input_string_2_L_array.m

%
% inputstring_2_L_array function
%
function [out, k] = input_string_2_L_array(s_input, d, subtype)
    % fixed coefficients
    b = 1600;
    c = 2 * d;
    r = b - c; % rate,  for every r-bit a section
    %
    s_len = length(s_input);
    s = char();
    for is = 1 : s_len
        s = strcat(s, dec2hex(double(s_input(is)), 2));
    end
    %
    r8 = r / 8; % every 1 char == 2 hex digits == 8-bit
    k = floor(s_len / r8) + 1;
    sr = mod(s_len, r8);
    %
    % 2 kinds of padding
    if strcmp(subtype, 'HASH') == 1
        if sr == r8 - 1
            s = strct(s, dec2hex(128 + 6, 2)); % padding 01100001
        elseif sr ~= r8 - 1
            s = strcat(s, dec2hex(6, 2)); % padding 01100000 ... 
            for i = 1 : (r8 - sr - 2)
                s = strcat(s, '00'); % padding ... 00000000 ...
            end
            s = strcat(s, dec2hex(128, 2)); % padding ... 00000001
        end
    elseif strcmp(subtype, 'XOF') == 1
        if sr == r8 - 1
            % padding 11111001 in reverse order, which means msb is actually the right-most bit
            s = strcat(s, dec2hex(128 + 16 + 15, 2));
        elseif sr ~= r8 - 1
            s = strcat(s, dec2hex(16 + 15, 2)); % padding 111110000 ... 
            for i = 1 : (r8 - sr - 2)
                s = strcat(s, '00'); % padding ... 00000000 ...
            end
            s = strcat(s, dec2hex(128, 2)); % padding ... 00000001
        end 
    end
    %
    % convert the message into the lane array
    r64 = r / 64; 
    Lk = char();
    index = 2;
    for ik = 1 : k
        for iy = 0 : 4
            for ix = 0 : 4
                % 2 conditions
                if (ix + 5*iy + 1) <= r64
                    for iz = 0 : 7
                        % fetch 2 hex-digit a time
                        Lk(ix + 1, iy + 1, 2*(8-iz) - 1 : 2*(8-iz), ik) = s(index - 1 : index);
                        index = index + 2;
                    end
                else
                    % padding 16 binary zero(4 hex-digit zero)
                    Lk(ix + 1, iy + 1, :, ik) = '0000000000000000';
                end
            end
        end
    end
    out = Lk;
    % [out, k] = [Lk, k];
return