blob: b9fbc2d6fed8c4b9cdf33e217629a9f07b4ce0f3 (
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
|
// Copyright 2016 The Draco Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// File provides direct encoding of bits with arithmetic encoder interface.
#ifndef DRACO_COMPRESSION_BIT_CODERS_DIRECT_BIT_DECODER_H_
#define DRACO_COMPRESSION_BIT_CODERS_DIRECT_BIT_DECODER_H_
#include <vector>
#include "draco/core/decoder_buffer.h"
namespace draco {
class DirectBitDecoder {
public:
DirectBitDecoder();
~DirectBitDecoder();
// Sets |source_buffer| as the buffer to decode bits from.
bool StartDecoding(DecoderBuffer *source_buffer);
// Decode one bit. Returns true if the bit is a 1, otherwise false.
bool DecodeNextBit() {
const uint32_t selector = 1 << (31 - num_used_bits_);
if (pos_ == bits_.end()) {
return false;
}
const bool bit = *pos_ & selector;
++num_used_bits_;
if (num_used_bits_ == 32) {
++pos_;
num_used_bits_ = 0;
}
return bit;
}
// Decode the next |nbits| and return the sequence in |value|. |nbits| must be
// > 0 and <= 32.
void DecodeLeastSignificantBits32(int nbits, uint32_t *value) {
DRACO_DCHECK_EQ(true, nbits <= 32);
DRACO_DCHECK_EQ(true, nbits > 0);
const int remaining = 32 - num_used_bits_;
if (nbits <= remaining) {
if (pos_ == bits_.end()) {
*value = 0;
return;
}
*value = (*pos_ << num_used_bits_) >> (32 - nbits);
num_used_bits_ += nbits;
if (num_used_bits_ == 32) {
++pos_;
num_used_bits_ = 0;
}
} else {
if (pos_ + 1 == bits_.end()) {
*value = 0;
return;
}
const uint32_t value_l = ((*pos_) << num_used_bits_);
num_used_bits_ = nbits - remaining;
++pos_;
const uint32_t value_r = (*pos_) >> (32 - num_used_bits_);
*value = (value_l >> (32 - num_used_bits_ - remaining)) | value_r;
}
}
void EndDecoding() {}
private:
void Clear();
std::vector<uint32_t> bits_;
std::vector<uint32_t>::const_iterator pos_;
uint32_t num_used_bits_;
};
} // namespace draco
#endif // DRACO_COMPRESSION_BIT_CODERS_DIRECT_BIT_DECODER_H_
|
