Coder
分类: C/C++
2010-08-18 23:19:14
Name
uuid_generate, uuid_generate_random, uuid_generate_time - create a new
unique UUID value
Synopsis
#include <>
void uuid_generate(uuid_t out);
void uuid_generate_random(uuid_t out);
void uuid_generate_time(uuid_t out);
Description
The uuid_generate function creates a new universally unique
identifier (UUID). The uuid will be generated based on high-quality randomness
from
/dev/urandom, if
available. If it is not available, then uuid_generate
will use an alternative algorithm which uses the current time, the local
ethernet MAC address (if available), and random data generated using a
pseudo-random generator.
The uuid_generate_random function forces the use of the all-random
UUID format, even if a high-quality random number generator (i.e., /dev/urandom)
is not available, in which case a pseudo-random generator will be subsituted.
Note that the use of a pseudo-random generator may compromise the uniqueness of
UUID's generated in this fashion.
The uuid_generate_time function forces the use of the alternative
algorithm which uses the current time and the local ethernet MAC address (if
available). This algorithm used to be the default one used to generate UUID,
but because of the use of the ethernet MAC address, it can leak information
about when and where the UUID was generated. This can cause privacy problems in
some applications, so the uuid_generate function only uses this
algorithm if a high-quality source of randomness is not available.
The UUID is 16 bytes (128 bits) long, which gives approximately 3.4x10^38
unique values (there are approximately 10^80 elemntary particles in the
universe according to Carl Sagan's Cosmos). The new UUID can reasonably
be considered unique among all UUIDs created on the local system, and among
UUIDs created on other systems in the past and in the future.
Return Value
The newly created UUID is returned in the memory location pointed to by out.
Conforming To
OSF DCE 1.1
Author
Theodore Y. Ts'o
Availability
See Also
(3), (1),
(3), (3), (3), (3), (3), (3), (3)
Referenced By
(3)