class TDataSetManagerFile: public TDataSetManager

 Main constructor

 Main constructor

 Do the real inititialization

 Init the local cache if required

 Parse the input string and set the init bits accordingly
 Format is
    dir:<datasetdir> [mss:<mss-url>] [opt:<base-options>]
 The <datasetdir> is mandatory.
 See TDataSetManager::ParseInitOpts for the available
 base options.
 The base options are already initialized by the base constructor

 Returns path of the indicated dataset. The extension is '.root' for all files
 except for 'dsName==ls' which have extension '.txt'.
 If 'local' is kTRUE the local cache path is returned instead in the form
 <cachedir>/<group>.<user>.<dsName>.<ext>.
 NB: contains a static TString for result, so copy result before using twice.

 Save into the <datasetdir>/kDataSet_DataSetList file the name of the updated
 or created or modified dataset. For still existing datasets, fill the
 modification date in seconds anf the checksum.
 Returns 0 on success, -1 on error

 Create or recreate the dataset lists for 'uri'.
 The list are saved in text form in 'uri'/ls.txt for fast browsing and in
 'uri'/ls.root in form of TMacro for optimized and portable transfer.
 Return 0 on success, 1 if the file was empty, -1 on error

 Adds the dataset in the folder of group, user to the list in target.
 If dsName is defined, only the information about the specified dataset
 is processed.

 The unsigned int 'option' is forwarded to GetDataSet and BrowseDataSet.
 Available options (to be .or.ed):
    kPrint          print the dataset content
    kQuotaUpdate    update quotas
    kExport         use export naming
    kList           get a list of dataset names

 NB1: options "kPrint", "kQuoatUpdate" and "kExport" are mutually exclusive
 NB2: for options "kPrint" and "kQuotaUpdate" return is null.

 General purpose call to go through the existing datasets.
 If <user> is 0 or "*", act on all datasets for the given <group>.
 If <group> is 0 or "*", act on all datasets.
 If <dsName> is defined, only the information about the specified dataset
 is processed.
 Action depends on option; available options:

    kExport         Return a TMap object containing all the information about
                    datasets in the form:
                    { <group>, <map of users> }
                                     |
                             { <map of datasets>, <dataset>}
                    (<dataset> are TFileCollection objects)
    kShowDefault    as kExport with in addition a default selection including
                    the datasets from the current user, the ones from the group
                    and the common ones

    kPrint          print the dataset content; no output is returned
    kList           get a list of available dataset names
    kForceScan      Re-open files while processing kPrint (do not use the
                    pre-processed information)
    kNoHeaderPrint  Labelling header is not printed
    kQuotaUpdate    update {group, user} quotas; no output is returned

 NB1: options "kPrint", "kQuoatUpdate" and "kExport" are mutually exclusive
 NB2: for options "kPrint" and "kQuoatUpdate" return is null.

 Check for the 'ls.txt' for 'group' and 'user' and fill the path for the
 ls file in 'out'.
 If 'dsname' is defined, open the file and extract the relevant line.
 Return 0 on success, -1 on failure

 Returns the dataset <dsName> of user <user> in group <group> .
 If checksum is non-zero, it will contain the pointer to a TMD5 sum object
 with the checksum of the file, has to be deleted by the user.
 If option has the bi kReadShort set, the shortobject is read, that does not
 contain the list of files. This is much faster.

 Check if the local cache information for group, user, dsName is up-to-date
 If not, make the relevant updates
 Return 0 if OK, 1 if the dataset does not exists anymore, -1 on failure

 Clear cached information matching uri

 Show cached information matching uri

 Writes indicated dataset.
 If option has the bit kFileMustExist set, the file must still exist,
 otherwise the new dataset is not written (returns 3 in this case).
 If checksum is non-zero the files current checksum is checked against it,
 if it does not match the file is not written (the function returns 2 in this
 case, if the file has disappeared it is also not written (i.e. checksum
 implies the bit kFileMustExist set in option).
 Returns != 0 for success, 0 for error

 Calculate the checksum of the indicated dataset at 'path' and save it to the
 appropriate file 'md5path'. The MD5 string is returned in 'md5sum'.
 Return 0 on success, -1 on error.

 Removes the indicated dataset

 Checks if the indicated dataset exits

 Register a dataset, perfoming quota checkings and verification, if required.
 If a dataset with the same name already exists the action fails unless 'opts'
 contains 'O', in which case the old dataset is overwritten, or contains 'U',
 in which case 'newDataSet' is added to the existing dataset (duplications are
 ignored, if any).
 If 'opts' contains 'V' the dataset files are also verified (if the dataset manager
 is configured to allow so). By default the dataset is not verified.
 If 'opts' contains 'T' the in the dataset object (status bits, meta,...)
 is trusted, i.e. not reset (if the dataset manager is configured to allow so).
 Returns 0 on success, -1 on failure

 Scans the dataset indicated by <uri> and returns the number of missing files.
 Returns -1 if any failure occurs, >= 0 on success.
 For more details, see documentation of
 ScanDataSet(TFileCollection *dataset, const char *option)

 See documentation of ScanDataSet(TFileCollection *dataset, UInt_t option)

 Returns all datasets for the <group> and <user> specified by <uri>.
 If <user> is 0, it returns all datasets for the given <group>.
 If <group> is 0, it returns all datasets.
 The returned TMap contains:
    <group> --> <map of users> --> <map of datasets> --> <dataset> (TFileCollection)

 The unsigned int 'option' is forwarded to GetDataSet and BrowseDataSet.
 Available options (to be .or.ed):
    kShowDefault    a default selection is shown that include the ones from
                    the current user, the ones from the group and the common ones
    kPrint          print the dataset content
    kQuotaUpdate    update quotas
    kExport         use export naming

 NB1: options "kPrint", "kQuoatUpdate" and "kExport" are mutually exclusive
 NB2: for options "kPrint" and "kQuoatUpdate" return is null.

 Utility function used in various methods for user dataset upload.

 Removes the indicated dataset

 Checks if the indicated dataset exits

 updates the used space maps

 Gets last dataset modification time. Returns -1 on error, or number of
 seconds since epoch on success