/* xz.h - XZ decompressor */ /* * GRUB -- GRand Unified Bootloader * Copyright (C) 2010 Free Software Foundation, Inc. * * GRUB is free software: you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation, either version 3 of the License, or * (at your option) any later version. * * GRUB is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with GRUB. If not, see <http://www.gnu.org/licenses/>. */ /* * This file is based on code from XZ embedded project * http://tukaani.org/xz/embedded.html */ #ifndef XZ_H #define XZ_H #include <stdint.h> /** * enum xz_ret - Return codes * @XZ_OK: Everything is OK so far. More input or more output * space is required to continue. * @XZ_STREAM_END: Operation finished successfully. * @XZ_MEMLIMIT_ERROR: Not enough memory was preallocated at decoder * initialization time. * @XZ_FORMAT_ERROR: File format was not recognized (wrong magic bytes). * @XZ_OPTIONS_ERROR: This implementation doesn't support the requested * compression options. In the decoder this means that * the header CRC32 matches, but the header itself * specifies something that we don't support. * @XZ_DATA_ERROR: Compressed data is corrupt. * @XZ_BUF_ERROR: Cannot make any progress. Details are slightly * different between multi-call and single-call mode; * more information below. * * In multi-call mode, XZ_BUF_ERROR is returned when two consecutive calls * to XZ code cannot consume any input and cannot produce any new output. * This happens when there is no new input available, or the output buffer * is full while at least one output byte is still pending. Assuming your * code is not buggy, you can get this error only when decoding a compressed * stream that is truncated or otherwise corrupt. * * In single-call mode, XZ_BUF_ERROR is returned only when the output buffer * is too small, or the compressed input is corrupt in a way that makes the * decoder produce more output than the caller expected. When it is * (relatively) clear that the compressed input is truncated, XZ_DATA_ERROR * is used instead of XZ_BUF_ERROR. */ enum xz_ret { XZ_OK, XZ_STREAM_END, XZ_MEMLIMIT_ERROR, XZ_FORMAT_ERROR, XZ_OPTIONS_ERROR, XZ_DATA_ERROR, XZ_BUF_ERROR }; /** * struct xz_buf - Passing input and output buffers to XZ code * @in: Beginning of the input buffer. This may be NULL if and only * if in_pos is equal to in_size. * @in_pos: Current position in the input buffer. This must not exceed * in_size. * @in_size: Size of the input buffer * @out: Beginning of the output buffer. This may be NULL if and only * if out_pos is equal to out_size. * @out_pos: Current position in the output buffer. This must not exceed * out_size. * @out_size: Size of the output buffer * * Only the contents of the output buffer from out[out_pos] onward, and * the variables in_pos and out_pos are modified by the XZ code. */ struct xz_buf { const uint8_t *in; size_t in_pos; size_t in_size; uint8_t *out; size_t out_pos; size_t out_size; }; /** * struct xz_dec - Opaque type to hold the XZ decoder state */ struct xz_dec; /** * xz_dec_init() - Allocate and initialize a XZ decoder state * @dict_max: Maximum size of the LZMA2 dictionary (history buffer) for * multi-call decoding, or special value of zero to indicate * single-call decoding mode. * * If dict_max > 0, the decoder is initialized to work in multi-call mode. * dict_max number of bytes of memory is preallocated for the LZMA2 * dictionary. This way there is no risk that xz_dec_run() could run out * of memory, since xz_dec_run() will never allocate any memory. Instead, * if the preallocated dictionary is too small for decoding the given input * stream, xz_dec_run() will return XZ_MEMLIMIT_ERROR. Thus, it is important * to know what kind of data will be decoded to avoid allocating excessive * amount of memory for the dictionary. * * LZMA2 dictionary is always 2^n bytes or 2^n + 2^(n-1) bytes (the latter * sizes are less common in practice). In the kernel, dictionary sizes of * 64 KiB, 128 KiB, 256 KiB, 512 KiB, and 1 MiB are probably the only * reasonable values. * * If dict_max == 0, the decoder is initialized to work in single-call mode. * In single-call mode, xz_dec_run() decodes the whole stream at once. The * caller must provide enough output space or the decoding will fail. The * output space is used as the dictionary buffer, which is why there is * no need to allocate the dictionary as part of the decoder's internal * state. * * Because the output buffer is used as the workspace, streams encoded using * a big dictionary are not a problem in single-call. It is enough that the * output buffer is is big enough to hold the actual uncompressed data; it * can be smaller than the dictionary size stored in the stream headers. * * On success, xz_dec_init() returns a pointer to struct xz_dec, which is * ready to be used with xz_dec_run(). On error, xz_dec_init() returns NULL. */ struct xz_dec * xz_dec_init(uint32_t dict_max); /** * xz_dec_run() - Run the XZ decoder * @s: Decoder state allocated using xz_dec_init() * @b: Input and output buffers * * In multi-call mode, this function may return any of the values listed in * enum xz_ret. * * In single-call mode, this function never returns XZ_OK. If an error occurs * in single-call mode (return value is not XZ_STREAM_END), 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. * * NOTE: In single-call mode, the contents of the output buffer are undefined * also after XZ_BUF_ERROR. This is because with some filter chains, there * may be a second pass over the output buffer, and this pass cannot be * properly done if the output buffer is truncated. Thus, you cannot give * the single-call decoder a too small buffer and then expect to get that * amount valid data from the beginning of the stream. You must use the * multi-call decoder if you don't want to uncompress the whole stream. */ enum xz_ret xz_dec_run(struct xz_dec *s, struct xz_buf *b); /** * xz_dec_reset() - Reset an already allocated decoder state * @s: Decoder state allocated using xz_dec_init() * * This function can be used to reset the multi-call decoder state without * freeing and reallocating memory with xz_dec_end() and xz_dec_init(). * * In single-call mode, xz_dec_reset() is always called in the beginning of * xz_dec_run(). Thus, explicit call to xz_dec_reset() is useful only in * multi-call mode. */ void xz_dec_reset(struct xz_dec *s); /** * xz_dec_end() - Free the memory allocated for the decoder state * @s: Decoder state allocated using xz_dec_init(). If s is NULL, * this function does nothing. */ void xz_dec_end(struct xz_dec *s); #endif