external/public-domain/xz/dist/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 struct lzma_coder_s {
  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 };
  41
  42
  43 static lzma_ret
  44 index_encode(lzma_coder *coder,
  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         // Position where to start calculating CRC32. The idea is that we
  54         // need to call lzma_crc32() only once per call to index_encode().
  55         const size_t out_start = *out_pos;
  56
  57         // Return value to use if we return at the end of this function.
  58         // We use "goto out" to jump out of the while-switch construct
  59         // instead of returning directly, because that way we don't need
  60         // to copypaste the lzma_crc32() call to many places.
  61         lzma_ret ret = LZMA_OK;
  62
  63         while (*out_pos < out_size)
  64         switch (coder->sequence) {
  65         case SEQ_INDICATOR:
  66                 out[*out_pos] = 0x00;
  67                 ++*out_pos;
  68                 coder->sequence = SEQ_COUNT;
  69                 break;
  70
  71         case SEQ_COUNT: {
  72                 const lzma_vli count = lzma_index_block_count(coder->index);
  73                 ret = lzma_vli_encode(count, &coder->pos,
  74                                 out, out_pos, out_size);
  75                 if (ret != LZMA_STREAM_END)
  76                         goto out;
  77
  78                 ret = LZMA_OK;
  79                 coder->pos = 0;
  80                 coder->sequence = SEQ_NEXT;
  81                 break;
  82         }
  83
  84         case SEQ_NEXT:
  85                 if (lzma_index_iter_next(
  86                                 &coder->iter, LZMA_INDEX_ITER_BLOCK)) {
  87                         // Get the size of the Index Padding field.
  88                         coder->pos = lzma_index_padding_size(coder->index);
  89                         assert(coder->pos <= 3);
  90                         coder->sequence = SEQ_PADDING;
  91                         break;
  92                 }
  93
  94                 coder->sequence = SEQ_UNPADDED;
  95
  96         // Fall through
  97
  98         case SEQ_UNPADDED:
  99         case SEQ_UNCOMPRESSED: {
 100                 const lzma_vli size = coder->sequence == SEQ_UNPADDED
 101                                 ? coder->iter.block.unpadded_size
 102                                 : coder->iter.block.uncompressed_size;
 103
 104                 ret = lzma_vli_encode(size, &coder->pos,
 105                                 out, out_pos, out_size);
 106                 if (ret != LZMA_STREAM_END)
 107                         goto out;
 108
 109                 ret = LZMA_OK;
 110                 coder->pos = 0;
 111
 112                 // Advance to SEQ_UNCOMPRESSED or SEQ_NEXT.
 113                 ++coder->sequence;
 114                 break;
 115         }
 116
 117         case SEQ_PADDING:
 118                 if (coder->pos > 0) {
 119                         --coder->pos;
 120                         out[(*out_pos)++] = 0x00;
 121                         break;
 122                 }
 123
 124                 // Finish the CRC32 calculation.
 125                 coder->crc32 = lzma_crc32(out + out_start,
 126                                 *out_pos - out_start, coder->crc32);
 127
 128                 coder->sequence = SEQ_CRC32;
 129
 130         // Fall through
 131
 132         case SEQ_CRC32:
 133                 // We don't use the main loop, because we don't want
 134                 // coder->crc32 to be touched anymore.
 135                 do {
 136                         if (*out_pos == out_size)
 137                                 return LZMA_OK;
 138
 139                         out[*out_pos] = (coder->crc32 >> (coder->pos * 8))
 140                                         & 0xFF;
 141                         ++*out_pos;
 142
 143                 } while (++coder->pos < 4);
 144
 145                 return LZMA_STREAM_END;
 146
 147         default:
 148                 assert(0);
 149                 return LZMA_PROG_ERROR;
 150         }
 151
 152 out:
 153         // Update the CRC32.
 154         coder->crc32 = lzma_crc32(out + out_start,
 155                         *out_pos - out_start, coder->crc32);
 156
 157         return ret;
 158 }
 159
 160
 161 static void
 162 index_encoder_end(lzma_coder *coder, const lzma_allocator *allocator)
 163 {
 164         lzma_free(coder, allocator);
 165         return;
 166 }
 167
 168
 169 static void
 170 index_encoder_reset(lzma_coder *coder, const lzma_index *i)
 171 {
 172         lzma_index_iter_init(&coder->iter, i);
 173
 174         coder->sequence = SEQ_INDICATOR;
 175         coder->index = i;
 176         coder->pos = 0;
 177         coder->crc32 = 0;
 178
 179         return;
 180 }
 181
 182
 183 extern lzma_ret
 184 lzma_index_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 185                 const lzma_index *i)
 186 {
 187         lzma_next_coder_init(&lzma_index_encoder_init, next, allocator);
 188
 189         if (i == NULL)
 190                 return LZMA_PROG_ERROR;
 191
 192         if (next->coder == NULL) {
 193                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 194                 if (next->coder == NULL)
 195                         return LZMA_MEM_ERROR;
 196
 197                 next->code = &index_encode;
 198                 next->end = &index_encoder_end;
 199         }
 200
 201         index_encoder_reset(next->coder, i);
 202
 203         return LZMA_OK;
 204 }
 205
 206
 207 extern LZMA_API(lzma_ret)
 208 lzma_index_encoder(lzma_stream *strm, const lzma_index *i)
 209 {
 210         lzma_next_strm_init(lzma_index_encoder_init, strm, i);
 211
 212         strm->internal->supported_actions[LZMA_RUN] = true;
 213         strm->internal->supported_actions[LZMA_FINISH] = true;
 214
 215         return LZMA_OK;
 216 }
 217
 218
 219 extern LZMA_API(lzma_ret)
 220 lzma_index_buffer_encode(const lzma_index *i,
 221                 uint8_t *out, size_t *out_pos, size_t out_size)
 222 {
 223         // Validate the arguments.
 224         if (i == NULL || out == NULL || out_pos == NULL || *out_pos > out_size)
 225                 return LZMA_PROG_ERROR;
 226
 227         // Don't try to encode if there's not enough output space.
 228         if (out_size - *out_pos < lzma_index_size(i))
 229                 return LZMA_BUF_ERROR;
 230
 231         // The Index encoder needs just one small data structure so we can
 232         // allocate it on stack.
 233         lzma_coder coder;
 234         index_encoder_reset(&coder, i);
 235
 236         // Do the actual encoding. This should never fail, but store
 237         // the original *out_pos just in case.
 238         const size_t out_start = *out_pos;
 239         lzma_ret ret = index_encode(&coder, NULL, NULL, NULL, 0,
 240                         out, out_pos, out_size, LZMA_RUN);
 241
 242         if (ret == LZMA_STREAM_END) {
 243                 ret = LZMA_OK;
 244         } else {
 245                 // We should never get here, but just in case, restore the
 246                 // output position and set the error accordingly if something
 247                 // goes wrong and debugging isn't enabled.
 248                 assert(0);
 249                 *out_pos = out_start;
 250                 ret = LZMA_PROG_ERROR;
 251         }
 252
 253         return ret;
 254 }