g2_unpack1.c

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#include <stdio.h>
#include <stdlib.h>
#include "grib2.h"
 
g2int
g2_unpack1(unsigned char *cgrib, g2int *iofst, g2int **ids, g2int *idslen)
{
 
    g2int i, lensec, nbits, ierr, isecnum;
    /* The map holds the number of bytes used by each value in section
     * 1. */
    g2int mapid[13]={2, 2, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1};
 
    ierr = 0;
    *idslen = 13;
 
    gbit(cgrib, &lensec, *iofst, 32);        /* Get Length of Section */
    *iofst = *iofst + 32;
    gbit(cgrib, &isecnum, *iofst, 8);         /* Get Section Number */
    *iofst = *iofst + 8;
 
    if (isecnum != 1)
    {
        ierr = 2;
        *idslen = 13;
        fprintf(stderr, "g2_unpack1: Not Section 1 data.\n");
        return(ierr);
    }
 
    /* Unpack each value into array ids from the appropriate number of
     * octets, which are specified in` corresponding entries in array
     * mapid. */
    *ids = calloc(*idslen, sizeof(g2int));
    if (*ids == 0)
    {
        ierr = 6;
        return(ierr);
    }
 
    for (i = 0; i < *idslen; i++)
    {
        nbits = mapid[i] * 8;
        gbit(cgrib, *ids + i, *iofst, nbits);
        *iofst = *iofst + nbits;
    }
 
    return(ierr);    // End of Section 1 processing
}