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#include <stdio.h>
#include "grib2.h"
#define MAPSEC1LEN 13
g2int g2_create(unsigned char *cgrib,g2int *listsec0,g2int *listsec1)
//$$$ SUBPROGRAM DOCUMENTATION BLOCK
// . . . .
// SUBPROGRAM: g2_create
// PRGMMR: Gilbert ORG: W/NP11 DATE: 2002-10-31
//
// ABSTRACT: This routine initializes a new GRIB2 message and packs
// GRIB2 sections 0 (Indicator Section) and 1 (Identification Section).
// This routine is used with routines "g2_addlocal", "g2_addgrid",
// "g2_addfield", and "g2_gribend" to create a complete GRIB2 message.
// g2_create must be called first to initialize a new GRIB2 message.
// Also, a call to g2_gribend is required to complete GRIB2 message
// after all fields have been added.
//
// PROGRAM HISTORY LOG:
// 2002-10-31 Gilbert
//
// USAGE: int g2_create(unsigned char *cgrib,g2int *listsec0,g2int *listsec1)
// INPUT ARGUMENTS:
// cgrib - Character array to contain the GRIB2 message
// listsec0 - Contains information needed for GRIB Indicator Section 0.
// Must be dimensioned >= 2.
// listsec0[0]=Discipline-GRIB Master Table Number
// (see Code Table 0.0)
// listsec0[1]=GRIB Edition Number (currently 2)
// listsec1 - Contains information needed for GRIB Identification Section 1.
// Must be dimensioned >= 13.
// listsec1[0]=Id of orginating centre (Common Code Table C-1)
// listsec1[1]=Id of orginating sub-centre (local table)
// listsec1[2]=GRIB Master Tables Version Number (Code Table 1.0)
// listsec1[3]=GRIB Local Tables Version Number (Code Table 1.1)
// listsec1[4]=Significance of Reference Time (Code Table 1.2)
// listsec1[5]=Reference Time - Year (4 digits)
// listsec1[6]=Reference Time - Month
// listsec1[7]=Reference Time - Day
// listsec1[8]=Reference Time - Hour
// listsec1[9]=Reference Time - Minute
// listsec1[10]=Reference Time - Second
// listsec1[11]=Production status of data (Code Table 1.3)
// listsec1[12]=Type of processed data (Code Table 1.4)
//
// OUTPUT ARGUMENTS:
// cgrib - Char array to contain the new GRIB2 message.
// Must be allocated large enough to store the entire
// GRIB2 message.
//
// RETURN VALUES:
// ierr - return code.
// > 0 = Current size of new GRIB2 message
// -1 = Tried to use for version other than GRIB Edition 2
//
// REMARKS: This routine is intended for use with routines "g2_addlocal",
// "g2_addgrid", "g2_addfield", and "g2_gribend" to create a complete
// GRIB2 message.
//
// ATTRIBUTES:
// LANGUAGE: C
// MACHINE:
//
//$$$
{
g2int ierr;
g2int zero=0,one=1;
g2int mapsec1len=MAPSEC1LEN;
g2int mapsec1[MAPSEC1LEN]={ 2,2,1,1,1,2,1,1,1,1,1,1,1 };
g2int i,lensec0,lensec1,iofst,ibeg,nbits,len;
ierr=0;
//
// Currently handles only GRIB Edition 2.
//
if (listsec0[1] != 2) {
printf("g2_create: can only code GRIB edition 2.");
ierr=-1;
return (ierr);
}
//
// Pack Section 0 - Indicator Section
// ( except for total length of GRIB message )
//
cgrib[0]=0x47; // 'G' // Beginning of GRIB message
cgrib[1]=0x52; // 'R'
cgrib[2]=0x49; // 'I'
cgrib[3]=0x42; // 'B'
sbit(cgrib,&zero,32,16); // reserved for future use
sbit(cgrib,listsec0+0,48,8); // Discipline
sbit(cgrib,listsec0+1,56,8); // GRIB edition number
lensec0=16; // bytes (octets)
//
// Pack Section 1 - Identification Section
//
ibeg=lensec0*8; // Calculate offset for beginning of section 1
iofst=ibeg+32; // leave space for length of section
sbit(cgrib,&one,iofst,8); // Store section number ( 1 )
iofst=iofst+8;
//
// Pack up each input value in array listsec1 into the
// the appropriate number of octets, which are specified in
// corresponding entries in array mapsec1.
//
for (i=0;i<mapsec1len;i++) {
nbits=mapsec1[i]*8;
sbit(cgrib,listsec1+i,iofst,nbits);
iofst=iofst+nbits;
}
//
// Calculate length of section 1 and store it in octets
// 1-4 of section 1.
//
lensec1=(iofst-ibeg)/8;
sbit(cgrib,&lensec1,ibeg,32);
//
// Put current byte total of message into Section 0
//
sbit(cgrib,&zero,64,32);
len=lensec0+lensec1;
sbit(cgrib,&len,96,32);
return (len);
}
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