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fix: tolerate a FAT entry that points past the file under Permissive - #91
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A FAT entry pointing beyond the last sector rejected the whole file even when no chain ran through it. Under Permissive validation the entry now ends its chain instead, so only a stream that actually uses that sector is truncated. Strict validation still rejects the file.
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Fixes #80.
A FAT entry pointing beyond the last sector rejected the whole file even when no chain ran through it, unlike the neighbouring FAT and DIFAT marker checks, which repair under
Permissive. The entry now ends its chain underPermissive, so only a stream that actually uses that sector is affected (its read fails withUnexpectedEof);Strictstill rejects the file with the same message.Ending the chain rather than marking the sector free keeps it off the free list, so it cannot be handed out for new data, and a chain reaching it truncates instead of erroring on the walk.
Tests include the reproduction from the issue, its
Strictcounterpart, and a case where a live chain runs through the bad entry.