src/liblzma/common/index_encoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       index_encoder.c
   4 /// \brief      Encodes the Index field
   5 //
   6 //  Author:     Lasse Collin
   7 //
   8 //  This file has been put into the public domain.
   9 //  You can do whatever you want with this file.
  10 //
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 #include "index_encoder.h"
  14 #include "index.h"
  15 #include "check.h"
  16
  17
  18 typedef struct {
  19         enum {
  20                 SEQ_INDICATOR,
  21                 SEQ_COUNT,
  22                 SEQ_UNPADDED,
  23                 SEQ_UNCOMPRESSED,
  24                 SEQ_NEXT,
  25                 SEQ_PADDING,
  26                 SEQ_CRC32,
  27         } sequence;
  28
  29         /// Index being encoded
  30         const lzma_index *index;
  31
  32         /// Iterator for the Index being encoded
  33         lzma_index_iter iter;
  34
  35         /// Position in integers
  36         size_t pos;
  37
  38         /// CRC32 of the List of Records field
  39         uint32_t crc32;
  40 } lzma_index_coder;
  41
  42
  43 static lzma_ret
  44 index_encode(void *coder_ptr,
  45                 const lzma_allocator *allocator lzma_attribute((__unused__)),
  46                 const uint8_t *restrict in lzma_attribute((__unused__)),
  47                 size_t *restrict in_pos lzma_attribute((__unused__)),
  48                 size_t in_size lzma_attribute((__unused__)),
  49                 uint8_t *restrict out, size_t *restrict out_pos,
  50                 size_t out_size,
  51                 lzma_action action lzma_attribute((__unused__)))
  52 {
  53         lzma_index_coder *coder = coder_ptr;
  54
  55         // Position where to start calculating CRC32. The idea is that we
  56         // need to call lzma_crc32() only once per call to index_encode().
  57         const size_t out_start = *out_pos;
  58
  59         // Return value to use if we return at the end of this function.
  60         // We use "goto out" to jump out of the while-switch construct
  61         // instead of returning directly, because that way we don't need
  62         // to copypaste the lzma_crc32() call to many places.
  63         lzma_ret ret = LZMA_OK;
  64
  65         while (*out_pos < out_size)
  66         switch (coder->sequence) {
  67         case SEQ_INDICATOR:
  68                 out[*out_pos] = INDEX_INDICATOR;
  69                 ++*out_pos;
  70                 coder->sequence = SEQ_COUNT;
  71                 break;
  72
  73         case SEQ_COUNT: {
  74                 const lzma_vli count = lzma_index_block_count(coder->index);
  75                 ret = lzma_vli_encode(count, &coder->pos,
  76                                 out, out_pos, out_size);
  77                 if (ret != LZMA_STREAM_END)
  78                         goto out;
  79
  80                 ret = LZMA_OK;
  81                 coder->pos = 0;
  82                 coder->sequence = SEQ_NEXT;
  83                 break;
  84         }
  85
  86         case SEQ_NEXT:
  87                 if (lzma_index_iter_next(
  88                                 &coder->iter, LZMA_INDEX_ITER_BLOCK)) {
  89                         // Get the size of the Index Padding field.
  90                         coder->pos = lzma_index_padding_size(coder->index);
  91                         assert(coder->pos <= 3);
  92                         coder->sequence = SEQ_PADDING;
  93                         break;
  94                 }
  95
  96                 coder->sequence = SEQ_UNPADDED;
  97
  98         // Fall through
  99
 100         case SEQ_UNPADDED:
 101         case SEQ_UNCOMPRESSED: {
 102                 const lzma_vli size = coder->sequence == SEQ_UNPADDED
 103                                 ? coder->iter.block.unpadded_size
 104                                 : coder->iter.block.uncompressed_size;
 105
 106                 ret = lzma_vli_encode(size, &coder->pos,
 107                                 out, out_pos, out_size);
 108                 if (ret != LZMA_STREAM_END)
 109                         goto out;
 110
 111                 ret = LZMA_OK;
 112                 coder->pos = 0;
 113
 114                 // Advance to SEQ_UNCOMPRESSED or SEQ_NEXT.
 115                 ++coder->sequence;
 116                 break;
 117         }
 118
 119         case SEQ_PADDING:
 120                 if (coder->pos > 0) {
 121                         --coder->pos;
 122                         out[(*out_pos)++] = 0x00;
 123                         break;
 124                 }
 125
 126                 // Finish the CRC32 calculation.
