fits: add nasty hack around LDAC FITS format idiosyncracies

This is about the LDAC FITS variant:
http://marvinweb.astro.uni-bonn.de/data_products/THELIWWW/LDAC/LDAC_concepts.html

The first (LDAC_IMHEAD) table extension contains a single-cell table
where the cell's content is an array of FITS headers.
In auto-format-detection mode this confuses STIL into thinking
that the file is in colfits format, which in turn means that
the StarTableFactory.makeStarTables method ignores the second
(LDAC_OBJECTS) table extension, since colfits is not
multi-table-capable.

Add a hack to spot LDAC_IMHEAD HDUs in colfits and reject them as
colfits.

Author: mbtaylor

fits/src/main/uk/ac/starlink/fits/ColFitsStarTable.java

@@ -43,8 +43,11 @@ public class ColFitsStarTable extends AbstractStarTable {
      * @param   hdr   header of the HDU containing the table
      * @param   dataPos  offset into <code>file</code> of the start of the
      *          data part of the HDU
+     * @param   force  true to make a table if we possibly can,
+     *                 false to reject if it doesn't look very much like one
      */
-    public ColFitsStarTable( DataSource datsrc, Header hdr, long dataPos )
+    public ColFitsStarTable( DataSource datsrc, Header hdr, long dataPos,
+                             boolean force )
             throws IOException {
         HeaderCards cards = new HeaderCards( hdr );
 
@@ -61,6 +64,21 @@ public ColFitsStarTable( DataSource datsrc, Header hdr, long dataPos )
         /* Find the number of columns. */
         ncol_ = cards.getIntValue( "TFIELDS" ).intValue();
 
+        /* Nasty hack.
+         * LDAC is a somewhat eccentric FITS variant that has a single-cell
+         * BINTABLE as HDU1 containing an array of FITS header cards.
+         * That looks like colfits, and causes the later HDU to be
+         * ignored in format auto-detection mode, since colfits is not
+         * a multi-table-capable format.  So reject this HDU explicitly here,
+         * in auto-detection format it will get passed on to some other
+         * format handler (basic FITS).
+         * See http://marvinweb.astro.uni-bonn.de/
+         *     data_products/THELIWWW/LDAC/LDAC_concepts.html */
+        if ( ! force &&
+             "LDAC_IMHEAD".equals( cards.getStringValue( "EXTNAME" ) ) ) {
+            throw new TableFormatException( "Reject LDAC_IMHEAD table" );
+        }
+
         /* Read metadata for each column from the FITS header cards. */
         long nrow = 0;
         valReaders_ = new ValueReader[ ncol_ ];
@@ -192,7 +210,7 @@ public BasicInput createInput( boolean isSeq )
             }
         }
 
-        /* Otherwise use a different stream for each collumn. */
+        /* Otherwise use a different stream for each column. */
         else {
             if ( isFile && datsrc.getCompression() != Compression.NONE ) {
                 logger_.warning( "Can't map compressed file " + datsrc.getName()

fits/src/main/uk/ac/starlink/fits/ColFitsTableBuilder.java

@@ -72,6 +72,6 @@ public StarTable makeStarTable( DataSource datsrc, boolean wantRandom,
             in.close();
         }
 
-        return new ColFitsStarTable( datsrc, hdr, pos );
+        return new ColFitsStarTable( datsrc, hdr, pos, false );
     }
 }

topcat/src/docs/sun253.xml

@@ -20797,6 +20797,8 @@ introduced since the last version:
         in the <ref id="SsaMultiWindow">Multiple SSA Query</ref> window.
         This long-standing bug would have stopped this window working at all
         with well-behaved SSA services.</li>
+    <li>Add a hack that allows LDAC FITS tables to be treated sensibly
+        in auto-format-detection mode.</li>
     </ul>
     </p></dd>
 

ttools/src/docs/sun256.xml

@@ -10108,6 +10108,8 @@ eds. C. Gabriel et al., ASP Conf. Ser. 351, p. 666 (2006)
         <code>coneskymatch</code>.
         This long-standing bug would have stopped this command working at all
         with well-behaved SSA services.</li>
+    <li>Add a hack that allows LDAC FITS tables to be treated sensibly
+        in auto-format-detection mode.</li>
     </ul>
     </p></dd>
 

votable/src/main/uk/ac/starlink/votable/ColFitsPlusTableBuilder.java

@@ -98,7 +98,8 @@ public StarTable makeStarTable( DataSource datsrc, boolean wantRandom,
         }
 
         /* Get the table itself from the next HDU. */
-        StarTable tableData = new ColFitsStarTable( datsrc, hdr, dataPos );
+        StarTable tableData =
+            new ColFitsStarTable( datsrc, hdr, dataPos, false );
 
         /* If we got a TABLE element, combine the metadata from that and
          * the data from the FITS table to provide the output table. */