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59 lines
1.2 KiB
Fortran
59 lines
1.2 KiB
Fortran
subroutine encode174_91(message77,codeword)
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!
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! Add a 14-bit CRC to a 77-bit message and return a 174-bit codeword
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!
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use, intrinsic :: iso_c_binding
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use iso_c_binding, only: c_loc,c_size_t
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use crc
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integer, parameter:: N=174, K=91, M=N-K
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character*91 tmpchar
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integer*1 codeword(N)
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integer*1 gen(M,K)
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integer*1 message77(77),message(K)
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integer*1 pchecks(M)
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integer*1, target :: i1MsgBytes(12)
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include "ldpc_174_91_c_generator.f90"
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logical first
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data first/.true./
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save first,gen
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if( first ) then ! fill the generator matrix
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gen=0
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do i=1,M
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do j=1,23
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read(g(i)(j:j),"(Z1)") istr
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ibmax=4
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if(j.eq.23) ibmax=3
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do jj=1, ibmax
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icol=(j-1)*4+jj
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if( btest(istr,4-jj) ) gen(i,icol)=1
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enddo
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enddo
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enddo
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first=.false.
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endif
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! Add 14-bit CRC to form 91-bit message+CRC14
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write(tmpchar,'(77i1)') message77
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tmpchar(78:80)='000'
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i1MsgBytes=0
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read(tmpchar,'(10b8)') i1MsgBytes(1:10)
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ncrc14 = crc14 (c_loc (i1MsgBytes), 12)
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write(tmpchar(78:91),'(b14)') ncrc14
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read(tmpchar,'(91i1)') message
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do i=1,M
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nsum=0
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do j=1,K
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nsum=nsum+message(j)*gen(i,j)
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enddo
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pchecks(i)=mod(nsum,2)
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enddo
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codeword(1:K)=message
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codeword(K+1:N)=pchecks
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return
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end subroutine encode174_91
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