
+      // is added multiple times at the end of the ID3 tag. More information
+      // about this issue can be found at
+      // https://github.com/aadsm/jsmediatags/issues/58#issuecomment-313865336
+      if (
+        frameId === 'MP3e' || frameId === '\x00MP3' ||
+        frameId === '\x00\x00MP' || frameId === ' MP3'
+      ) {
+        break;
+      }
 
       var unsyncData;
       if (flags && flags.format.unsynchronisation) {

src/__tests__/ID3v2FrameReader-test.js

@@ -370,4 +370,26 @@ describe("ID3v2FrameReader", function() {
       subFrames: {}
     });
   });
+
+  it("should ignore faulty MP3ext padding", function() {
+    var artistName = bin("Lead Artist");
+    var mp3extPadding = bin("MP3ext V3.3.19(ansi) MP3ext V3.3.19(ansi)");
+    var fileData = [].concat(
+      // Good tag
+      bin("TPE1"),
+      [0x00, 0x00, 0x00, 1 + artistName.length], // size
+      [0x00, 0x00], // flags
+      [0x00], // text encoding
+      artistName, // content
+      // MP3ext faulty padding
+      mp3extPadding
+    );
+    var fileReader = new ArrayFileReader(fileData);
+    var id3header = {major: 4};
+
+    var tags = ID3v2FrameReader.readFrames(
+      0, fileData.length, fileReader, id3header
+    );
+    expect(tags.MP3e).not.toBeDefined();
+  });
 });