1 /*
2  * XZ decompressor
3  *
4  * Authors: Lasse Collin <lasse.collin@tukaani.org>
5  *          Igor Pavlov <http://7-zip.org/>
6  *
7  * This file has been put into the public domain.
8  * You can do whatever you want with this file.
9  */
10 
11 #ifndef XZ_H
12 #define XZ_H
13 
14 #ifdef __KERNEL__
15 #	include <linux/stddef.h>
16 #	include <linux/types.h>
17 #else
18 #	include <stddef.h>
19 #	include <stdint.h>
20 #endif
21 
22 #ifdef __cplusplus
23 extern "C" {
24 #endif
25 
26 /* In Linux, this is used to make extern functions static when needed. */
27 #ifndef XZ_EXTERN
28 #	define XZ_EXTERN extern
29 #endif
30 
31 /**
32  * enum xz_mode - Operation mode
33  *
34  * @XZ_SINGLE:              Single-call mode. This uses less RAM than
35  *                          than multi-call modes, because the LZMA2
36  *                          dictionary doesn't need to be allocated as
37  *                          part of the decoder state. All required data
38  *                          structures are allocated at initialization,
39  *                          so xz_dec_run() cannot return XZ_MEM_ERROR.
40  * @XZ_PREALLOC:            Multi-call mode with preallocated LZMA2
41  *                          dictionary buffer. All data structures are
42  *                          allocated at initialization, so xz_dec_run()
43  *                          cannot return XZ_MEM_ERROR.
44  * @XZ_DYNALLOC:            Multi-call mode. The LZMA2 dictionary is
45  *                          allocated once the required size has been
46  *                          parsed from the stream headers. If the
47  *                          allocation fails, xz_dec_run() will return
48  *                          XZ_MEM_ERROR.
49  *
50  * It is possible to enable support only for a subset of the above
51  * modes at compile time by defining XZ_DEC_SINGLE, XZ_DEC_PREALLOC,
52  * or XZ_DEC_DYNALLOC. The xz_dec kernel module is always compiled
53  * with support for all operation modes, but the preboot code may
54  * be built with fewer features to minimize code size.
55  */
56 enum xz_mode {
57 	XZ_SINGLE,
58 	XZ_PREALLOC,
59 	XZ_DYNALLOC
60 };
61 
62 /**
63  * enum xz_ret - Return codes
64  * @XZ_OK:                  Everything is OK so far. More input or more
65  *                          output space is required to continue. This
66  *                          return code is possible only in multi-call mode
67  *                          (XZ_PREALLOC or XZ_DYNALLOC).
68  * @XZ_STREAM_END:          Operation finished successfully.
69  * @XZ_UNSUPPORTED_CHECK:   Integrity check type is not supported. Decoding
70  *                          is still possible in multi-call mode by simply
71  *                          calling xz_dec_run() again.
72  *                          Note that this return value is used only if
73  *                          XZ_DEC_ANY_CHECK was defined at build time,
74  *                          which is not used in the kernel. Unsupported
75  *                          check types return XZ_OPTIONS_ERROR if
76  *                          XZ_DEC_ANY_CHECK was not defined at build time.
77  * @XZ_MEM_ERROR:           Allocating memory failed. This return code is
78  *                          possible only if the decoder was initialized
79  *                          with XZ_DYNALLOC. The amount of memory that was
80  *                          tried to be allocated was no more than the
81  *                          dict_max argument given to xz_dec_init().
82  * @XZ_MEMLIMIT_ERROR:      A bigger LZMA2 dictionary would be needed than
83  *                          allowed by the dict_max argument given to
84  *                          xz_dec_init(). This return value is possible
85  *                          only in multi-call mode (XZ_PREALLOC or
86  *                          XZ_DYNALLOC); the single-call mode (XZ_SINGLE)
87  *                          ignores the dict_max argument.
88  * @XZ_FORMAT_ERROR:        File format was not recognized (wrong magic
89  *                          bytes).
90  * @XZ_OPTIONS_ERROR:       This implementation doesn't support the requested
91  *                          compression options. In the decoder this means
92  *                          that the header CRC32 matches, but the header
93  *                          itself specifies something that we don't support.
94  * @XZ_DATA_ERROR:          Compressed data is corrupt.
95  * @XZ_BUF_ERROR:           Cannot make any progress. Details are slightly
96  *                          different between multi-call and single-call
97  *                          mode; more information below.
98  *
99  * In multi-call mode, XZ_BUF_ERROR is returned when two consecutive calls
100  * to XZ code cannot consume any input and cannot produce any new output.
