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subroutine encode_128_90(message77,codeword)
!
! Add a 13-bit CRC to a 77-bit message and return a 128-bit codeword
!
use, intrinsic :: iso_c_binding
use iso_c_binding, only: c_loc,c_size_t
use crc
integer, parameter:: N=128, K=90, M=N-K
character*90 tmpchar
integer*1 codeword(N)
integer*1 gen(M,K)
integer*1 message77(77),message(K)
integer*1 pchecks(M)
integer*1, target :: i1MsgBytes(12)
include "ldpc_128_90_generator.f90"
logical first
data first/.true./
save first,gen
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=2
do jj=1, ibmax
icol=(j-1)*4+jj
if( btest(istr,4-jj) ) gen(i,icol)=1
enddo
enddo
enddo
first=.false.
endif
! Add 13 bit CRC to form 90-bit message+CRC13
write(tmpchar,'(77i1)') message77
tmpchar(78:80)='000'
i1MsgBytes=0
read(tmpchar,'(10b8)') i1MsgBytes(1:10)
ncrc13 = crc13 (c_loc (i1MsgBytes), 12)
write(tmpchar(78:90),'(b13)') ncrc13
read(tmpchar,'(90i1)') message
do i=1,M
nsum=0
do j=1,K
nsum=nsum+message(j)*gen(i,j)
enddo
pchecks(i)=mod(nsum,2)
enddo
codeword(1:K)=message
codeword(K+1:N)=pchecks
return
end subroutine encode_128_90
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