Avoid throwing NotSupportedException in ReaderFactory hot path - #400
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adamhathcock merged 1 commit intoJul 10, 2018
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`ReaderFactory.Open()` calls `ZipArchive.IsZipFile()` to determine if the `Stream` is a zip archive, which calls into `ZipHeaderFactory.ReadHeader()`, which throws a `NotSupportedException` when the `Stream` is not a zip archive. To be clear, this exception is caught and `IsZipFile()` returns `false`, but when called in a hot-path, these exceptions can become expensive. To address this issue, `ReadHeader` now returns `null` in the default cause instead of throwing. All callsites were already checking for and handling `null`, so no behavior changes.
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Thanks, this does make more sense. |
This was referenced May 9, 2026
This was referenced Jul 24, 2026
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ReaderFactory.Open()callsZipArchive.IsZipFile()to determine if the stream is a zip archive, which calls intoZipHeaderFactory.ReadHeader(), which throws aNotSupportedExceptionwhen the bytes do not match a valid header.To be clear, this exception is caught and
IsZipFile()returnsfalse, but when called in a hot-path, these exceptions can become expensive.To address this issue,
ReadHeadernow returnsnullin the default cause instead of throwing. All callsites were already checking for and handlingnull, so no behavior should change.