fix(7z): handle empty-stream entries in WriteToDirectory (fixes #1217)#1218
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YoshihiroIto wants to merge 1 commit intoadamhathcock:masterfrom
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fix(7z): handle empty-stream entries in WriteToDirectory (fixes #1217)#1218YoshihiroIto wants to merge 1 commit intoadamhathcock:masterfrom
YoshihiroIto wants to merge 1 commit intoadamhathcock:masterfrom
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- Handles zero-byte files in 7z archives by returning a null stream. - Adds a test to verify that writing an archive containing an empty stream to a directory does not throw an exception. - Adds a new archive to the test suite.
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Code Review SummaryStatus: No Issues Found | Recommendation: Merge Files Reviewed (2 files)
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adamhathcock
approved these changes
Feb 14, 2026
Owner
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Looks sound. I'll probably base it on release to get it out faster. |
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Pull request overview
Fixes a 7z extraction crash in the solid-extraction reader path by treating valid “empty stream” entries (HasStream == false) as zero-byte files during WriteToDirectory.
Changes:
- Add an early
HasStreamguard inSevenZipArchive.SevenZipReader.GetEntryStream()to return an empty stream for empty-stream entries. - Add a regression test that exercises the real failing API (
WriteToDirectory) against a dedicated 7z fixture. - Add a new test archive containing an empty-stream file entry.
Reviewed changes
Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/SharpCompress/Archives/SevenZip/SevenZipArchive.cs | Avoids null-folder dereference by short-circuiting empty-stream entries to Stream.Null. |
| tests/SharpCompress.Test/SevenZip/SevenZipArchiveTests.cs | Adds regression coverage for WriteToDirectory extracting an empty-stream entry without throwing and producing a zero-byte file. |
| tests/TestArchives/Archives/7Zip.EmptyStream.7z | New fixture archive to reproduce the empty-stream entry scenario. |
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Owner
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Been merged into master now |
Owner
|
Originally contributed by @YoshihiroIto in #1218 (ported to release in #1219). |
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Summary
Fixes a
NullReferenceExceptionwhen extracting 7z archives that contain empty-stream file entries (HasStream == false) viaWriteToDirectory.This PR addresses: #1217
Root cause
In
SevenZipArchivereader flow, non-directory entries were always routed to folder stream handling.For valid 7z empty-stream file entries, no folder stream exists, and this led to a null-folder dereference downstream.
Changes
SevenZipArchiveentry stream creation:!entry.FilePart.Header.HasStream, returnCreateEntryStream(Stream.Null).WriteToDirectory) with7Zip.EmptyStream.7z.tests/TestArchives/Archives/7Zip.EmptyStream.7zWhy this is correct
For 7z empty-stream file entries, the correct behavior is to create an empty output file without attempting folder-
based decompression.
Returning
Stream.Nullpreserves that behavior and avoids the NRE.Verification
NullReferenceExceptionfrom 7z extraction path duringWriteToDirectory.7Zip.EmptyStream.7z.dotnet test tests/SharpCompress.Test/SharpCompress.Test.csproj -c Release --filter "SevenZipArchive_EmptyStream_WriteToDirectory_DoesNotThrow"