gribinfo.f

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      subroutine gribinfo(cgrib,lcgrib,listsec0,listsec1,
     &                    numlocal,numfields,maxvals,ierr)
 
      character(len=1),intent(in) :: cgrib(lcgrib)
      integer,intent(in) :: lcgrib
      integer,intent(out) :: listsec0(3),listsec1(13),maxvals(7)
      integer,intent(out) :: numlocal,numfields,ierr
      
      character(len=4),parameter :: grib='GRIB',c7777='7777'
      character(len=4) :: ctemp
      integer,parameter :: zero=0,one=1
      integer,parameter :: mapsec1len=13
      integer,parameter :: 
     &        mapsec1(mapsec1len)=(/ 2,2,1,1,1,2,1,1,1,1,1,1,1 /)
      integer iofst,ibeg,istart
 
      ierr=0
      numlocal=0
      numfields=0
      maxsec2len=1
      maxgdstmpl=1
      maxdeflist=1
      maxpdstmpl=1
      maxcoordlist=1
      maxdrstmpl=1
      maxgridpts=0
!
!  Check for beginning of GRIB message in the first 100 bytes
!
      istart=0
      do j=1,100
        ctemp=cgrib(j)//cgrib(j+1)//cgrib(j+2)//cgrib(j+3)
        if (ctemp.eq.grib ) then
          istart=j
          exit
        endif
      enddo
      if (istart.eq.0) then
        print *,'gribinfo:  Beginning characters GRIB not found.'
        ierr=1
        return
      endif
!
!  Unpack Section 0 - Indicator Section 
!
      iofst=8*(istart+5)
      call g2_gbytec(cgrib,listsec0(1),iofst,8)     ! Discipline
      iofst=iofst+8
      call g2_gbytec(cgrib,listsec0(2),iofst,8)     ! GRIB edition number
      iofst=iofst+8
      iofst=iofst+32
      call g2_gbytec(cgrib,lengrib,iofst,32)        ! Length of GRIB message
      iofst=iofst+32
      listsec0(3)=lengrib
      lensec0=16
      ipos=istart+lensec0
!
!  Currently handles only GRIB Edition 2.
!  
      if (listsec0(2).ne.2) then
        print *,'gribinfo: can only decode GRIB edition 2.'
        ierr=2
        return
      endif
!
!  Unpack Section 1 - Identification Section
!
      call g2_gbytec(cgrib,lensec1,iofst,32)        ! Length of Section 1
      iofst=iofst+32
      call g2_gbytec(cgrib,isecnum,iofst,8)         ! Section number ( 1 )
      iofst=iofst+8
      if (isecnum.ne.1) then
        print *,'gribinfo: Could not find section 1.'
        ierr=3
        return
      endif
      !
      !   Unpack each input value in array listsec1 into the
      !   the appropriate number of octets, which are specified in
      !   corresponding entries in array mapsec1.
      !
      do i=1,mapsec1len
        nbits=mapsec1(i)*8
        call g2_gbytec(cgrib,listsec1(i),iofst,nbits)
        iofst=iofst+nbits
      enddo
      ipos=ipos+lensec1
!
!  Loop through the remaining sections keeping track of the 
!  length of each.  Also count the number of times Section 2
!  and Section 4 appear.
!
      do
        ctemp=cgrib(ipos)//cgrib(ipos+1)//cgrib(ipos+2)//cgrib(ipos+3)
        if (ctemp.eq.c7777 ) then
          ipos=ipos+4
          if (ipos.ne.(istart+lengrib)) then
            print *,'gribinfo: "7777" found, but not where expected.'
            ierr=4
            return
          endif
          exit
        endif
        iofst=(ipos-1)*8
        call g2_gbytec(cgrib,lensec,iofst,32)        ! Get Length of Section
        iofst=iofst+32
        call g2_gbytec(cgrib,isecnum,iofst,8)         ! Get Section number
        iofst=iofst+8
        ipos=ipos+lensec                 ! Update beginning of section pointer
        if (ipos.gt.(istart+lengrib)) then
          print *,'gribinfo: "7777"  not found at end of GRIB message.'
          ierr=5
          return
        endif
        if (isecnum.eq.2) then     ! Local Section 2
           !   increment counter for total number of local sections found
           !   and determine largest Section 2 in message
           numlocal=numlocal+1
           lenposs=lensec-5
           if ( lenposs.gt.maxsec2len ) maxsec2len=lenposs
        elseif (isecnum.eq.3) then
           iofst=iofst+8                      ! skip source of grid def.
           call g2_gbytec(cgrib,ngdpts,iofst,32)         ! Get Num of Grid Points
           iofst=iofst+32
           call g2_gbytec(cgrib,nbyte,iofst,8)      ! Get Num octets for opt. list
           iofst=iofst+8
           if (ngdpts.gt.maxgridpts) maxgridpts=ngdpts
           lenposs=lensec-14
           if ( lenposs.gt.maxgdstmpl ) maxgdstmpl=lenposs
           if (nbyte.ne.0) then
              lenposs=lenposs/nbyte
              if ( lenposs.gt.maxdeflist ) maxdeflist=lenposs
           endif
        elseif (isecnum.eq.4) then
          numfields=numfields+1
           call g2_gbytec(cgrib,numcoord,iofst,16)      ! Get Num of Coord Values
           iofst=iofst+16
           if (numcoord.ne.0) then
              if (numcoord.gt.maxcoordlist) maxcoordlist=numcoord
           endif
           lenposs=lensec-9
           if ( lenposs.gt.maxpdstmpl ) maxpdstmpl=lenposs
        elseif (isecnum.eq.5) then
           lenposs=lensec-11
           if ( lenposs.gt.maxdrstmpl ) maxdrstmpl=lenposs
        endif
        
      enddo
 
      maxvals(1)=maxsec2len
      maxvals(2)=maxgdstmpl
      maxvals(3)=maxdeflist
      maxvals(4)=maxpdstmpl
      maxvals(5)=maxcoordlist
      maxvals(6)=maxdrstmpl
      maxvals(7)=maxgridpts
 
      return
      end