src/liblzma/common/index_encoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       index_encoder.c
   4 /// \brief      Encodes the Index field
   5 //
   6 //  Copyright (C) 2008 Lasse Collin
   7 //
   8 //  This library is free software; you can redistribute it and/or
   9 //  modify it under the terms of the GNU Lesser General Public
  10 //  License as published by the Free Software Foundation; either
  11 //  version 2.1 of the License, or (at your option) any later version.
  12 //
  13 //  This library is distributed in the hope that it will be useful,
  14 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 //  Lesser General Public License for more details.
  17 //
  18 ///////////////////////////////////////////////////////////////////////////////
  19
  20 #include "index_encoder.h"
  21 #include "index.h"
  22 #include "check.h"
  23
  24
  25 struct lzma_coder_s {
  26         enum {
  27                 SEQ_INDICATOR,
  28                 SEQ_COUNT,
  29                 SEQ_TOTAL,
  30                 SEQ_UNCOMPRESSED,
  31                 SEQ_NEXT,
  32                 SEQ_PADDING,
  33                 SEQ_CRC32,
  34         } sequence;
  35
  36         /// Index given to us to encode. Note that we modify it in sense that
  37         /// we read it, and read position is tracked in lzma_index structure.
  38         lzma_index *index;
  39
  40         /// The current Index Record being encoded
  41         lzma_index_record record;
  42
  43         /// Position in integers
  44         size_t pos;
  45
  46         /// CRC32 of the List of Records field
  47         uint32_t crc32;
  48 };
  49
  50
  51 static lzma_ret
  52 index_encode(lzma_coder *coder,
  53                 lzma_allocator *allocator lzma_attribute((unused)),
  54                 const uint8_t *restrict in lzma_attribute((unused)),
  55                 size_t *restrict in_pos lzma_attribute((unused)),
  56                 size_t in_size lzma_attribute((unused)),
  57                 uint8_t *restrict out, size_t *restrict out_pos,
  58                 size_t out_size, lzma_action action lzma_attribute((unused)))
  59 {
  60         // Position where to start calculating CRC32. The idea is that we
  61         // need to call lzma_crc32() only once per call to index_encode().
  62         const size_t out_start = *out_pos;
  63
  64         // Return value to use if we return at the end of this function.
  65         // We use "goto out" to jump out of the while-switch construct
  66         // instead of returning directly, because that way we don't need
  67         // to copypaste the lzma_crc32() call to many places.
  68         lzma_ret ret = LZMA_OK;
  69
  70         while (*out_pos < out_size)
  71         switch (coder->sequence) {
  72         case SEQ_INDICATOR:
  73                 out[*out_pos] = 0x00;
  74                 ++*out_pos;
  75                 coder->sequence = SEQ_COUNT;
  76                 break;
  77
  78         case SEQ_COUNT: {
  79                 const lzma_vli index_count = lzma_index_count(coder->index);
  80                 ret = lzma_vli_encode(index_count, &coder->pos,
  81                                 out, out_pos, out_size);
  82                 if (ret != LZMA_STREAM_END)
  83                         goto out;
  84
  85                 ret = LZMA_OK;
  86                 coder->pos = 0;
  87                 coder->sequence = SEQ_NEXT;
  88                 break;
  89         }
  90
  91         case SEQ_NEXT:
  92                 if (lzma_index_read(coder->index, &coder->record)) {
  93                         // Get the size of the Index Padding field.
  94                         coder->pos = lzma_index_padding_size(coder->index);
  95                         assert(coder->pos <= 3);
  96                         coder->sequence = SEQ_PADDING;
  97                         break;
  98                 }
  99
 100                 // Total Size must be a multiple of four.
 101                 if (coder->record.total_size & 3)
 102                         return LZMA_PROG_ERROR;
 103
 104                 coder->sequence = SEQ_TOTAL;
 105
 106         // Fall through
 107
 108         case SEQ_TOTAL:
 109         case SEQ_UNCOMPRESSED: {
 110                 const lzma_vli size = coder->sequence == SEQ_TOTAL
 111                                 ? total_size_encode(coder->record.total_size)
 112                                 : coder->record.uncompressed_size;
 113
 114                 ret = lzma_vli_encode(size, &coder->pos,
 115                                 out, out_pos, out_size);
 116                 if (ret != LZMA_STREAM_END)
 117                         goto out;
 118
 119                 ret = LZMA_OK;
 120                 coder->pos = 0;
 121
 122                 // Advance to SEQ_UNCOMPRESSED or SEQ_NEXT.
 123                 ++coder->sequence;
 124                 break;
 125         }
 126
 127         case SEQ_PADDING:
 128                 if (coder->pos > 0) {
 129                         --coder->pos;
 130                         out[(*out_pos)++] = 0x00;
 131                         break;
 132                 }
 133
 134                 // Finish the CRC32 calculation.
 135                 coder->crc32 = lzma_crc32(out + out_start,
 136                                 *out_pos - out_start, coder->crc32);
 137
 138                 coder->sequence = SEQ_CRC32;
 139
 140         // Fall through
 141
 142         case SEQ_CRC32:
 143                 // We don't use the main loop, because we don't want
 144                 // coder->crc32 to be touched anymore.
 145                 do {
 146                         if (*out_pos == out_size)
 147                                 return LZMA_OK;
 148
 149                         out[*out_pos] = (coder->crc32 >> (coder->pos * 8))
 150                                         & 0xFF;
 151                         ++*out_pos;
 152
 153                 } while (++coder->pos < 4);
 154
 155                 return LZMA_STREAM_END;
 156
 157         default:
 158                 assert(0);
 159                 return LZMA_PROG_ERROR;
 160         }
 161
 162 out:
 163         // Update the CRC32.
 164         coder->crc32 = lzma_crc32(out + out_start,
 165                         *out_pos - out_start, coder->crc32);
 166
 167         return ret;
 168 }
 169
 170
 171 static void
 172 index_encoder_end(lzma_coder *coder, lzma_allocator *allocator)
 173 {
 174         lzma_free(coder, allocator);
 175         return;
 176 }
 177
 178
 179 extern lzma_ret
 180 lzma_index_encoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 181                 lzma_index *i)
 182 {
 183         lzma_next_coder_init(lzma_index_encoder_init, next, allocator);
 184
 185         if (i == NULL)
 186                 return LZMA_PROG_ERROR;
 187
 188         if (next->coder == NULL) {
 189                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 190                 if (next->coder == NULL)
 191                         return LZMA_MEM_ERROR;
 192
 193                 next->code = &index_encode;
 194                 next->end = &index_encoder_end;
 195         }
 196
 197         lzma_index_rewind(i);
 198
 199         next->coder->sequence = SEQ_INDICATOR;
 200         next->coder->index = i;
 201         next->coder->pos = 0;
 202         next->coder->crc32 = 0;
 203
 204         return LZMA_OK;
 205 }
 206
 207
 208 extern LZMA_API lzma_ret
 209 lzma_index_encoder(lzma_stream *strm, lzma_index *i)
 210 {
 211         lzma_next_strm_init(lzma_index_encoder_init, strm, i);
 212
 213         strm->internal->supported_actions[LZMA_RUN] = true;
 214
 215         return LZMA_OK;
 216 }