    copy_string(fromBegin, aSrcEnd, writer);
  }

void
AppendUnicodeTo( const nsAString::const_iterator& aSrcStart,
                 const nsAString::const_iterator& aSrcEnd,
                 nsAString& aDest )
  {
    nsAString::iterator writer;
    uint32_t oldLength = aDest.Length();
    if(!SetLengthForWriting(aDest, oldLength + Distance(aSrcStart, aSrcEnd)))
        return;
