src/liblzma/common/block_decoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       block_decoder.c
   4 /// \brief      Decodes .lzma Blocks
   5 //
   6 //  Copyright (C) 2007 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 "block_decoder.h"
  21 #include "filter_decoder.h"
  22 #include "check.h"
  23
  24
  25 struct lzma_coder_s {
  26         enum {
  27                 SEQ_CODE,
  28                 SEQ_PADDING,
  29                 SEQ_CHECK,
  30         } sequence;
  31
  32         /// The filters in the chain; initialized with lzma_raw_decoder_init().
  33         lzma_next_coder next;
  34
  35         /// Decoding options; we also write Compressed Size and Uncompressed
  36         /// Size back to this structure when the encoding has been finished.
  37         lzma_block *options;
  38
  39         /// Compressed Size calculated while encoding
  40         lzma_vli compressed_size;
  41
  42         /// Uncompressed Size calculated while encoding
  43         lzma_vli uncompressed_size;
  44
  45         /// Maximum allowed Compressed Size; this takes into account the
  46         /// size of the Block Header and Check fields when Compressed Size
  47         /// is unknown.
  48         lzma_vli compressed_limit;
  49
  50         /// Position when reading the Check field
  51         size_t check_pos;
  52
  53         /// Check of the uncompressed data
  54         lzma_check_state check;
  55 };
  56
  57
  58 static inline bool
  59 update_size(lzma_vli *size, lzma_vli add, lzma_vli limit)
  60 {
  61         if (limit > LZMA_VLI_MAX)
  62                 limit = LZMA_VLI_MAX;
  63
  64         if (limit < *size || limit - *size < add)
  65                 return true;
  66
  67         *size += add;
  68
  69         return false;
  70 }
  71
  72
  73 static inline bool
  74 is_size_valid(lzma_vli size, lzma_vli reference)
  75 {
  76         return reference == LZMA_VLI_UNKNOWN || reference == size;
  77 }
  78
  79
  80 static lzma_ret
  81 block_decode(lzma_coder *coder, lzma_allocator *allocator,
  82                 const uint8_t *restrict in, size_t *restrict in_pos,
  83                 size_t in_size, uint8_t *restrict out,
  84                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  85 {
  86         switch (coder->sequence) {
  87         case SEQ_CODE: {
  88                 const size_t in_start = *in_pos;
  89                 const size_t out_start = *out_pos;
  90
  91                 const lzma_ret ret = coder->next.code(coder->next.coder,
  92                                 allocator, in, in_pos, in_size,
  93                                 out, out_pos, out_size, action);
  94
  95                 const size_t in_used = *in_pos - in_start;
  96                 const size_t out_used = *out_pos - out_start;
  97
  98                 // NOTE: We compare to compressed_limit here, which prevents
  99                 // the total size of the Block growing past LZMA_VLI_MAX.
 100                 if (update_size(&coder->compressed_size, in_used,
 101                                         coder->compressed_limit)
 102                                 || update_size(&coder->uncompressed_size,
 103                                         out_used,
 104                                         coder->options->uncompressed_size))
 105                         return LZMA_DATA_ERROR;
 106
 107                 lzma_check_update(&coder->check, coder->options->check,
 108                                 out + out_start, out_used);
 109
 110                 if (ret != LZMA_STREAM_END)
 111                         return ret;
 112
 113                 coder->sequence = SEQ_PADDING;
 114         }
 115
 116         // Fall through
 117
 118         case SEQ_PADDING:
 119                 // Compressed Data is padded to a multiple of four bytes.
 120                 while (coder->compressed_size & 3) {
 121                         if (*in_pos >= in_size)
 122                                 return LZMA_OK;
 123
 124                         if (in[(*in_pos)++] != 0x00)
 125                                 return LZMA_DATA_ERROR;
 126
 127                         if (update_size(&coder->compressed_size, 1,
 128                                         coder->compressed_limit))
 129                                 return LZMA_DATA_ERROR;
 130                 }
 131
 132                 // Compressed and Uncompressed Sizes are now at their final
 133                 // values. Verify that they match the values given to us.
 134                 if (!is_size_valid(coder->compressed_size,
 135                                         coder->options->compressed_size)
 136                                 || !is_size_valid(coder->uncompressed_size,
 137                                         coder->options->uncompressed_size))
 138                         return LZMA_DATA_ERROR;
 139
 140                 // Copy the values into coder->options. The caller
 141                 // may use this information to construct Index.
