class HldGrepFileSource: public HldFileSourceBase

  This "data source" reads the HLD data from files on disk.
  The user provides a directory name and the source will grep
  the newest files from the disk. If after a given check interval
  a new file is found, the current one will be closed and the reading
  continues with the new one. The source will run in an endless loop
  and wait for new files. The user has to exit the program by himself.

  dir          : directory where the hld files are located
  opt          : select between the 2 possible modes of the source
                 1. "Grep" (default) : search for the newest files in intervals
                    of grepInterval seconds
                 2. "Date: 02/05/2005 22:00:00" select all files newer than date
                    and read them sequentional
                 3. "File: myname.hld" select all files newer than this file and
                    read them sequential
  grepInterval : time interval for checking for new files
  refId        : -1 (default) reference run for init procedure

 Destructor for a LMD file data source

 Get the run Id from the file filename
 In case of failure returns -1

 Tries to read a new event from the LMD file and put
 the info into the HEvent structure.
 The set directory is checked in interval seconds
 for new files. If a new file is available
 it is opened for reading. If the last event of
 the current file is reached an endless loop
 for new files on the disk is performed. The
 loop ends only in case of success!

 check if a new file is on the disk.
 performs endless loop until succes!
 A sleep of the set time interval in seconds
 is performed before next try.

 Checks the directory dir. In case of empty
 strings (default) or not existing directory
 this function exit the program. No chance
 to go on for lazy users ...Strategy of breaking
 as soon as possible. If the directory name does
 not end with "/" the slash is added

 Decodes the option string. In case of not known
 option or wrong format this function exit the program.
 No chance to go on for lazy users ...Strategy of breaking
 as soon as possible. Depending on the decoded option
 the mode (=1 for "Grep", =2 for sequential reading) switch
 is set.
  opt  : select between the 2 possible modes of the source
         1. "Grep" (default) : search for the newest files in intervals
            of grepInterval seconds
         2. "Date: 02/05/2005 22:00:00" select all files newer than date
             and read them sequentional
         3. "File: myname.hld" select all files newer than this file and
            read them sequential

 This is the select function called with scandir(.....)
 Selects files going to the list of files for sorting/selection.
 Returns 1 if a file is selected otherwise 0.
 Only hld files and files newer or equal than the time stamp
 lastfile are taken into account. Files smaller 500k are
 ignored.

 Loops on the set directory for new hld files.
 the dir is scanned with scandir(). The selected
 files newer or equal time stamp lastfile goes
 to the list of candidates. The list will be sorted
 by last modification of the files.
 In "Grep" mode (mode=1) the second newest file
 is opened (preventing from reading a file which is
 in writing process). The time stamp lastfile is set
 to the selected files last modification time.
 In "File/Date" mode (mode=2) the list is sequential
 read.