Package org.orekit.data

Interface DataFilter

All Known Implementing Classes:

GzipFilter, HatanakaCompressFilter, NsgfV00Filter, TruncatingFilter, UnixCompressFilter

public interface DataFilter

Interface for filtering data (typically uncompressing it) in data providers before passing it to data loaders.

Since:

9.2

Author:

Luc Maisonobe

See Also:

DataProvider, DataLoader

Method Summary

Modifier and Type	Method	Description
DataSource	filter(DataSource original)	Filter the data source.

Method Detail

filter

DataSource filter(DataSource original)
           throws IOException

Filter the data source.

Filtering is often based on suffix. For example a gzip compressed file will have an original name of the form base.ext.gz when the corresponding uncompressed file will have a filtered name base.ext.

A filter must never open the DataSource by itself, regardless of the fact it will return the original instance or a filtered instance. The rationale is that it is the upper layer that will decide to open (or not) the returned value and that a DataSource can be opened only once; this is the core principle of lazy-opening provided by DataSource.

Beware that as the data providers manager will attempt to pile all filters in a stack as long as their implementation of this method returns a value different from the original parameter. This implies that the filter, must perform some checks to see if it must be applied or not. If for example there is a need for a deciphering filter to be applied once to all data, then the filter should for example check for a suffix in the name and create a new filtered DataSource instance only if the suffix is present, removing the suffix from the filtered instance. Failing to do so and simply creating a filtered instance with one deciphering layer without changing the name would result in an infinite stack of deciphering filters being built, until a stack overflow or memory exhaustion exception occurs.

Parameters:

original - original data source

Returns:

filtered data source, or original if this filter does not apply to this data source

Throws:

IOException - if filtered stream cannot be created