function BigInteger::randomBits

Generates a pseudo-random number in the range 0 to 2^numBits - 1.

Using the default random bytes generator, this method is suitable for cryptographic use.

@psalm-param (callable(int): string)|null $randomBytesGenerator

Parameters

int $numBits The number of bits.:

callable|null $randomBytesGenerator A function that accepts a number of bytes as an integer, and returns a: string of random bytes of the given length. Defaults to the `random_bytes()` function.

Throws

\InvalidArgumentException If $numBits is negative.

1 call to BigInteger::randomBits()

BigInteger::randomRange in vendor/brick/math/src/BigInteger.php

Generates a pseudo-random number between `$min` and `$max`.

File

vendor/brick/math/src/BigInteger.php, line 213

Class

BigInteger

An arbitrary-size integer.

Namespace

Brick\Math

Code

public static function randomBits(int $numBits, ?callable $randomBytesGenerator = null) : BigInteger {
    if ($numBits < 0) {
        throw new \InvalidArgumentException('The number of bits cannot be negative.');
    }
    if ($numBits === 0) {
        return BigInteger::zero();
    }
    if ($randomBytesGenerator === null) {
        $randomBytesGenerator = random_bytes(...);
    }
    
    /** @var int<1, max> $byteLength */
    $byteLength = \intdiv($numBits - 1, 8) + 1;
    $extraBits = $byteLength * 8 - $numBits;
    $bitmask = \chr(0xff >> $extraBits);
    $randomBytes = $randomBytesGenerator($byteLength);
    $randomBytes[0] = $randomBytes[0] & $bitmask;
    return self::fromBytes($randomBytes, false);
}