@Override
  public String toString() {
    StringBuilder buffer = new StringBuilder();
    buffer.append("mockFs{files:[");
    for(int i=0; i < files.size(); ++i) {
      if (i != 0) {
        buffer.append(", ");
      }
      buffer.append(files.get(i));
    }
    buffer.append("]}");
    return buffer.toString();
  }
Compute the number of bytes that overlap between the two ranges.
@param offset1 start of range1
@param length1 length of range1
@param offset2 start of range2
@param length2 length of range2
@return the number of bytes in the overlap range
common/src/test/org/apache/hive/common/util/MockFileSystem.java