a mutex with non-zero default-, and implicit uninitialized-state, hereafter 'the idea'. i herewith consider the idea public and attributable to degski, the administrator, hereafter 'the admin', of https://github.com/degski/non-zero-mutex , hereafter 'the repo'. the idea is particularly useful in lockless data structure designs.
in (the art of) programming for concurrency, the use of atomic flags is mandated in order to implement the 'Waiting on an Element'-idiom (the idiom is non-optional). the idiom entails that a non-zero atomic_flag (constructed with value == true) indicates (atomically) 'construction-is-finalized' of the specific object under construction, by virtue of being the last class member (in the definition order of the class). due to its unlocked state being non-zero*, defining a a non-zero mutex as the last member of (an) object allows for that mutex to cameo as a construction-finalized-flag while the object is under construction. after construction, the mutex allows for fine-grained locking. the uninitialized state is implicit by not being any of the possible valid states, including unlocked (value == 1). a read-write-spinlock, can be designed at zero-extra-cost as compared to a write-spinlock using the same basic design. the idea allows the user to not end up with a atomic variable that has to be set to true at all time when using the 'Waiting on an Element'-idiom*. the mutex offers an attractive alternative to the boolean construction flag.
an example implementation of the idea, a test-test-and-swap read-write spinlock, is implemented and included in the repo, hereafter 'the library'.
the library licensing follows the logic of the Microsoft Visual Studio 2019 licensing Scheme. the library is licensed under a fixed dual licensing scheme.
i herewith grant any entity that qualifies for a free Microsoft Visual Studio 2019 Community Edition License, the right to freely use this library subject to the MIT License.
any entitiy that does not qualify for a free license is required to obtain a commercial license.
- any entity that requires a commecial license, should contact the admin of the repo;
- the basis of the license-fee is last year's reported consolidated 12-month net turnover, hereafter 'the turnover';
- the annual license-fee, hereafter 'the fee', is calculated as €0.015 of fee / €1'000.00 of turnover;
- the fee is capped at €100'000;
- the fee is due in €;
- an implicit waiver is issued in case the annual fee does not surpass €100;
- the licensing scheme can not be modified;
- the commercial license will lapse to a free license after 20 years after publication of the repo.
send a proposal.