uk.ac.starlink.table

## Interface TableBuilder

- All Known Subinterfaces:
    MultiTableBuilder
  All Known Implementing Classes:
    AsciiTableBuilder, CdfTableBuilder, CoinsTableBuilder, ColFitsPlusTableBuilder, ColFitsTableBuilder, CsvTableBuilder, DocumentedTableBuilder, EcsvTableBuilder, FeatherTableBuilder, FitsPlusTableBuilder, FitsTableBuilder, GbinTableBuilder, IpacTableBuilder, MrtTableBuilder, ParquetTableBuilder, TstTableBuilder, VOTableBuilder, WDCTableBuilder

      public interface TableBuilder

  Interface for objects which can construct a `StarTable` from a data resource. TableBuilder implementations may also choose to implement `MultiTableBuilder`.

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `canImport(java.awt.datatransfer.DataFlavor flavor)` Indicates whether this builder is able to turn a resource of media type indicated by `flavor` into a table.
    `java.lang.String` | `getFormatName()` Returns the name of the format which can be read by this handler.
    `boolean` | `looksLikeFile(java.lang.String location)` Indicates whether the given location string is of a familiar form for this builder.
    `StarTable` | `makeStarTable(DataSource datsrc, boolean wantRandom, StoragePolicy storagePolicy)` Constructs a `StarTable` based on a given `DataSource`.
    `void` | `streamStarTable(java.io.InputStream istrm, TableSink sink, java.lang.String pos)` Reads a table from an input stream and writes it a row at a time to a sink.

- - ### Method Detail

    - #### makeStarTable

          StarTable makeStarTable(DataSource datsrc,
                                  boolean wantRandom,
                                  StoragePolicy storagePolicy)
                           throws java.io.IOException

      Constructs a `StarTable` based on a given `DataSource`. If the source is not recognised or this builder does not know how to construct a table from it, then a `TableFormatException` should be thrown. If this builder thinks it should be able to handle the source but an error occurs during processing, an `IOException` can be thrown.

      The `wantRandom` parameter is used to indicate whether, ideally, a random-access table should be returned. There is no requirement for the builder to honour this request, but if it knows how to make both random and non-random tables, it can use this flag to decide which to return.

      Note: the presence of the `wantRandom` parameter is somewhat misleading. TableBuilder implementations usually should, and do, ignore it (it would be removed from the interface if it were not for backward compatibility issues). Regardless of the value of this parameter, implementations should return a random-access table only if it is easy for them to do so; in particular they should not use the supplied `storagePolicy`, or any other resource-expensive measure, to randomise a sequential table just because the `wantRandom` parameter is true.

      Parameters:
        `datsrc` - the DataSource containing the table resource
        `wantRandom` - whether, preferentially, a random access table should be returned
        `storagePolicy` - a StoragePolicy object which may be used to supply scratch storage if the builder needs it
      Returns:
        a StarTable made out of `datsrc`
      Throws:
        `TableFormatException` - if the table is not of a kind that can be handled by this handler
        `java.io.IOException` - if an unexpected I/O error occurs during processing

    - #### streamStarTable

          void streamStarTable(java.io.InputStream istrm,
                               TableSink sink,
                               java.lang.String pos)
                        throws java.io.IOException

      Reads a table from an input stream and writes it a row at a time to a sink. Not all implementations will be able to do this; for instance, extracting the table from the data may be a two-pass process. Implementations which are unable to perform this function should throw a `TableFormatException`.

      The input stream should be prepared for use prior to calling this method, so implementations should not in general attempt to decompress or buffer `istrm`.

      Parameters:
        `istrm` - input stream containing table data
        `sink` - destination of the table
        `pos` - position identifier describing the location of the table within the stream; see `DataSource.getPosition()` (may be null)
      Throws:
        `TableFormatException` - if the table can't be streamed or the data is malformed
        `java.io.IOException` - if some other error occurs

    - #### canImport

          boolean canImport(java.awt.datatransfer.DataFlavor flavor)

      Indicates whether this builder is able to turn a resource of media type indicated by `flavor` into a table. It should return `true` if it thinks that its `streamStarTable(java.io.InputStream, uk.ac.starlink.table.TableSink, java.lang.String)` method stands a reasonable chance of successfully constructing a `StarTable` from a `DataSource` whose input stream is described by the `DataFlavor` `flavor`. It will typically make this determination based on the flavor's MIME type.

      This method should only return `true` if the flavor looks like it is targeted at this builder; for instance a builder which uses a text-based format should return false for a flavor which indicates a MIME type of `text/plain`.

      This method is used in supporting drag and drop functionality (see `StarTableFactory.canImport(java.awt.datatransfer.DataFlavor[])`).

      Parameters:
        `flavor` - the DataFlavor whose suitability as stream input is to be assessed
      Returns:
        `true` iff this builder reckons it stands a good chance of turning a stream of type `flavor` into a `StarTable`

    - #### looksLikeFile

          boolean looksLikeFile(java.lang.String location)

      Indicates whether the given location string is of a familiar form for this builder. Implementations should return `true` if there is a good chance that a file with the given `location` can be interpreted by this reader, for instance if it has a suitable file extension.

      This method may be used to guess, on a best-efforts basis, whether this builder is suitable for reading a file from a given location. Attempts may still be made to read inputs for which this method returns false. It is less important for builders that can recognise files by magic number, which is generally preferable to using filenames.

      Parameters:
        `location` - the location string, such as a filename or URL (not null)
      Returns:
        true iff there is a good chance that the named input can be interpreted by this reader

    - #### getFormatName

          java.lang.String getFormatName()

      Returns the name of the format which can be read by this handler. Matching against this string may be used by callers to identify or select this handler from a list.
      Returns:
        one-word description of this handler's format