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xz.h
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Editing: xz.h
/* * XZ decompressor * * Authors: Lasse Collin <lasse.collin@tukaani.org> * Igor Pavlov <http://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 #ifdef __FreeBSD__ # include <sys/stddef.h> # include <sys/types.h> #else # include <stddef.h> # include <stdint.h> #endif #endif #ifdef __cplusplus extern "C" { #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 * 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); /* * 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 CRC64 support has been enabled with XZ_USE_CRC64, a CRC64 * implementation is needed too. */ #ifndef XZ_USE_CRC64 # undef XZ_INTERNAL_CRC64 # define XZ_INTERNAL_CRC64 0 #endif #ifndef XZ_INTERNAL_CRC64 # ifdef __KERNEL__ # error Using CRC64 in the kernel has not been implemented. # else # define XZ_INTERNAL_CRC64 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 #if XZ_INTERNAL_CRC64 /* * This must be called before any other xz_* function (except xz_crc32_init()) * to initialize the CRC64 lookup table. */ XZ_EXTERN void xz_crc64_init(void); /* * Update CRC64 value using the polynomial from ECMA-182. 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 uint64_t xz_crc64(const uint8_t *buf, size_t size, uint64_t crc); #endif #ifdef __cplusplus } #endif #endif
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