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264 lines
11 KiB
264 lines
11 KiB
/* |
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* XZ decompressor |
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* |
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* Authors: Lasse Collin <[email protected]> |
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* Igor Pavlov <https://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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* 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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