UnigramDev/Unigram/ocr-extract-recovery • c3efb81 • 1 files, +64/-20
Recover from a damaged OCR model archive

Extracting Ocr_x64.zip crashed the app with an InvalidDataException,
"The archive entry was compressed using an unsupported compression
method". The message is misleading: Inflater maps zlib's Z_DATA_ERROR
onto that string, and the failure came from mid-entry writes in
DeflateStream.CopyToAsyncStream rather than from ZipArchiveEntry.Open,
so the deflate data was corrupt or truncated, not compressed with a
method the reader doesn't support. Why the local copy was damaged is
not established.

ExtractModelAsync had no try/catch and RecognizeText is async void, so
the failure reached the app unhandled. Catch it, delete the archive so
that the next attempt downloads a fresh copy, delete the partially
written model so that the readiness check in EnsureReadyAsync doesn't
accept it, and report the extraction as unavailable.

Separately, _extractLock.Release() sat outside any finally, so a throw
during extraction leaked the semaphore for the rest of the session:
every later extraction then returned early at Wait(0), leaving OCR
broken until restart.

Reported by crash telemetry on 12.9.1.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

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