src/liblzma/common/auto_decoder.c

   1 // SPDX-License-Identifier: 0BSD
   2
   3 ///////////////////////////////////////////////////////////////////////////////
   4 //
   5 /// \file       auto_decoder.c
   6 /// \brief      Autodetect between .xz, .lzma (LZMA_Alone), and .lz (lzip)
   7 //
   8 //  Author:     Lasse Collin
   9 //
  10 ///////////////////////////////////////////////////////////////////////////////
  11
  12 #include "stream_decoder.h"
  13 #include "alone_decoder.h"
  14 #ifdef HAVE_LZIP_DECODER
  15 #       include "lzip_decoder.h"
  16 #endif
  17
  18
  19 typedef struct {
  20         /// .xz Stream decoder, LZMA_Alone decoder, or lzip decoder
  21         lzma_next_coder next;
  22
  23         uint64_t memlimit;
  24         uint32_t flags;
  25
  26         enum {
  27                 SEQ_INIT,
  28                 SEQ_CODE,
  29                 SEQ_FINISH,
  30         } sequence;
  31 } lzma_auto_coder;
  32
  33
  34 static lzma_ret
  35 auto_decode(void *coder_ptr, const lzma_allocator *allocator,
  36                 const uint8_t *restrict in, size_t *restrict in_pos,
  37                 size_t in_size, uint8_t *restrict out,
  38                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  39 {
  40         lzma_auto_coder *coder = coder_ptr;
  41
  42         switch (coder->sequence) {
  43         case SEQ_INIT:
  44                 if (*in_pos >= in_size)
  45                         return LZMA_OK;
  46
  47                 // Update the sequence now, because we want to continue from
  48                 // SEQ_CODE even if we return some LZMA_*_CHECK.
  49                 coder->sequence = SEQ_CODE;
  50
  51                 // Detect the file format. .xz files start with 0xFD which
  52                 // cannot be the first byte of .lzma (LZMA_Alone) format.
  53                 // The .lz format starts with 0x4C which could be the
  54                 // first byte of a .lzma file but luckily it would mean
  55                 // lc/lp/pb being 4/3/1 which liblzma doesn't support because
  56                 // lc + lp > 4. So using just 0x4C to detect .lz is OK here.
  57                 if (in[*in_pos] == 0xFD) {
  58                         return_if_error(lzma_stream_decoder_init(
  59                                         &coder->next, allocator,
  60                                         coder->memlimit, coder->flags));
  61 #ifdef HAVE_LZIP_DECODER
  62                 } else if (in[*in_pos] == 0x4C) {
  63                         return_if_error(lzma_lzip_decoder_init(
  64                                         &coder->next, allocator,
  65                                         coder->memlimit, coder->flags));
  66 #endif
  67                 } else {
  68                         return_if_error(lzma_alone_decoder_init(&coder->next,
  69                                         allocator, coder->memlimit, true));
  70
  71                         // If the application wants to know about missing
  72                         // integrity check or about the check in general, we
  73                         // need to handle it here, because LZMA_Alone decoder
  74                         // doesn't accept any flags.
  75                         if (coder->flags & LZMA_TELL_NO_CHECK)
  76                                 return LZMA_NO_CHECK;
  77
  78                         if (coder->flags & LZMA_TELL_ANY_CHECK)
  79                                 return LZMA_GET_CHECK;
  80                 }
  81
  82         // Fall through
  83
  84         case SEQ_CODE: {
  85                 const lzma_ret ret = coder->next.code(
  86                                 coder->next.coder, allocator,
  87                                 in, in_pos, in_size,
  88                                 out, out_pos, out_size, action);
  89                 if (ret != LZMA_STREAM_END
  90                                 || (coder->flags & LZMA_CONCATENATED) == 0)
  91                         return ret;
  92
  93                 coder->sequence = SEQ_FINISH;
  94         }
  95
  96         // Fall through
  97
  98         case SEQ_FINISH:
  99                 // When LZMA_CONCATENATED was used and we were decoding
 100                 // a LZMA_Alone file, we need to check that there is no
 101                 // trailing garbage and wait for LZMA_FINISH.
