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
191
192
193
194
195
196
197
198
199
200
201
/*
* Copyright 2007 ZXing 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.
*/
//package com.google.zxing.common;
use std::cmp;
use std::io::{ErrorKind, Read};
use crate::Exceptions;
use crate::common::Result;
/**
* <p>This provides an easy abstraction to read bits at a time from a sequence of bytes, where the
* number of bits read is not often a multiple of 8.</p>
*
* <p>This class is thread-safe but not reentrant -- unless the caller modifies the bytes array
* it passed in, in which case all bets are off.</p>
*
* @author Sean Owen
*/
pub struct BitSource<'a> {
bytes: &'a [u8],
byte_offset: usize,
bit_offset: usize,
}
impl<'a> BitSource<'a> {
/**
* @param bytes bytes from which this will read bits. Bits will be read from the first byte first.
* Bits are read within a byte from most-significant to least-significant bit.
*/
pub const fn new(bytes: &'a [u8]) -> Self {
BitSource {
bytes,
byte_offset: 0,
bit_offset: 0,
}
}
/**
* @return index of next bit in current byte which would be read by the next call to {@link #readBits(int)}.
*/
pub const fn getBitOffset(&self) -> usize {
self.bit_offset
}
/**
* @return index of next byte in input byte array which would be read by the next call to {@link #readBits(int)}.
*/
pub const fn getByteOffset(&self) -> usize {
self.byte_offset
}
/**
* @param numBits number of bits to read
* @return int representing the bits read. The bits will appear as the least-significant
* bits of the int
* @throws IllegalArgumentException if numBits isn't in [1,32] or more than is available
*/
pub fn readBits(&mut self, numBits: usize) -> Result<u32> {
if !(1..=32).contains(&numBits) || numBits > self.available() {
return Err(Exceptions::illegal_argument_with(numBits.to_string()));
}
let mut result: u32 = 0;
let mut num_bits = numBits;
// First, read remainder from current byte
if self.bit_offset > 0 {
let bitsLeft = 8 - self.bit_offset;
let toRead = cmp::min(num_bits, bitsLeft);
let bitsToNotRead = bitsLeft - toRead;
let mask = (0xFF >> (8 - toRead)) << bitsToNotRead;
result = (self.bytes[self.byte_offset] & mask) as u32 >> bitsToNotRead;
num_bits -= toRead;
self.bit_offset += toRead;
if self.bit_offset == 8 {
self.bit_offset = 0;
self.byte_offset += 1;
}
}
// Next read whole bytes
if num_bits > 0 {
while num_bits >= 8 {
result = (result << 8) | self.bytes[self.byte_offset] as u32;
// result = ((result as u16) << 8) as u8 | (self.bytes[self.byte_offset]);
self.byte_offset += 1;
num_bits -= 8;
}
// Finally read a partial byte
if num_bits > 0 {
let bits_to_not_read = 8 - num_bits;
let mask = (0xFF >> bits_to_not_read) << bits_to_not_read;
result = (result << num_bits)
| ((self.bytes[self.byte_offset] & mask) as u32 >> bits_to_not_read);
self.bit_offset += num_bits;
}
}
Ok(result)
}
pub fn peak_bits(&self, numBits: usize) -> Result<u32> {
if !(1..=32).contains(&numBits) || numBits > self.available() {
return Err(Exceptions::illegal_argument_with(numBits.to_string()));
}
let mut bit_offset = self.bit_offset;
let mut byte_offset = self.byte_offset;
let mut result: u32 = 0;
let mut num_bits = numBits;
// First, read remainder from current byte
if self.bit_offset > 0 {
let bitsLeft = 8 - self.bit_offset;
let toRead = cmp::min(num_bits, bitsLeft);
let bitsToNotRead = bitsLeft - toRead;
let mask = (0xFF >> (8 - toRead)) << bitsToNotRead;
result = (self.bytes[self.byte_offset] & mask) as u32 >> bitsToNotRead;
num_bits -= toRead;
bit_offset += toRead;
if bit_offset == 8 {
//bit_offset = 0;
byte_offset += 1;
}
}
// Next read whole bytes
if num_bits > 0 {
while num_bits >= 8 {
result = (result << 8) | self.bytes[byte_offset] as u32;
// result = ((result as u16) << 8) as u8 | (self.bytes[self.byte_offset]);
byte_offset += 1;
num_bits -= 8;
}
// Finally read a partial byte
if num_bits > 0 {
let bits_to_not_read = 8 - num_bits;
let mask = (0xFF >> bits_to_not_read) << bits_to_not_read;
result = (result << num_bits)
| ((self.bytes[byte_offset] & mask) as u32 >> bits_to_not_read);
//bit_offset += num_bits; // Removed, this is a holdover from setting the actual values in c++
}
}
Ok(result)
}
/**
* @return number of bits that can be read successfully
*/
pub fn available(&self) -> usize {
8 * (self.bytes.len() - self.byte_offset) - self.bit_offset
}
}
impl Read for BitSource<'_> {
fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
let requested_bytes = buf.len();
let available = self.available();
let to_read = if requested_bytes <= available {
requested_bytes
} else {
available
};
for byte in buf.iter_mut().take(to_read) {
let Ok(bits) = self.readBits(8) else {
return Err(std::io::Error::new(
ErrorKind::Unsupported,
"unable to read bits",
));
};
*byte = bits as u8;
}
Ok(to_read)
}
}