C++26: std::hive
The report discusses the introduction of std::hive in C++26, a new container that offers a unique combination of stability, efficiency, and cache locality. Unlike traditional containers like std::vector and std::list, std::hive uses multiple memory blocks instead of a single contiguous allocation. This design choice allows for O(1) amortized insertion and erasure operations while maintaining stable pointers and iterators.
The key features of std::hive include multiple memory blocks, a skipfield for efficient iteration past erased elements, and slot reuse for subsequent insertions. These design decisions make std::hive particularly suitable for applications like game engines, where multiple subsystems need to hold cross-references to entities without invalidating pointers and iterators.
The skipfield, which encodes the run length of consecutive erased slots, enables efficient iteration without the performance issues associated with boolean "is-alive" flags.
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