1 /* 2 * XZ decompressor 3 * 4 * Authors: Lasse Collin <lasse.collin (at) 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
