hsivonen / hsivonen/encoding_rs

Port UTF-8 to UTF-16 and UTF-16 to UTF-8 conversions from simdutf

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Dominant language
Rust
Stars
464
Forks
70
Avg merge
2d 4h
Merged PRs (30d)
2

Description

Figure out the portable commonality of the AVX2 and aarch64 implementations in https://github.com/simdutf/simdutf/ and port them to core::simd and possible some vendor operations.

This should probably go into a separate crate to allow use without the non-UTF encodings supported by encoding_rs.

Instead of first validating the whole input, perhaps piecewise UTF-8 validation from the simdutf8 crate either needs to be exposed to the UTF-8 to UTF-16 conversion on copypasted.

Since the UTF-16 conversions use very large lookup tables, application-context benchmarking is probably needed to understand the cache effects and to decide what input is long enough for the extra cache evictions to be worth it.

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First steps

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  3. Fork the repository and make your change on a branch.
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Research direction

Start by comparing the AVX2 and aarch64 implementations in simdutf, then inspect core::simd, vendor operations, and the simdutf8 crate for portable UTF-8 validation. Define a separate-crate approach for UTF-8/UTF-16 conversion and benchmark realistic input sizes to evaluate lookup-table cache effects and determine when the optimized path is worthwhile.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
performance
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Quiet
Clarity
Needs clarification
Newbie friendliness
30/100

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