101  * This happens when there is no new input available, or the output buffer
102  * is full while at least one output byte is still pending. Assuming your
103  * code is not buggy, you can get this error only when decoding a compressed
104  * stream that is truncated or otherwise corrupt.
105  *
106  * In single-call mode, XZ_BUF_ERROR is returned only when the output buffer
107  * is too small or the compressed input is corrupt in a way that makes the
108  * decoder produce more output than the caller expected. When it is
109  * (relatively) clear that the compressed input is truncated, XZ_DATA_ERROR
110  * is used instead of XZ_BUF_ERROR.
111  */
112 enum xz_ret {
113 	XZ_OK,
114 	XZ_STREAM_END,
115 	XZ_UNSUPPORTED_CHECK,
116 	XZ_MEM_ERROR,
117 	XZ_MEMLIMIT_ERROR,
118 	XZ_FORMAT_ERROR,
119 	XZ_OPTIONS_ERROR,
120 	XZ_DATA_ERROR,
121 	XZ_BUF_ERROR
122 };
123 
124 /**
125  * struct xz_buf - Passing input and output buffers to XZ code
126  * @in:         Beginning of the input buffer. This may be NULL if and only
127  *              if in_pos is equal to in_size.
128  * @in_pos:     Current position in the input buffer. This must not exceed
129  *              in_size.
130  * @in_size:    Size of the input buffer
131  * @out:        Beginning of the output buffer. This may be NULL if and only
132  *              if out_pos is equal to out_size.
133  * @out_pos:    Current position in the output buffer. This must not exceed
134  *              out_size.
135  * @out_size:   Size of the output buffer
136  *
137  * Only the contents of the output buffer from out[out_pos] onward, and
138  * the variables in_pos and out_pos are modified by the XZ code.
139  */
140 struct xz_buf {
141 	const uint8_t *in;
142 	size_t in_pos;
143 	size_t in_size;
144 
145 	uint8_t *out;
146 	size_t out_pos;
147 	size_t out_size;
148 };
149 
150 /**
151  * struct xz_dec - Opaque type to hold the XZ decoder state
152  */
153 struct xz_dec;
154 
155 /**
156  * xz_dec_init() - Allocate and initialize a XZ decoder state
157  * @mode:       Operation mode
158  * @dict_max:   Maximum size of the LZMA2 dictionary (history buffer) for
159  *              multi-call decoding. This is ignored in single-call mode
160  *              (mode == XZ_SINGLE). LZMA2 dictionary is always 2^n bytes
161  *              or 2^n + 2^(n-1) bytes (the latter sizes are less common
162  *              in practice), so other values for dict_max don't make sense.
163  *              In the kernel, dictionary sizes of 64 KiB, 128 KiB, 256 KiB,
164  *              512 KiB, and 1 MiB are probably the only reasonable values,
165  *              except for kernel and initramfs images where a bigger
166  *              dictionary can be fine and useful.
167  *
168  * Single-call mode (XZ_SINGLE): xz_dec_run() decodes the whole stream at
169  * once. The caller must provide enough output space or the decoding will
170  * fail. The output space is used as the dictionary buffer, which is why
171  * there is no need to allocate the dictionary as part of the decoder's
172  * internal state.
173  *
174  * Because the output buffer is used as the workspace, streams encoded using
175  * a big dictionary are not a problem in single-call mode. It is enough that
176  * the output buffer is big enough to hold the actual uncompressed data; it
177  * can be smaller than the dictionary size stored in the stream headers.
178  *
179  * Multi-call mode with preallocated dictionary (XZ_PREALLOC): dict_max bytes
180  * of memory is preallocated for the LZMA2 dictionary. This way there is no
181  * risk that xz_dec_run() could run out of memory, since xz_dec_run() will
182  * never allocate any memory. Instead, if the preallocated dictionary is too
183  * small for decoding the given input stream, xz_dec_run() will return
184  * XZ_MEMLIMIT_ERROR. Thus, it is important to know what kind of data will be
185  * decoded to avoid allocating excessive amount of memory for the dictionary.
186  *
187  * Multi-call mode with dynamically allocated dictionary (XZ_DYNALLOC):
188  * dict_max specifies the maximum allowed dictionary size that xz_dec_run()
189  * may allocate once it has parsed the dictionary size from the stream
190  * headers. This way excessive allocations can be avoided while still
191  * limiting the maximum memory usage to a sane value to prevent running the
192  * system out of memory when decompressing streams from untrusted sources.
