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
  23
  24 struct lzma_coder_s {
  25         lzma_next_coder next;
  26
  27         enum {
  28                 SEQ_PROPERTIES,
  29                 SEQ_DICTIONARY_SIZE,
  30                 SEQ_UNCOMPRESSED_SIZE,
  31                 SEQ_CODER_INIT,
  32                 SEQ_CODE,
  33         } sequence;
  34
  35         /// Position in the header fields
  36         size_t pos;
  37
  38         /// Uncompressed size decoded from the header
  39         lzma_vli uncompressed_size;
  40
  41         /// Options decoded from the header needed to initialize
  42         /// the LZMA decoder
  43         lzma_options_lzma options;
  44 };
  45
  46
  47 static lzma_ret
  48 alone_decode(lzma_coder *coder,
  49                 lzma_allocator *allocator lzma_attribute((unused)),
  50                 const uint8_t *restrict in, size_t *restrict in_pos,
  51                 size_t in_size, uint8_t *restrict out,
  52                 size_t *restrict out_pos, size_t out_size,
  53                 lzma_action action)
  54 {
  55         while (*out_pos < out_size
  56                         && (coder->sequence == SEQ_CODE || *in_pos < in_size))
  57         switch (coder->sequence) {
  58         case SEQ_PROPERTIES:
  59                 if (lzma_lzma_decode_properties(&coder->options, in[*in_pos]))
  60                         return LZMA_FORMAT_ERROR;
  61
  62                 coder->sequence = SEQ_DICTIONARY_SIZE;
  63                 ++*in_pos;
  64                 break;
  65
  66         case SEQ_DICTIONARY_SIZE:
  67                 coder->options.dictionary_size
  68                                 |= (size_t)(in[*in_pos]) << (coder->pos * 8);
  69
  70                 if (++coder->pos == 4) {
  71                         if (coder->options.dictionary_size
  72                                         < LZMA_DICTIONARY_SIZE_MIN
  73                                         || coder->options.dictionary_size
  74                                         > LZMA_DICTIONARY_SIZE_MAX)
  75                                 return LZMA_FORMAT_ERROR;
  76
  77                         // A hack to ditch tons of false positives: We allow
  78                         // only dictionary sizes that are 2^n or 2^n + 2^(n-1).
  79                         // LZMA_Alone created only files with 2^n, but accepts
  80                         // any dictionary size. If someone complains, this
  81                         // will be reconsidered.
  82                         uint32_t d = coder->options.dictionary_size - 1;
  83                         d |= d >> 2;
  84                         d |= d >> 3;
  85                         d |= d >> 4;
  86                         d |= d >> 8;
  87                         d |= d >> 16;
  88                         ++d;
  89
  90                         if (d != coder->options.dictionary_size)
  91                                 return LZMA_FORMAT_ERROR;
  92
  93                         coder->pos = 0;
  94                         coder->sequence = SEQ_UNCOMPRESSED_SIZE;
  95                 }
  96
  97                 ++*in_pos;
  98                 break;
  99
 100         case SEQ_UNCOMPRESSED_SIZE:
 101                 coder->uncompressed_size
 102                                 |= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
 103
 104                 if (++coder->pos == 8) {
 105                         // Another hack to ditch false positives: Assume that
 106                         // if the uncompressed size is known, it must be less
 107                         // than 256 GiB. Again, if someone complains, this
 108                         // will be reconsidered.
 109                         if (coder->uncompressed_size != LZMA_VLI_VALUE_UNKNOWN
 110                                         && coder->uncompressed_size
 111                                                 >= (LZMA_VLI_C(1) << 38))
 112                                 return LZMA_FORMAT_ERROR;
 113
 114                         coder->pos = 0;
 115                         coder->sequence = SEQ_CODER_INIT;
 116                 }
 117
 118                 ++*in_pos;
 119                 break;
 120
 121         case SEQ_CODER_INIT: {
 122                 // Two is enough because there won't be implicit filters.
 123                 lzma_filter_info filters[2] = {
 124                         {
 125                                 .init = &lzma_lzma_decoder_init,
 126                                 .options = &coder->options,
 127                         }, {
 128                                 .init = NULL,
 129                         }
 130                 };
 131
 132                 const lzma_ret ret = lzma_next_filter_init(&coder->next,
 133                                 allocator, filters);
 134                 if (ret != LZMA_OK)
 135                         return ret;
 136
 137                 // Use a hack to set the uncompressed size.
 138                 lzma_lzma_decoder_uncompressed_size(&coder->next,
 139                                 coder->uncompressed_size);
 140
 141                 coder->sequence = SEQ_CODE;
 142         }
 143
 144         // Fall through
 145
 146         case SEQ_CODE: {
 147                 return coder->next.code(coder->next.coder,
 148                                 allocator, in, in_pos, in_size,
 149                                 out, out_pos, out_size, action);
 150         }
 151
 152         default:
 153                 return LZMA_PROG_ERROR;
 154         }
 155
 156         return LZMA_OK;
 157 }
 158
 159
 160 static void
 161 alone_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
 162 {
 163         lzma_next_coder_end(&coder->next, allocator);
 164         lzma_free(coder, allocator);
 165         return;
 166 }
 167
 168
 169 static lzma_ret
 170 alone_decoder_init(lzma_next_coder *next, lzma_allocator *allocator)
 171 {
 172         if (next->coder == NULL) {
 173                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 174                 if (next->coder == NULL)
 175                         return LZMA_MEM_ERROR;
 176
 177                 next->code = &alone_decode;
 178                 next->end = &alone_decoder_end;
 179                 next->coder->next = LZMA_NEXT_CODER_INIT;
 180         }
 181
 182         next->coder->sequence = SEQ_PROPERTIES;
 183         next->coder->pos = 0;
 184         next->coder->options.dictionary_size = 0;
 185         next->coder->uncompressed_size = 0;
 186
 187         return LZMA_OK;
 188 }
 189
 190
 191 extern lzma_ret
 192 lzma_alone_decoder_init(lzma_next_coder *next, lzma_allocator *allocator)
 193 {
 194         lzma_next_coder_init0(alone_decoder_init, next, allocator);
 195 }
 196
 197
 198 extern LZMA_API lzma_ret
 199 lzma_alone_decoder(lzma_stream *strm)
 200 {
 201         lzma_next_strm_init0(strm, alone_decoder_init);
 202
 203         strm->internal->supported_actions[LZMA_RUN] = true;
 204         strm->internal->supported_actions[LZMA_SYNC_FLUSH] = true;
 205
 206         return LZMA_OK;
 207 }