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