summaryrefslogtreecommitdiff
path: root/lib/qt-tar-xz/xz.h
blob: 470f6df0dc84178c6b606d5751f0b8a20c035461 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
/*
 * 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.
 */

#define XZ_DEC_ANY_CHECK

#ifndef XZ_H
#define XZ_H

#ifdef __KERNEL__
#	include <linux/stddef.h>
#	include <linux/types.h>
#else
#	include <stddef.h>
#	include <stdint.h>
#endif

/* In Linux, this is used to make extern functions static when needed. */
#ifndef XZ_EXTERN
#	define XZ_EXTERN extern
#endif

/* In Linux, this is used to mark the functions with __init when needed. */
#ifndef XZ_FUNC
#	define XZ_FUNC
#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: 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_FUNC 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: 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_FUNC 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_FUNC 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_FUNC 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 XZ_INTERNAL_CRC32
/*
 * This must be called before any other xz_* function to initialize
 * the CRC32 lookup table.
 */
XZ_EXTERN void XZ_FUNC 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_FUNC xz_crc32(
		const uint8_t *buf, size_t size, uint32_t crc);
#endif
#endif