 142                 coder->options->compressed_size = coder->compressed_size;
 143                 coder->options->uncompressed_size = coder->uncompressed_size;
 144
 145                 if (coder->options->check == LZMA_CHECK_NONE)
 146                         return LZMA_STREAM_END;
 147
 148                 lzma_check_finish(&coder->check, coder->options->check);
 149                 coder->sequence = SEQ_CHECK;
 150
 151         // Fall through
 152
 153         case SEQ_CHECK: {
 154                 const bool chksup = lzma_check_is_supported(
 155                                 coder->options->check);
 156
 157                 while (*in_pos < in_size) {
 158                         // coder->check.buffer[] may be uninitialized when
 159                         // the Check ID is not supported.
 160                         if (chksup && coder->check.buffer.u8[coder->check_pos]
 161                                         != in[*in_pos]) {
 162                                 ++*in_pos;
 163                                 return LZMA_DATA_ERROR;
 164                         }
 165
 166                         ++*in_pos;
 167
 168                         if (++coder->check_pos == lzma_check_size(
 169                                         coder->options->check))
 170                                 return LZMA_STREAM_END;
 171                 }
 172
 173                 return LZMA_OK;
 174         }
 175         }
 176
 177         return LZMA_PROG_ERROR;
 178 }
 179
 180
 181 static void
 182 block_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
 183 {
 184         lzma_next_end(&coder->next, allocator);
 185         lzma_free(coder, allocator);
 186         return;
 187 }
 188
 189
 190 extern lzma_ret
 191 lzma_block_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 192                 lzma_block *options)
 193 {
 194         lzma_next_coder_init(lzma_block_decoder_init, next, allocator);
 195
 196         // While lzma_block_total_size_get() is meant to calculate the Total
 197         // Size, it also validates the options excluding the filters.
 198         if (lzma_block_total_size_get(options) == 0)
 199                 return LZMA_PROG_ERROR;
 200
 201         // options->check is used for array indexing so we need to know that
 202         // it is in the valid range.
 203         if ((unsigned)(options->check) > LZMA_CHECK_ID_MAX)
 204                 return LZMA_PROG_ERROR;
 205
 206         // Allocate and initialize *next->coder if needed.
 207         if (next->coder == NULL) {
 208                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 209                 if (next->coder == NULL)
 210                         return LZMA_MEM_ERROR;
 211
 212                 next->code = &block_decode;
 213                 next->end = &block_decoder_end;
 214                 next->coder->next = LZMA_NEXT_CODER_INIT;
 215         }
 216
 217         // Basic initializations
 218         next->coder->sequence = SEQ_CODE;
 219         next->coder->options = options;
 220         next->coder->compressed_size = 0;
 221         next->coder->uncompressed_size = 0;
 222
 223         // If Compressed Size is not known, we calculate the maximum allowed
 224         // value so that Total Size of the Block still is a valid VLI and
 225         // a multiple of four.
 226         next->coder->compressed_limit
 227                         = options->compressed_size == LZMA_VLI_UNKNOWN
 228                                 ? (LZMA_VLI_MAX & ~LZMA_VLI_C(3))
 229                                         - options->header_size
 230                                         - lzma_check_size(options->check)
 231                                 : options->compressed_size;
 232
 233         // Initialize the check. It's caller's problem if the Check ID is not
 234         // supported, and the Block decoder cannot verify the Check field.
 235         // Caller can test lzma_checks[options->check].
 236         next->coder->check_pos = 0;
 237         lzma_check_init(&next->coder->check, options->check);
 238
 239         // Initialize the filter chain.
 240         return lzma_raw_decoder_init(&next->coder->next, allocator,
 241                         options->filters);
 242 }
 243
 244
 245 extern LZMA_API lzma_ret
 246 lzma_block_decoder(lzma_stream *strm, lzma_block *options)
 247 {
 248         lzma_next_strm_init(lzma_block_decoder_init, strm, options);
 249
 250         strm->internal->supported_actions[LZMA_RUN] = true;
 251         strm->internal->supported_actions[LZMA_FINISH] = true;
 252
 253         return LZMA_OK;
 254 }