VHDX LogEntry.TryRead() Bug Fix and Improvements #5
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I made some changes back in 2017 in the DiscUtils/DiscUtils repo, and then more recently noticed a bug in this code related to those changes. I originally opened a pull request in DiscUtils/DiscUtils with changes very similar to these, but that repo is basically abandoned, so I ported the changes for this repo. |
glenebob
commented
Feb 29, 2024
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| var sig = EndianUtilities.ToUInt32LittleEndian(sectorBuffer, 0); |
glenebob
commented
Feb 29, 2024
| var header = new LogEntryHeader(); | ||
| header.ReadFrom(sectorBuffer.AsSpan(0, LogSectorSize)); | ||
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| if (!header.IsValid || header.EntryLength > logStream.Length) |
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This data availability check would be broken when working within a stream starting at an offset > 0. ReadMaximum() below does the availability check correctly.
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Thanks a lot for the contribution! I'll just take a look at the changes before I merge the PR. But it looks like a good improvement. |
Change LogEntryHeader member variables to properties. Read header into 64-byte, stackalloc'd buffer, then read remaining bytes directly into logEntryBuffer. Remove buggy byte availability calculation. Remove redundant signature check (which is done in LogEntryHeader.IsValid). Use ReadMaximum instread of ReadExactly to guarantee no exception will be thrown, and use its return value to verify correct byte count.
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Change LogEntryHeader member variables to properties.
Read header into 64-byte, stackalloc'd buffer, then read remaining bytes directly into logEntryBuffer.
Remove buggy byte availability calculation.
Remove redundant signature check (which is done in LogEntryHeader.IsValid).
Use ReadMaximum() instread of ReadExactly() to guarantee no exception will be thrown, and use its return value to verify correct byte count.