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#include <sys/libkern.h>
#include <sys/random.h>
The arc4rand() function will return very good quality random numbers, better suited for security-related purposes. The random numbers from arc4rand() are seeded from the entropy device if it is available. Automatic reseeds happen after a certain timeinterval and after a certain number of bytes have been delivered. A forced reseed can be forced by passing a non-zero value in the reseed argument.
The read_random() function is used to return entropy directly from the entropy device if it has been loaded. If the entropy device is not loaded, then the buffer is ignored and zero is returned. The buffer is filled with no more than count bytes. It is strongly advised that read_random() is not used; instead use arc4rand() unless it is necessary to know that no entropy has been returned.
The read_random_uio() function behaves identically to read(2) on /dev/random. The uio argument points to a buffer where random data should be stored. This function only returns data if the random device is seeded. It blocks if unseeded, except when the nonblock argument is true.
All the bits returned by random(), arc4rand(), read_random(), and read_random_uio() are usable. For example, 'random()&01' will produce a random binary value.
The arc4random() is a convenience function which calls arc4rand() to return a 32 bit pseudo-random integer.
The arc4rand() function uses the RC4 algorithm to generate successive pseudo-random bytes. The arc4random() function uses arc4rand() to generate pseudo-random numbers in the range from 0 to 232-1.
The read_random() function returns the number of bytes placed in buffer.
read_random_uio() returns zero when successful, otherwise an error code is returned.
[EFAULT] | |
uio points to an invalid memory region. | |
[EWOULDBLOCK] | |
The random device is unseeded and nonblock is true. | |
RANDOM (9) | July 16, 2015 |
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