WSJT-X/lib/extractmessage144.f90

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Fortran
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subroutine extractmessage144(decoded,msgreceived,nhashflag)
use iso_c_binding, only: c_loc,c_size_t
use packjt
use hashing
character*22 msgreceived
integer*1 decoded(80)
integer*1, target:: i1Dec8BitBytes(10)
integer*1 i1hashdec
integer*4 i4Dec6BitWords(12)
! Collapse 80 decoded bits to 10 bytes. Bytes 1-9 are the message, byte 10 is the hash
do ibyte=1,10
itmp=0
do ibit=1,8
itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*8+ibit))
enddo
i1Dec8BitBytes(ibyte)=itmp
enddo
! Calculate the hash using the first 9 bytes.
ihashdec=nhash(c_loc(i1Dec8BitBytes),int(9,c_size_t),146)
ihashdec=2*iand(ihashdec,255)
! Compare calculated hash with received byte 10 - if they agree, keep the message.
i1hashdec=ihashdec
if( i1hashdec .eq. i1Dec8BitBytes(10) ) then
! Good hash --- unpack 72-bit message
do ibyte=1,12
itmp=0
do ibit=1,6
itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*6+ibit))
enddo
i4Dec6BitWords(ibyte)=itmp
enddo
call unpackmsg(i4Dec6BitWords,msgreceived)
nhashflag=1
else
msgreceived=' '
nhashflag=-1
endif
return
end subroutine extractmessage144