subroutine gb_info(cgrib,lcgrib,listsec0,listsec1, 2,8
& numfields,numlocal,maxlocal,ierr)
!$$$ SUBPROGRAM DOCUMENTATION BLOCK
! . . . .
! SUBPROGRAM: gb_info
! PRGMMR: Gilbert ORG: W/NP11 DATE: 2000-05-25
!
! ABSTRACT: This subroutine searches through a GRIB2 message and
! returns the number of gridded fields found in the message and
! the number (and maximum size) of Local Use Sections.
! Also various checks are performed
! to see if the message is a valid GRIB2 message.
!
! PROGRAM HISTORY LOG:
! 2000-05-25 Gilbert
!
! USAGE: CALL gb_info(cgrib,lcgrib,listsec0,listsec1,
! & numfields,numlocal,maxlocal,ierr)
! INPUT ARGUMENT LIST:
! cgrib - Character array that contains the GRIB2 message
! lcgrib - Length (in bytes) of GRIB message in array cgrib.
!
! OUTPUT ARGUMENT LIST:
! listsec0 - Contains information decoded from GRIB Indicator Section 0.
! Must be dimensioned >= 2.
! listsec0(1)=Discipline-GRIB Master Table Number
! (see Code Table 0.0)
! listsec0(2)=GRIB Edition Number (currently 2)
! listsec0(3)=Length of GRIB message
! listsec1 - Contains information read from GRIB Identification Section 1.
! Must be dimensioned >= 13.
! listsec1(1)=Id of orginating centre (Common Code Table C-1)
! listsec1(2)=Id of orginating sub-centre (local table)
! listsec1(3)=GRIB Master Tables Version Number (Code Table 1.0)
! listsec1(4)=GRIB Local Tables Version Number
! listsec1(5)=Significance of Reference Time (Code Table 1.1)
! listsec1(6)=Reference Time - Year (4 digits)
! listsec1(7)=Reference Time - Month
! listsec1(8)=Reference Time - Day
! listsec1(9)=Reference Time - Hour
! listsec1(10)=Reference Time - Minute
! listsec1(11)=Reference Time - Second
! listsec1(12)=Production status of data (Code Table 1.2)
! listsec1(13)=Type of processed data (Code Table 1.3)
! numfields- The number of gridded fieldse found in the GRIB message.
! numlocal - The number of Local Use Sections ( Section 2 ) found in
! the GRIB message.
! maxlocal- The size of the largest Local Use Section ( Section 2 ).
! Can be used to ensure that the return array passed
! to subroutine getlocal is dimensioned large enough.
! ierr - Error return code.
! 0 = no error
! 1 = Beginning characters "GRIB" not found.
! 2 = GRIB message is not Edition 2.
! 3 = Could not find Section 1, where expected.
! 4 = End string "7777" found, but not where expected.
! 5 = End string "7777" not found at end of message.
! 6 = Invalid section number found.
!
! REMARKS: None
!
! ATTRIBUTES:
! LANGUAGE: Fortran 90
! MACHINE: IBM SP
!
!$$$
character(len=1),intent(in) :: cgrib(lcgrib)
integer,intent(in) :: lcgrib
integer,intent(out) :: listsec0(3),listsec1(13)
integer,intent(out) :: numlocal,numfields,maxlocal,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
maxlocal=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 *,'gb_info: Beginning characters GRIB not found.'
ierr=1
return
endif
!
! Unpack Section 0 - Indicator Section
!
iofst=8*(istart+5)
call gbyte
(cgrib,listsec0(1),iofst,8) ! Discipline
iofst=iofst+8
call gbyte(cgrib,listsec0(2),iofst,8) ! GRIB edition number
iofst=iofst+8
iofst=iofst+32
call gbyte(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 *,'gb_info: can only decode GRIB edition 2.'
ierr=2
return
endif
!
! Unpack Section 1 - Identification Section
!
call gbyte(cgrib,lensec1,iofst,32) ! Length of Section 1
iofst=iofst+32
call gbyte(cgrib,isecnum,iofst,8) ! Section number ( 1 )
iofst=iofst+8
if (isecnum.ne.1) then
print *,'gb_info: 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 gbyte(cgrib,listsec1(i),iofst,nbits)
iofst=iofst+nbits
enddo
ipos=ipos+lensec1
!
! Loop through the remaining sections to see if they are valid.
! 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 *,'gb_info: "7777" found, but not where expected.'
ierr=4
return
endif
exit
endif
iofst=(ipos-1)*8
call gbyte(cgrib,lensec,iofst,32) ! Get Length of Section
iofst=iofst+32
call gbyte(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 *,'gb_info: "7777" not found at end of GRIB message.'
ierr=5
return
endif
if ( isecnum.ge.2.AND.isecnum.le.7 ) then
if (isecnum.eq.2) then ! Local Section 2
! increment counter for total number of local sections found
numlocal=numlocal+1
lenposs=lensec-5
if ( lenposs.gt.maxlocal ) maxlocal=lenposs
elseif (isecnum.eq.4) then
! increment counter for total number of fields found
numfields=numfields+1
endif
else
print *,'gb_info: Invalid section number found in GRIB',
& ' message: ',isecnum
ierr=6
return
endif
enddo
return
end