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