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comparison mupdf-source/thirdparty/brotli/c/enc/write_bits.h @ 2:b50eed0cc0ef upstream

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ADD: MuPDF v1.26.7: the MuPDF source as downloaded by a default build of PyMuPDF 1.26.4. The directory name has changed: no version number in the expanded directory now.
author Franz Glasner <fzglas.hg@dom66.de>
date Mon, 15 Sep 2025 11:43:07 +0200
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1:1d09e1dec1d9 2:b50eed0cc0ef
1 /* Copyright 2010 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 /* Write bits into a byte array. */
8
9 #ifndef BROTLI_ENC_WRITE_BITS_H_
10 #define BROTLI_ENC_WRITE_BITS_H_
11
12 #include <brotli/types.h>
13
14 #include "../common/platform.h"
15
16 #if defined(__cplusplus) || defined(c_plusplus)
17 extern "C" {
18 #endif
19
20 /* This function writes bits into bytes in increasing addresses, and within
21 a byte least-significant-bit first.
22
23 The function can write up to 56 bits in one go with WriteBits
24 Example: let's assume that 3 bits (Rs below) have been written already:
25
26 BYTE-0 BYTE+1 BYTE+2
27
28 0000 0RRR 0000 0000 0000 0000
29
30 Now, we could write 5 or less bits in MSB by just shifting by 3
31 and OR'ing to BYTE-0.
32
33 For n bits, we take the last 5 bits, OR that with high bits in BYTE-0,
34 and locate the rest in BYTE+1, BYTE+2, etc. */
35 static BROTLI_INLINE void BrotliWriteBits(size_t n_bits,
36 uint64_t bits,
37 size_t* BROTLI_RESTRICT pos,
38 uint8_t* BROTLI_RESTRICT array) {
39 BROTLI_LOG(("WriteBits %2d 0x%08x%08x %10d\n", (int)n_bits,
40 (uint32_t)(bits >> 32), (uint32_t)(bits & 0xFFFFFFFF),
41 (int)*pos));
42 BROTLI_DCHECK((bits >> n_bits) == 0);
43 BROTLI_DCHECK(n_bits <= 56);
44 #if defined(BROTLI_LITTLE_ENDIAN)
45 /* This branch of the code can write up to 56 bits at a time,
46 7 bits are lost by being perhaps already in *p and at least
47 1 bit is needed to initialize the bit-stream ahead (i.e. if 7
48 bits are in *p and we write 57 bits, then the next write will
49 access a byte that was never initialized). */
50 {
51 uint8_t* p = &array[*pos >> 3];
52 uint64_t v = (uint64_t)(*p); /* Zero-extend 8 to 64 bits. */
53 v |= bits << (*pos & 7);
54 BROTLI_UNALIGNED_STORE64LE(p, v); /* Set some bits. */
55 *pos += n_bits;
56 }
57 #else
58 /* implicit & 0xFF is assumed for uint8_t arithmetics */
59 {
60 uint8_t* array_pos = &array[*pos >> 3];
61 const size_t bits_reserved_in_first_byte = (*pos & 7);
62 size_t bits_left_to_write;
63 bits <<= bits_reserved_in_first_byte;
64 *array_pos++ |= (uint8_t)bits;
65 for (bits_left_to_write = n_bits + bits_reserved_in_first_byte;
66 bits_left_to_write >= 9;
67 bits_left_to_write -= 8) {
68 bits >>= 8;
69 *array_pos++ = (uint8_t)bits;
70 }
71 *array_pos = 0;
72 *pos += n_bits;
73 }
74 #endif
75 }
76
77 static BROTLI_INLINE void BrotliWriteBitsPrepareStorage(
78 size_t pos, uint8_t* array) {
79 BROTLI_LOG(("WriteBitsPrepareStorage %10d\n", (int)pos));
80 BROTLI_DCHECK((pos & 7) == 0);
81 array[pos >> 3] = 0;
82 }
83
84 #if defined(__cplusplus) || defined(c_plusplus)
85 } /* extern "C" */
86 #endif
87
88 #endif /* BROTLI_ENC_WRITE_BITS_H_ */