xz/xz.h

   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