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## Copyright (C) 2007 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 2 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/>.
##
## This code was adapted from, Paul Kienzle <pkienzle@users.sf.net>
##
## -*- texinfo -*-
## @deftypefn {Function File} @var{rval}= {} base64decode(@var{code})
## @deftypefnx {Function File} @var{rval}= {} base64decode(@var{code},@var{as_string})
## convert a base64 @var{code} (a string of printable characters according to RFC 2045)
## into the original ASCII data set of range 0-255. If option @var{as_string} is
## passed, the return value is converted into a string.
##
## @example
## @group
## ##base64decode(base64encode('Hakuna Matata'),true)
## base64decode('SGFrdW5hIE1hdGF0YQ==',true)
## ##returns 'Hakuna Matata'
## @end group
## @end example
## @end deftypefn
## @seealso {base64encode}
##
##
## Y = base64decode(X)
##
## Convert X into string of printable characters according to RFC 2045.
## The input may be a string or a matrix of integers in the range 0..255.
##
## See: http://www.ietf.org/rfc/rfc2045.txt
##
function z = base64decode(X,as_string)
if (nargin < 1 )
usage("Y = base64decode(X); X need to be a 4-row N-col matrix");
elseif nargin == 1
as_string=false;
endif
if ( any(X(:) < 0) || any(X(:) > 255))
error("base64decode is expecting integers in the range 0 .. 255");
endif
##
## decompose strings into the 4xN matrices
## formatting issues.
##
if( rows(X) == 1 )
Y=[];
L=length(X);
for z=4:4:L
Y=[Y X(z-3:z)']; #keep adding columns
end
if min(size(Y))==1
Y=reshape(Y,[L, 1]);
else
Y=reshape(Y,[4,L/4]);
end
X=Y;
Y=[];
end
X = toascii(X);
Xa= X;
##
## Work backwards. Starting at step in table,
## lookup the index of the element in the table.
##
## 6-bit encoding table, plus 1 for padding
## 26*2 + 10 + 2 + 1 = 64 + 1, '=' is EOF stop mark.
table = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
S=size(X);
SRows=S(1);
SCols=S(2);
Y=zeros(S);
## decode the incoming matrix &
## write the values into Xa matrix.
##
for idx_r = 1:SRows
for idx_c=1:SCols
v=Xa(idx_r,idx_c);
w=-1;
if (v >= 'A' && v <= 'Z')
w=v-'A';
elseif (v >= 'a' && v<='z')
w=v-'a'+26;
elseif (v >= '0' && v<= '9')
w=v-'0'+52;
elseif (v == '+')
w=62;
elseif (v == '/')
w=63;
elseif (v == '=')
w=0;%ignore me
end
Xa(idx_r,idx_c)=w;
end
end
Y=Xa;
Y1=Y(1,:);
if (SRows > 1)
Y2=Y(2,:);
else
Y2=zeros(1,SCols);
end;
if (SRows > 2)
Y3=Y(3,:);
else
Y3=zeros(1,SCols);
end;
if (SRows > 3)
Y4=Y(4,:);
else
Y4=zeros(1,SCols);
end;
## +1 not required due to ASCII subtraction
## actual decoding work
b1 = Y1*4 + fix(Y2/16);
b2 = mod(Y2,16)*16+fix(Y3/4);
b3 = mod(Y3,4)*64 + Y4;
ZEROS=sum(sum(Y==0));
L=length(b1)*3;
z=zeros(1,L);
z(1:3:end)=b1;
if (SRows > 1)
z(2:3:end)=b2;
else
z(2:3:end)=[];
end;
if (SRows > 2)
z(3:3:end)=b3;
else
z(3:3:end)=[];
end
##
## FIXME
## is this expected behaviour?
##
if ( as_string )
L=length(z);
while ( ( L > 0) && ( z(L)==0 ) )
L=L-1;
end
z=char(z(1:L));
end
return
endfunction
%!
%!assert(base64decode(base64encode('Hakuna Matata'),true),'Hakuna Matata')
%!assert(base64decode(base64encode([1:255])),[1:255])
%!assert(base64decode(base64encode('taken'),true),'taken')
%!assert(base64decode(base64encode('sax'),true),'sax')
%!assert(base64decode(base64encode('H'),true),'H')
%!assert(base64decode(base64encode('Ta'),true),'Ta')
%!
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