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/*
* XZ decompressor
*
* Authors: Lasse Collin <lasse.collin@tukaani.org>
* Igor Pavlov <https://7-zip.org/>
*
* This file has been put into the public domain.
* You can do whatever you want with this file.
*/
#ifndef XZ_H
#define XZ_H
#ifdef __KERNEL__
# include <linux/stddef.h>
# include <linux/types.h>
#else
# include <stddef.h>
# include <stdint.h>
#endif
/* In Linux, this is used to make extern functions static when needed. */
#ifndef XZ_EXTERN
# define XZ_EXTERN extern
#endif
/**
* enum xz_mode - Operation mode
*
* @XZ_SINGLE: Single-call mode. This uses less RAM than
* multi-call modes, because the LZMA2
* dictionary doesn't need to be allocated as
* part of the decoder state. All required data
* structures are allocated at initialization,
* so xz_dec_run() cannot return XZ_MEM_ERROR.
* @XZ_PREALLOC: Multi-call mode with preallocated LZMA2
* dictionary buffer. All data structures are
* allocated at initialization, so xz_dec_run()
* cannot return XZ_MEM_ERROR.
* @XZ_DYNALLOC: Multi-call mode. The LZMA2 dictionary is
* allocated once the required size has been
* parsed from the stream headers. If the
* allocation fails, xz_dec_run() will return
* XZ_MEM_ERROR.
*
* It is possible to enable support only for a subset of the above
* modes at compile time by defining XZ_DEC_SINGLE, XZ_DEC_PREALLOC,
* or XZ_DEC_DYNALLOC. The xz_dec kernel module is always compiled
* with support for all operation modes, but the preboot code may
* be built with fewer features to minimize code size.
*/
enum xz_mode {
XZ_SINGLE,
XZ_PREALLOC,
XZ_DYNALLOC
};
/**
* enum xz_ret - Return codes
* @XZ_OK: Everything is OK so far. More input or more
* output space is required to continue. This
* return code is possible only in multi-call mode
* (XZ_PREALLOC or XZ_DYNALLOC).
* @XZ_STREAM_END: Operation finished successfully.
* @XZ_UNSUPPORTED_CHECK: Integrity check type is not supported. Decoding
* is still possible in multi-call mode by simply
* calling xz_dec_run() again.
* Note that this return value is used only if
* XZ_DEC_ANY_CHECK was defined at build time,
* which is not used in the kernel. Unsupported
* check types return XZ_OPTIONS_ERROR if
* XZ_DEC_ANY_CHECK was not defined at build time.
* @XZ_MEM_ERROR: Allocating memory failed. This return code is
* possible only if the decoder was initialized
* with XZ_DYNALLOC. The amount of memory that was
* tried to be allocated was no more than the
* dict_max argument given to xz_dec_init().
* @XZ_MEMLIMIT_ERROR: A bigger LZMA2 dictionary would be needed than
* allowed by the dict_max argument given to
* xz_dec_init(). This return value is possible
* only in multi-call mode (XZ_PREALLOC or
* XZ_DYNALLOC); the single-call mode (XZ_SINGLE)
* ignores the dict_max argument.
* @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_UNSUPPORTED_CHECK,
XZ_MEM_ERROR,
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
* @mode: Operation mode
* @dict_max: Maximum size of the LZMA2 dictionary (history buffer) for
* multi-call decoding. This is ignored in single-call mode
* (mode == XZ_SINGLE). LZMA2 dictionary is always 2^n bytes
* or 2^n + 2^(n-1) bytes (the latter sizes are less common
* in practice), so other values for dict_max don't make sense.
* In the kernel, dictionary sizes of 64 KiB, 128 KiB, 256 KiB,
* 512 KiB, and 1 MiB are probably the only reasonable values,
* except for kernel and initramfs images where a bigger
* dictionary can be fine and useful.
*
* Single-call mode (XZ_SINGLE): 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 mode. It is enough that
* the output buffer is big enough to hold the actual uncompressed data; it
* can be smaller than the dictionary size stored in the stream headers.
*
* Multi-call mode with preallocated dictionary (XZ_PREALLOC): dict_max 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.
*
* Multi-call mode with dynamically allocated dictionary (XZ_DYNALLOC):
* dict_max specifies the maximum allowed dictionary size that xz_dec_run()
* may allocate once it has parsed the dictionary size from the stream
* headers. This way excessive allocations can be avoided while still
* limiting the maximum memory usage to a sane value to prevent running the
* system out of memory when decompressing streams from untrusted sources.
*
* On success, xz_dec_init() returns a pointer to struct xz_dec, which is
* ready to be used with xz_dec_run(). If memory allocation fails,
* xz_dec_init() returns NULL.
*/
XZ_EXTERN struct xz_dec *xz_dec_init(enum xz_mode mode, uint32_t dict_max);
/**
* xz_dec_run() - Run the XZ decoder
* @s: Decoder state allocated using xz_dec_init()
* @b: Input and output buffers
*
* The possible return values depend on build options and operation mode.
* See enum xz_ret for details.
*
* Note that 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. This is true even after XZ_BUF_ERROR, 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.
*/
XZ_EXTERN 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.
*/
XZ_EXTERN 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.
*/
XZ_EXTERN void xz_dec_end(struct xz_dec *s);
/*
* Decompressor for MicroLZMA, an LZMA variant with a very minimal header.
* See xz_dec_microlzma_alloc() below for details.
*
* These functions aren't used or available in preboot code and thus aren't
* marked with XZ_EXTERN. This avoids warnings about static functions that
* are never defined.
