Class MrtTableBuilder

  • All Implemented Interfaces:
    Documented, DocumentedIOHandler, TableBuilder

    public class MrtTableBuilder
    extends DocumentedTableBuilder
    Input handler for the so-called "Machine-Readable Table" format used by AAS journals. This is a horrid format, based on the VizieR readMe files, which are themselves underdocumented, but picking and leaving whatever bits and pieces they feel like, without any careful documentation of that process. This reader has mainly been put together by looking at given instances of files claimed to be in this format.
    Since:
    30 Apr 2021
    Author:
    Mark Taylor
    See Also:
    https://journals.aas.org/mrt-standards/
    • Field Summary

      Fields 
      Modifier and Type Field Description
      static java.lang.String MAGIC_TXT
      Should be present at the start of all MRT files.
    • Constructor Summary

      Constructors 
      Constructor Description
      MrtTableBuilder()
      Default constructor.
      MrtTableBuilder​(ErrorMode errorMode, boolean checkMagic)
      Constructor with configuration options.
    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method 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.
      boolean canStream()
      Indicates whether this handler can read tables from a stream.
      boolean docIncludesExample()
      Indicates whether the serialization of some (short) example table should be added to the user documentation for this handler.
      java.lang.String getFormatName()
      Returns "MRT".
      java.lang.String getXmlDescription()
      Returns user-directed documentation in XML format.
      static boolean isMagic​(byte[] intro)
      Indicates whether the given buffer starts with the MRT magic number "Title: ".
      StarTable makeStarTable​(uk.ac.starlink.util.DataSource datsrc, boolean wantRandom, StoragePolicy storage)
      Constructs a StarTable based on a given DataSource.
      void setCheckMagic​(boolean checkMagic)
      Sets whether the handler will attempt to guess by looking at the file whether it appears to be an MRT file before attempting to parse it as one.
      void setErrorMode​(ErrorMode errorMode)
      Sets the error handling mode.
      void streamStarTable​(java.io.InputStream in, TableSink sink, java.lang.String pos)
      Reads a table from an input stream and writes it a row at a time to a sink.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
    • Field Detail

      • MAGIC_TXT

        public static final java.lang.String MAGIC_TXT
        Should be present at the start of all MRT files.
        See Also:
        Constant Field Values
    • Constructor Detail

      • MrtTableBuilder

        public MrtTableBuilder()
        Default constructor.
      • MrtTableBuilder

        public MrtTableBuilder​(ErrorMode errorMode,
                               boolean checkMagic)
        Constructor with configuration options.
        Parameters:
        errorMode - error handling mode
        checkMagic - whether to require finding the magic number before attempting to parse
    • Method Detail

      • getFormatName

        public java.lang.String getFormatName()
        Returns "MRT".
        Returns:
        one-word description of this handler's format
      • canImport

        public boolean canImport​(java.awt.datatransfer.DataFlavor flavor)
        Description copied from interface: TableBuilder
        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 TableBuilder.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
      • setErrorMode

        @ConfigMethod(property="errmode",
                      doc="<p>Indicates what action should be taken if formatting errors\nare detected in the file at read time.\n</p>",
                      example="FAIL")
        public void setErrorMode​(ErrorMode errorMode)
        Sets the error handling mode.
        Parameters:
        errorMode - error handling mode
      • setCheckMagic

        @ConfigMethod(property="checkmagic",
                      doc="<p>Determines whether an initial test is made to see whether\nthe file looks like MRT before attempting to read it as one;\nthe test is that it starts with the string\n\"<code>Title: </code>\".\nSetting this true is generally a good idea\nto avoid attempting to parse non-MRT files,\nbut you can set it false to attempt to read an MRT file\nthat starts with the wrong sequence.\n</p>",
                      example="false")
        public void setCheckMagic​(boolean checkMagic)
        Sets whether the handler will attempt to guess by looking at the file whether it appears to be an MRT file before attempting to parse it as one. This is generally a good idea, since otherwise it will attempt to make MRT sense of any old file, but you can set it false to try to parse MRT files with unexpected first few bytes.
        Parameters:
        checkMagic - true to require magic number presence
      • makeStarTable

        public StarTable makeStarTable​(uk.ac.starlink.util.DataSource datsrc,
                                       boolean wantRandom,
                                       StoragePolicy storage)
                                throws java.io.IOException
        Description copied from interface: TableBuilder
        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
        storage - 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

        public void streamStarTable​(java.io.InputStream in,
                                    TableSink sink,
                                    java.lang.String pos)
                             throws java.io.IOException
        Description copied from interface: TableBuilder
        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:
        in - 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
      • canStream

        public boolean canStream()
        Description copied from class: DocumentedTableBuilder
        Indicates whether this handler can read tables from a stream.
        Specified by:
        canStream in class DocumentedTableBuilder
        Returns:
        true iff this handler can read from streams
      • docIncludesExample

        public boolean docIncludesExample()
        Description copied from interface: DocumentedIOHandler
        Indicates whether the serialization of some (short) example table should be added to the user documentation for this handler. Binary formats, or instances for which the Documented.getXmlDescription() method already includes some example output, should return false.
        Returns:
        true if the user documentation would benefit from the addition of an example serialization
      • getXmlDescription

        public java.lang.String getXmlDescription()
        Description copied from interface: Documented
        Returns user-directed documentation in XML format.

        The output should be a sequence of one or more <P> elements, using XHTML-like XML. Since rendering may be done in a number of contexts however, use of the full range of XHTML elements is discouraged. Where possible, the content should stick to simple markup such as the elements P, A, UL, OL, LI, DL, DT, DD EM, STRONG, I, B, CODE, TT, PRE.

        Returns:
        XML description of this object
      • isMagic

        public static boolean isMagic​(byte[] intro)
        Indicates whether the given buffer starts with the MRT magic number "Title: ".
        Parameters:
        intro - byte buffer
        Returns:
        true iff magic number is present