blob: 2bb9a1918225380fead5c5f9fd40c9ba5d536a38 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
|
// Copyright 2014 Google Inc. All Rights Reserved.
//
// Use of this source code is governed by a BSD-style license
// that can be found in the COPYING file in the root of the source
// tree. An additional intellectual property rights grant can be found
// in the file PATENTS. All contributing project authors may
// be found in the AUTHORS file in the root of the source tree.
// -----------------------------------------------------------------------------
//
// Specific inlined methods for boolean decoder [VP8GetBit() ...]
// This file should be included by the .c sources that actually need to call
// these methods.
//
// Author: Skal (pascal.massimino@gmail.com)
#ifndef WEBP_UTILS_BIT_READER_INL_UTILS_H_
#define WEBP_UTILS_BIT_READER_INL_UTILS_H_
#ifdef HAVE_CONFIG_H
#include "../webp/config.h"
#endif
#include <string.h> // for memcpy
#include "../dsp/dsp.h"
#include "../utils/bit_reader_utils.h"
#include "../utils/endian_inl_utils.h"
#include "../utils/utils.h"
#ifdef __cplusplus
extern "C" {
#endif
//------------------------------------------------------------------------------
// Derived type lbit_t = natural type for memory I/O
#if (BITS > 32)
typedef uint64_t lbit_t;
#elif (BITS > 16)
typedef uint32_t lbit_t;
#elif (BITS > 8)
typedef uint16_t lbit_t;
#else
typedef uint8_t lbit_t;
#endif
extern const uint8_t kVP8Log2Range[128];
extern const uint8_t kVP8NewRange[128];
// special case for the tail byte-reading
void VP8LoadFinalBytes(VP8BitReader* const br);
//------------------------------------------------------------------------------
// Inlined critical functions
// makes sure br->value_ has at least BITS bits worth of data
static WEBP_UBSAN_IGNORE_UNDEF WEBP_INLINE
void VP8LoadNewBytes(VP8BitReader* const br) {
assert(br != NULL && br->buf_ != NULL);
// Read 'BITS' bits at a time if possible.
if (br->buf_ < br->buf_max_) {
// convert memory type to register type (with some zero'ing!)
bit_t bits;
#if defined(WEBP_USE_MIPS32)
// This is needed because of un-aligned read.
lbit_t in_bits;
lbit_t* p_buf_ = (lbit_t*)br->buf_;
__asm__ volatile(
".set push \n\t"
".set at \n\t"
".set macro \n\t"
"ulw %[in_bits], 0(%[p_buf_]) \n\t"
".set pop \n\t"
: [in_bits]"=r"(in_bits)
: [p_buf_]"r"(p_buf_)
: "memory", "at"
);
#else
lbit_t in_bits;
memcpy(&in_bits, br->buf_, sizeof(in_bits));
#endif
br->buf_ += BITS >> 3;
#if !defined(WORDS_BIGENDIAN)
#if (BITS > 32)
bits = BSwap64(in_bits);
bits >>= 64 - BITS;
#elif (BITS >= 24)
bits = BSwap32(in_bits);
bits >>= (32 - BITS);
#elif (BITS == 16)
bits = BSwap16(in_bits);
#else // BITS == 8
bits = (bit_t)in_bits;
#endif // BITS > 32
#else // WORDS_BIGENDIAN
bits = (bit_t)in_bits;
if (BITS != 8 * sizeof(bit_t)) bits >>= (8 * sizeof(bit_t) - BITS);
#endif
br->value_ = bits | (br->value_ << BITS);
br->bits_ += BITS;
} else {
VP8LoadFinalBytes(br); // no need to be inlined
}
}
// Read a bit with proba 'prob'. Speed-critical function!
static WEBP_INLINE int VP8GetBit(VP8BitReader* const br, int prob) {
// Don't move this declaration! It makes a big speed difference to store
// 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't
// alter br->range_ value.
range_t range = br->range_;
if (br->bits_ < 0) {
VP8LoadNewBytes(br);
}
{
const int pos = br->bits_;
const range_t split = (range * prob) >> 8;
const range_t value = (range_t)(br->value_ >> pos);
const int bit = (value > split);
if (bit) {
range -= split;
br->value_ -= (bit_t)(split + 1) << pos;
} else {
range = split + 1;
}
{
const int shift = 7 ^ BitsLog2Floor(range);
range <<= shift;
br->bits_ -= shift;
}
br->range_ = range - 1;
return bit;
}
}
// simplified version of VP8GetBit() for prob=0x80 (note shift is always 1 here)
static WEBP_UBSAN_IGNORE_UNSIGNED_OVERFLOW WEBP_INLINE
int VP8GetSigned(VP8BitReader* const br, int v) {
if (br->bits_ < 0) {
VP8LoadNewBytes(br);
}
{
const int pos = br->bits_;
const range_t split = br->range_ >> 1;
const range_t value = (range_t)(br->value_ >> pos);
const int32_t mask = (int32_t)(split - value) >> 31; // -1 or 0
br->bits_ -= 1;
br->range_ += mask;
br->range_ |= 1;
br->value_ -= (bit_t)((split + 1) & mask) << pos;
return (v ^ mask) - mask;
}
}
static WEBP_INLINE int VP8GetBitAlt(VP8BitReader* const br, int prob) {
// Don't move this declaration! It makes a big speed difference to store
// 'range' *before* calling VP8LoadNewBytes(), even if this function doesn't
// alter br->range_ value.
range_t range = br->range_;
if (br->bits_ < 0) {
VP8LoadNewBytes(br);
}
{
const int pos = br->bits_;
const range_t split = (range * prob) >> 8;
const range_t value = (range_t)(br->value_ >> pos);
int bit; // Don't use 'const int bit = (value > split);", it's slower.
if (value > split) {
range -= split + 1;
br->value_ -= (bit_t)(split + 1) << pos;
bit = 1;
} else {
range = split;
bit = 0;
}
if (range <= (range_t)0x7e) {
const int shift = kVP8Log2Range[range];
range = kVP8NewRange[range];
br->bits_ -= shift;
}
br->range_ = range;
return bit;
}
}
#ifdef __cplusplus
} // extern "C"
#endif
#endif // WEBP_UTILS_BIT_READER_INL_UTILS_H_
|