*/
/**
* struct xz_dec_microlzma - Opaque type to hold the MicroLZMA decoder state
*/
struct xz_dec_microlzma;
/**
* xz_dec_microlzma_alloc() - Allocate memory for the MicroLZMA decoder
* @mode XZ_SINGLE or XZ_PREALLOC
* @dict_size LZMA dictionary size. This must be at least 4 KiB and
* at most 3 GiB.
*
* In contrast to xz_dec_init(), this function only allocates the memory
* and remembers the dictionary size. xz_dec_microlzma_reset() must be used
* before calling xz_dec_microlzma_run().
*
* The amount of allocated memory is a little less than 30 KiB with XZ_SINGLE.
* With XZ_PREALLOC also a dictionary buffer of dict_size bytes is allocated.
*
* On success, xz_dec_microlzma_alloc() returns a pointer to
* struct xz_dec_microlzma. If memory allocation fails or
* dict_size is invalid, NULL is returned.
*
* The compressed format supported by this decoder is a raw LZMA stream
* whose first byte (always 0x00) has been replaced with bitwise-negation
* of the LZMA properties (lc/lp/pb) byte. For example, if lc/lp/pb is
* 3/0/2, the first byte is 0xA2. This way the first byte can never be 0x00.
* Just like with LZMA2, lc + lp <= 4 must be true. The LZMA end-of-stream
* marker must not be used. The unused values are reserved for future use.
* This MicroLZMA header format was created for use in EROFS but may be used
* by others too.
*/
extern struct xz_dec_microlzma *xz_dec_microlzma_alloc(enum xz_mode mode,
uint32_t dict_size);
/**
* xz_dec_microlzma_reset() - Reset the MicroLZMA decoder state
* @s Decoder state allocated using xz_dec_microlzma_alloc()
* @comp_size Compressed size of the input stream
* @uncomp_size Uncompressed size of the input stream. A value smaller
* than the real uncompressed size of the input stream can
* be specified if uncomp_size_is_exact is set to false.
* uncomp_size can never be set to a value larger than the
* expected real uncompressed size because it would eventually
* result in XZ_DATA_ERROR.
* @uncomp_size_is_exact This is an int instead of bool to avoid
* requiring stdbool.h. This should normally be set to true.
* When this is set to false, error detection is weaker.
*/
extern void xz_dec_microlzma_reset(struct xz_dec_microlzma *s,
uint32_t comp_size, uint32_t uncomp_size,
int uncomp_size_is_exact);
/**
* xz_dec_microlzma_run() - Run the MicroLZMA decoder
* @s Decoder state initialized using xz_dec_microlzma_reset()
* @b: Input and output buffers
*
* This works similarly to xz_dec_run() with a few important differences.
* Only the differences are documented here.
*
* The only possible return values are XZ_OK, XZ_STREAM_END, and
* XZ_DATA_ERROR. This function cannot return XZ_BUF_ERROR: if no progress
* is possible due to lack of input data or output space, this function will
* keep returning XZ_OK. Thus, the calling code must be written so that it
* will eventually provide input and output space matching (or exceeding)
* comp_size and uncomp_size arguments given to xz_dec_microlzma_reset().
* If the caller cannot do this (for example, if the input file is truncated
* or otherwise corrupt), the caller must detect this error by itself to
* avoid an infinite loop.
*
* If the compressed data seems to be corrupt, XZ_DATA_ERROR is returned.
* This can happen also when incorrect dictionary, uncompressed, or
* compressed sizes have been specified.
*
* With XZ_PREALLOC only: As an extra feature, b->out may be NULL to skip over
* uncompressed data. This way the caller doesn't need to provide a temporary
* output buffer for the bytes that will be ignored.
*
* With XZ_SINGLE only: In contrast to xz_dec_run(), the return value XZ_OK
* is also possible and thus XZ_SINGLE is actually a limited multi-call mode.
* After XZ_OK the bytes decoded so far may be read from the output buffer.
* It is possible to continue decoding but the variables b->out and b->out_pos
* MUST NOT be changed by the caller. Increasing the value of b->out_size is
* allowed to make more output space available; one doesn't need to provide
* space for the whole uncompressed data on the first call. The input buffer
* may be changed normally like with XZ_PREALLOC. This way input data can be
* provided from non-contiguous memory.
*/
extern enum xz_ret xz_dec_microlzma_run(struct xz_dec_microlzma *s,
struct xz_buf *b);
/**
* xz_dec_microlzma_end() - Free the memory allocated for the decoder state
* @s: Decoder state allocated using xz_dec_microlzma_alloc().
* If s is NULL, this function does nothing.
*/
extern void xz_dec_microlzma_end(struct xz_dec_microlzma *s);
/*
* Standalone build (userspace build or in-kernel build for boot time use)
* needs a CRC32 implementation. For normal in-kernel use, kernel's own
* CRC32 module is used instead, and users of this module don't need to
* care about the functions below.
*/
#ifndef XZ_INTERNAL_CRC32
# ifdef __KERNEL__
# define XZ_INTERNAL_CRC32 0
# else
# define XZ_INTERNAL_CRC32 1
# endif
#endif
#if XZ_INTERNAL_CRC32
/*
* This must be called before any other xz_* function to initialize
* the CRC32 lookup table.
*/
XZ_EXTERN void xz_crc32_init(void);
/*
* Update CRC32 value using the polynomial from IEEE-802.3. To start a new
* calculation, the third argument must be zero. To continue the calculation,
* the previously returned value is passed as the third argument.
*/
XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc);
#endif
#endif