Add extractmessage144.f90

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@6779 ab8295b8-cf94-4d9e-aec4-7959e3be5d79

CMakeLists.txt

@@ -329,6 +329,7 @@ set (wsjt_FSRCS
   lib/ephem.f90
   lib/extract.f90
   lib/extract4.f90
+  lib/extractmessage144.f90
   lib/fano232.f90
   lib/fast9.f90
   lib/fast_decode.f90
@@ -386,7 +387,6 @@ set (wsjt_FSRCS
   lib/jt9_decode.f90
   lib/jt9fano.f90
   lib/JTMSKsim.f90
-  lib/msk144sim.f90
   lib/jtmsk_decode.f90
   lib/jtmsk_short.f90
   lib/ldpcsim.f90
@@ -401,6 +401,7 @@ set (wsjt_FSRCS
   lib/mskdt.f90
   lib/msk144d.f90
   lib/msk144_decode.f90
+  lib/msk144sim.f90
   lib/options.f90
   lib/packjt.f90
   lib/pctile.f90

lib/extractmessage144.f90

@@ -0,0 +1,43 @@
+subroutine extractmessage144(decoded,msgreceived,nhashflag)
+  use iso_c_binding, only: c_loc,c_size_t
+  use packjt
+  use hashing
+
+  character*22 msgreceived
+  integer*1 decoded(80)
+  integer*1, target::  i1Dec8BitBytes(10)
+  integer*1 i1hashdec
+  integer*4 i4Dec6BitWords(12)
+  
+! Collapse 80 decoded bits to 10 bytes. Bytes 1-9 are the message, byte 10 is the hash
+  do ibyte=1,10
+      itmp=0
+    do ibit=1,8
+      itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*8+ibit))
+    enddo
+    i1Dec8BitBytes(ibyte)=itmp
+  enddo
+
+! Calculate the hash using the first 9 bytes.
+  ihashdec=nhash(c_loc(i1Dec8BitBytes),int(9,c_size_t),146)
+  ihashdec=2*iand(ihashdec,255)
+
+! Compare calculated hash with received byte 10 - if they agree, keep the message.
+  i1hashdec=ihashdec
+  if( i1hashdec .eq. i1Dec8BitBytes(10) ) then
+! Good hash --- unpack 72-bit message
+    do ibyte=1,12
+      itmp=0
+      do ibit=1,6
+        itmp=ishft(itmp,1)+iand(1,decoded((ibyte-1)*6+ibit))
+      enddo
+      i4Dec6BitWords(ibyte)=itmp
+    enddo
+    call unpackmsg(i4Dec6BitWords,msgreceived)
+    nhashflag=1
+  else
+    msgreceived=' '
+    nhashflag=-1
+  endif 
+  return
+  end subroutine extractmessage144