cpptooling.utility.global_unique source code

1 /**
2 Copyright: Copyright (c) 2017, Joakim Brännström. All rights reserved.
3 License: MPL-2
4 Author: Joakim Brännström (joakim.brannstrom@gmx.com)
5 
6 This Source Code Form is subject to the terms of the Mozilla Public License,
7 v.2.0. If a copy of the MPL was not distributed with this file, You can obtain
8 one at http://mozilla.org/MPL/2.0/.
9 
10 Contains facilities to generate globally unique numbers.
11 */
12 module cpptooling.utility.global_unique;
13 
14 private shared(size_t) _nextSequence;
15 
16 static this() {
17     // Use a fixed number to minimize the difference between two sets of
18     // generated data.
19     //
20     // Keeping it fixed to make it easier to debug, read the logs. Aka
21     // reproduce the result.
22     //
23     // It is extremly important to minimize differences.
24     // Diffs are used as the basis to evaluate changes.
25     // No diff, no evaluation needed from an architectural point of view.
26     // A change? Further inspection needed.
27     _nextSequence = 42;
28 }
29 
30 size_t nextNumber() @trusted nothrow {
31     import core.atomic;
32 
33     size_t rval;
34 
35     synchronized {
36         if (_nextSequence == size_t.max) {
37             _nextSequence = size_t.min;
38         }
39 
40         core.atomic.atomicOp!"+="(_nextSequence, 1);
41         rval = _nextSequence;
42     }
43 
44     return rval;
45 }