contrib/xz/src/liblzma/common/alone_decoder.c

   1 ///////////////////////////////////////////////////////////////////////////////
   2 //
   3 /// \file       alone_decoder.c
   4 /// \brief      Decoder for LZMA_Alone files
   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 "alone_decoder.h"
  14 #include "lzma_decoder.h"
  15 #include "lz_decoder.h"
  16
  17
  18 struct lzma_coder_s {
  19         lzma_next_coder next;
  20
  21         enum {
  22                 SEQ_PROPERTIES,
  23                 SEQ_DICTIONARY_SIZE,
  24                 SEQ_UNCOMPRESSED_SIZE,
  25                 SEQ_CODER_INIT,
  26                 SEQ_CODE,
  27         } sequence;
  28
  29         /// Position in the header fields
  30         size_t pos;
  31
  32         /// Uncompressed size decoded from the header
  33         lzma_vli uncompressed_size;
  34
  35         /// Memory usage limit
  36         uint64_t memlimit;
  37
  38         /// Amount of memory actually needed (only an estimate)
  39         uint64_t memusage;
  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_lclppb_decode(&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.dict_size
  68                                 |= (size_t)(in[*in_pos]) << (coder->pos * 8);
  69
  70                 if (++coder->pos == 4) {
  71                         if (coder->options.dict_size != UINT32_MAX) {
  72                                 // A hack to ditch tons of false positives:
  73                                 // We allow only dictionary sizes that are
  74                                 // 2^n or 2^n + 2^(n-1). LZMA_Alone created
  75                                 // only files with 2^n, but accepts any
  76                                 // dictionary size. If someone complains, this
  77                                 // will be reconsidered.
  78                                 uint32_t d = coder->options.dict_size - 1;
  79                                 d |= d >> 2;
  80                                 d |= d >> 3;
  81                                 d |= d >> 4;
  82                                 d |= d >> 8;
  83                                 d |= d >> 16;
  84                                 ++d;
  85
  86                                 if (d != coder->options.dict_size)
  87                                         return LZMA_FORMAT_ERROR;
  88                         }
  89
  90                         coder->pos = 0;
  91                         coder->sequence = SEQ_UNCOMPRESSED_SIZE;
  92                 }
  93
  94                 ++*in_pos;
  95                 break;
  96
  97         case SEQ_UNCOMPRESSED_SIZE:
  98                 coder->uncompressed_size
  99                                 |= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
 100                 ++*in_pos;
 101                 if (++coder->pos < 8)
 102                         break;
 103
 104                 // Another hack to ditch false positives: Assume that
 105                 // if the uncompressed size is known, it must be less
 106                 // than 256 GiB. Again, if someone complains, this
 107                 // will be reconsidered.
 108                 if (coder->uncompressed_size != LZMA_VLI_UNKNOWN
 109                                 && coder->uncompressed_size
 110                                         >= (LZMA_VLI_C(1) << 38))
 111                         return LZMA_FORMAT_ERROR;
 112
 113                 // Calculate the memory usage so that it is ready
 114                 // for SEQ_CODER_INIT.
 115                 coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
 116                                 + LZMA_MEMUSAGE_BASE;
 117
 118                 coder->pos = 0;
 119                 coder->sequence = SEQ_CODER_INIT;
 120
 121         // Fall through
 122
 123         case SEQ_CODER_INIT: {
 124                 if (coder->memusage > coder->memlimit)
 125                         return LZMA_MEMLIMIT_ERROR;
 126
 127                 lzma_filter_info filters[2] = {
 128                         {
 129                                 .init = &lzma_lzma_decoder_init,
 130                                 .options = &coder->options,
 131                         }, {
 132                                 .init = NULL,
 133                         }
 134                 };
 135
 136                 const lzma_ret ret = lzma_next_filter_init(&coder->next,
 137                                 allocator, filters);
 138                 if (ret != LZMA_OK)
 139                         return ret;
 140
 141                 // Use a hack to set the uncompressed size.
 142                 lzma_lz_decoder_uncompressed(coder->next.coder,
 143                                 coder->uncompressed_size);
 144
 145                 coder->sequence = SEQ_CODE;
 146                 break;
 147         }
 148
 149         case SEQ_CODE: {
 150                 return coder->next.code(coder->next.coder,
 151                                 allocator, in, in_pos, in_size,
 152                                 out, out_pos, out_size, action);
 153         }
 154
 155         default:
 156                 return LZMA_PROG_ERROR;
 157         }
 158
 159         return LZMA_OK;
 160 }
 161
 162
 163 static void
 164 alone_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
 165 {
 166         lzma_next_end(&coder->next, allocator);
 167         lzma_free(coder, allocator);
 168         return;
 169 }
 170
 171
 172 static lzma_ret
 173 alone_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,
 174                 uint64_t *old_memlimit, uint64_t new_memlimit)
 175 {
 176         *memusage = coder->memusage;
 177         *old_memlimit = coder->memlimit;
 178
 179         if (new_memlimit != 0) {
 180                 if (new_memlimit < coder->memusage)
 181                         return LZMA_MEMLIMIT_ERROR;
 182
 183                 coder->memlimit = new_memlimit;
 184         }
 185
 186         return LZMA_OK;
 187 }
 188
 189
 190 extern lzma_ret
 191 lzma_alone_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
 192                 uint64_t memlimit)
 193 {
 194         lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);
 195
 196         if (memlimit == 0)
 197                 return LZMA_PROG_ERROR;
 198
 199         if (next->coder == NULL) {
 200                 next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
 201                 if (next->coder == NULL)
 202                         return LZMA_MEM_ERROR;
 203
 204                 next->code = &alone_decode;
 205                 next->end = &alone_decoder_end;
 206                 next->memconfig = &alone_decoder_memconfig;
 207                 next->coder->next = LZMA_NEXT_CODER_INIT;
 208         }
 209
 210         next->coder->sequence = SEQ_PROPERTIES;
 211         next->coder->pos = 0;
 212         next->coder->options.dict_size = 0;
 213         next->coder->options.preset_dict = NULL;
 214         next->coder->options.preset_dict_size = 0;
 215         next->coder->uncompressed_size = 0;
 216         next->coder->memlimit = memlimit;
 217         next->coder->memusage = LZMA_MEMUSAGE_BASE;
 218
 219         return LZMA_OK;
 220 }
 221
 222
 223 extern LZMA_API(lzma_ret)
 224 lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
 225 {
 226         lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit);
 227
 228         strm->internal->supported_actions[LZMA_RUN] = true;
 229         strm->internal->supported_actions[LZMA_FINISH] = true;
 230
 231         return LZMA_OK;
 232 }