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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/* In Linux, this is used to make extern functions static when needed. */
23#ifndef XZ_EXTERN
24# define XZ_EXTERN extern
25#endif
26
27/* In Linux, this is used to mark the functions with __init when needed. */
28#ifndef XZ_FUNC
29# define XZ_FUNC
30#endif
31
32/**
33 * enum xz_ret - Return codes
34 * @XZ_OK: Everything is OK so far. More input or more
35 * output space is required to continue.
36 * @XZ_STREAM_END: Operation finished successfully.
37 * @XZ_UNSUPPORTED_CHECK: Integrity check type is not supported. Decoding
38 * is still possible in multi-call mode by simply
39 * calling xz_dec_run() again.
40 * NOTE: This return value is used only if
41 * XZ_DEC_ANY_CHECK was defined at build time,
42 * which is not used in the kernel. Unsupported
43 * check types return XZ_OPTIONS_ERROR if
44 * XZ_DEC_ANY_CHECK was not defined at build time.
45 * @XZ_MEMLIMIT_ERROR: Not enough memory was preallocated at decoder
46 * initialization time.
47 * @XZ_FORMAT_ERROR: File format was not recognized (wrong magic
48 * bytes).
49 * @XZ_OPTIONS_ERROR: This implementation doesn't support the requested
50 * compression options. In the decoder this means
51 * that the header CRC32 matches, but the header
52 * itself specifies something that we don't support.
53 * @XZ_DATA_ERROR: Compressed data is corrupt.
54 * @XZ_BUF_ERROR: Cannot make any progress. Details are slightly
55 * different between multi-call and single-call
56 * mode; more information below.
57 *
58 * In multi-call mode, XZ_BUF_ERROR is returned when two consecutive calls
59 * to XZ code cannot consume any input and cannot produce any new output.
60 * This happens when there is no new input available, or the output buffer
61 * is full while at least one output byte is still pending. Assuming your
62 * code is not buggy, you can get this error only when decoding a compressed
63 * stream that is truncated or otherwise corrupt.
64 *
65 * In single-call mode, XZ_BUF_ERROR is returned only when the output buffer
66 * is too small, or the compressed input is corrupt in a way that makes the
67 * decoder produce more output than the caller expected. When it is
68 * (relatively) clear that the compressed input is truncated, XZ_DATA_ERROR
69 * is used instead of XZ_BUF_ERROR.
70 */
71enum xz_ret {
72 XZ_OK,
73 XZ_STREAM_END,
74 XZ_UNSUPPORTED_CHECK,
75 XZ_MEMLIMIT_ERROR,
76 XZ_FORMAT_ERROR,
77 XZ_OPTIONS_ERROR,
78 XZ_DATA_ERROR,
79 XZ_BUF_ERROR
80};
81
82/**
83 * struct xz_buf - Passing input and output buffers to XZ code
84 * @in: Beginning of the input buffer. This may be NULL if and only
85 * if in_pos is equal to in_size.
86 * @in_pos: Current position in the input buffer. This must not exceed
87 * in_size.
88 * @in_size: Size of the input buffer
89 * @out: Beginning of the output buffer. This may be NULL if and only
90 * if out_pos is equal to out_size.
91 * @out_pos: Current position in the output buffer. This must not exceed
92 * out_size.
93 * @out_size: Size of the output buffer
94 *
95 * Only the contents of the output buffer from out[out_pos] onward, and
96 * the variables in_pos and out_pos are modified by the XZ code.
97 */
98struct xz_buf {
99 const uint8_t *in;
100 size_t in_pos;
101 size_t in_size;
102
103 uint8_t *out;
104 size_t out_pos;
105 size_t out_size;
106};
107
108/**
109 * struct xz_dec - Opaque type to hold the XZ decoder state
110 */
111struct xz_dec;
112
113/**
114 * xz_dec_init() - Allocate and initialize a XZ decoder state
115 * @dict_max: Maximum size of the LZMA2 dictionary (history buffer) for
116 * multi-call decoding, or special value of zero to indicate
117 * single-call decoding mode.
118 *
119 * If dict_max > 0, the decoder is initialized to work in multi-call mode.
120 * dict_max number of bytes of memory is preallocated for the LZMA2
121 * dictionary. This way there is no risk that xz_dec_run() could run out
122 * of memory, since xz_dec_run() will never allocate any memory. Instead,
123 * if the preallocated dictionary is too small for decoding the given input
124 * stream, xz_dec_run() will return XZ_MEMLIMIT_ERROR. Thus, it is important
125 * to know what kind of data will be decoded to avoid allocating excessive
126 * amount of memory for the dictionary.
