/usr/share/octave/packages/communications-1.2.1/huffmandeco.m is in octave-communications-common 1.2.1-2.
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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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 | ## Copyright (C) 2006 Muthiah Annamalai <muthiah.annamalai@uta.edu>
## Copyright (C) 2011 Ferran Mesas Garcia <ferran.mesas01@gmail.com>
##
## 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} {@var{sig} =} huffmandeco (@var{hcode}, @var{dict})
## Decode signal encoded by @code{huffmanenco}.
##
## This function uses a dict built from the
## @code{huffmandict} and uses it to decode a signal list into a Huffman
## list. A restriction is that @var{hcode} is expected to be a binary code
##
## The returned @var{sig} set that strictly belongs in the range @code{[1,N]}
## with @code{N = length (@var{dict})}. Also @var{dict} can only be from the
## @code{huffmandict} routine. Whenever decoding fails, those signal values a
## re indicated by @code{-1}, and we successively try to restart decoding
## from the next bit that hasn't failed in decoding, ad-infinitum. An example
## of the use of @code{huffmandeco} is:
##
## @example
## @group
## hd = huffmandict (1:4, [0.5 0.25 0.15 0.10]);
## hcode = huffmanenco (1:4, hd);
## back = huffmandeco (hcode, hd)
## @result{} [1 2 3 4]
## @end group
## @end example
## @seealso{huffmandict, huffmanenco}
## @end deftypefn
function symbols = huffmandeco (hcode, dict)
if (nargin != 2)
print_usage ();
elseif (!all ((hcode == 1) + (hcode == 0)) || !isvector (hcode))
error ("huffmandeco: HCODE must be a binary vector");
elseif (! iscell (dict))
error ("huffmandeco: DICT must be a dictionary from huffmandict");
endif
## Convert the Huffman Dictionary to a Huffman Tree represented by
## an array.
tree = dict2tree (dict);
## Traverse the tree and store the symbols.
symbols = [];
pointer = 1; # a pointer to a node of the tree.
for i = 1:length (hcode);
if (tree(pointer) != -1)
symbols = [symbols, tree(pointer)];
pointer = 1;
endif
pointer = 2 * pointer + hcode(i);
endfor
## Check if decodification was successful
if (tree(pointer) == -1)
warning ("huffmandeco: could not decode last symbol")
endif
symbols = [symbols, tree(pointer)];
endfunction
function tree = dict2tree (dict)
L = length (dict);
lengths = zeros (1, L);
## the depth of the tree is limited by the maximum word length.
for i = 1:L
lengths(i) = length (dict{i});
endfor
m = max (lengths);
tree = zeros (1, 2^(m+1)-1)-1;
for i = 1:L
pointer = 1;
word = dict{i};
for bit = word
pointer = 2 * pointer + bit;
endfor
tree(pointer) = i;
endfor
endfunction
%!assert (huffmandeco (huffmanenco (1:4, huffmandict (1:4, [0.5 0.25 0.15 0.10])), huffmandict (1:4, [0.5 0.25 0.15 0.10])), [1:4], 0)
%!assert (huffmandeco (huffmanenco ([1:100 100:-1:1], huffmandict (1:100, ones (1, 100)/100)), huffmandict (1:100, ones (1, 100)/100)), [1:100 100:-1:1], 0)
%!assert (huffmandeco ([huffmanenco(1:4, huffmandict (1:4, [0.5 0.25 0.15 0.10])) 0], huffmandict (1:4, [0.5 0.25 0.15 0.10])), [1:4 -1], 0)
%!fail ("huffmandeco ([huffmanenco(1:4, huffmandict (1:4, [0.5 0.25 0.15 0.10])) 0], huffmandict (1:4, [0.5 0.25 0.15 0.10]))", "warning")
%!fail ("huffmandeco ('this is not a code', huffmandict (1:4, [0.5 0.25 0.15 0.10]))")
%!fail ("huffmandeco ([1 0 1 0], 'this is not a dictionary')")
%% Test input validation
%!error huffmandeco ()
%!error huffmandeco (1)
%!error huffmandeco (1, 2, 3)
%!error huffmandeco (1, 2)
%!error huffmandeco (2, {})
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