Move br(count) attribute to desugar to binrw::helpers::count

jam1garner / binrw

A Rust crate for helping parse and rebuild binary data using ✨macro magic✨.

https://binrw.rs

MIT License

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Move br(count) attribute to desugar to binrw::helpers::count #52

Open jam1garner opened 3 years ago

jam1garner commented 3 years ago

Unlike the count attribute, which is limited to supporting Vec<T>, the count helper function works for any type which implements FromIterator<T>.

Upsides:

Less magic implementation, more type safe
Adds support for more types

Possible pitfalls:

Perf regression due to the lack of "fake specialization" provided for Vec<u8>
Breaking some existing use-case maybe?

roblabla commented 3 years ago

FWIW, if there's a measurable perf regression, this sounds exactly like the kind of use-cases where autoref specialization could be used to recover the lost perf.