/src/brotli/c/dec/bit_reader.c
Line | Count | Source (jump to first uncovered line) |
1 | | /* Copyright 2013 Google Inc. All Rights Reserved. |
2 | | |
3 | | Distributed under MIT license. |
4 | | See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
5 | | */ |
6 | | |
7 | | /* Bit reading helpers */ |
8 | | |
9 | | #include "bit_reader.h" |
10 | | |
11 | | #include "../common/platform.h" |
12 | | |
13 | | #if defined(__cplusplus) || defined(c_plusplus) |
14 | | extern "C" { |
15 | | #endif |
16 | | |
17 | | const BROTLI_MODEL("small") |
18 | | brotli_reg_t kBrotliBitMask[33] = { 0x00000000, |
19 | | 0x00000001, 0x00000003, 0x00000007, 0x0000000F, |
20 | | 0x0000001F, 0x0000003F, 0x0000007F, 0x000000FF, |
21 | | 0x000001FF, 0x000003FF, 0x000007FF, 0x00000FFF, |
22 | | 0x00001FFF, 0x00003FFF, 0x00007FFF, 0x0000FFFF, |
23 | | 0x0001FFFF, 0x0003FFFF, 0x0007FFFF, 0x000FFFFF, |
24 | | 0x001FFFFF, 0x003FFFFF, 0x007FFFFF, 0x00FFFFFF, |
25 | | 0x01FFFFFF, 0x03FFFFFF, 0x07FFFFFF, 0x0FFFFFFF, |
26 | | 0x1FFFFFFF, 0x3FFFFFFF, 0x7FFFFFFF, 0xFFFFFFFF |
27 | | }; |
28 | | |
29 | 2.41k | void BrotliInitBitReader(BrotliBitReader* const br) { |
30 | 2.41k | br->val_ = 0; |
31 | 2.41k | br->bit_pos_ = 0; |
32 | 2.41k | } |
33 | | |
34 | 165k | BROTLI_BOOL BrotliWarmupBitReader(BrotliBitReader* const br) { |
35 | 165k | size_t aligned_read_mask = (sizeof(br->val_) >> 1) - 1; |
36 | | /* Fixing alignment after unaligned BrotliFillWindow would result accumulator |
37 | | overflow. If unalignment is caused by BrotliSafeReadBits, then there is |
38 | | enough space in accumulator to fix alignment. */ |
39 | 165k | if (BROTLI_UNALIGNED_READ_FAST) { |
40 | 165k | aligned_read_mask = 0; |
41 | 165k | } |
42 | 165k | if (BrotliGetAvailableBits(br) == 0) { |
43 | 17.4k | br->val_ = 0; |
44 | 17.4k | if (!BrotliPullByte(br)) { |
45 | 619 | return BROTLI_FALSE; |
46 | 619 | } |
47 | 17.4k | } |
48 | | |
49 | 165k | while ((((size_t)br->next_in) & aligned_read_mask) != 0) { |
50 | 0 | if (!BrotliPullByte(br)) { |
51 | | /* If we consumed all the input, we don't care about the alignment. */ |
52 | 0 | return BROTLI_TRUE; |
53 | 0 | } |
54 | 0 | } |
55 | 165k | return BROTLI_TRUE; |
56 | 165k | } |
57 | | |
58 | | BROTLI_BOOL BrotliSafeReadBits32Slow(BrotliBitReader* const br, |
59 | 0 | brotli_reg_t n_bits, brotli_reg_t* val) { |
60 | 0 | brotli_reg_t low_val; |
61 | 0 | brotli_reg_t high_val; |
62 | 0 | BrotliBitReaderState memento; |
63 | 0 | BROTLI_DCHECK(n_bits <= 32); |
64 | 0 | BROTLI_DCHECK(n_bits > 24); |
65 | 0 | BrotliBitReaderSaveState(br, &memento); |
66 | 0 | if (!BrotliSafeReadBits(br, 16, &low_val) || |
67 | 0 | !BrotliSafeReadBits(br, n_bits - 16, &high_val)) { |
68 | 0 | BrotliBitReaderRestoreState(br, &memento); |
69 | 0 | return BROTLI_FALSE; |
70 | 0 | } |
71 | 0 | *val = low_val | (high_val << 16); |
72 | 0 | return BROTLI_TRUE; |
73 | 0 | } |
74 | | |
75 | | #if defined(__cplusplus) || defined(c_plusplus) |
76 | | } /* extern "C" */ |
77 | | #endif |