private int rand() {
            random_seed = (random_seed * 214013 + 2531011);
            return (random_seed >> 16) & 0x7FFF;
        }
transfer character stream of HWPTAG_PARA_TEXT to STRING

@param reader
@param datasize
@param buf
@throws IOException
tika-parsers/tika-parsers-standard/tika-parsers-standard-modules/tika-parser-miscoffice-module/src/main/java/org/apache/tika/parser/hwp/HwpTextExtractorV5.java