1/* SPDX-License-Identifier: 0BSD */
2
3/**
4 * \file lzma/stream_flags.h
5 * \brief .xz Stream Header and Stream Footer encoder and decoder
6 * \note Never include this file directly. Use <lzma.h> instead.
7 */
8
9/*
10 * Author: Lasse Collin
11 */
12
13#ifndef LZMA_H_INTERNAL
14# error Never include this file directly. Use <lzma.h> instead.
15#endif
16
17
18/**
19 * \brief Size of Stream Header and Stream Footer
20 *
21 * Stream Header and Stream Footer have the same size and they are not
22 * going to change even if a newer version of the .xz file format is
23 * developed in future.
24 */
25#define LZMA_STREAM_HEADER_SIZE 12
26
27
28/**
29 * \brief Options for encoding/decoding Stream Header and Stream Footer
30 */
31typedef struct {
32 /**
33 * \brief Stream Flags format version
34 *
35 * To prevent API and ABI breakages if new features are needed in
36 * Stream Header or Stream Footer, a version number is used to
37 * indicate which members in this structure are in use. For now,
38 * version must always be zero. With non-zero version, the
39 * lzma_stream_header_encode() and lzma_stream_footer_encode()
40 * will return LZMA_OPTIONS_ERROR.
41 *
42 * lzma_stream_header_decode() and lzma_stream_footer_decode()
43 * will always set this to the lowest value that supports all the
44 * features indicated by the Stream Flags field. The application
45 * must check that the version number set by the decoding functions
46 * is supported by the application. Otherwise it is possible that
47 * the application will decode the Stream incorrectly.
48 */
49 uint32_t version;
50
51 /**
52 * \brief Backward Size
53 *
54 * Backward Size must be a multiple of four bytes. In this Stream
55 * format version, Backward Size is the size of the Index field.
56 *
57 * Backward Size isn't actually part of the Stream Flags field, but
58 * it is convenient to include in this structure anyway. Backward
59 * Size is present only in the Stream Footer. There is no need to
60 * initialize backward_size when encoding Stream Header.
61 *
62 * lzma_stream_header_decode() always sets backward_size to
63 * LZMA_VLI_UNKNOWN so that it is convenient to use
64 * lzma_stream_flags_compare() when both Stream Header and Stream
65 * Footer have been decoded.
66 */
67 lzma_vli backward_size;
68
69 /**
70 * \brief Minimum value for lzma_stream_flags.backward_size
71 */
72# define LZMA_BACKWARD_SIZE_MIN 4
73
74 /**
75 * \brief Maximum value for lzma_stream_flags.backward_size
76 */
77# define LZMA_BACKWARD_SIZE_MAX (LZMA_VLI_C(1) << 34)
78
79 /**
80 * \brief Check ID
81 *
82 * This indicates the type of the integrity check calculated from
83 * uncompressed data.
84 */
85 lzma_check check;
86
87 /*
88 * Reserved space to allow possible future extensions without
89 * breaking the ABI. You should not touch these, because the
90 * names of these variables may change.
91 *
92 * (We will never be able to use all of these since Stream Flags
93 * is just two bytes plus Backward Size of four bytes. But it's
94 * nice to have the proper types when they are needed.)
95 */
96
97 /** \private Reserved member. */
98 lzma_reserved_enum reserved_enum1;
99
100 /** \private Reserved member. */
101 lzma_reserved_enum reserved_enum2;
102
103 /** \private Reserved member. */
104 lzma_reserved_enum reserved_enum3;
105
106 /** \private Reserved member. */
107 lzma_reserved_enum reserved_enum4;
108
109 /** \private Reserved member. */
110 lzma_bool reserved_bool1;
111
112 /** \private Reserved member. */
113 lzma_bool reserved_bool2;
114
115 /** \private Reserved member. */
116 lzma_bool reserved_bool3;
117
118 /** \private Reserved member. */
119 lzma_bool reserved_bool4;
120
121 /** \private Reserved member. */
122 lzma_bool reserved_bool5;
123
124 /** \private Reserved member. */
125 lzma_bool reserved_bool6;
126
127 /** \private Reserved member. */
128 lzma_bool reserved_bool7;
129
130 /** \private Reserved member. */
131 lzma_bool reserved_bool8;
132
133 /** \private Reserved member. */
134 uint32_t reserved_int1;
135
136 /** \private Reserved member. */
137 uint32_t reserved_int2;
138
139} lzma_stream_flags;
140
141
142/**
143 * \brief Encode Stream Header
144 *
145 * \param options Stream Header options to be encoded.
146 * options->backward_size is ignored and doesn't
147 * need to be initialized.
148 * \param[out] out Beginning of the output buffer of
149 * LZMA_STREAM_HEADER_SIZE bytes.
150 *
151 * \return Possible lzma_ret values:
152 * - LZMA_OK: Encoding was successful.
153 * - LZMA_OPTIONS_ERROR: options->version is not supported by
154 * this liblzma version.
155 * - LZMA_PROG_ERROR: Invalid options.
