(Please CC your replies to me, I'm not on the list.) An initial version of the .xz file format decoder for Linux is now available at <git://ctrl.tukaani.org/xz-embedded.git>. It supports both stateful and single-call decoding using the LZMA2 algorithm.
Two buffers (1.2 KiB and 28 KiB) are allocated with kmalloc() for internal data. For stateful decoding, also a dictionary is allocated with vmalloc(), which probably will usually be from 64 KiB to 1 MiB. The dictionary is allocated when the decoder is created, so the decoder never allocates memory in the middle of decoding. This means that if the preallocated dictionary was too small for the input stream, decoding will fail. In single-call mode, the destination buffer is used as the dictionary, thus a separate dictionary doesn't need to be allocated. On x86, xz_dec.ko is 11-14 KiB. Stack usage is around 120-240 bytes, depending on the GCC version and compiler flags. I hope it is not too much, but I can try to reduce it slightly if needed. BCJ filters are not added yet. They will increase the code size a little but they should save more space by increasing compression ratio of executables (and naturally it will be possible to disable these filters in the kernel config). There is some code (mostly in xz_boot.c), which hopefully makes it easier to add support for XZ compressed kernel and initramfs. I hope that someone else does the actual work to get XZ support in the arch- specific trees (IIRC, there were some patches to add bzip2 and LZMA support already), but I'm happy to help if my code needs some adjustments to support that work. I have tried to follow to the kernel coding style as well as I can, but if there are style issues that should be fixed, please let me know. I want to keep the code usable outside Linux, which why there are some extra #ifdefs and such. I hope this is OK. I haven't tested the code much yet. It appears to work in userspace. The kernel module compiles cleanly on x86, but I haven't tested it in kernel space, because I currently have no code to feed data to the XZ decoder in the kernel space. -- Lasse Collin | IRC: Larhzu @ IRCnet & Freenode -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
