Add a useful package (from Source forge) for octave

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

diff --git a/octave_packages/communications-1.1.1/rsencof.m b/octave_packages/communications-1.1.1/rsencof.m
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+## Copyright (C) 2003 David Bateman
+##
+## 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} {} rsencof (@var{in},@var{out})
+## @deftypefnx {Function File} {} rsencof (@var{in},@var{out},@var{t})
+## @deftypefnx {Function File} {} rsencof (@var{...},@var{pad})
+##
+## Encodes an ascii file using a Reed-Solomon coder. The input file is
+## defined by @var{in} and the result is written to the output file @var{out}.
+## The type of coding to use is determined by whether the input file is 7-
+## or 8-bit. If the input file is 7-bit, the default coding is [127,117].
+## while the default coding for an 8-bit file is a [255, 235]. This allows
+## for 5 or 10 error characters in 127 or 255 symbols to be corrected 
+## respectively. The number of errors that can be corrected can be overridden 
+## by the variable @var{t}.
+##
+## If the file is not an integer multiple of the message size (127 or 255)
+## in length, then the file is padded with the EOT (ascii character 4)
+## characters before coding. Whether these characters are written to the
+## output is defined by the @var{pad} variable. Valid values for @var{pad}
+## are "pad" (the default) and "nopad", which write or not the padding
+## respectively.
+##
+## @end deftypefn
+## @seealso{rsdecof}
+
+function rsencof(in, out, varargin)
+
+  if ((nargin < 2) || (nargin > 4))
+    usage("rsencof (in, out [, t [, pad]])");
+  endif
+
+  if (!ischar(in) || !ischar(out))
+    error ("rsencof: input and output filenames must be strings");
+  endif
+
+  t = 0;
+  pad = 1;
+  for i=1:length(varargin)
+    arg = varargin{i};
+    if (ischar(arg))
+      if (strcmp(arg,"pad"))
+       pad = 1;
+      elseif (strcmp(arg,"nopad"))
+       pad = 0;
+      else
+       error ("rsencof: unrecognized string argument");
+      endif
+    else
+      if (!isscalar(t) || (t != floor(d)) || (t < 1))
+       error ("rsencof: t must be a postive, non-zero integer");
+      endif
+    endif
+  end
+
+  try fid = fopen(in, "r");
+  catch
+    error ("rsencof: can not open input file");
+  end
+  [msg, count] = fread(fid, Inf, "char");
+  fclose(fid);
+
+  is8bit = (max(msg) > 127);
+
+  if (is8bit)
+    m = 8;
+    n = 255;
+    if (t == 0)
+      t = 10;
+    endif
+  else
+    m = 7;
+    n = 127;
+    if (t == 0)
+      t = 5;
+    endif
+  endif
+  k = n - 2 * t;
+
+  ncodewords = ceil(count / k);
+  npad = k * ncodewords - count;
+  msg = reshape([msg ; 4 * ones(npad,1)],k,ncodewords)';
+
+  code = rsenc(gf(msg,m), n, k,"beginning")';
+  code = code(:);
+
+  try fid = fopen(out, "w");
+  catch
+    error ("rsencof: can not open output file");
+  end
+  if (pad)
+    fwrite(fid, code, "char");
+  else
+    fwrite(fid, code(1:(ncodewords*n-npad)), "char");
+  endif
+  fclose(fid);
+
+endfunction