#include <stdio.h>

#include <stdlib.h>

#include "grib2.h"

g2int g2_unpack6(unsigned char *cgrib,g2int cgrib_length,g2int *iofst,g2int ngpts,g2int *ibmap,

               g2int **bmap)

//$$$  SUBPROGRAM DOCUMENTATION BLOCK

//                .      .    .                                       .

// SUBPROGRAM:    g2_unpack6

//   PRGMMR: Gilbert         ORG: W/NP11    DATE: 2002-10-31

//

// ABSTRACT: This subroutine unpacks Section 6 (Bit-Map Section)

//           as defined in GRIB Edition 2.

//

// PROGRAM HISTORY LOG:

// 2002-10-31  Gilbert

//

// USAGE:    int g2_unpack6(unsigned char *cgrib,g2int *iofst,g2int ngpts,

//                          g2int *ibmap,g2int **bmap)

//   INPUT ARGUMENTS:

//     cgrib    - char array containing Section 6 of the GRIB2 message

//     iofst    - Bit offset of the beginning of Section 6 in cgrib.

//     ngpts    - Number of grid points specified in the bit-map

//

//   OUTPUT ARGUMENTS:

//     iofst    - Bit offset at the end of Section 6, returned.

//     ibmap    - Bitmap indicator ( see Code Table 6.0 )

//                0 = bitmap applies and is included in Section 6.

//                1-253 = Predefined bitmap applies

//                254 = Previously defined bitmap applies to this field

//                255 = Bit map does not apply to this product.

//     bmap     - Pointer to an integer array containing decoded bitmap.

//                ( if ibmap=0 )

//

//   RETURN VALUES:

//     ierr     - Error return code.

//                0 = no error

//                2 = Not Section 6

//                4 = Unrecognized pre-defined bit-map.

//                6 = memory allocation error

//

// REMARKS: None

//

// ATTRIBUTES:

//   LANGUAGE: C

//   MACHINE:

//

//$$$//

{

      g2int j,ierr,isecnum;

      g2int *lbmap=0;

      g2int *intbmap;

      ierr=0;

      *bmap=0;    //NULL

      *iofst=*iofst+32;    // skip Length of Section

      gbit(cgrib,&isecnum,*iofst,8);         // Get Section Number

      *iofst=*iofst+8;

      if ( isecnum != 6 ) {

         ierr=2;

         fprintf(stderr,"g2_unpack6: Not Section 6 data.\n");

         return(ierr);

      }

      gbit(cgrib,ibmap,*iofst,8);    // Get bit-map indicator

      *iofst=*iofst+8;

      if (*ibmap == 0) {               // Unpack bitmap

         if (ngpts > 0) lbmap=(g2int *)calloc(ngpts,sizeof(g2int));

         if (lbmap == 0) {

            ierr=6;

            return(ierr);

         }

         else {

            *bmap=lbmap;

         }

         intbmap=(g2int *)calloc(ngpts,sizeof(g2int));

         gbits(cgrib,cgrib_length,intbmap,*iofst,1,0,ngpts);

         *iofst=*iofst+ngpts;

         for (j=0;j<ngpts;j++) {

           lbmap[j]=(g2int)intbmap[j];

         }

         free(intbmap);

//      else if (*ibmap.eq.254)               ! Use previous bitmap

//        return(ierr);

//      else if (*ibmap.eq.255)               ! No bitmap in message

//        bmap(1:ngpts)=.true.

//      else {

//        print *,'gf_unpack6: Predefined bitmap ',*ibmap,' not recognized.'

//        ierr=4;

      }

      return(ierr);    // End of Section 6 processing

}