156 */
157extern LZMA_API(lzma_ret) lzma_stream_header_encode(
158 const lzma_stream_flags *options, uint8_t *out)
159 lzma_nothrow lzma_attr_warn_unused_result;
160
161
162/**
163 * \brief Encode Stream Footer
164 *
165 * \param options Stream Footer options to be encoded.
166 * \param[out] out Beginning of the output buffer of
167 * LZMA_STREAM_HEADER_SIZE bytes.
168 *
169 * \return Possible lzma_ret values:
170 * - LZMA_OK: Encoding was successful.
171 * - LZMA_OPTIONS_ERROR: options->version is not supported by
172 * this liblzma version.
173 * - LZMA_PROG_ERROR: Invalid options.
174 */
175extern LZMA_API(lzma_ret) lzma_stream_footer_encode(
176 const lzma_stream_flags *options, uint8_t *out)
177 lzma_nothrow lzma_attr_warn_unused_result;
178
179
180/**
181 * \brief Decode Stream Header
182 *
183 * options->backward_size is always set to LZMA_VLI_UNKNOWN. This is to
184 * help comparing Stream Flags from Stream Header and Stream Footer with
185 * lzma_stream_flags_compare().
186 *
187 * \note When decoding .xz files that contain multiple Streams, it may
188 * make sense to print "file format not recognized" only if
189 * decoding of the Stream Header of the \a first Stream gives
190 * LZMA_FORMAT_ERROR. If non-first Stream Header gives
191 * LZMA_FORMAT_ERROR, the message used for LZMA_DATA_ERROR is
192 * probably more appropriate.
193 * For example, the Stream decoder in liblzma uses
194 * LZMA_DATA_ERROR if LZMA_FORMAT_ERROR is returned by
195 * lzma_stream_header_decode() when decoding non-first Stream.
196 *
197 * \param[out] options Target for the decoded Stream Header options.
198 * \param in Beginning of the input buffer of
199 * LZMA_STREAM_HEADER_SIZE bytes.
200 *
201 *
202 * \return Possible lzma_ret values:
203 * - LZMA_OK: Decoding was successful.
204 * - LZMA_FORMAT_ERROR: Magic bytes don't match, thus the given
205 * buffer cannot be Stream Header.
206 * - LZMA_DATA_ERROR: CRC32 doesn't match, thus the header
207 * is corrupt.
208 * - LZMA_OPTIONS_ERROR: Unsupported options are present
209 * in the header.
210 */
211extern LZMA_API(lzma_ret) lzma_stream_header_decode(
212 lzma_stream_flags *options, const uint8_t *in)
213 lzma_nothrow lzma_attr_warn_unused_result;
214
215
216/**
217 * \brief Decode Stream Footer
218 *
219 * \note If Stream Header was already decoded successfully, but
220 * decoding Stream Footer returns LZMA_FORMAT_ERROR, the
221 * application should probably report some other error message
222 * than "file format not recognized". The file likely
223 * is corrupt (possibly truncated). The Stream decoder in liblzma
224 * uses LZMA_DATA_ERROR in this situation.
225 *
226 * \param[out] options Target for the decoded Stream Footer options.
227 * \param in Beginning of the input buffer of
228 * LZMA_STREAM_HEADER_SIZE bytes.
229 *
230 * \return Possible lzma_ret values:
231 * - LZMA_OK: Decoding was successful.
232 * - LZMA_FORMAT_ERROR: Magic bytes don't match, thus the given
233 * buffer cannot be Stream Footer.
234 * - LZMA_DATA_ERROR: CRC32 doesn't match, thus the Stream Footer
235 * is corrupt.
236 * - LZMA_OPTIONS_ERROR: Unsupported options are present
237 * in Stream Footer.
238 */
239extern LZMA_API(lzma_ret) lzma_stream_footer_decode(
240 lzma_stream_flags *options, const uint8_t *in)
241 lzma_nothrow lzma_attr_warn_unused_result;
242
243
244/**
245 * \brief Compare two lzma_stream_flags structures
246 *
247 * backward_size values are compared only if both are not
248 * LZMA_VLI_UNKNOWN.
249 *
250 * \param a Pointer to lzma_stream_flags structure
251 * \param b Pointer to lzma_stream_flags structure
252 *
253 * \return Possible lzma_ret values:
254 * - LZMA_OK: Both are equal. If either had backward_size set
255 * to LZMA_VLI_UNKNOWN, backward_size values were not
256 * compared or validated.
257 * - LZMA_DATA_ERROR: The structures differ.
258 * - LZMA_OPTIONS_ERROR: version in either structure is greater
259 * than the maximum supported version (currently zero).
260 * - LZMA_PROG_ERROR: Invalid value, e.g. invalid check or
261 * backward_size.
262 */
263extern LZMA_API(lzma_ret) lzma_stream_flags_compare(
264 const lzma_stream_flags *a, const lzma_stream_flags *b)
265 lzma_nothrow lzma_attr_pure;
266