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|
use io::bitreader::BitReader;
#[derive(Debug)]
pub enum CodebookError {
InvalidCodebook,
MemoryError,
InvalidCode,
}
type CodebookResult<T> = Result<T, CodebookError>;
pub struct FullCodebookDesc<S> {
code: u32,
bits: u8,
sym: S,
}
pub struct ShortCodebookDesc {
code: u32,
bits: u8,
}
pub trait CodebookDescReader<S> {
fn bits(&mut self, idx: usize) -> u8;
fn code(&mut self, idx: usize) -> u32;
fn sym (&mut self, idx: usize) -> S;
fn len (&mut self) -> usize;
}
#[allow(dead_code)]
pub struct Codebook<S> {
table: Vec<u32>,
syms: Vec<S>,
lut_bits: u8,
}
pub trait CodebookReader<S> {
fn read_cb(&mut self, cb: &Codebook<S>) -> CodebookResult<S>;
}
impl<S: Copy> Codebook<S> {
//todo allow add escapes
pub fn new(cb: &mut CodebookDescReader<S>) -> CodebookResult<Self> {
let mut maxbits = 0;
let mut nnz = 0;
for i in 0..cb.len() {
let bits = cb.bits(i);
if bits > 0 { nnz = nnz + 1; }
if bits > maxbits {
maxbits = bits;
}
}
if maxbits == 0 { return Err(CodebookError::InvalidCodebook); }
let mut table: Vec<u32> = Vec::new();
let mut syms: Vec<S> = Vec::new();
let tab_len = 1 << maxbits;
table.reserve(tab_len);
if table.capacity() < tab_len { return Err(CodebookError::MemoryError); }
table.resize(tab_len, 0xFF);
syms.reserve(nnz);
if syms.capacity() < nnz { return Err(CodebookError::MemoryError); }
let mut symidx: u32 = 0;
for i in 0..cb.len() {
let bits = cb.bits(i);
if bits == 0 { continue; }
let code = cb.code(i) << (maxbits - bits);
let fill_len = 1 << (maxbits - bits);
for j in 0..fill_len {
let idx = (code + j) as usize;
table[idx] = (symidx << 8) | (bits as u32);
}
symidx = symidx + 1;
}
for i in 0..cb.len() {
if cb.bits(i) > 0 {
syms.push(cb.sym(i));
}
}
Ok(Codebook { table: table, syms: syms, lut_bits: maxbits })
}
}
impl<'a, S: Copy> CodebookReader<S> for BitReader<'a> {
#[allow(unused_variables)]
fn read_cb(&mut self, cb: &Codebook<S>) -> CodebookResult<S> {
let lut_idx = self.peek(cb.lut_bits) as usize;
let bits = cb.table[lut_idx] & 0xFF;
let idx = (cb.table[lut_idx] >> 8) as usize;
if bits == 0xFF || (bits as isize) > self.left() {
return Err(CodebookError::InvalidCode);
}
if let Err(_) = self.skip(bits) {}
let sym = cb.syms[idx];
return Ok(sym)
}
}
pub struct FullCodebookDescReader<S> {
data: Vec<FullCodebookDesc<S>>,
}
impl<S> FullCodebookDescReader<S> {
pub fn new(data: Vec<FullCodebookDesc<S>>) -> Self {
FullCodebookDescReader { data: data }
}
}
impl<S: Copy> CodebookDescReader<S> for FullCodebookDescReader<S> {
fn bits(&mut self, idx: usize) -> u8 { self.data[idx].bits }
fn code(&mut self, idx: usize) -> u32 { self.data[idx].code }
fn sym (&mut self, idx: usize) -> S { self.data[idx].sym }
fn len(&mut self) -> usize { self.data.len() }
}
pub struct ShortCodebookDescReader {
data: Vec<ShortCodebookDesc>,
}
impl ShortCodebookDescReader {
pub fn new(data: Vec<ShortCodebookDesc<>>) -> Self {
ShortCodebookDescReader { data: data }
}
}
impl CodebookDescReader<u32> for ShortCodebookDescReader {
fn bits(&mut self, idx: usize) -> u8 { self.data[idx].bits }
fn code(&mut self, idx: usize) -> u32 { self.data[idx].code }
fn sym (&mut self, idx: usize) -> u32 { idx as u32 }
fn len(&mut self) -> usize { self.data.len() }
}
#[cfg(test)]
mod test {
use super::*;
use io::bitreader::*;
#[test]
fn test_cb() {
const BITS: [u8; 2] = [0b01011011, 0b10111100];
let cb_desc: Vec<FullCodebookDesc<i8>> = vec!(
FullCodebookDesc { code: 0b0, bits: 1, sym: 16 },
FullCodebookDesc { code: 0b10, bits: 2, sym: -3 },
FullCodebookDesc { code: 0b110, bits: 3, sym: 42 },
FullCodebookDesc { code: 0b1110, bits: 4, sym: -42 }
);
let buf = &BITS;
let mut br = BitReader::new(buf, buf.len(), BitReaderMode::BE);
let mut cfr = FullCodebookDescReader::new(cb_desc);
let cb = Codebook::new(&mut cfr).unwrap();
assert_eq!(br.read_cb(&cb).unwrap(), 16);
assert_eq!(br.read_cb(&cb).unwrap(), -3);
assert_eq!(br.read_cb(&cb).unwrap(), 42);
assert_eq!(br.read_cb(&cb).unwrap(), -42);
let ret = br.read_cb(&cb);
if let Err(e) = ret {
assert_eq!(e as i32, CodebookError::InvalidCode as i32);
} else {
assert_eq!(0, 1);
}
let scb_desc: Vec<ShortCodebookDesc> = vec!(
ShortCodebookDesc { code: 0b0, bits: 1 },
ShortCodebookDesc { code: 0, bits: 0 },
ShortCodebookDesc { code: 0b10, bits: 2 },
ShortCodebookDesc { code: 0, bits: 0 },
ShortCodebookDesc { code: 0, bits: 0 },
ShortCodebookDesc { code: 0b110, bits: 3 },
ShortCodebookDesc { code: 0, bits: 0 },
ShortCodebookDesc { code: 0b1110, bits: 4 }
);
let mut br2 = BitReader::new(buf, buf.len(), BitReaderMode::BE);
let mut cfr = ShortCodebookDescReader::new(scb_desc);
let cb = Codebook::new(&mut cfr).unwrap();
assert_eq!(br2.read_cb(&cb).unwrap(), 0);
assert_eq!(br2.read_cb(&cb).unwrap(), 2);
assert_eq!(br2.read_cb(&cb).unwrap(), 5);
assert_eq!(br2.read_cb(&cb).unwrap(), 7);
}
}
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