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use std::io::{Read, Result, Write};
#[derive(Debug, Clone)]
enum HT {
Branch(Box<HT>, Box<HT>),
Terminal(u8),
}
pub fn write_huff(buf: &[u8], w: &mut impl Write) -> Result<usize> {
let mut w = BitIO::new(w);
assert!(buf.len() <= 0xffffff, "huff frame too big");
w.wbyte((buf.len() & 0xff) as u8)?;
w.wbyte(((buf.len() >> 8) & 0xff) as u8)?;
w.wbyte(((buf.len() >> 16) & 0xff) as u8)?;
let mut probs = [0usize; 256];
for b in buf {
probs[*b as usize] += 1;
}
let tree = HT::from_probabilities(probs);
let mut table = [0u32; 256];
tree.create_lut(&mut table, 1);
tree.write(&mut w)?;
for b in buf {
let mut k = table[*b as usize];
while k != 1 {
w.wbit((k & 1) == 1)?;
k >>= 1;
}
}
w.flush()?;
eprintln!("{}", w.position);
Ok(w.position)
}
pub fn read_huff(r: &mut impl Read, buf: &mut Vec<u8>) -> Result<usize> {
let mut r = BitIO::new(r);
let mut len = 0usize;
len |= r.rbyte()? as usize;
len |= (r.rbyte()? as usize) << 8;
len |= (r.rbyte()? as usize) << 16;
eprintln!("len={len:?}");
let root = HT::read(&mut r)?;
// eprintln!("{root:?}");
let root = match &root {
HT::Branch(a, b) => [a, b],
_ => panic!("no!"),
};
let mut cursor = root;
while buf.len() != len {
let v = r.rbit()?;
match cursor[v as usize].as_ref() {
HT::Branch(a, b) => {
cursor = [a, b];
}
HT::Terminal(n) => {
buf.push(*n);
cursor = root;
}
}
}
eprintln!("len(buf)={}", buf.len());
eprintln!("{}", r.position);
Ok(r.position)
}
impl HT {
pub fn from_probabilities(ps: [usize; 256]) -> Self {
let mut parts = ps
.into_iter()
.enumerate()
.map(|(n, p)| (p, HT::Terminal(n as u8)))
.collect::<Vec<_>>();
while parts.len() != 1 {
parts.sort_by_key(|e| -(e.0 as isize));
let ((ap, at), (bp, bt)) = (parts.pop().unwrap(), parts.pop().unwrap());
parts.push((ap + bp + 1, HT::Branch(box at, box bt)))
}
parts[0].1.clone()
}
pub fn create_lut(&self, table: &mut [u32; 256], mut prefix: u32) {
assert!(self.depth() < 30, "too deep! doesnt fit {}", self.depth());
match self {
HT::Branch(a, b) => {
let pz = 32 - prefix.leading_zeros();
prefix ^= 1 << pz;
prefix ^= 1 << (pz - 1);
a.create_lut(table, prefix);
prefix ^= 1 << (pz - 1);
b.create_lut(table, prefix);
}
HT::Terminal(n) => {
assert_eq!(table[*n as usize], 0);
table[*n as usize] = prefix
}
}
}
pub fn depth(&self) -> usize {
match self {
HT::Branch(a, b) => a.depth().max(b.depth()) + 1,
HT::Terminal(_) => 0,
}
}
pub fn write(&self, w: &mut BitIO<impl Write>) -> Result<()> {
match self {
HT::Branch(a, b) => {
w.wbit(false)?;
a.write(w)?;
b.write(w)?;
}
HT::Terminal(n) => {
w.wbit(true)?;
w.wbyte(*n)?;
}
}
Ok(())
}
pub fn read(r: &mut BitIO<impl Read>) -> Result<Self> {
match r.rbit()? {
false => Ok(Self::Branch(box Self::read(r)?, box Self::read(r)?)),
true => Ok(Self::Terminal(r.rbyte()?)),
}
}
}
pub struct BitIO<T> {
inner: T,
byte: u8,
position: usize,
}
impl<T> BitIO<T> {
pub fn new(inner: T) -> Self {
Self {
inner,
byte: 0,
position: 0,
}
}
}
impl<T: Write> BitIO<T> {
#[inline]
pub fn wbit(&mut self, b: bool) -> Result<()> {
self.byte <<= 1;
self.byte |= b as u8;
self.position += 1;
if self.position & 0b111 == 0 {
self.inner.write_all(&[self.byte])?;
}
Ok(())
}
#[inline]
pub fn wbyte(&mut self, v: u8) -> Result<()> {
for i in 0..8 {
self.wbit((v & (1 << i)) != 0)?;
}
Ok(())
}
pub fn flush(&mut self) -> Result<()> {
while self.position & 0b111 != 0 {
self.wbit(false)?;
}
Ok(())
}
}
impl<T: Read> BitIO<T> {
#[inline]
pub fn rbit(&mut self) -> Result<bool> {
if self.position & 0b111 == 0 {
let mut buf = [0];
self.inner.read_exact(&mut buf)?;
self.byte = buf[0];
}
let v = (self.byte & 0b10000000) != 0;
self.byte <<= 1;
self.position += 1;
Ok(v)
}
#[inline]
pub fn rbyte(&mut self) -> Result<u8> {
let mut v = 0u8;
for i in 0..8 {
v |= (self.rbit()? as u8) << i;
}
Ok(v)
}
}
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