code: public void addLineOffset(int offset) {
          if (numLines >= lineNumberMap.length) {
              // Grow the line number map.
              int capacity = lineNumberMap.length * 2;
              int[] newLineNumberMap = new int[capacity];
              System.arraycopy(lineNumberMap, 0, newLineNumberMap, 0, lineNumberMap.length);
              lineNumberMap = newLineNumberMap;
          }
  
          lineNumberMap[numLines++] = offset;
      }
docs: Add a source line byte offset. This method should be called for each line
  in the source file, in order.
  
  @param offset
  the byte offset of the next source line