Add rst8.f90.

lib/superfox/rst8.f90

@@ -0,0 +1,70 @@
+program rst8
+
+  character arg*8
+  integer*1 dat0(223)                          !Generated data
+  integer*1 parity(32)                         !Parity symbols
+  integer*1 cword0(255)                        !Generated codeword
+  integer*1 cword(255)    !Rcvd codeword with errors; will be corrected in place
+  integer iera(0:200)                          !Positions of additional erasures
+      
+  nargs=iargc()
+  if(nargs.ne.3) then
+     print*,'Usage:   rst8  npad nera nerr'
+     print*,'Example: rst8   178   0   16'
+     go to 999
+  endif
+  nkv=0
+  call getarg(1,arg)
+  read(arg,*) npad
+  call getarg(2,arg)
+  read(arg,*) nera
+  call getarg(3,arg)
+  read(arg,*) nerr
+
+! The basic code RS(255,223) is punctured with npad leading zeros.
+  nn=255-npad
+  kk=223-npad
+  write(*,1000) nn,kk
+1000 format('Basic code is RS(255,223).  npad:',i4,'   N:',i4,'   K:',i4)
+
+! Generate a message, kk symbols with values 1 to kk.
+  do i=1,kk
+     dat0(i)=i
+  enddo
+
+  write(*,1002)
+1002 format('Generated message symbols:')
+  write(*,1004) dat0(1:kk)
+1004 format(20i4)
+
+  call encode_rs_8(dat0,parity)                 !Get parity symbols
+  cword0(1:kk)=dat0(1:kk)                       !Genetated codeword
+  cword0(kk+1:nn)=parity(1:nn-kk)
+  write(*,1006)
+1006 format(/'Encoded channel symbols')
+  write(*,1002) cword0(1:nn)
+  
+  cword=cword0
+  do i=1,nerr                                !Introduce errors
+     j=nn+1-i
+     cword(j)=mod(cword(j)+1,256)
+  enddo
+  write(*,1008) nera
+1008 format(/'Received channel symbols, with',i4,' errors at the end:')
+  write(*,1002) cword(1:nn)
+
+  do i=0,nera-1
+     iera(i)=i
+  enddo
+
+  call decode_rs_8(cword,iera,nera,npad)
+  ibad=count(cword(1:kk).ne.cword0(1:kk))
+
+  write(*,1010)
+1010 format(/'Decoded result:')
+  write(*,1002) cword(1:kk)
+  maxfix=(nn-kk)/2 + nera/2
+  write(*,1100) nerr,nera,nfixed,maxfix
+1100 format(/'nerr:',i3,'   nera:',i3,'   nfixed:',i3,'   maxfix:',i3)
+  
+999 end program rst8