 102                 if (*in_pos < in_size)
 103                         return LZMA_DATA_ERROR;
 104
 105                 return action == LZMA_FINISH ? LZMA_STREAM_END : LZMA_OK;
 106
 107         default:
 108                 assert(0);
 109                 return LZMA_PROG_ERROR;
 110         }
 111 }
 112
 113
 114 static void
 115 auto_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
 116 {
 117         lzma_auto_coder *coder = coder_ptr;
 118         lzma_next_end(&coder->next, allocator);
 119         lzma_free(coder, allocator);
 120         return;
 121 }
 122
 123
 124 static lzma_check
 125 auto_decoder_get_check(const void *coder_ptr)
 126 {
 127         const lzma_auto_coder *coder = coder_ptr;
 128
 129         // It is LZMA_Alone if get_check is NULL.
 130         return coder->next.get_check == NULL ? LZMA_CHECK_NONE
 131                         : coder->next.get_check(coder->next.coder);
 132 }
 133
 134
 135 static lzma_ret
 136 auto_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
 137                 uint64_t *old_memlimit, uint64_t new_memlimit)
 138 {
 139         lzma_auto_coder *coder = coder_ptr;
 140
 141         lzma_ret ret;
 142
 143         if (coder->next.memconfig != NULL) {
 144                 ret = coder->next.memconfig(coder->next.coder,
 145                                 memusage, old_memlimit, new_memlimit);
 146                 assert(*old_memlimit == coder->memlimit);
 147         } else {
 148                 // No coder is configured yet. Use the base value as
 149                 // the current memory usage.
 150                 *memusage = LZMA_MEMUSAGE_BASE;
 151                 *old_memlimit = coder->memlimit;
 152
 153                 ret = LZMA_OK;
 154                 if (new_memlimit != 0 && new_memlimit < *memusage)
 155                         ret = LZMA_MEMLIMIT_ERROR;
 156         }
 157
 158         if (ret == LZMA_OK && new_memlimit != 0)
 159                 coder->memlimit = new_memlimit;
 160
 161         return ret;
 162 }
 163
 164
 165 static lzma_ret
 166 auto_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 167                 uint64_t memlimit, uint32_t flags)
 168 {
 169         lzma_next_coder_init(&auto_decoder_init, next, allocator);
 170
 171         if (flags & ~LZMA_SUPPORTED_FLAGS)
 172                 return LZMA_OPTIONS_ERROR;
 173
 174         lzma_auto_coder *coder = next->coder;
 175         if (coder == NULL) {
 176                 coder = lzma_alloc(sizeof(lzma_auto_coder), allocator);
 177                 if (coder == NULL)
 178                         return LZMA_MEM_ERROR;
 179
 180                 next->coder = coder;
 181                 next->code = &auto_decode;
 182                 next->end = &auto_decoder_end;
 183                 next->get_check = &auto_decoder_get_check;
 184                 next->memconfig = &auto_decoder_memconfig;
 185                 coder->next = LZMA_NEXT_CODER_INIT;
 186         }
 187
 188         coder->memlimit = my_max(1, memlimit);
 189         coder->flags = flags;
 190         coder->sequence = SEQ_INIT;
 191
 192         return LZMA_OK;
 193 }
 194
 195
 196 extern LZMA_API(lzma_ret)
 197 lzma_auto_decoder(lzma_stream *strm, uint64_t memlimit, uint32_t flags)
 198 {
 199         lzma_next_strm_init(auto_decoder_init, strm, memlimit, flags);
 200
 201         strm->internal->supported_actions[LZMA_RUN] = true;
 202         strm->internal->supported_actions[LZMA_FINISH] = true;
 203
 204         return LZMA_OK;
 205 }