Functions
random.h File Reference

Thread safe random functions. More...

Functions

void ub_systemseed (unsigned int seed)
 Initialize the system randomness. More...
 
struct ub_randstate * ub_initstate (unsigned int seed, struct ub_randstate *from)
 Initialize a random generator state for use. More...
 
long int ub_random (struct ub_randstate *state)
 Generate next random number from the state passed along. More...
 
long int ub_random_max (struct ub_randstate *state, long int x)
 Generate random number between 0 and x-1. More...
 
void ub_randfree (struct ub_randstate *state)
 Delete the random state. More...
 

Detailed Description

Thread safe random functions.

Similar to arc4random() with an explicit initialisation routine.

Function Documentation

◆ ub_systemseed()

void ub_systemseed ( unsigned int  seed)

Initialize the system randomness.

Obtains entropy from the system before a chroot or privilege makes it unavailable. You do not have to call this, otherwise ub_initstate does so.

Parameters
seedseed value to create state (if no good entropy is found).

◆ ub_initstate()

struct ub_randstate* ub_initstate ( unsigned int  seed,
struct ub_randstate *  from 
)

Initialize a random generator state for use.

Parameters
seedseed value to create state contents. (ignored for arc4random).
fromif not NULL, the seed is taken from this random structure. can be used to seed random states via a parent-random-state that is itself seeded with entropy.
Returns
new state or NULL alloc failure.

Referenced by daemon_create_workers(), libworker_setup(), rnd_test(), ub_ctx_create_nopipe(), and worker_create().

◆ ub_random()

long int ub_random ( struct ub_randstate *  state)

Generate next random number from the state passed along.

Thread safe, so random numbers are repeatable.

Parameters
statemust have been initialised with ub_initstate.
Returns
: random 31 bit value.

Referenced by libworker_setup(), pending_tcp_query(), rnd_test(), select_id(), and serviced_perturb_qname().

◆ ub_random_max()

long int ub_random_max ( struct ub_randstate *  state,
long int  x 
)

Generate random number between 0 and x-1.

No modulo bias.

Parameters
statemust have been initialised with ub_initstate.
xan upper limit. not (negative or zero). must be smaller than 2**31.
Returns
: random value between 0..x-1. Possibly more than one random number is picked from the random stream to satisfy this.

Referenced by calc_next_probe(), iter_ns_probability(), iter_server_selection(), pick_outgoing_tcp(), rnd_test(), and select_ifport().

◆ ub_randfree()

void ub_randfree ( struct ub_randstate *  state)

Delete the random state.

Parameters
stateto delete.

Referenced by daemon_delete(), libworker_delete_env(), rnd_test(), ub_ctx_create(), ub_ctx_create_nopipe(), and ub_ctx_delete().