/src/CMake/Utilities/cmliblzma/liblzma/common/vli_decoder.c
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1 | | // SPDX-License-Identifier: 0BSD |
2 | | |
3 | | /////////////////////////////////////////////////////////////////////////////// |
4 | | // |
5 | | /// \file vli_decoder.c |
6 | | /// \brief Decodes variable-length integers |
7 | | // |
8 | | // Author: Lasse Collin |
9 | | // |
10 | | /////////////////////////////////////////////////////////////////////////////// |
11 | | |
12 | | #include "common.h" |
13 | | |
14 | | |
15 | | extern LZMA_API(lzma_ret) |
16 | | lzma_vli_decode(lzma_vli *restrict vli, size_t *vli_pos, |
17 | | const uint8_t *restrict in, size_t *restrict in_pos, |
18 | | size_t in_size) |
19 | 6.51k | { |
20 | | // If we haven't been given vli_pos, work in single-call mode. |
21 | 6.51k | size_t vli_pos_internal = 0; |
22 | 6.51k | if (vli_pos == NULL) { |
23 | 5.69k | vli_pos = &vli_pos_internal; |
24 | 5.69k | *vli = 0; |
25 | | |
26 | | // If there's no input, use LZMA_DATA_ERROR. This way it is |
27 | | // easy to decode VLIs from buffers that have known size, |
28 | | // and get the correct error code in case the buffer is |
29 | | // too short. |
30 | 5.69k | if (*in_pos >= in_size) |
31 | 20 | return LZMA_DATA_ERROR; |
32 | | |
33 | 5.69k | } else { |
34 | | // Initialize *vli when starting to decode a new integer. |
35 | 826 | if (*vli_pos == 0) |
36 | 826 | *vli = 0; |
37 | | |
38 | | // Validate the arguments. |
39 | 826 | if (*vli_pos >= LZMA_VLI_BYTES_MAX |
40 | 826 | || (*vli >> (*vli_pos * 7)) != 0) |
41 | 826 | return LZMA_PROG_ERROR;; |
42 | | |
43 | 826 | if (*in_pos >= in_size) |
44 | 0 | return LZMA_BUF_ERROR; |
45 | 826 | } |
46 | | |
47 | 13.3k | do { |
48 | | // Read the next byte. Use a temporary variable so that we |
49 | | // can update *in_pos immediately. |
50 | 13.3k | const uint8_t byte = in[*in_pos]; |
51 | 13.3k | ++*in_pos; |
52 | | |
53 | | // Add the newly read byte to *vli. |
54 | 13.3k | *vli += (lzma_vli)(byte & 0x7F) << (*vli_pos * 7); |
55 | 13.3k | ++*vli_pos; |
56 | | |
57 | | // Check if this is the last byte of a multibyte integer. |
58 | 13.3k | if ((byte & 0x80) == 0) { |
59 | | // We don't allow using variable-length integers as |
60 | | // padding i.e. the encoding must use the most the |
61 | | // compact form. |
62 | 6.42k | if (byte == 0x00 && *vli_pos > 1) |
63 | 46 | return LZMA_DATA_ERROR; |
64 | | |
65 | 6.37k | return vli_pos == &vli_pos_internal |
66 | 6.37k | ? LZMA_OK : LZMA_STREAM_END; |
67 | 6.42k | } |
68 | | |
69 | | // There is at least one more byte coming. If we have already |
70 | | // read maximum number of bytes, the integer is considered |
71 | | // corrupt. |
72 | | // |
73 | | // If we need bigger integers in future, old versions liblzma |
74 | | // will confusingly indicate the file being corrupt instead of |
75 | | // unsupported. I suppose it's still better this way, because |
76 | | // in the foreseeable future (writing this in 2008) the only |
77 | | // reason why files would appear having over 63-bit integers |
78 | | // is that the files are simply corrupt. |
79 | 6.97k | if (*vli_pos == LZMA_VLI_BYTES_MAX) |
80 | 16 | return LZMA_DATA_ERROR; |
81 | | |
82 | 6.97k | } while (*in_pos < in_size); |
83 | | |
84 | 60 | return vli_pos == &vli_pos_internal ? LZMA_DATA_ERROR : LZMA_OK; |
85 | 6.49k | } |