src/liblzma/common/alone_decoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       alone_decoder.c
   4 /// \brief      Decoder for LZMA_Alone files
   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 "alone_decoder.h"
  21 #include "lzma_decoder.h"
  22 #include "lz_decoder.h"
  23
  24
  25 struct lzma_coder_s {
  26         lzma_next_coder next;
  27
  28         enum {
  29                 SEQ_PROPERTIES,
  30                 SEQ_DICTIONARY_SIZE,
  31                 SEQ_UNCOMPRESSED_SIZE,
  32                 SEQ_CODER_INIT,
  33                 SEQ_CODE,
  34         } sequence;
  35
  36         /// Position in the header fields
  37         size_t pos;
  38
  39         /// Uncompressed size decoded from the header
  40         lzma_vli uncompressed_size;
  41
  42         /// Memory usage limit
  43         uint64_t memlimit;
  44
  45         /// Amount of memory actually needed (only an estimate)
  46         uint64_t memusage;
  47
  48         /// Options decoded from the header needed to initialize
  49         /// the LZMA decoder
  50         lzma_options_lzma options;
  51 };
  52
  53
  54 static lzma_ret
  55 alone_decode(lzma_coder *coder,
  56                 lzma_allocator *allocator lzma_attribute((unused)),
  57                 const uint8_t *restrict in, size_t *restrict in_pos,
  58                 size_t in_size, uint8_t *restrict out,
  59                 size_t *restrict out_pos, size_t out_size,
  60                 lzma_action action)
  61 {
  62         while (*out_pos < out_size
  63                         && (coder->sequence == SEQ_CODE || *in_pos < in_size))
  64         switch (coder->sequence) {
  65         case SEQ_PROPERTIES:
  66                 if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
  67                         return LZMA_FORMAT_ERROR;
  68
  69                 coder->sequence = SEQ_DICTIONARY_SIZE;
  70                 ++*in_pos;
  71                 break;
  72
  73         case SEQ_DICTIONARY_SIZE:
  74                 coder->options.dict_size
  75                                 |= (size_t)(in[*in_pos]) << (coder->pos * 8);
  76
  77                 if (++coder->pos == 4) {
  78                         if (coder->options.dict_size != UINT32_MAX) {
  79                                 // A hack to ditch tons of false positives:
  80                                 // We allow only dictionary sizes that are
  81                                 // 2^n or 2^n + 2^(n-1). LZMA_Alone created
  82                                 // only files with 2^n, but accepts any
  83                                 // dictionary size. If someone complains, this
  84                                 // will be reconsidered.
  85                                 uint32_t d = coder->options.dict_size - 1;
  86                                 d |= d >> 2;
  87                                 d |= d >> 3;
  88                                 d |= d >> 4;
  89                                 d |= d >> 8;
  90                                 d |= d >> 16;
  91                                 ++d;
  92
  93                                 if (d != coder->options.dict_size)
  94                                         return LZMA_FORMAT_ERROR;
  95                         }
  96
  97                         coder->pos = 0;
  98                         coder->sequence = SEQ_UNCOMPRESSED_SIZE;
  99                 }
 100
 101                 ++*in_pos;
 102                 break;
 103
 104         case SEQ_UNCOMPRESSED_SIZE:
 105                 coder->uncompressed_size
 106                                 |= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
 107                 ++*in_pos;
 108                 if (++coder->pos < 8)
 109                         break;
 110
 111                 // Another hack to ditch false positives: Assume that
 112                 // if the uncompressed size is known, it must be less
 113                 // than 256 GiB. Again, if someone complains, this
 114                 // will be reconsidered.
 115                 if (coder->uncompressed_size != LZMA_VLI_UNKNOWN
 116                                 && coder->uncompressed_size
 117                                         >= (LZMA_VLI_C(1) << 38))
 118                         return LZMA_FORMAT_ERROR;
 119
 120                 // Calculate the memory usage so that it is ready
 121                 // for SEQ_CODER_INIT.
 122                 coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
 123                                 + LZMA_MEMUSAGE_BASE;
 124
 125                 coder->pos = 0;
 126                 coder->sequence = SEQ_CODER_INIT;
 127
 128         // Fall through
 129
 130         case SEQ_CODER_INIT: {
 131                 if (coder->memusage > coder->memlimit)
 132                         return LZMA_MEMLIMIT_ERROR;
 133
 134                 lzma_filter_info filters[2] = {
 135                         {
 136                                 .init = &lzma_lzma_decoder_init,
 137                                 .options = &coder->options,
 138                         }, {
 139                                 .init = NULL,
 140                         }
 141                 };
 142
 143                 const lzma_ret ret = lzma_next_filter_init(&coder->next,
 144                                 allocator, filters);
 145                 if (ret != LZMA_OK)
 146                         return ret;
 147
 148                 // Use a hack to set the uncompressed size.
 149                 lzma_lz_decoder_uncompressed(coder->next.coder,
 150                                 coder->uncompressed_size);
 151
 152                 coder->sequence = SEQ_CODE;
 153                 break;
 154         }
 155
 156         case SEQ_CODE: {
 157                 return coder->next.code(coder->next.coder,
 158                                 allocator, in, in_pos, in_size,
 159                                 out, out_pos, out_size, action);
 160         }
 161
 162         default:
 163                 return LZMA_PROG_ERROR;
 164         }
 165
 166         return LZMA_OK;
 167 }
 168
 169
 170 static void
 171 alone_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
 172 {
 173         lzma_next_end(&coder->next, allocator);
 174         lzma_free(coder, allocator);
 175         return;
 176 }
 177
 178
 179 static lzma_ret
 180 alone_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,
 181                 uint64_t *old_memlimit, uint64_t new_memlimit)
 182 {
 183         if (new_memlimit != 0 && new_memlimit < coder->memusage)
 184                 return LZMA_MEMLIMIT_ERROR;
 185
 186         *memusage = coder->memusage;
 187         *old_memlimit = coder->memlimit;
 188         coder->memlimit = new_memlimit;
 189
 190         return LZMA_OK;
 191 }
 192
 193
 194 extern lzma_ret
 195 lzma_alone_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 196                 uint64_t memlimit)
 197 {
 198         lzma_next_coder_init(lzma_alone_decoder_init, next, allocator);
 199
 200         if (memlimit == 0)
 201                 return LZMA_PROG_ERROR;
 202
 203         if (next->coder == NULL) {
 204                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 205                 if (next->coder == NULL)
 206                         return LZMA_MEM_ERROR;
 207
 208                 next->code = &alone_decode;
 209                 next->end = &alone_decoder_end;
 210                 next->memconfig = &alone_decoder_memconfig;
 211                 next->coder->next = LZMA_NEXT_CODER_INIT;
 212         }
 213
 214         next->coder->sequence = SEQ_PROPERTIES;
 215         next->coder->pos = 0;
 216         next->coder->options.dict_size = 0;
 217         next->coder->options.preset_dict = NULL;
 218         next->coder->options.preset_dict_size = 0;
 219         next->coder->uncompressed_size = 0;
 220         next->coder->memlimit = memlimit;
 221         next->coder->memusage = LZMA_MEMUSAGE_BASE;
 222
 223         return LZMA_OK;
 224 }
 225
 226
 227 extern LZMA_API(lzma_ret)
 228 lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
 229 {
 230         lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit);
 231
 232         strm->internal->supported_actions[LZMA_RUN] = true;
 233         strm->internal->supported_actions[LZMA_FINISH] = true;
 234
 235         return LZMA_OK;
 236 }