/usr/share/octave/packages/communications-1.2.0/rsdecof.m is in octave-communications-common 1.2.0-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 | ## 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} {} rsdecof (@var{in}, @var{out})
## @deftypefnx {Function File} {} rsdecof (@var{in}, @var{out}, @var{t})
##
## Decodes 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)
## character before decoding.
##
## @seealso{rsencof}
## @end deftypefn
function rsdecof (in, out, t)
if (nargin < 2 || nargin > 3)
print_usage ();
endif
if (!ischar (in) || !ischar (out))
error ("rsdecof: IN and OUT must be strings");
endif
if (nargin != 3)
t = 0;
else
if (! (isscalar (t) && t == fix (t) && t > 0))
error ("rsdecof: T must be a positive integer");
endif
endif
try fid = fopen (in, "rt");
catch
error ("rsdecof: could not open '%s' for reading", in);
end_try_catch
[code, count] = fread (fid, Inf, "char");
fclose (fid);
is8bit = (max (code) > 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 / n);
npad = n * ncodewords - count;
code = reshape ([code ; 4 * ones(npad, 1)], n, ncodewords)';
msg = rsdec (gf (code, m), n, k, "beginning")';
msg = msg(:);
try fid = fopen (out, "w+t");
catch
error ("rsdecof: could not open '%s' for writing", out);
end_try_catch
fwrite (fid, msg(1:(ncodewords*k-npad)), "char");
fclose (fid);
endfunction
%% Test input validation
%!error rsdecof ()
%!error rsdecof (1)
%!error rsdecof (1, 2, 3, 4)
%!error rsdecof (1, 2)
%!error rsdecof ("in", "out", 0)
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