[neekolas]

Browser archive reads make a second JavaScript byte-array copy before copying the bytes into WASM memory. Use a checked Uint8Array cast to remove that allocation and save up to 100 MB per read. The 100,000,000-byte file limit, returned bytes, and byte-based import API stay unchanged.

Extend the existing boundary test to observe real typed-array constructor copies. It fails on the old reader and passes on this change. The full Browser migration suite and Rust/JavaScript formatting pass. The tested source and 259 staged assets plus five shipping artifacts remain unchanged.

This follows the merged migration PR #4455.

Note

Avoid duplicate Uint8Array copy in wasm migration archive reader

In wasm.rs, read no longer builds a new JavaScript Uint8Array from the value returned by read_output. It downcasts that value directly to Uint8Array and converts it to a Rust vector.

Behavioral Change: values that fail the downcast now return the mapped output error instead of being wrapped in a new array.

^{Macroscope summarized b19684f.}

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This is a narrowly scoped optimization that removes an intermediate browser byte-array copy while preserving archive limits and returned data, with focused regression coverage. Because it changes the production browser migration reader, human review is required for this migration-path change.

^{You can add or adjust custom eligibility rules. Learn more.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.93%. Comparing base (334dd7f) to head (b19684f).

Additional details and impacted files

@@               Coverage Diff               @@
##           self-hosted    #4500      +/-   ##
===============================================
+ Coverage        87.91%   87.93%   +0.02%     
===============================================
  Files              549      549              
  Lines           104073   104073              
===============================================
+ Hits             91497    91518      +21     
+ Misses           12576    12555      -21     

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