src/liblzma/lz/lz_decoder.h

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       lz_decoder.h
   4 /// \brief      LZ out window
   5 ///
   6 //  Authors:    Igor Pavlov
   7 //              Lasse Collin
   8 //
   9 //  This file has been put into the public domain.
  10 //  You can do whatever you want with this file.
  11 //
  12 ///////////////////////////////////////////////////////////////////////////////
  13
  14 #ifndef LZMA_LZ_DECODER_H
  15 #define LZMA_LZ_DECODER_H
  16
  17 #include "common.h"
  18
  19
  20 typedef struct {
  21         /// Pointer to the dictionary buffer. It can be an allocated buffer
  22         /// internal to liblzma, or it can a be a buffer given by the
  23         /// application when in single-call mode (not implemented yet).
  24         uint8_t *buf;
  25
  26         /// Write position in dictionary. The next byte will be written to
  27         /// buf[pos].
  28         size_t pos;
  29
  30         /// Indicates how full the dictionary is. This is used by
  31         /// dict_is_distance_valid() to detect corrupt files that would
  32         /// read beyond the beginning of the dictionary.
  33         size_t full;
  34
  35         /// Write limit
  36         size_t limit;
  37
  38         /// Size of the dictionary
  39         size_t size;
  40
  41         /// True when dictionary should be reset before decoding more data.
  42         bool need_reset;
  43
  44 } lzma_dict;
  45
  46
  47 typedef struct {
  48         size_t dict_size;
  49         const uint8_t *preset_dict;
  50         size_t preset_dict_size;
  51 } lzma_lz_options;
  52
  53
  54 typedef struct {
  55         /// Data specific to the LZ-based decoder
  56         void *coder;
  57
  58         /// Function to decode from in[] to *dict
  59         lzma_ret (*code)(void *coder,
  60                         lzma_dict *restrict dict, const uint8_t *restrict in,
  61                         size_t *restrict in_pos, size_t in_size);
  62
  63         void (*reset)(void *coder, const void *options);
  64
  65         /// Set the uncompressed size. If uncompressed_size == LZMA_VLI_UNKNOWN
  66         /// then allow_eopm will always be true.
  67         void (*set_uncompressed)(void *coder, lzma_vli uncompressed_size,
  68                         bool allow_eopm);
  69
  70         /// Free allocated resources
  71         void (*end)(void *coder, const lzma_allocator *allocator);
  72
  73 } lzma_lz_decoder;
  74
  75
  76 #define LZMA_LZ_DECODER_INIT \
  77         (lzma_lz_decoder){ \
  78                 .coder = NULL, \
  79                 .code = NULL, \
  80                 .reset = NULL, \
  81                 .set_uncompressed = NULL, \
  82                 .end = NULL, \
  83         }
  84
  85
  86 extern lzma_ret lzma_lz_decoder_init(lzma_next_coder *next,
  87                 const lzma_allocator *allocator,
  88                 const lzma_filter_info *filters,
  89                 lzma_ret (*lz_init)(lzma_lz_decoder *lz,
  90                         const lzma_allocator *allocator,
  91                         lzma_vli id, const void *options,
  92                         lzma_lz_options *lz_options));
  93
  94 extern uint64_t lzma_lz_decoder_memusage(size_t dictionary_size);
  95
  96
  97 //////////////////////
  98 // Inline functions //
  99 //////////////////////
 100
 101 /// Get a byte from the history buffer.
 102 static inline uint8_t
 103 dict_get(const lzma_dict *const dict, const uint32_t distance)
 104 {
 105         return dict->buf[dict->pos - distance - 1
 106                         + (distance < dict->pos ? 0 : dict->size)];
 107 }
 108
 109
 110 /// Test if dictionary is empty.
 111 static inline bool
 112 dict_is_empty(const lzma_dict *const dict)
 113 {
 114         return dict->full == 0;
 115 }
 116
 117
 118 /// Validate the match distance
 119 static inline bool
 120 dict_is_distance_valid(const lzma_dict *const dict, const size_t distance)
 121 {
 122         return dict->full > distance;
 123 }
 124
 125
 126 /// Repeat *len bytes at distance.
