external/public-domain/xz/dist/src/liblzma/common/auto_decoder.c

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