Commit | Line | Data |
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90aa4e6b KS |
1 | #[derive(Debug)] |
2 | pub enum BitReaderMode { | |
3 | BE, | |
a961f92b KS |
4 | LE, |
5 | LE16MSB, | |
6 | LE32MSB, | |
90aa4e6b KS |
7 | } |
8 | ||
9 | #[derive(Debug)] | |
10 | pub enum BitReaderError { | |
11 | BitstreamEnd, | |
12 | TooManyBitsRequested, | |
a961f92b | 13 | InvalidValue, |
90aa4e6b KS |
14 | } |
15 | ||
16 | use self::BitReaderError::*; | |
17 | ||
a961f92b | 18 | pub type BitReaderResult<T> = Result<T, BitReaderError>; |
90aa4e6b KS |
19 | |
20 | #[derive(Debug)] | |
21 | pub struct BitReader<'a> { | |
22 | cache: u64, | |
23 | bits: u8, | |
24 | pos: usize, | |
90aa4e6b KS |
25 | src: &'a [u8], |
26 | mode: BitReaderMode, | |
27 | } | |
28 | ||
e243ceb4 | 29 | #[allow(clippy::identity_op)] |
90aa4e6b KS |
30 | impl<'a> BitReader<'a> { |
31 | ||
fa90ccfb KS |
32 | pub fn new(src: &'a [u8], mode: BitReaderMode) -> Self { |
33 | BitReader{ cache: 0, pos: 0, bits: 0, src, mode } | |
90aa4e6b KS |
34 | } |
35 | ||
36 | pub fn tell(&self) -> usize { | |
37 | self.pos * 8 - (self.bits as usize) | |
38 | } | |
39 | ||
40 | pub fn left(&self) -> isize { | |
fa90ccfb | 41 | ((self.src.len() as isize) - (self.pos as isize)) * 8 + (self.bits as isize) |
90aa4e6b KS |
42 | } |
43 | ||
44 | fn fill32be(&mut self, src: &[u8]) { | |
e243ceb4 KS |
45 | let nw = (u32::from(src[0]) << 24) | |
46 | (u32::from(src[1]) << 16) | | |
47 | (u32::from(src[2]) << 8) | | |
48 | (u32::from(src[3]) << 0); | |
49 | self.cache |= u64::from(nw) << (32 - self.bits); | |
90aa4e6b KS |
50 | } |
51 | ||
8ab3904c | 52 | fn fill32le16(&mut self, src: &[u8]) { |
e243ceb4 KS |
53 | let nw = (u32::from(src[1]) << 24) | |
54 | (u32::from(src[0]) << 16) | | |
55 | (u32::from(src[3]) << 8) | | |
56 | (u32::from(src[2]) << 0); | |
57 | self.cache |= u64::from(nw) << (32 - self.bits); | |
90aa4e6b KS |
58 | } |
59 | ||
8ab3904c | 60 | fn fill32le32(&mut self, src: &[u8], lsb: bool) { |
e243ceb4 KS |
61 | let nw = (u32::from(src[3]) << 24) | |
62 | (u32::from(src[2]) << 16) | | |
63 | (u32::from(src[1]) << 8) | | |
64 | (u32::from(src[0]) << 0); | |
8ab3904c | 65 | if lsb { |
e243ceb4 | 66 | self.cache |= u64::from(nw) << self.bits; |
8ab3904c | 67 | } else { |
e243ceb4 | 68 | self.cache |= u64::from(nw) << (32 - self.bits); |
8ab3904c | 69 | } |
90aa4e6b KS |
70 | } |
71 | ||
83b49341 | 72 | #[inline(always)] |
90aa4e6b | 73 | fn refill(&mut self) -> BitReaderResult<()> { |
fa90ccfb | 74 | if self.pos >= self.src.len() { return Err(BitstreamEnd) } |
90aa4e6b | 75 | while self.bits <= 32 { |
fa90ccfb | 76 | if self.pos + 4 <= self.src.len() { |
90aa4e6b KS |
77 | let buf = &self.src[self.pos..]; |
78 | match self.mode { | |
a961f92b | 79 | BitReaderMode::BE => self.fill32be (buf), |
8ab3904c KS |
80 | BitReaderMode::LE16MSB => self.fill32le16(buf), |
81 | BitReaderMode::LE => self.fill32le32(buf, true), | |
82 | BitReaderMode::LE32MSB => self.fill32le32(buf, false), | |