 127                 coder->crc32 = lzma_crc32(out + out_start,
 128                                 *out_pos - out_start, coder->crc32);
 129
 130                 coder->sequence = SEQ_CRC32;
 131
 132         // Fall through
 133
 134         case SEQ_CRC32:
 135                 // We don't use the main loop, because we don't want
 136                 // coder->crc32 to be touched anymore.
 137                 do {
 138                         if (*out_pos == out_size)
 139                                 return LZMA_OK;
 140
 141                         out[*out_pos] = (coder->crc32 >> (coder->pos * 8))
 142                                         & 0xFF;
 143                         ++*out_pos;
 144
 145                 } while (++coder->pos < 4);
 146
 147                 return LZMA_STREAM_END;
 148
 149         default:
 150                 assert(0);
 151                 return LZMA_PROG_ERROR;
 152         }
 153
 154 out:
 155         // Update the CRC32.
 156         //
 157         // Avoid null pointer + 0 (undefined behavior) in "out + out_start".
 158         // In such a case we had no input and thus out_used == 0.
 159         {
 160                 const size_t out_used = *out_pos - out_start;
 161                 if (out_used > 0)
 162                         coder->crc32 = lzma_crc32(out + out_start,
 163                                         out_used, coder->crc32);
 164         }
 165
 166         return ret;
 167 }
 168
 169
 170 static void
 171 index_encoder_end(void *coder, const lzma_allocator *allocator)
 172 {
 173         lzma_free(coder, allocator);
 174         return;
 175 }
 176
 177
 178 static void
 179 index_encoder_reset(lzma_index_coder *coder, const lzma_index *i)
 180 {
 181         lzma_index_iter_init(&coder->iter, i);
 182
 183         coder->sequence = SEQ_INDICATOR;
 184         coder->index = i;
 185         coder->pos = 0;
 186         coder->crc32 = 0;
 187
 188         return;
 189 }
 190
 191
 192 extern lzma_ret
 193 lzma_index_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 194                 const lzma_index *i)
 195 {
 196         lzma_next_coder_init(&lzma_index_encoder_init, next, allocator);
 197
 198         if (i == NULL)
 199                 return LZMA_PROG_ERROR;
 200
 201         if (next->coder == NULL) {
 202                 next->coder = lzma_alloc(sizeof(lzma_index_coder), allocator);
 203                 if (next->coder == NULL)
 204                         return LZMA_MEM_ERROR;
 205
 206                 next->code = &index_encode;
 207                 next->end = &index_encoder_end;
 208         }
 209
 210         index_encoder_reset(next->coder, i);
 211
 212         return LZMA_OK;
 213 }
 214
 215
 216 extern LZMA_API(lzma_ret)
 217 lzma_index_encoder(lzma_stream *strm, const lzma_index *i)
 218 {
 219         lzma_next_strm_init(lzma_index_encoder_init, strm, i);
 220
 221         strm->internal->supported_actions[LZMA_RUN] = true;
 222         strm->internal->supported_actions[LZMA_FINISH] = true;
 223
 224         return LZMA_OK;
 225 }
 226
 227
 228 extern LZMA_API(lzma_ret)
 229 lzma_index_buffer_encode(const lzma_index *i,
 230                 uint8_t *out, size_t *out_pos, size_t out_size)
 231 {
 232         // Validate the arguments.
 233         if (i == NULL || out == NULL || out_pos == NULL || *out_pos > out_size)
 234                 return LZMA_PROG_ERROR;
 235
 236         // Don't try to encode if there's not enough output space.
 237         if (out_size - *out_pos < lzma_index_size(i))
 238                 return LZMA_BUF_ERROR;
 239
 240         // The Index encoder needs just one small data structure so we can
 241         // allocate it on stack.
 242         lzma_index_coder coder;
 243         index_encoder_reset(&coder, i);
 244
 245         // Do the actual encoding. This should never fail, but store
 246         // the original *out_pos just in case.
 247         const size_t out_start = *out_pos;
 248         lzma_ret ret = index_encode(&coder, NULL, NULL, NULL, 0,
 249                         out, out_pos, out_size, LZMA_RUN);
 250
 251         if (ret == LZMA_STREAM_END) {
 252                 ret = LZMA_OK;
 253         } else {
 254                 // We should never get here, but just in case, restore the
 255                 // output position and set the error accordingly if something
 256                 // goes wrong and debugging isn't enabled.
 257                 assert(0);
 258                 *out_pos = out_start;
 259                 ret = LZMA_PROG_ERROR;
 260         }
 261
 262         return ret;
 263 }