/*
* Copyright 1998-2009 University Corporation for Atmospheric Research/Unidata
*
* Portions of this software were developed by the Unidata Program at the
* University Corporation for Atmospheric Research.
*
* Access and use of this software shall impose the following obligations
* and understandings on the user. The user is granted the right, without
* any fee or cost, to use, copy, modify, alter, enhance and distribute
* this software, and any derivative works thereof, and its supporting
* documentation for any purpose whatsoever, provided that this entire
* notice appears in all copies of the software, derivative works and
* supporting documentation. Further, UCAR requests that the user credit
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* software or in any product that includes this software. The names UCAR
* and/or Unidata, however, may not be used in any advertising or publicity
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*
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*/
package ucar.nc2.iosp.gempak;
import ucar.grib.NoValidGribException;
import ucar.grib.NotSupportedException;
import ucar.grib.QuasiRegular;
import ucar.grib.grib2.*;
import ucar.unidata.io.RandomAccessFile;
import java.io.IOException;
/**
* A class used to extract Grib2 data from a Gempak file.
* see <a href="../../../IndexFormat.txt"> IndexFormat.txt</a>
*
* @author Robb Kambic
*/
public final class GempakGrib2Data {
/**
* used to hold open file descriptor
*/
private RandomAccessFile raf = null;
/**
* Expand Quasi-Regular grids
*/
private boolean expandQuasi = true;
/**
* Constructs a GempakGrib2Data object for a RandomAccessFile.
*
* @param raf ucar.unidata.io.RandomAccessFile with GRIB content
*/
public GempakGrib2Data(RandomAccessFile raf) {
this.raf = raf;
}
/**
* Constructs a GempakGrib2Data object for a RandomAccessFile.
*
* @param raf ucar.unidata.io.RandomAccessFile with GRIB content.
* @param expandQuasi whether to expand Quasi grids, default is true.
*/
public GempakGrib2Data(RandomAccessFile raf, boolean expandQuasi) {
this.raf = raf;
this.expandQuasi = expandQuasi;
}
/**
* Reads the Grib data with a certain offsets in the file.
*
* @param start starting point for reads
* @param refTime reference time in msecs
* @return float[]
* @throws IOException if raf does not contain a valid GRIB record.
*/
public final float[] getData(long start, long refTime) throws IOException {
long time = System.currentTimeMillis();
Grib2IdentificationSection id = null;
Grib2LocalUseSection lus = null;
Grib2GridDefinitionSection gds = null;
Grib2ProductDefinitionSection pds = null;
Grib2DataRepresentationSection drs = null;
Grib2BitMapSection bms = null;
Grib2DataSection ds = null;
raf.order(raf.BIG_ENDIAN);
raf.seek(start);
int secLength = raf.readInt();
if (secLength > 0) {
id = new Grib2IdentificationSection(raf); // Section 1
}
secLength = raf.readInt();
if (secLength > 0) {
// check for Local Use Section 2
lus = new Grib2LocalUseSection(raf);
}
secLength = raf.readInt();
if (secLength > 0) {
// Need section 3, 4, 5, 6, and 7 to read/interpet the data
gds = new Grib2GridDefinitionSection(raf, false); // Section 3 no checksum
}
secLength = raf.readInt();
if (secLength > 0) {
pds = new Grib2ProductDefinitionSection(raf, refTime); // Section 4
}
secLength = raf.readInt();
if (secLength > 0) {
drs = new Grib2DataRepresentationSection(raf); // Section 5
}
secLength = raf.readInt();
if (secLength > 0) {
bms = new Grib2BitMapSection(true, raf, gds); // Section 6
}
if (bms.getBitmapIndicator() == 254) { //previously defined in the same GRIB2 record
long offset = raf.getFilePointer();
//raf.seek(GdsOffset); // go get it
//Grib2GridDefinitionSection savegds = gds;
gds = new Grib2GridDefinitionSection(raf, false);
Grib2ProductDefinitionSection savepds = pds;
pds = new Grib2ProductDefinitionSection(raf, refTime); // Section 4
Grib2DataRepresentationSection savedrs = drs;
drs = new Grib2DataRepresentationSection(raf); // Section 5
bms = new Grib2BitMapSection(true, raf, gds); // Section 6
// reset pds, drs
pds = savepds;
drs = savedrs;
raf.seek(offset);
}
secLength = raf.readInt();
if (secLength > 0) {
ds = new Grib2DataSection(true, raf, gds, drs, bms); // Section 7
}
//System.out.println("DS offset=" + ds.getOffset() );
// not a quasi grid or don't expand Quasi
if ((gds.getOlon() == 0) || !expandQuasi) {
return ds.getData();
} else {
QuasiRegular qr = new QuasiRegular(ds.getData(), (Object) gds);
return qr.getData();
}
} // end getData
} // end GempakGrib2Data