// Spludlow Software
// Copyright © Samuel P. Ludlow 2020 All Rights Reserved
// Distributed under the terms of the GNU General Public License version 3
// Distributed WITHOUT ANY WARRANTY; without implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE
// https://www.spludlow.co.uk/LICENCE.TXT
// The Spludlow logo is a registered trademark of Samuel P. Ludlow and may not be used without permission
// v1.14
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.IO;
namespace Spludlow.MetSat
{
//0: Indicator Section
//1: Identification Section
//2: Local Use Section(optional)
//3: Grid Definition Section
//4: Product Definition Section
//5: Data Representation Section
//6: Bit-Map Section
//7: Data Section
//8: End Section
public class IndicatorSection
{
public String Grib; // 1-4 “GRIB” (coded according to the International Alphabet No. 5)
public UInt16 Reserved; // 5-6 Reserved
public Byte Discipline; // 7 Discipline – GRIB Master Table Number(see Code Table 0.0)
public Byte EditionNumber; // 8 GRIB Edition Number(currently 2)
public UInt64 Totallength; // 9-16 Total length of GRIB message in octets(including Section 0)
}
public class IdentificationSection
{
public UInt32 SectionLength; //1-4 Length of section in octets(21 or nn)
public Byte SectionNumber; //5 Number of Section(“1”)
public UInt16 GeneratingCentre; //6-7 Identification of originating/generating centre(see Common Code Table C-1)
public UInt16 GeneratingSubCentre; //8-9 Identification of originating/generating sub-centre(allocated by originating/ generating centre)
public Byte MasterTablesVersion; //10 GRIB Master Tables Version Number(see Code Table 1.0)
public Byte LocalTablesVersion; //11 GRIB Local Tables Version Number(see Code Table 1.1)
public Byte SignificanceOfReference; //12 Significance of Reference Time(see Code Table 1.2)
public UInt16 Year; //13-14 Year(4 digits)
public Byte Month; //15 Month
public Byte Day; //16 Day
public Byte Hour; //17 Hour
public Byte Minute; //18 Minute
public Byte Second; //19 Second
public Byte ProductionStatus; //20 Production status of processed data in this GRIB message (see Code Table 1.3)
public Byte DataType; //21 Type of processed data in this GRIB message (see Code Table 1.4)
//22-nn Reserved: need not be present
}
//1-4 Length of section in octets(nn)
//5 Number of Section(“3”)
//6 Source of grid definition(see Code Table 3.0 and Note 1)
//7-10 Number of data points
//11 Number of octets for optional list of numbers defining number of points(see Note 2)
//12 Interpretation of list of numbers defining number of points(see Code Table 3.11)
//13-14 Grid Definition Template Number(N) (see Code Table 3.1)
//15-xx Grid Definition Template(see Template 3.N, where N is the Grid Definition Template Number given in octets 13-14)
//[xx+1]-nn Optional list of numbers defining number of points(see Notes 2, 3, and 4)
/// <summary>
/// GRIB Handling
/// </summary>
public class GRIB
{
public IndicatorSection IndicatorSection;
public IdentificationSection IdentificationSection;
public UInt32 NumberOfDataPoints;
public UInt16 NumberOfCoordinateValues;
public UInt16 ProductDefinitionTemplateNumber;
public UInt16 DataRepresentationTemplateNumber;
public byte[] Data;
private int[] IndicatorSection_StringLengths = new int[] { 4 };
private bool Endian = true;
public GRIB(byte[] data)
{
using (MemoryStream stream = new MemoryStream(data))
{
this.Load(stream);
}
}
public GRIB(string filename)
{
using (FileStream stream = new FileStream(filename, FileMode.Open))
{
this.Load(stream);
}
}
public GRIB(FileStream stream)
{
this.Load(stream);
}
public void Load(Stream stream)
{
long read;
byte[] data;
using (BinaryReader reader = new BinaryReader(stream))
{
//0: Indicator Section
this.IndicatorSection = new IndicatorSection();
