xz_dec_run(9)

💜 xz_dec_run(9) — the one that actually runs the XZ decoder 💜

okay so bestie, welcome to xz_dec_run(9) from the Kernel API Manual — yes the kernel has a whole manpage vibe and honestly? iconic. this is the function that literally runs the XZ decoder. let's get into it 🫶

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✨ SYNOPSIS ✨

enum xz_ret xz_dec_run (struct xz_dec *s , struct xz_buf *b );

like, that's it. two args. slay.

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🎀 ARGUMENTS 🎀

• s — the decoder state, and no you can't just make one up out of thin air, it has to be allocated using xz_dec_init. main character energy only 💅
• b — the input and output buffers. that's the whole vibe, in and out.

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🦋 DESCRIPTION 🦋

so the possible return values depend on build options and operation mode — like, it's giving ✨situational✨. for the details you gotta go see enum xz_ret. iykyk 🌈

⚠️ okay this part is important, don't skip it ⚠️

note that if an error occurs in single-call mode (aka the return value is not XZ_STREAM_END), then b->in_pos and b->out_pos are not modified, and the contents of the output buffer from b->out[b->out_pos] onward are undefined. 😭 like literally undefined-undefined, not "probably fine"-undefined.

and bestie, this is true even after XZ_BUF_ERROR — because with some filter chains, there may be a second pass over the output buffer, and that pass cannot be properly done if the output buffer is truncated. so no, you cannot hand the single-call decoder a too-small buffer and then expect to get that amount of valid data from the beginning of the stream. that's not how any of this works, ngl 💀

translation: if you don't want to uncompress the whole entire stream, you must use the multi-call decoder. periodt. 🔥

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🌸 SEE ALSO 🌸

• Kernel file ./include/linux/xz.h
• enum xz_mode(9)
• enum xz_ret(9)
• struct xz_buf(9)
• xz_dec_init(9)
• xz_dec_reset(9)
• xz_dec_end(9)
• MicroLZMA decompressor(9)
• xz_dec_microlzma_alloc(9)
• xz_dec_microlzma_reset(9)
• xz_dec_microlzma_run(9)
• xz_dec_microlzma_end(9)

like a whole little friend group of functions, obsessed 💖

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and that's the page!! this one lives over in ./include/linux and it's dated October 2026 — so go forth and decode responsibly, bestie. mwah 💋✨🧚