“Datum: A Compact Bitwise Copyable Variant Type”

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" summary

Datum is an eight byte compact variant on 32-bit that uses NaN-boxing of IEEE-754 doubles to represent regular doubles natively and repurpose NaN payload space for 15 discriminated types, remaining bitwise copyable and trivially destructible. Small strings up to six characters live inline with a length byte, larger strings allocate on the heap. Benchmarks compile with gcc 8 -O2, run 10k iterations creating 100k objects, and show substantially lower memory use and generally faster creation/access than std::variant except for some string/view cases.

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" chapters (19)

1. 0:00Introduction
2. 0:22Motivation for Datum
3. 1:08Bloomberg data representation
4. 4:02What is Datum
5. 4:44IEEE-754 double precision format
6. 7:42Datum value representation
7. 12:44Extended type discrimination
8. 14:10Heap allocation and destruction
9. 15:14String views in Datum
10. 16:1864-bit integer optimizations
11. 17:04Aggregate and recursive types
12. 17:2664-bit platform implementation
13. 18:10Datum vs std::variant comparison
14. 20:26Benchmark methodology
15. 21:31Performance results
16. 23:40Memory and allocation analysis
17. 24:22Conclusion and use cases
18. 24:44Datum availability and licensing
19. 25:30Q&A session