public int peek() {
    if (type == MUST_READ) {
      int argAndType = in.readByte() & 0xff;
      type = argAndType & 0x1f;
      arg = (argAndType & 0xe0) >> 5;
    }
    return type;
  }
Returns the type of the next value to read.
android/android_framework/dex-maker/src/main/java/com/android/dex/EncodedValueReader.java