function BigInteger::toBytes

Returns a string of bytes containing the binary representation of this BigInteger.

The string is in big-endian byte-order: the most significant byte is in the zeroth element.

If `$signed` is true, the output will be in two's-complement representation, and a sign bit will be prepended to the output. If `$signed` is false, no sign bit will be prepended, and this method will throw an exception if the number is negative.

The string will contain the minimum number of bytes required to represent this BigInteger, including a sign bit if `$signed` is true.

This representation is compatible with the `fromBytes()` factory method, as long as the `$signed` flags match.

Parameters

bool $signed Whether to output a signed number in two's-complement representation with a leading sign bit.:

Throws

NegativeNumberException If $signed is false, and the number is negative.

File

vendor/brick/math/src/BigInteger.php, line 975

Class

BigInteger

An arbitrary-size integer.

Namespace

Brick\Math

Code

public function toBytes(bool $signed = true) : string {
    if (!$signed && $this->isNegative()) {
        throw new NegativeNumberException('Cannot convert a negative number to a byte string when $signed is false.');
    }
    $hex = $this->abs()
        ->toBase(16);
    if (\strlen($hex) % 2 !== 0) {
        $hex = '0' . $hex;
    }
    $baseHexLength = \strlen($hex);
    if ($signed) {
        if ($this->isNegative()) {
            $bin = \hex2bin($hex);
            assert($bin !== false);
            $hex = \bin2hex(~$bin);
            $hex = self::fromBase($hex, 16)->plus(1)
                ->toBase(16);
            $hexLength = \strlen($hex);
            if ($hexLength < $baseHexLength) {
                $hex = \str_repeat('0', $baseHexLength - $hexLength) . $hex;
            }
            if ($hex[0] < '8') {
                $hex = 'FF' . $hex;
            }
        }
        else {
            if ($hex[0] >= '8') {
                $hex = '00' . $hex;
            }
        }
    }
    return \hex2bin($hex);
}