64 lines
1.5 KiB
PHP
64 lines
1.5 KiB
PHP
<?php
|
|
|
|
namespace FG\ASN1;
|
|
|
|
use FG\Utility\BigInteger;
|
|
use InvalidArgumentException;
|
|
|
|
/**
|
|
* A base-128 decoder.
|
|
*/
|
|
class Base128
|
|
{
|
|
/**
|
|
* @param int $value
|
|
*
|
|
* @return string
|
|
*/
|
|
public static function encode($value)
|
|
{
|
|
$value = BigInteger::create($value);
|
|
$octets = chr($value->modulus(0x80)->toInteger());
|
|
|
|
$value = $value->shiftRight(7);
|
|
while ($value->compare(0) > 0) {
|
|
$octets .= chr(0x80 | $value->modulus(0x80)->toInteger());
|
|
$value = $value->shiftRight(7);
|
|
}
|
|
|
|
return strrev($octets);
|
|
}
|
|
|
|
/**
|
|
* @param string $octets
|
|
*
|
|
* @throws InvalidArgumentException if the given octets represent a malformed base-128 value or the decoded value would exceed the the maximum integer length
|
|
*
|
|
* @return int
|
|
*/
|
|
public static function decode($octets)
|
|
{
|
|
$bitsPerOctet = 7;
|
|
$value = BigInteger::create(0);
|
|
$i = 0;
|
|
|
|
while (true) {
|
|
if (!isset($octets[$i])) {
|
|
throw new InvalidArgumentException(sprintf('Malformed base-128 encoded value (0x%s).', strtoupper(bin2hex($octets)) ?: '0'));
|
|
}
|
|
|
|
$octet = ord($octets[$i++]);
|
|
|
|
$l1 = $value->shiftLeft($bitsPerOctet);
|
|
$r1 = $octet & 0x7f;
|
|
$value = $l1->add($r1);
|
|
|
|
if (0 === ($octet & 0x80)) {
|
|
break;
|
|
}
|
|
}
|
|
|
|
return (string)$value;
|
|
}
|
|
}
|