90aa4e6b KS |
83 | } |
84 | self.pos += 4; | |
85 | self.bits += 32; | |
86 | } else { | |
87 | let mut buf: [u8; 4] = [0, 0, 0, 0]; | |
88 | let mut newbits: u8 = 0; | |
e243ceb4 | 89 | for out in buf.iter_mut().take(3) { |
fa90ccfb | 90 | if self.pos < self.src.len() { |
e243ceb4 KS |
91 | *out = self.src[self.pos]; |
92 | self.pos += 1; | |
90aa4e6b KS |
93 | newbits += 8; |
94 | } | |
95 | } | |
96 | if newbits == 0 { break; } | |
97 | match self.mode { | |
a961f92b | 98 | BitReaderMode::BE => self.fill32be (&buf), |
8ab3904c KS |
99 | BitReaderMode::LE16MSB => self.fill32le16(&buf), |
100 | BitReaderMode::LE => self.fill32le32(&buf, true), | |
101 | BitReaderMode::LE32MSB => self.fill32le32(&buf, false), | |
90aa4e6b KS |
102 | } |
103 | self.bits += newbits; | |
104 | } | |
105 | } | |
106 | Ok(()) | |
107 | } | |
108 | ||
83b49341 | 109 | #[inline(always)] |
90aa4e6b KS |
110 | fn read_cache(&mut self, nbits: u8) -> u32 { |
111 | let res = match self.mode { | |
a961f92b | 112 | BitReaderMode::LE => ((1u64 << nbits) - 1) & self.cache, |
e243ceb4 | 113 | _ => self.cache >> (64 - nbits), |
90aa4e6b KS |
114 | }; |
115 | res as u32 | |
116 | } | |
117 | ||
a961f92b KS |
118 | fn read_cache_s(&mut self, nbits: u8) -> i32 { |
119 | let res = match self.mode { | |
120 | BitReaderMode::LE => ((self.cache as i64) << (64 - nbits)) >> (64 - nbits), | |
121 | _ => (self.cache as i64) >> (64 - nbits), | |
122 | }; | |
123 | res as i32 | |
124 | } | |
125 | ||
83b49341 | 126 | #[inline(always)] |
90aa4e6b KS |
127 | fn skip_cache(&mut self, nbits: u8) { |
128 | match self.mode { | |
a961f92b KS |
129 | BitReaderMode::LE => self.cache >>= nbits, |
130 | _ => self.cache <<= nbits, | |
90aa4e6b KS |
131 | }; |
132 | self.bits -= nbits; | |
133 | } | |
134 | ||
83b49341 | 135 | #[inline(always)] |
90aa4e6b KS |
136 | fn reset_cache(&mut self) { |
137 | self.bits = 0; | |
138 | self.cache = 0; | |
139 | } | |
140 | ||
83b49341 | 141 | #[inline(always)] |
90aa4e6b | 142 | pub fn read(&mut self, nbits: u8) -> BitReaderResult<u32> { |
a961f92b | 143 | if nbits == 0 { return Ok(0) } |
90aa4e6b KS |
144 | if nbits > 32 { return Err(TooManyBitsRequested) } |
145 | if self.bits < nbits { | |
146 | if let Err(err) = self.refill() { return Err(err) } | |
147 | if self.bits < nbits { return Err(BitstreamEnd) } | |
148 | } | |
149 | let res = self.read_cache(nbits); | |
150 | self.skip_cache(nbits); | |
a961f92b KS |
151 | Ok(res) |
152 | } | |
153 | ||
154 | pub fn read_s(&mut self, nbits: u8) -> BitReaderResult<i32> { | |
155 | if nbits == 0 || nbits > 32 { return Err(TooManyBitsRequested) } | |
156 | if self.bits < nbits { | |
157 | if let Err(err) = self.refill() { return Err(err) } | |
158 | if self.bits < nbits { return Err(BitstreamEnd) } | |
159 | } | |
160 | let res = self.read_cache_s(nbits); | |
161 | self.skip_cache(nbits); | |
162 | Ok(res) | |
90aa4e6b KS |
163 | } |
164 | ||
83b49341 | 165 | #[inline(always)] |
