dumpfile: Use named escapes and only escape '=' in xattr fields#271
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cgwalters wants to merge 3 commits intocomposefs:mainfrom
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dumpfile: Use named escapes and only escape '=' in xattr fields#271cgwalters wants to merge 3 commits intocomposefs:mainfrom
cgwalters wants to merge 3 commits intocomposefs:mainfrom
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The composefs-dump(5) spec leaves several fields unspecified or explicitly ignored. Canonicalize them at parse time so that parsed entries have a single canonical representation regardless of which implementation produced them: - **Directory sizes**: "This is ignored for directories." Drop the size field from Item::Directory, always emit 0. - **Hardlink metadata**: "We ignore all the fields except the payload." Zero uid/gid/mode/mtime and skip xattrs, matching the C parser which bails out early (mkcomposefs.c:477-491). - **Xattr ordering**: The spec doesn't define an order. Sort lexicographically so output is deterministic regardless of on-disk ordering. The parser still accepts any input values for backward compatibility. Assisted-by: OpenCode (Claude Opus 4) Signed-off-by: Colin Walters <walters@verbum.org>
XFS limits symlink targets to 1024 bytes, and since generic Linux containers are commonly backed by XFS, enforce that limit in both the dumpfile parser and the EROFS reader rather than allowing up to PATH_MAX (4096). This also avoids exercising a known limitation in our EROFS reader where symlink data that spills into a non-inline data block (which can happen with long symlinks + xattrs) is not read back correctly. See composefs/composefs#342 for the corresponding C fix for that edge case. Assisted-by: OpenCode (Claude Opus 4) Signed-off-by: Colin Walters <walters@verbum.org>
Increase alignment for dumpfile generation with the composefs C implementation - on general principle but also motivated by the goal of reimplementing it in Rust here. The C composefs implementation uses named escapes for backslash, newline, carriage return, and tab (\\ \n \r \t), while our writer was hex-escaping them uniformly (\x5c \x0a etc). Both forms parse correctly, but byte-identical output matters for cross-implementation comparison. Similarly, C only escapes '=' in xattr key/value fields (where it separates key from value). We were escaping it as \x3d in all fields including paths and content, where '=' is a normal graphic character. Assisted-by: OpenCode (Claude Opus 4) Signed-off-by: Colin Walters <walters@verbum.org>
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Increase alignment for dumpfile generation with the composefs C implementation - on general principle but also motivated by the goal of reimplementing it in Rust here.
The C composefs implementation uses named escapes for backslash, newline, carriage return, and tab (\ \n \r \t), while our writer was hex-escaping them uniformly (\x5c \x0a etc). Both forms parse correctly, but byte-identical output matters for cross-implementation comparison.
Similarly, C only escapes '=' in xattr key/value fields (where it separates key from value). We were escaping it as \x3d in all fields including paths and content, where '=' is a normal graphic character.
Assisted-by: OpenCode (Claude Opus 4)