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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 typedef struct {
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 } lzma_auto_coder;
30
31
32 static lzma_ret
33 auto_decode(void *coder_ptr, 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         lzma_auto_coder *coder = coder_ptr;
39
40         switch (coder->sequence) {
41         case SEQ_INIT:
42                 if (*in_pos >= in_size)
43                         return LZMA_OK;
44
45                 // Update the sequence now, because we want to continue from
46                 // SEQ_CODE even if we return some LZMA_*_CHECK.
47                 coder->sequence = SEQ_CODE;
48
49                 // Detect the file format. For now this is simple, since if
50                 // it doesn't start with 0xFD (the first magic byte of the
51                 // new format), it has to be LZMA_Alone, or something that
52                 // we don't support at all.
53                 if (in[*in_pos] == 0xFD) {
54                         return_if_error(lzma_stream_decoder_init(
55                                         &coder->next, allocator,
56                                         coder->memlimit, coder->flags));
57                 } else {
58                         return_if_error(lzma_alone_decoder_init(&coder->next,
59                                         allocator, coder->memlimit, true));
60
61                         // If the application wants to know about missing
62                         // integrity check or about the check in general, we
63                         // need to handle it here, because LZMA_Alone decoder
64                         // doesn't accept any flags.
65                         if (coder->flags & LZMA_TELL_NO_CHECK)
66                                 return LZMA_NO_CHECK;
67
68                         if (coder->flags & LZMA_TELL_ANY_CHECK)
69                                 return LZMA_GET_CHECK;
70                 }
71
72         // Fall through
73
74         case SEQ_CODE: {
75                 const lzma_ret ret = coder->next.code(
76                                 coder->next.coder, allocator,
77                                 in, in_pos, in_size,
78                                 out, out_pos, out_size, action);
79                 if (ret != LZMA_STREAM_END
80                                 || (coder->flags & LZMA_CONCATENATED) == 0)
81                         return ret;
82
83                 coder->sequence = SEQ_FINISH;
84         }
85
86         // Fall through
87
88         case SEQ_FINISH:
89                 // When LZMA_DECODE_CONCATENATED was used and we were decoding
90                 // LZMA_Alone file, we need to check check that there is no
91                 // trailing garbage and wait for LZMA_FINISH.
92                 if (*in_pos < in_size)
93                         return LZMA_DATA_ERROR;
94
95                 return action == LZMA_FINISH ? LZMA_STREAM_END : LZMA_OK;
96
97         default:
98                 assert(0);
99                 return LZMA_PROG_ERROR;
100         }
101 }
102
103
104 static void
105 auto_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
106 {
107         lzma_auto_coder *coder = coder_ptr;
108         lzma_next_end(&coder->next, allocator);
109         lzma_free(coder, allocator);
110         return;
111 }
112
113
114 static lzma_check
115 auto_decoder_get_check(const void *coder_ptr)
116 {
117         const lzma_auto_coder *coder = coder_ptr;
118
119         // It is LZMA_Alone if get_check is NULL.
120         return coder->next.get_check == NULL ? LZMA_CHECK_NONE
121                         : coder->next.get_check(coder->next.coder);
122 }
123
124
125 static lzma_ret
126 auto_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
127                 uint64_t *old_memlimit, uint64_t new_memlimit)
128 {
129         lzma_auto_coder *coder = coder_ptr;
130
131         lzma_ret ret;
132
133         if (coder->next.memconfig != NULL) {
134                 ret = coder->next.memconfig(coder->next.coder,
135                                 memusage, old_memlimit, new_memlimit);
136                 assert(*old_memlimit == coder->memlimit);
137         } else {
138                 // No coder is configured yet. Use the base value as
139                 // the current memory usage.
140                 *memusage = LZMA_MEMUSAGE_BASE;
141                 *old_memlimit = coder->memlimit;
142
143                 ret = LZMA_OK;
144                 if (new_memlimit != 0 && new_memlimit < *memusage)
145                         ret = LZMA_MEMLIMIT_ERROR;
146         }
147
148         if (ret == LZMA_OK && new_memlimit != 0)
149                 coder->memlimit = new_memlimit;
150
151         return ret;
152 }
153
154
155 static lzma_ret
156 auto_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
157                 uint64_t memlimit, uint32_t flags)
158 {
159         lzma_next_coder_init(&auto_decoder_init, next, allocator);
160
161         if (flags & ~LZMA_SUPPORTED_FLAGS)
162                 return LZMA_OPTIONS_ERROR;
163
164         lzma_auto_coder *coder = next->coder;
165         if (coder == NULL) {
166                 coder = lzma_alloc(sizeof(lzma_auto_coder), allocator);
167                 if (coder == NULL)
168                         return LZMA_MEM_ERROR;
169
170                 next->coder = coder;
171                 next->code = &auto_decode;
172                 next->end = &auto_decoder_end;
173                 next->get_check = &auto_decoder_get_check;
174                 next->memconfig = &auto_decoder_memconfig;
175                 coder->next = LZMA_NEXT_CODER_INIT;
176         }
177
178         coder->memlimit = my_max(1, memlimit);
179         coder->flags = flags;
180         coder->sequence = SEQ_INIT;
181
182         return LZMA_OK;
183 }
184
185
186 extern LZMA_API(lzma_ret)
187 lzma_auto_decoder(lzma_stream *strm, uint64_t memlimit, uint32_t flags)
188 {
189         lzma_next_strm_init(auto_decoder_init, strm, memlimit, flags);
190
191         strm->internal->supported_actions[LZMA_RUN] = true;
192         strm->internal->supported_actions[LZMA_FINISH] = true;
193
194         return LZMA_OK;
195 }