0a1d94d9 KS |
166 | pub fn read_bool(&mut self) -> BitReaderResult<bool> { |
167 | if self.bits < 1 { | |
168 | if let Err(err) = self.refill() { return Err(err) } | |
169 | if self.bits < 1 { return Err(BitstreamEnd) } | |
170 | } | |
171 | let res = self.read_cache(1); | |
172 | self.skip_cache(1); | |
173 | Ok(res == 1) | |
174 | } | |
175 | ||
83b49341 | 176 | #[inline(always)] |
90aa4e6b KS |
177 | pub fn peek(&mut self, nbits: u8) -> u32 { |
178 | if nbits > 32 { return 0 } | |
179 | if self.bits < nbits { let _ = self.refill(); } | |
180 | self.read_cache(nbits) | |
181 | } | |
182 | ||
83b49341 | 183 | #[inline(always)] |
90aa4e6b | 184 | pub fn skip(&mut self, nbits: u32) -> BitReaderResult<()> { |
e243ceb4 | 185 | if u32::from(self.bits) >= nbits { |
90aa4e6b KS |
186 | self.skip_cache(nbits as u8); |
187 | return Ok(()); | |
188 | } | |
e243ceb4 | 189 | let mut skip_bits = nbits - u32::from(self.bits); |
90aa4e6b KS |
190 | self.reset_cache(); |
191 | self.pos += ((skip_bits / 32) * 4) as usize; | |
e243ceb4 | 192 | skip_bits &= 0x1F; |
90aa4e6b KS |
193 | self.refill()?; |
194 | if skip_bits > 0 { | |
195 | self.skip_cache(skip_bits as u8); | |
196 | } | |
197 | Ok(()) | |
198 | } | |
199 | ||
200 | pub fn seek(&mut self, nbits: u32) -> BitReaderResult<()> { | |
fa90ccfb | 201 | if ((nbits + 7) >> 3) as usize > self.src.len() { return Err(TooManyBitsRequested); } |
90aa4e6b KS |
202 | self.reset_cache(); |
203 | self.pos = ((nbits / 32) * 4) as usize; | |
204 | self.skip(nbits & 0x1F) | |
205 | } | |
06fd8c88 KS |
206 | |
207 | pub fn align(&mut self) { | |
208 | let pos = self.bits & 7; | |
209 | if pos != 0 { | |
210 | self.skip_cache(pos); | |
211 | } | |
212 | } | |
213 | } | |
214 | ||
215 | pub fn reverse_bits(inval: u32, len: u8) -> u32 { | |
216 | if len == 0 { return 0; } | |
217 | const REV_TAB: [u8; 16] = [ | |
218 | 0b0000, 0b1000, 0b0100, 0b1100, 0b0010, 0b1010, 0b0110, 0b1110, | |
219 | 0b0001, 0b1001, 0b0101, 0b1101, 0b0011, 0b1011, 0b0111, 0b1111, | |
220 | ]; | |
221 | ||
222 | let mut ret = 0; | |
223 | let mut val = inval; | |
224 | for _ in 0..8 { | |
e243ceb4 KS |
225 | ret = (ret << 4) | u32::from(REV_TAB[(val & 0xF) as usize]); |
226 | val >>= 4; | |
06fd8c88 KS |
227 | } |
228 | ret >> (32 - len) | |
90aa4e6b KS |
229 | } |
230 | ||
231 | #[cfg(test)] | |
232 | mod test { | |
233 | use super::*; | |
234 | ||
235 | #[test] | |
236 | fn br_works() { | |
237 | const DATA: [u8; 18] = [0b00011011; 18]; | |
238 | let src = &DATA; | |
fa90ccfb | 239 | let mut br = BitReader::new(src, BitReaderMode::LE16MSB); |
90aa4e6b KS |
240 | |
241 | for _ in 0..8 { | |
242 | assert_eq!(br.read(16).unwrap(), 0x1B1B); | |
243 | } | |
a961f92b KS |
244 | const DATA2: [u8; 1] = [ 0b00011011 ]; |
245 | let src = &DATA2; | |
fa90ccfb | 246 | let mut br = BitReader::new(src, BitReaderMode::LE); |
a961f92b | 247 | assert_eq!(br.read_s(5).unwrap(), -5); |
90aa4e6b KS |
248 | } |
249 | } |