265 lines
11 KiB
C
265 lines
11 KiB
C
/*
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* XZ decompressor
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*
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* Authors: Lasse Collin <lasse.collin@tukaani.org>
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* Igor Pavlov <http://7-zip.org/>
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*
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* This file has been put into the public domain.
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* You can do whatever you want with this file.
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*/
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#ifndef XZ_H
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#define XZ_H
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#ifdef __KERNEL__
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# include <linux/stddef.h>
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# include <linux/types.h>
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#else
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# include <stddef.h>
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# include <stdint.h>
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#endif
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/* In Linux, this is used to make extern functions static when needed. */
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#ifndef XZ_EXTERN
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# define XZ_EXTERN extern
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#endif
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/**
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* enum xz_mode - Operation mode
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*
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* @XZ_SINGLE: Single-call mode. This uses less RAM than
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* than multi-call modes, because the LZMA2
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* dictionary doesn't need to be allocated as
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* part of the decoder state. All required data
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* structures are allocated at initialization,
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* so xz_dec_run() cannot return XZ_MEM_ERROR.
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* @XZ_PREALLOC: Multi-call mode with preallocated LZMA2
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* dictionary buffer. All data structures are
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* allocated at initialization, so xz_dec_run()
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* cannot return XZ_MEM_ERROR.
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* @XZ_DYNALLOC: Multi-call mode. The LZMA2 dictionary is
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* allocated once the required size has been
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* parsed from the stream headers. If the
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* allocation fails, xz_dec_run() will return
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* XZ_MEM_ERROR.
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*
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* It is possible to enable support only for a subset of the above
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* modes at compile time by defining XZ_DEC_SINGLE, XZ_DEC_PREALLOC,
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* or XZ_DEC_DYNALLOC. The xz_dec kernel module is always compiled
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* with support for all operation modes, but the preboot code may
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* be built with fewer features to minimize code size.
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*/
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enum xz_mode {
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XZ_SINGLE,
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XZ_PREALLOC,
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XZ_DYNALLOC
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};
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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
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* output space is required to continue. This
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* return code is possible only in multi-call mode
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* (XZ_PREALLOC or XZ_DYNALLOC).
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* @XZ_STREAM_END: Operation finished successfully.
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* @XZ_UNSUPPORTED_CHECK: Integrity check type is not supported. Decoding
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* is still possible in multi-call mode by simply
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* calling xz_dec_run() again.
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* Note that this return value is used only if
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* XZ_DEC_ANY_CHECK was defined at build time,
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* which is not used in the kernel. Unsupported
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* check types return XZ_OPTIONS_ERROR if
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* XZ_DEC_ANY_CHECK was not defined at build time.
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* @XZ_MEM_ERROR: Allocating memory failed. This return code is
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* possible only if the decoder was initialized
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* with XZ_DYNALLOC. The amount of memory that was
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* tried to be allocated was no more than the
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* dict_max argument given to xz_dec_init().
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* @XZ_MEMLIMIT_ERROR: A bigger LZMA2 dictionary would be needed than
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* allowed by the dict_max argument given to
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* xz_dec_init(). This return value is possible
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* only in multi-call mode (XZ_PREALLOC or
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* XZ_DYNALLOC); the single-call mode (XZ_SINGLE)
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* ignores the dict_max argument.
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* @XZ_FORMAT_ERROR: File format was not recognized (wrong magic
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* 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
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* that the header CRC32 matches, but the header
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* itself 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
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* mode; 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_UNSUPPORTED_CHECK,
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XZ_MEM_ERROR,
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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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* @mode: Operation mode
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* @dict_max: Maximum size of the LZMA2 dictionary (history buffer) for
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* multi-call decoding. This is ignored in single-call mode
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* (mode == XZ_SINGLE). LZMA2 dictionary is always 2^n bytes
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* or 2^n + 2^(n-1) bytes (the latter sizes are less common
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* in practice), so other values for dict_max don't make sense.
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* In the kernel, dictionary sizes of 64 KiB, 128 KiB, 256 KiB,
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* 512 KiB, and 1 MiB are probably the only reasonable values,
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* except for kernel and initramfs images where a bigger
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* dictionary can be fine and useful.
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*
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* Single-call mode (XZ_SINGLE): xz_dec_run() decodes the whole stream at
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* once. The caller must provide enough output space or the decoding will
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* fail. The output space is used as the dictionary buffer, which is why
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* there is no need to allocate the dictionary as part of the decoder's
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* internal 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 mode. It is enough that
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* the output buffer 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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* Multi-call mode with preallocated dictionary (XZ_PREALLOC): dict_max bytes
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* of memory is preallocated for the LZMA2 dictionary. This way there is no
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* risk that xz_dec_run() could run out of memory, since xz_dec_run() will
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* never allocate any memory. Instead, if the preallocated dictionary is too
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* small for decoding the given input stream, xz_dec_run() will return
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* XZ_MEMLIMIT_ERROR. Thus, it is important to know what kind of data will be
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* decoded to avoid allocating excessive amount of memory for the dictionary.
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*
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* Multi-call mode with dynamically allocated dictionary (XZ_DYNALLOC):
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* dict_max specifies the maximum allowed dictionary size that xz_dec_run()
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* may allocate once it has parsed the dictionary size from the stream
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* headers. This way excessive allocations can be avoided while still
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* limiting the maximum memory usage to a sane value to prevent running the
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* system out of memory when decompressing streams from untrusted sources.
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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(). If memory allocation fails,
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* xz_dec_init() returns NULL.
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*/
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XZ_EXTERN struct xz_dec *xz_dec_init(enum xz_mode mode, 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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* The possible return values depend on build options and operation mode.
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* See enum xz_ret for details.
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*
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* Note that if an error occurs in single-call mode (return value is not
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* XZ_STREAM_END), b->in_pos and b->out_pos are not modified and the
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* contents of the output buffer from b->out[b->out_pos] onward are
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* undefined. This is true even after XZ_BUF_ERROR, because with some filter
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* chains, there may be a second pass over the output buffer, and this pass
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* cannot be properly done if the output buffer is truncated. Thus, you
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* cannot give the single-call decoder a too small buffer and then expect to
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* get that amount valid data from the beginning of the stream. You must use
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* the multi-call decoder if you don't want to uncompress the whole stream.
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*/
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XZ_EXTERN 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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XZ_EXTERN 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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XZ_EXTERN void xz_dec_end(struct xz_dec *s);
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/*
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* Standalone build (userspace build or in-kernel build for boot time use)
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* needs a CRC32 implementation. For normal in-kernel use, kernel's own
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* CRC32 module is used instead, and users of this module don't need to
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* care about the functions below.
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*/
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#ifndef XZ_INTERNAL_CRC32
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# ifdef __KERNEL__
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# define XZ_INTERNAL_CRC32 0
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# else
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# define XZ_INTERNAL_CRC32 1
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# endif
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#endif
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#if XZ_INTERNAL_CRC32
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/*
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* This must be called before any other xz_* function to initialize
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* the CRC32 lookup table.
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*/
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XZ_EXTERN void xz_crc32_init(void);
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/*
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* Update CRC32 value using the polynomial from IEEE-802.3. To start a new
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* calculation, the third argument must be zero. To continue the calculation,
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* the previously returned value is passed as the third argument.
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*/
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XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc);
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#endif
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#endif
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