127 *
128 * LZMA2 dictionary is always 2^n bytes or 2^n + 2^(n-1) bytes (the latter
129 * sizes are less common in practice). In the kernel, dictionary sizes of
130 * 64 KiB, 128 KiB, 256 KiB, 512 KiB, and 1 MiB are probably the only
131 * reasonable values.
132 *
133 * If dict_max == 0, the decoder is initialized to work in single-call mode.
134 * In single-call mode, xz_dec_run() decodes the whole stream at once. The
135 * caller must provide enough output space or the decoding will fail. The
136 * output space is used as the dictionary buffer, which is why there is
137 * no need to allocate the dictionary as part of the decoder's internal
138 * state.
139 *
140 * Because the output buffer is used as the workspace, streams encoded using
141 * a big dictionary are not a problem in single-call. It is enough that the
142 * output buffer is big enough to hold the actual uncompressed data; it
143 * can be smaller than the dictionary size stored in the stream headers.
144 *
145 * On success, xz_dec_init() returns a pointer to struct xz_dec, which is
146 * ready to be used with xz_dec_run(). On error, xz_dec_init() returns NULL.
147 */
148XZ_EXTERN struct xz_dec * XZ_FUNC xz_dec_init(uint32_t dict_max);
149
150/**
151 * xz_dec_run() - Run the XZ decoder
152 * @s: Decoder state allocated using xz_dec_init()
153 * @b: Input and output buffers
154 *
155 * In multi-call mode, this function may return any of the values listed in
156 * enum xz_ret.
157 *
158 * In single-call mode, this function never returns XZ_OK. If an error occurs
159 * in single-call mode (return value is not XZ_STREAM_END), b->in_pos and
160 * b->out_pos are not modified, and the contents of the output buffer from
161 * b->out[b->out_pos] onward are undefined.
162 *
163 * NOTE: In single-call mode, the contents of the output buffer are undefined
164 * also after XZ_BUF_ERROR. This is because with some filter chains, there
165 * may be a second pass over the output buffer, and this pass cannot be
166 * properly done if the output buffer is truncated. Thus, you cannot give
167 * the single-call decoder a too small buffer and then expect to get that
168 * amount valid data from the beginning of the stream. You must use the
169 * multi-call decoder if you don't want to uncompress the whole stream.
170 */
171XZ_EXTERN enum xz_ret XZ_FUNC xz_dec_run(struct xz_dec *s, struct xz_buf *b);
172
173/**
174 * xz_dec_reset() - Reset an already allocated decoder state
175 * @s: Decoder state allocated using xz_dec_init()
176 *
177 * This function can be used to reset the multi-call decoder state without
178 * freeing and reallocating memory with xz_dec_end() and xz_dec_init().
179 *
180 * In single-call mode, xz_dec_reset() is always called in the beginning of
181 * xz_dec_run(). Thus, explicit call to xz_dec_reset() is useful only in
182 * multi-call mode.
183 */
184XZ_EXTERN void XZ_FUNC xz_dec_reset(struct xz_dec *s);
185
186/**
187 * xz_dec_end() - Free the memory allocated for the decoder state
188 * @s: Decoder state allocated using xz_dec_init(). If s is NULL,
189 * this function does nothing.
190 */
191XZ_EXTERN void XZ_FUNC xz_dec_end(struct xz_dec *s);
192
193/*
194 * Standalone build (userspace build or in-kernel build for boot time use)
195 * needs a CRC32 implementation. For normal in-kernel use, kernel's own
196 * CRC32 module is used instead, and users of this module don't need to
197 * care about the functions below.
198 */
199#ifndef XZ_INTERNAL_CRC32
200# ifdef __KERNEL__
201# define XZ_INTERNAL_CRC32 0
202# else
203# define XZ_INTERNAL_CRC32 1
204# endif
205#endif
206
207#if XZ_INTERNAL_CRC32
208/*
209 * This must be called before any other xz_* function to initialize
210 * the CRC32 lookup table.
211 */
212XZ_EXTERN void XZ_FUNC xz_crc32_init(void);
213
214/*
215 * Update CRC32 value using the polynomial from IEEE-802.3. To start a new
216 * calculation, the third argument must be zero. To continue the calculation,
217 * the previously returned value is passed as the third argument.
218 */
219XZ_EXTERN uint32_t XZ_FUNC xz_crc32(
220 const uint8_t *buf, size_t size, uint32_t crc);
221#endif
222#endif