193  *
194  * On success, xz_dec_init() returns a pointer to struct xz_dec, which is
195  * ready to be used with xz_dec_run(). If memory allocation fails,
196  * xz_dec_init() returns NULL.
197  */
198 XZ_EXTERN struct xz_dec *xz_dec_init(enum xz_mode mode, uint32_t dict_max);
199 
200 /**
201  * xz_dec_run() - Run the XZ decoder
202  * @s:          Decoder state allocated using xz_dec_init()
203  * @b:          Input and output buffers
204  *
205  * The possible return values depend on build options and operation mode.
206  * See enum xz_ret for details.
207  *
208  * Note that if an error occurs in single-call mode (return value is not
209  * XZ_STREAM_END), b->in_pos and b->out_pos are not modified and the
210  * contents of the output buffer from b->out[b->out_pos] onward are
211  * undefined. This is true even after XZ_BUF_ERROR, because with some filter
212  * chains, there may be a second pass over the output buffer, and this pass
213  * cannot be properly done if the output buffer is truncated. Thus, you
214  * cannot give the single-call decoder a too small buffer and then expect to
215  * get that amount valid data from the beginning of the stream. You must use
216  * the multi-call decoder if you don't want to uncompress the whole stream.
217  */
218 XZ_EXTERN enum xz_ret xz_dec_run(struct xz_dec *s, struct xz_buf *b);
219 
220 /**
221  * xz_dec_reset() - Reset an already allocated decoder state
222  * @s:          Decoder state allocated using xz_dec_init()
223  *
224  * This function can be used to reset the multi-call decoder state without
225  * freeing and reallocating memory with xz_dec_end() and xz_dec_init().
226  *
227  * In single-call mode, xz_dec_reset() is always called in the beginning of
228  * xz_dec_run(). Thus, explicit call to xz_dec_reset() is useful only in
229  * multi-call mode.
230  */
231 XZ_EXTERN void xz_dec_reset(struct xz_dec *s);
232 
233 /**
234  * xz_dec_end() - Free the memory allocated for the decoder state
235  * @s:          Decoder state allocated using xz_dec_init(). If s is NULL,
236  *              this function does nothing.
237  */
238 XZ_EXTERN void xz_dec_end(struct xz_dec *s);
239 
240 /*
241  * Standalone build (userspace build or in-kernel build for boot time use)
242  * needs a CRC32 implementation. For normal in-kernel use, kernel's own
243  * CRC32 module is used instead, and users of this module don't need to
244  * care about the functions below.
245  */
246 #ifndef XZ_INTERNAL_CRC32
247 #	ifdef __KERNEL__
248 #		define XZ_INTERNAL_CRC32 0
249 #	else
250 #		define XZ_INTERNAL_CRC32 1
251 #	endif
252 #endif
253 
254 /*
255  * If CRC64 support has been enabled with XZ_USE_CRC64, a CRC64
256  * implementation is needed too.
257  */
258 #ifndef XZ_USE_CRC64
259 #	undef XZ_INTERNAL_CRC64
260 #	define XZ_INTERNAL_CRC64 0
261 #endif
262 #ifndef XZ_INTERNAL_CRC64
263 #	ifdef __KERNEL__
264 #		error Using CRC64 in the kernel has not been implemented.
265 #	else
266 #		define XZ_INTERNAL_CRC64 1
267 #	endif
268 #endif
269 
270 #if XZ_INTERNAL_CRC32
271 /*
272  * This must be called before any other xz_* function to initialize
273  * the CRC32 lookup table.
274  */
275 XZ_EXTERN void xz_crc32_init(void);
276 
277 /*
278  * Update CRC32 value using the polynomial from IEEE-802.3. To start a new
279  * calculation, the third argument must be zero. To continue the calculation,
280  * the previously returned value is passed as the third argument.
281  */
282 XZ_EXTERN uint32_t xz_crc32(const uint8_t *buf, size_t size, uint32_t crc);
283 #endif
284 
285 #if XZ_INTERNAL_CRC64
286 /*
287  * This must be called before any other xz_* function (except xz_crc32_init())
288  * to initialize the CRC64 lookup table.
289  */
290 XZ_EXTERN void xz_crc64_init(void);
291 
292 /*
293  * Update CRC64 value using the polynomial from ECMA-182. To start a new
294  * calculation, the third argument must be zero. To continue the calculation,
295  * the previously returned value is passed as the third argument.
296  */
297 XZ_EXTERN uint64_t xz_crc64(const uint8_t *buf, size_t size, uint64_t crc);
298 #endif
299 
300 #ifdef __cplusplus
301 }
302 #endif
303 
304 #endif
305