Convert Java Code to PHP: Convert signed hex value to big-endian binary?

[sookyboo]

Anyone know how to convert this java code to php?

 

// Take the signature passed, a signed hexadecimal value and

// and convert to a byte array in 2's compliment, big-endian.

// We wrap in a try-catch in case the signature is not a signed

// hexadecimal number

byte[] barray = new BigInteger(signature,16).toByteArray();

 

Thanks in advance

[btherl]

Try this:

 

$hex = $argv[1];

function hex_to_bytes($hex) {
  $intval = base_convert($hex, 16, 10);
  $mult = 1;
  $bytes = array();
  while ($intval > 0) {
    $bytes[] = $intval % 256;
    $intval = floor($intval / 256);
  }
  $bytes = array_reverse($bytes);
  return $bytes;
}

$bytes = hex_to_bytes($hex);
print "{$argv[1]} => " . implode(',', $bytes) . "\n";

 

It's written to run as a CLI script, but you can extract the function.

[sookyboo]

thanks I tried:

base_convert($hex, 16, 2);

The binary value is shorter than the hex value though... so... I am npt sure if its right...

 

I can only test if it really is the right value after I encrypt it, which I am also having trouble with

Thanks very much for the help though

 

http://www.phpfreaks.com/forums/index.php?topic=168552.new;topicseen#new

[btherl]

Are you looking for a bit array or byte array?

 

The value is probably shorter because the result is not fixed width.  Eg, if you convert hex "10" then you will get binary "10000", not binary "00010000".  You can pad it afterwards.

 

Also heed the warning on the base_convert() description - if you use this function for values greater than your int size (probably 32 bit) then it will use floating point, and you will lose precision.  So you must do the conversion in small enough chunks.