Add basic support for squashfs #837
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Seems the rest of clippy errors are on unrelated code. The UI tests really tripped me. 😅 Seems a single |
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Fixes #830
The code mostly follows Zip implementations, using internal buffers for
Seekrequirement.Unresolved questions:
Which extension to mention in docs?
.squashfsor.sqfs?I'm currently picking
sqfs.There is not canonical extension for squashfs, but there are two semi-official ones:
.squashfs: The most popular one from a quick search on GitHub. Also used by some distros.https://github.com/NixOS/nixpkgs/blob/6576d979e9a64d870b1f298a5c598116891a6c25/nixos/modules/installer/cd-dvd/iso-image.nix#L797
.sqfs: Mentioned inman mksquashfsby squashfs-tools, the reference implementation.https://github.com/plougher/squashfs-tools/blob/9f9bbd79016ff04967800f4301c7a9d0024c0c91/Documentation/manpages/mksquashfs.1#L494
backhanddependsliblzma, a maintainedxz2fork, which conflicts with our dependencyxz2. I disabled the Xz support ofbackhandto mitigate this. How can we fix this?How to pass compression options for squashfs compressor? It is done inside squashfs format (per-chunk compression) thus does not use chained formats. We probably need a new CLI argument for it.
Currently, during compression, it buffers the whole squashfs in memory but we can write directly into file (which supports
Seek). We did a special case in decompression, but it causes some code duplication and we does not do this for Zip compression either. Is there a better way to do so, or should we also add a special case in compression?Do we want streaming compression support
.sqfs.zstd(archive-then-compress instead or compress-per-chunk)? It could be done using some tricks like reserving spaces and emit ZSTD Literal Frame. Not sure about other compression formats. I don't think we want to support this, at least for now, given that decompression cannot be streamed anyway.How should we support multiple input paths? Typically squashfs has a single "root directory". Currently, it reports an error if the input is not a single path to a directory. It would be weird to either "merge" all paths into one tree, or put multiple directory under the root directory (What mode/permission should the root use? Surprising behavior difference between one and more than one paths.).