WSJT-X/lib/fsk4hf/encode174_74.f90

48 lines
1.0 KiB
Fortran

subroutine encode174_74(message,codeword)
use, intrinsic :: iso_c_binding
use iso_c_binding, only: c_loc,c_size_t
use crc
integer, parameter:: N=174, K=74, M=N-K
character*24 c24
integer*1 codeword(N)
integer*1 gen(M,K)
integer*1 message(K)
integer*1 pchecks(M)
integer*1, target :: i1MsgBytes(10)
integer*4 ncrc24
include "ldpc_174_74_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=1,19
read(g(i)(j:j),"(Z1)") istr
ibmax=4
if(j.eq.19) 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
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 encode174_74