src/liblzma/common/auto_decoder.c

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