blob: f163006d1495ba9e30459b8538b249115cb610bc (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
// file : libbutl/uuid-freebsd.cxx -*- C++ -*-
// copyright : Copyright (c) 2014-2019 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#ifndef BUILD2_BOOTSTRAP
#include <libbutl/uuid.hxx>
#include <sys/uuid.h>
#include <errno.h>
#include <cassert>
#include <cstring> // memcpy()
#include <system_error>
using namespace std;
namespace butl
{
void
uuid_throw_weak (); // uuid.cxx
uuid uuid_system_generator::
generate (bool strong)
{
// While FreeBSD shares the uuid_*() (<uuid.h>, uuid(3)) API with other
// BSDs, its documentation is quite light on the kind of UUID we get and
// with what guarantees. The implementation of uuid_create() simply calls
// the uuidgen() system call (<sys/uuid.h>, uuidgen(2)) which has some
// details.
//
// Specifically (and as of FreeBSD 11.2), we get a version 1 (MAC/time-
// based) UUID and it seems there is provision for getting the time in a
// collision-safe:
//
// "According to the algorithm of generating time-based UUIDs, this will
// also force a new random clock sequence, thereby increasing the
// likelihood for the identifier to be unique."
//
// So we will assume a MAC/time-based UUID is strong. We also assume a
// random UUID is strong as well in case in the future this will becomes
// the default (as seems to be the trend); presumably, FreeBSD folks are
// smart enough not to start return random UUIDs without a good source of
// randomness, at least not by default.
//
struct ::uuid d;
if (uuidgen (&d, 1) != 0)
throw system_error (errno, system_category ());
uuid r;
// This is effectively just memcpy() but let's reference the member names
// in case anything changes on either side.
//
r.time_low = d.time_low;
r.time_mid = d.time_mid;
r.time_hiv = d.time_hi_and_version;
r.clock_seq_hir = d.clock_seq_hi_and_reserved;
r.clock_seq_low = d.clock_seq_low;
memcpy (r.node, d.node, 6);
assert (r.variant () == uuid_variant::dce); // Sanity check.
if (strong)
{
switch (r.version ())
{
case uuid_version::time:
case uuid_version::random: break;
default: uuid_throw_weak ();
}
}
return r;
}
void uuid_system_generator::
initialize ()
{
}
void uuid_system_generator::
terminate ()
{
}
}
#endif // BUILD2_BOOTSTRAP
|
