Convert hex to ascii characters

Question

Is it possible to represent a sequence of hex characters (0-9A-F) with a sequence of 0-9a-zA-Z characters, so the the result sequence is smaller and can be decoded?

For example:

$hex = '5d41402abc4b2a76b9719d911017c592';
echo $string = encode($hex); // someASCIIletters123
echo decode(string) == $hex; //true

Answer 1

You can trivially adapt the solution I presented here using the function base_convert_arbitrary.

Edit: I had not read carefully enough :) Base 16 to base 62 is still very doable, as above.

See it in action.

Answer 2

I think you're looking for this:

function hex2str($hex) {
    $str = '';
    for($i=0;$i<strlen($hex);$i+=2) $str .= chr(hexdec(substr($hex,$i,2)));
    return $str;
}

(From http://www.linux-support.com/cms/php-convert-hex-strings-to-ascii-strings/) (Works like this javascript tool: http://www.dolcevie.com/js/converter.html)

Answer 3

You mean want to convert a string of hex digits into actual hex values?

$hex_string = "A1B2C3D4F5"; // 10 chars/bytes
$packed_string = pack('H*', $hex_string); // 0xA1B2C3D4F5 // 5 chars/bytes.

Answer 4

Well, something similar, yes... parse the hex characters as a binary value, then convert to base64. That uses a little bit more than 0-9 a-z A-Z, but only a few more characters. Are you okay to use three other characters in addition to those 62? You can use base64_encode to perform the encoding if so.

(You could convert to base32 instead, but that wouldn't be as compact. Converting to bases which aren't powers of 2 is also feasible, but less appealing.)

You'd also need some way of representing a final half-byte if your input sequence had an odd number of characters. You'll probably want to think about that before calling pack to do the original parsing...