public ClassData readClassData(ClassDef classDef) {
    int offset = classDef.getClassDataOffset();
    if (offset == 0) {
      throw new IllegalArgumentException("offset == 0");
    }
    return open(offset).readClassData();
  }
Returns a copy of the the bytes of this dex.
android/android_framework/dex-maker/src/main/java/com/android/dex/Dex.java