File Content: Flags.php <?php declare (strict_types=1); namespace Platform360\SpomkyLabs\Pki\ASN1\Util; use Platform360\Brick\Math\BigInteger; use OutOfBoundsException; use RuntimeException; use Platform360\SpomkyLabs\Pki\ASN1\Type\Primitive\BitString; use function assert; use function count; use function is_array; use function ord; /** * Class to handle a bit string as a field of flags. * @see \SpomkyLabs\Pki\Test\ASN1\Util\FlagsTest */ final class Flags { /** * Flag octets. */ private string $_flags; /** * @param BigInteger|int|string $flags Flags * @param int $_width The number of flags. If width is larger than * number of bits in $flags, zeroes are prepended * to flag field. */ private function __construct(BigInteger|int|string $flags, private readonly int $_width) { if ($_width === 0) { $this->_flags = ''; return; } // calculate number of unused bits in last octet $last_octet_bits = $_width % 8; $unused_bits = $last_octet_bits !== 0 ? 8 - $last_octet_bits : 0; // mask bits outside bitfield width $num = BigInteger::of($flags); $mask = BigInteger::of(1)->shiftedLeft($_width)->minus(1); $num = $num->and($mask); // shift towards MSB if needed $data = $num->shiftedLeft($unused_bits)->toBytes(\false); $octets = \unpack('C*', $data); assert(is_array($octets), new RuntimeException('unpack() failed')); $bits = count($octets) * 8; // pad with zeroes while ($bits < $_width) { \array_unshift($octets, 0); $bits += 8; } $this->_flags = \pack('C*', ...$octets); } public static function create(BigInteger|int|string $flags, int $_width) : self { return new self($flags, $_width); } /** * Initialize from `BitString`. */ public static function fromBitString(BitString $bs, int $width) : self { $num_bits = $bs->numBits(); $data = $bs->string(); $num = $data === '' ? BigInteger::of(0) : BigInteger::fromBytes($bs->string(), \false); $num = $num->shiftedRight($bs->unusedBits()); if ($num_bits < $width) { $num = $num->shiftedLeft($width - $num_bits); } return self::create($num, $width); } /** * Check whether a bit at given index is set. * * Index 0 is the leftmost bit. */ public function test(int $idx) : bool { if ($idx >= $this->_width) { throw new OutOfBoundsException('Index is out of bounds.'); } // octet index $oi = (int) \floor($idx / 8); $byte = $this->_flags[$oi]; // bit index $bi = $idx % 8; // index 0 is the most significant bit in byte $mask = 0x1 << 7 - $bi; return (ord($byte) & $mask) > 0; } /** * Get flags as an octet string. * * Zeroes are appended to the last octet if width is not divisible by 8. */ public function string() : string { return $this->_flags; } /** * Get flags as a base 10 integer. * * @return string Integer as a string */ public function number() : string { $num = BigInteger::fromBytes($this->_flags, \false); $last_octet_bits = $this->_width % 8; $unused_bits = $last_octet_bits !== 0 ? 8 - $last_octet_bits : 0; $num = $num->shiftedRight($unused_bits); return $num->toBase(10); } /** * Get flags as an integer. */ public function intNumber() : int { $num = BigInt::create($this->number()); return $num->toInt(); } /** * Get flags as a `BitString` object. * * Unused bits are set accordingly. Trailing zeroes are not stripped. */ public function bitString() : BitString { $last_octet_bits = $this->_width % 8; $unused_bits = $last_octet_bits !== 0 ? 8 - $last_octet_bits : 0; return BitString::create($this->_flags, $unused_bits); } } Submit