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/* 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
* 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 <>.
* This file is based on code from XZ embedded project
#ifndef XZ_H
#define XZ_H
#include <stdint.h>
#include <unistd.h>
#include <string.h>
#include <grub/misc.h>
typedef enum { false = 0, true = 1 } bool;
* 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 {
* 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);