WSJT-X/lib/ft8/encode174_91_nocrc.f90

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subroutine encode174_91_nocrc(message,codeword)
!
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! Encode a 91-bit message and return a 174-bit codeword.
!
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use, intrinsic :: iso_c_binding
use iso_c_binding, only: c_loc,c_size_t
use crc
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integer, parameter:: N=174, K=91, M=N-K
integer*1 codeword(N)
integer*1 gen(M,K)
integer*1 message(K)
integer*1 pchecks(M)
include "ldpc_174_91_c_generator.f90"
logical first
data first/.true./
save first,gen
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if( first ) then ! fill the generator matrix
gen=0
do i=1,M
do j=1,23
read(g(i)(j:j),"(Z1)") istr
ibmax=4
if(j.eq.23) ibmax=3
do jj=1, ibmax
icol=(j-1)*4+jj
if( btest(istr,4-jj) ) gen(i,icol)=1
enddo
enddo
enddo
first=.false.
endif
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do i=1,M
nsum=0
do j=1,K
nsum=nsum+message(j)*gen(i,j)
enddo
pchecks(i)=mod(nsum,2)
enddo
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codeword(1:K)=message
codeword(K+1:N)=pchecks
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return
end subroutine encode174_91_nocrc