read = Spludlow.Io.BinaryIO.ReadBinary(reader, this.IndicatorSection, this.Endian, this.IndicatorSection_StringLengths);
if (this.IndicatorSection.Grib != "GRIB")
throw new ApplicationException("Not a GRIB");
if ((long)this.IndicatorSection.Totallength != stream.Length)
throw new ApplicationException("GRIB Bad File length, header:" + this.IndicatorSection.Totallength + ", stream:" + stream.Length);
//1: Identification Section
this.IdentificationSection = new IdentificationSection();
read = Spludlow.Io.BinaryIO.ReadBinary(reader, this.IdentificationSection, this.Endian); //, this.IdentificationSection_StringLengths);
if (this.IdentificationSection.SectionNumber != 1)
throw new ApplicationException("Not GRIB Identification Section");
reader.ReadBytes((int)this.IdentificationSection.SectionLength - 21);
//2: Local Use Section(optional)
UInt32 nextLength = Spludlow.Io.BinaryIO.ReadUInt32(reader, this.Endian);
Byte nextSectionNumber = reader.ReadByte();
if (nextSectionNumber == 2)
{
reader.ReadBytes((int)nextLength - 5);
nextLength = Spludlow.Io.BinaryIO.ReadUInt32(reader, this.Endian);
nextSectionNumber = reader.ReadByte();
}
//3: Grid Definition Section
UInt32 gridDefinitionLength = nextLength;
Byte gridDefinitionNumber = nextSectionNumber;
if (gridDefinitionNumber != 3)
throw new ApplicationException("Not GRIB Grid Definition Section");
reader.ReadBytes((int)gridDefinitionLength - 5);
//4: Product Definition Section
data = this.ReadSection(reader, 4, "Product Definition");
// 6 - 7 Number of coordinate values after Template(see Note 1)
this.NumberOfCoordinateValues = Spludlow.Io.BinaryIO.ReadUInt16(data, 5, this.Endian);
// 8 - 9 Product Definition Template Number(see Code Table 4.0)
this.ProductDefinitionTemplateNumber = Spludlow.Io.BinaryIO.ReadUInt16(data, 7, this.Endian);
// 10 - xx Product Definition Template(see Template 4.X, where X is the Product Definition Template Number given in octets 8 - 9)
// [xx + 1] - nn Optional list of coordinate values(see Notes 2 and 3)
//throw new ApplicationException(this.NumberOfCoordinateValues + " " + this.ProductDefinitionTemplateNumber); 0 30 30 Satellite product
//5: Data Representation Section
data = this.ReadSection(reader, 5, "Data Representation");
// 6 - 9 Number of data points where one or more values are specified in Section 7 when a bit map is present, total number of data points when a bit map is absent
this.NumberOfDataPoints = Spludlow.Io.BinaryIO.ReadUInt32(data, 5, this.Endian);
// 10 - 11 Data Representation Template Number(see code Table 5.0)
this.DataRepresentationTemplateNumber = Spludlow.Io.BinaryIO.ReadUInt16(data, 9, this.Endian);
// 12 - nn Data Representation Template(see Template 5.X, where X is the Data Representation Template Number given in octets 10 - 11)
//throw new ApplicationException(this.NumberOfDataPoints.ToString());
//6: Bit-Map Section
this.ReadSection(reader, 6, "Bit-Map");
//7: Data Section
UInt32 dataLength = Spludlow.Io.BinaryIO.ReadUInt32(reader, this.Endian);
Byte dataNumber = reader.ReadByte();
if (dataNumber != 7)
throw new ApplicationException("Not GRIB Data Section");
this.Data = reader.ReadBytes((int)dataLength - 5);
//8: End Section
if (Encoding.ASCII.GetString(reader.ReadBytes(4)) != "7777")
throw new ApplicationException("GRIB Bad End");
if ((long)this.IndicatorSection.Totallength != stream.Position)
throw new ApplicationException("GRIB Unexpected data on End");
}
}
private byte[] ReadSection(BinaryReader reader, byte sectionNumber, string sectionName)
{
UInt32 length = Spludlow.Io.BinaryIO.ReadUInt32(reader, this.Endian);
Byte number = reader.ReadByte();
if (number != sectionNumber)
throw new ApplicationException("Not GRIB " + sectionName + " Section");
byte[] data = new byte[length];
reader.Read(data, 5, (int)length - 5);
return data;
}
}
}