 127 static inline bool
 128 dict_repeat(lzma_dict *dict, uint32_t distance, uint32_t *len)
 129 {
 130         // Don't write past the end of the dictionary.
 131         const size_t dict_avail = dict->limit - dict->pos;
 132         uint32_t left = my_min(dict_avail, *len);
 133         *len -= left;
 134
 135         // Repeat a block of data from the history. Because memcpy() is faster
 136         // than copying byte by byte in a loop, the copying process gets split
 137         // into three cases.
 138         if (distance < left) {
 139                 // Source and target areas overlap, thus we can't use
 140                 // memcpy() nor even memmove() safely.
 141                 do {
 142                         dict->buf[dict->pos] = dict_get(dict, distance);
 143                         ++dict->pos;
 144                 } while (--left > 0);
 145
 146         } else if (distance < dict->pos) {
 147                 // The easiest and fastest case
 148                 memcpy(dict->buf + dict->pos,
 149                                 dict->buf + dict->pos - distance - 1,
 150                                 left);
 151                 dict->pos += left;
 152
 153         } else {
 154                 // The bigger the dictionary, the more rare this
 155                 // case occurs. We need to "wrap" the dict, thus
 156                 // we might need two memcpy() to copy all the data.
 157                 assert(dict->full == dict->size);
 158                 const uint32_t copy_pos
 159                                 = dict->pos - distance - 1 + dict->size;
 160                 uint32_t copy_size = dict->size - copy_pos;
 161
 162                 if (copy_size < left) {
 163                         memmove(dict->buf + dict->pos, dict->buf + copy_pos,
 164                                         copy_size);
 165                         dict->pos += copy_size;
 166                         copy_size = left - copy_size;
 167                         memcpy(dict->buf + dict->pos, dict->buf, copy_size);
 168                         dict->pos += copy_size;
 169                 } else {
 170                         memmove(dict->buf + dict->pos, dict->buf + copy_pos,
 171                                         left);
 172                         dict->pos += left;
 173                 }
 174         }
 175
 176         // Update how full the dictionary is.
 177         if (dict->full < dict->pos)
 178                 dict->full = dict->pos;
 179
 180         return unlikely(*len != 0);
 181 }
 182
 183
 184 /// Puts one byte into the dictionary. Returns true if the dictionary was
 185 /// already full and the byte couldn't be added.
 186 static inline bool
 187 dict_put(lzma_dict *dict, uint8_t byte)
 188 {
 189         if (unlikely(dict->pos == dict->limit))
 190                 return true;
 191
 192         dict->buf[dict->pos++] = byte;
 193
 194         if (dict->pos > dict->full)
 195                 dict->full = dict->pos;
 196
 197         return false;
 198 }
 199
 200
 201 /// Copies arbitrary amount of data into the dictionary.
 202 static inline void
 203 dict_write(lzma_dict *restrict dict, const uint8_t *restrict in,
 204                 size_t *restrict in_pos, size_t in_size,
 205                 size_t *restrict left)
 206 {
 207         // NOTE: If we are being given more data than the size of the
 208         // dictionary, it could be possible to optimize the LZ decoder
 209         // so that not everything needs to go through the dictionary.
 210         // This shouldn't be very common thing in practice though, and
 211         // the slowdown of one extra memcpy() isn't bad compared to how
 212         // much time it would have taken if the data were compressed.
 213
 214         if (in_size - *in_pos > *left)
 215                 in_size = *in_pos + *left;
 216
 217         *left -= lzma_bufcpy(in, in_pos, in_size,
 218                         dict->buf, &dict->pos, dict->limit);
 219
 220         if (dict->pos > dict->full)
 221                 dict->full = dict->pos;
 222
 223         return;
 224 }
 225
 226
 227 static inline void
 228 dict_reset(lzma_dict *dict)
 229 {
 230         dict->need_reset = true;
 231         return;
 232 }
 233
 234 #endif