How can i speed up the following for loop?

Hi everyone,

I have a large .bin file. I read the .bin file and swap the bytes by modulo 4 and write to txt file. For example consider the .bin files starts with bytes.

D0 40 03 BC 00 FB 03 00 04 01 00 02 0F 00 C1 38 00 39 00 0F 00 0F 00 EE FF BB CC DD ...

After I swap the bytes I get

BC 03 40 D0 00 03 FB 00 02 00 01 04 38 C1 00 0F 0F 00 39 00 EE 00 0F 00 DD CC BB FF and so on.

After writing to a txt file I get

BC 03 40 D0

00 03 FB 00

02 00 01 04

38 C1 00 0F

0F 00 39 00

EE 00 0F 00

DD CC BB FF

Here is my code:

FID_Huz_file        = fopen(Huz_file_path);
Huz_file_Data_total = fread(FID_Huz_file);
Huz_file_Data       = Huz_file_Data_total(1:huz_file_lenght); -- lenght is calculated somewhere before this line
Huz_file_hex        = dec2hex(Huz_file_Data);

Huz_data_text_dir   = fullfile(Huz_data_text);
Huz_data_text_fid   = fopen(Huz_data_text_dir,'w');
[row, ~] = size(Huz_file_hex);
tic;
for i = 1:row/4
    temp_array = Huz_file_hex((4*(i-1)+1):4*i,:);
    
    for j = 1:4
        temp_array_valid (j,:) =  temp_array(5-j,:);
    end
    
    for j = 1:4
        temp_array_tp((2*j-1:2*j)) = temp_array_valid(j,:);
    end
    
    fprintf(Huz_data_text_fid,'%s\n',temp_array_tp);
end
toc;
fclose(Huz_data_text_fid);

The problem is when Huz_file_Data is very big (greater then 40 MB) it takes to much to create txt file. Here are some performance statisitics for several .bin files.

Bin file length : 54525952 Byte

huz_file_lenght : 5112320 Byte

Elapsed time is 16.610973 seconds.

--------------------------------------------------

Bin file length : 54525952 Byte

huz_file_lenght : 10224124 Byte

Elapsed time is 16.610973 seconds.

--------------------------------------------------

Bin file length : 54525952 Byte

huz_file_lenght : 20447744 Byte

Elapsed time is 58.783637 seconds

--------------------------------------------------

Bin file length : 54525952 Byte

huz_file_lenght : 40894976 Byte

Elapsed time is 127.972875 seconds.