Question

What is a simple way to convert a 64 bit integer encoded as a hex string to a decimal string on a 32 bit system. It needs to be the full value, it can not be in scientific notation or truncated :/

“0c80000000000063” == “900719925474099299”

“0c80000000000063” != 9.007199254741E+17

PHP’s base_convert() and hexdec() don’t do the job right.

Answer 1

You need to use BC Math PHP extension (bundled).

First split your input string to get high and low bytes, next convert it to decimal and then do calculation via BC functions like this:

$input = "0C80000000000063";

$str_high = substr($input, 0, 8);
$str_low = substr($input, 8, 8);

$dec_high = hexdec($str_high);
$dec_low  = hexdec($str_low);

//workaround for argument 0x100000000
$temp = bcmul ($dec_high, 0xffffffff);
$temp2 = bcadd ($temp, $dec_high);

$result = bcadd ($temp2, $dec_low);

echo $result;

/*
900719925474099299
*/