Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / communications-1.1.1 / fibosplitstream.m

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+## Copyright (C) 2006 Muthiah Annamalai <muthiah.annamalai@uta.edu>
+##
+## This program is free software; you can redistribute it and/or modify it under
+## the terms of the GNU General Public License as published by the Free Software
+## Foundation; either version 3 of the License, or (at your option) any later
+## version.
+##
+## This program is distributed in the hope that it will be useful, but WITHOUT
+## ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+## FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
+## details.
+##
+## You should have received a copy of the GNU General Public License along with
+## this program; if not, see <http://www.gnu.org/licenses/>.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} { } fibosplitstream (@var{code})
+##
+## Returns the split data stream at the word boundaries.
+## Assuming the stream was originally encoded using @code{fiboenco}
+## and this routine splits the stream at the points where '11'
+## occur together & gives us the code-words which
+## can later be decoded from the @code{fibodeco} This however doesnt
+## mean that we intend to verify if all the codewords are correct,
+## and infact the last symbol in th return list can or can-not be
+## a valid codeword.
+##
+## A example use of @code{fibosplitstream} would be
+## @example
+## @group
+##
+## fibodeco(fibosplitstream([fiboenco(randint(1,100,[0 255]))@{:@}]))
+## fibodeco(fibosplitstream([fiboenco(1:10)@{:@}]))
+##
+## @end group
+## @end example
+## @seealso{fiboenco,fibodeco}
+## @end deftypefn
+
+function symbols=fibosplitstream(stream)
+  if nargin < 1
+     error('usage: fibosplitstream(stream); see help')
+  end
+
+  symbols={};
+  itr=1;
+  L=length(stream);
+
+  %
+  % Plain & Simple Algorithm. O(N)
+  % Walk till marker '11' or find it.
+  % Then split & save. A little tricky to
+  % handle the edge case_ without tripping over.
+  %
+  idx=[];
+  mark=1;
+  prev_bit=stream(1);
+  just_decoded=0;
+
+  for i=2:L
+    if(~just_decoded && (stream(i)+prev_bit)==2 )
+       symbols{itr}=[stream(mark:i)];
+       mark=i+1;
+       prev_bit=0;
+       just_decoded=1;
+       itr=itr+1;
+    else
+      prev_bit=stream(i);
+      just_decoded=0;
+    end
+    
+  end
+  if(mark < L)
+    symbols{itr}=stream(mark:end);
+  end
+  
+  return
+end
+%!
+%!assert(fibodeco(fibosplitstream([fiboenco(1:10){:}])),[1:10])
+%!