Byte operations

M

Matesax

Guest
Hi,
in BASH script I need to write (append) dword aligned string (that's stored in variable - UTF-8 - aligned by zero char) to one file. And also append two integer variables into this file - with word alignment. (word (2 bytes) + word = dword => I need dword (4 bytes) aligned record) How can I make this in easy way? (dword dword dword dword ... word word dword dword dword ... word word dword ...) (blab lah\0 0xA2B5 0xC4D8 lore m\ ip sum\0 0x1852 ...)
Thank you.
 
Last edited:


M

Matesax

Guest
OK - I have:
Code:
printf %.4x numberHere | xxd -r -p >> FileTable
BUT - how can I write in Little Endian - only manualy? (AA55 as 55AA)
($((43605 & 255)) and $((43605 >> 8)) looks very horrible)
Thank you.

OK - result:
Code:
writeInteger()
{
    printf %.4x $(((($1 & 255) << 8) | ($1 >> 8))) | xxd -r -p >> $temp/FileTable
}

...

    writeInteger $total
    writeInteger $count

    fileName=`basename $1`
    echo -n $fileName >> $temp/FileTable
    align=$((`echo -n $fileName | wc -c` % 4))

    if [ $align -gt 0 ]
    then
        truncate -s +$((4 - $align)) $temp/FileTable
    fi
It works, but I think, that it can be better...

Simple output:
Code:
06 00 04 00 65 64 69 74 2E 62 69 6E 0A 00 03 00 66 69 6C 65 6D 61 6E 2E 62 69 6E 00 0D 00 08 00 68 61 6E 67 6D 61 6E 2E 62 69 6E 00 15 00 02 00 6B 65 79 62 6F 61 72 64 2E 62 69 6E 17 00 02 00 6D 6F 6E 69 74 6F 72 2E 62 69 6E 00 19 00 01 00 73 65 72 69 61 6C 2E 62 69 6E 00 00 1A 00 02 00 76 69 65 77 65 72 2E 62 69 6E 00 00 1C 00 AA 03 74 65 73 74 2E 62 6D 70
 
Last edited:
M

Matesax

Guest
Yes! :D
Code:
writeIntegers()
{
    perl <<END
    open FS, '>>', "$temp/FileTable" or die "Unable to open: $!";
    print FS pack('v', $1), pack('v', $2);
    close FS;
END
}

...

perl <<END
    open FS, '+<', "$fs" or die "Unable to open: $!";
    seek FS, 689, 0;
    print FS pack('s<', $total), pack('s<', $count);
    close FS;
END
 
Last edited:


Members online


Top