2 pub enum BitReaderMode {
10 pub enum BitReaderError {
16 use self::BitReaderError::*;
18 pub type BitReaderResult<T> = Result<T, BitReaderError>;
21 pub struct BitReader<'a> {
30 #[allow(clippy::identity_op)]
31 impl<'a> BitReader<'a> {
33 pub fn new(src: &'a [u8], size: usize, mode: BitReaderMode) -> Self {
34 if src.len() < size { panic!("size is less than needed"); }
35 BitReader{ cache: 0, pos: 0, bits: 0, end: size, src, mode }
38 pub fn tell(&self) -> usize {
39 self.pos * 8 - (self.bits as usize)
42 pub fn left(&self) -> isize {
43 ((self.end as isize) - (self.pos as isize)) * 8 + (self.bits as isize)
46 fn fill32be(&mut self, src: &[u8]) {
47 let nw = (u32::from(src[0]) << 24) |
48 (u32::from(src[1]) << 16) |
49 (u32::from(src[2]) << 8) |
50 (u32::from(src[3]) << 0);
51 self.cache |= u64::from(nw) << (32 - self.bits);
54 fn fill32le16(&mut self, src: &[u8]) {
55 let nw = (u32::from(src[1]) << 24) |
56 (u32::from(src[0]) << 16) |
57 (u32::from(src[3]) << 8) |
58 (u32::from(src[2]) << 0);
59 self.cache |= u64::from(nw) << (32 - self.bits);
62 fn fill32le32(&mut self, src: &[u8], lsb: bool) {
63 let nw = (u32::from(src[3]) << 24) |
64 (u32::from(src[2]) << 16) |
65 (u32::from(src[1]) << 8) |
66 (u32::from(src[0]) << 0);
68 self.cache |= u64::from(nw) << self.bits;
70 self.cache |= u64::from(nw) << (32 - self.bits);
75 fn refill(&mut self) -> BitReaderResult<()> {
76 if self.pos >= self.end { return Err(BitstreamEnd) }
77 while self.bits <= 32 {
78 if self.pos + 4 <= self.end {
79 let buf = &self.src[self.pos..];
81 BitReaderMode::BE => self.fill32be (buf),
82 BitReaderMode::LE16MSB => self.fill32le16(buf),
83 BitReaderMode::LE => self.fill32le32(buf, true),
84 BitReaderMode::LE32MSB => self.fill32le32(buf, false),
89 let mut buf: [u8; 4] = [0, 0, 0, 0];
90 let mut newbits: u8 = 0;
91 for out in buf.iter_mut().take(3) {
92 if self.pos < self.end {
93 *out = self.src[self.pos];
98 if newbits == 0 { break; }
100 BitReaderMode::BE => self.fill32be (&buf),
101 BitReaderMode::LE16MSB => self.fill32le16(&buf),
102 BitReaderMode::LE => self.fill32le32(&buf, true),
103 BitReaderMode::LE32MSB => self.fill32le32(&buf, false),
105 self.bits += newbits;
112 fn read_cache(&mut self, nbits: u8) -> u32 {
113 let res = match self.mode {
114 BitReaderMode::LE => ((1u64 << nbits) - 1) & self.cache,
115 _ => self.cache >> (64 - nbits),
120 fn read_cache_s(&mut self, nbits: u8) -> i32 {
121 let res = match self.mode {
122 BitReaderMode::LE => ((self.cache as i64) << (64 - nbits)) >> (64 - nbits),
123 _ => (self.cache as i64) >> (64 - nbits),
129 fn skip_cache(&mut self, nbits: u8) {
131 BitReaderMode::LE => self.cache >>= nbits,
132 _ => self.cache <<= nbits,
138 fn reset_cache(&mut self) {
144 pub fn read(&mut self, nbits: u8) -> BitReaderResult<u32> {
145 if nbits == 0 { return Ok(0) }
146 if nbits > 32 { return Err(TooManyBitsRequested) }
147 if self.bits < nbits {
148 if let Err(err) = self.refill() { return Err(err) }
149 if self.bits < nbits { return Err(BitstreamEnd) }
151 let res = self.read_cache(nbits);
152 self.skip_cache(nbits);
156 pub fn read_s(&mut self, nbits: u8) -> BitReaderResult<i32> {
157 if nbits == 0 || nbits > 32 { return Err(TooManyBitsRequested) }
158 if self.bits < nbits {
159 if let Err(err) = self.refill() { return Err(err) }
160 if self.bits < nbits { return Err(BitstreamEnd) }
162 let res = self.read_cache_s(nbits);
163 self.skip_cache(nbits);
168 pub fn read_bool(&mut self) -> BitReaderResult<bool> {
170 if let Err(err) = self.refill() { return Err(err) }
171 if self.bits < 1 { return Err(BitstreamEnd) }
173 let res = self.read_cache(1);
179 pub fn peek(&mut self, nbits: u8) -> u32 {
180 if nbits > 32 { return 0 }
181 if self.bits < nbits { let _ = self.refill(); }
182 self.read_cache(nbits)
186 pub fn skip(&mut self, nbits: u32) -> BitReaderResult<()> {
187 if u32::from(self.bits) >= nbits {
188 self.skip_cache(nbits as u8);
191 let mut skip_bits = nbits - u32::from(self.bits);
193 self.pos += ((skip_bits / 32) * 4) as usize;
197 self.skip_cache(skip_bits as u8);
202 pub fn seek(&mut self, nbits: u32) -> BitReaderResult<()> {
203 if ((nbits + 7) >> 3) as usize > self.end { return Err(TooManyBitsRequested); }
205 self.pos = ((nbits / 32) * 4) as usize;
206 self.skip(nbits & 0x1F)
209 pub fn align(&mut self) {
210 let pos = self.bits & 7;
212 self.skip_cache(pos);
217 pub fn reverse_bits(inval: u32, len: u8) -> u32 {
218 if len == 0 { return 0; }
219 const REV_TAB: [u8; 16] = [
220 0b0000, 0b1000, 0b0100, 0b1100, 0b0010, 0b1010, 0b0110, 0b1110,
221 0b0001, 0b1001, 0b0101, 0b1101, 0b0011, 0b1011, 0b0111, 0b1111,
227 ret = (ret << 4) | u32::from(REV_TAB[(val & 0xF) as usize]);
239 const DATA: [u8; 18] = [0b00011011; 18];
241 let mut br = BitReader::new(src, src.len(), BitReaderMode::LE16MSB);
244 assert_eq!(br.read(16).unwrap(), 0x1B1B);
246 const DATA2: [u8; 1] = [ 0b00011011 ];
248 let mut br = BitReader::new(src, src.len(), BitReaderMode::LE);
249 assert_eq!(br.read_s(5).unwrap(), -5);