matklad / once_cell

Rust library for single assignment cells and lazy statics without macros

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AlmostOnceCell

tkaitchuck opened this issue · comments

As an alternative to #61 or #53
in the case of a no_std environment where lazy initialization is needed, it would be useful to have an implementation which did not block (and hence depend on locking) or spin, but simply re-ran the initialization logic.

So if the initialization has been completed the existing result is used. However if init is attempted from multiple threads concurrently, then it just gets run more than once. For cases where the init is deterministic this provides a clean, zero-dependency, solution.

Well it does look inconsistent with the others. I don't know if there is a reason for that.
Unsync has Lazy and OnceCell,
Sync has Lazy and OnceCell,
but Race has OnceBox, OnceNonZeroUsize and OnceBool.

OnceBox appears to be the same as OnceCell in the others but is not named similarly. (It's docs look copied and pasted and make no mention of races).
Lazy is missing. I don't know if there is a reason for that. But if not it is useful and would be good to add.
The other two classes I haven't considered as they don't fit my app's needs.