uint32_t
randomid(
randomid_t ctx
)
randomid_t
randomid_new(
int bits
, long timeo
)
void
randomid_delete(
randomid_t ctx
)
)
function provides pseudo-random data stream,
which is guaranteed not to generate the same number twice during
a certain duration.
ctx
is the context which holds internal state for the random number generator.
To initialize a context,
randomid_new
is used.
bits
specifies the bitwidth of the value generated by
randomid().
Currently 32, 20, and 16 are supported.
timeo
specifies the reinitialization interval in seconds.
timeo
has to be bigger than
RANDOMID_TIMEO_MIN
.
randomid_new
returns a dynamically-allocated memory region allocated by
malloc(3).
randomid_delete()
will
free(3)
the internal state
ctx
.
The same number may appear after two reinitialization events of the internal state,
ctx
.
Reinitialization happens when the random number generator cycle is exhausted,
or
timeo
seconds have passed since the last reinitialization.
For instance,
ctx
configured to generate 16 bit data stream will reinitialize its internal state
every 30000 calls to
randomid()
(or after
timeo
seconds,)
therefore the same data will not appear until after 30000 calls to
randomid()
timeo
seconds
(or after.)
The internal state,
ctx
,
determines the data stream generated by
randomid().
ctx
must be allocated per data stream
(such as a specific data field).
It must not be shared among multiple data streams with different usage.
#include <stdio.h>
#include <sys/types.h>
#include <randomid.h>
uint32_t
genid(void)
{
static randomid_t ctx = NULL;
if (!ctx)
ctx = randomid_new(16, (long)3600);
return randomid(ctx);
}
)
returns
NULL
on error and sets the external variable
errno.
)
is a generalized version of the generator, reworked by Jun-ichiro itojun Hagino,
and was introduced in
NetBSD2.0.