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#[macro_use] mod utils; mod base64; mod bitreader; mod error; use bitreader::RevBitReader; use std::char::decode_utf16; use std::result; pub use error::{Error, Result}; #[derive(Default)] struct State { n_bits: u8, enlarge_in: u64, dict: Vec<Vec<u16>>, res: Vec<u16>, last: (usize, usize), } impl State { fn reset(&mut self) { self.n_bits = 2; self.enlarge_in = 5; self.dict.clear(); for i in 0..3 { self.dict.push(vec![i]); } self.res.clear(); self.last = (0, 0); } } pub struct Decoder { state: State, } impl Decoder { pub fn new() -> Self { let state = State::default(); Decoder { state } } pub fn decode_base64_to(&mut self, input: &str, dst: &mut String) -> Result<()> { let reader = RevBitReader::from_iter(base64::DecodeIterator::from_str(input)); self.decode_impl(reader, dst) } pub fn decode_base64(&mut self, input: &str) -> Result<String> { let mut dst = String::new(); self.decode_base64_to(input, &mut dst).and(Ok(dst)) } pub fn decode_to(&mut self, input: &[u8], dst: &mut String) -> Result<()> { let reader = RevBitReader::from_bytes(input); self.decode_impl(reader, dst) } pub fn decode(&mut self, input: &[u8]) -> Result<String> { let mut dst = String::new(); self.decode_to(input, &mut dst).and(Ok(dst)) } pub fn decode_impl<I, E>(&mut self, mut reader: RevBitReader<I>, dst: &mut String) -> Result<()> where E: Into<Error>, I: Iterator<Item = result::Result<u8, E>>, { self.state.reset(); let slice = self.state.next(&mut reader)?; if slice.is_empty() { return Ok(()); } self.state.last = (0, 1); self.state.n_bits += 1; loop { let before = self.state.res.len(); let slice = self.state.next(&mut reader)?; if slice.is_empty() { return self.flush(dst); } let mut last = self.state.res[self.state.last.0..self.state.last.1].to_owned(); last.push(slice[0]); self.state.add_to_dict(&last); self.state.last = (before, self.state.res.len()); } } fn flush(&mut self, dst: &mut String) -> Result<()> { let chars = self.state.res.iter().map(|u| *u); for chr in decode_utf16(chars) { let chr = chr?; dst.push(chr); } Ok(()) } } impl State { fn next<I, E>(&mut self, reader: &mut RevBitReader<I>) -> Result<Vec<u16>> where E: Into<Error>, I: Iterator<Item = result::Result<u8, E>>, { let bits = take(reader, self.n_bits)?; match bits { 0 => self.litteral(reader, 8), 1 => self.litteral(reader, 16), 2 => Ok(vec![]), c if (c as usize) < self.dict.len() => self.dict_entry(c as usize), c if (c as usize) == self.dict.len() => self.repeat_last(), c => Err(Error::InvalidHeader(c)), } } fn litteral<I, E>(&mut self, reader: &mut RevBitReader<I>, n_bits: u8) -> Result<Vec<u16>> where E: Into<Error>, I: Iterator<Item = result::Result<u8, E>>, { let bits = take(reader, n_bits)? as u16; self.add_to_dict(&[bits]); self.res.push(bits); Ok(self.res[self.res.len() - 1..].to_owned()) } fn dict_entry(&mut self, idx: usize) -> Result<Vec<u16>> { let entry = &self.dict[idx]; self.res.extend(entry); Ok(entry.to_owned()) } fn repeat_last(&mut self) -> Result<Vec<u16>> { let mut value = self.res[self.last.0..self.last.1].to_owned(); value.push(value[0]); self.res.extend(value.iter()); Ok(value) } fn add_to_dict(&mut self, entry: &[u16]) { self.dict.push(entry.to_owned()); self.enlarge_in -= 1; if self.enlarge_in == 0 { self.enlarge_in = 1 << self.n_bits; self.n_bits += 1; } } } fn take<I, E>(reader: &mut RevBitReader<I>, n: u8) -> Result<u64> where E: Into<Error>, I: Iterator<Item = result::Result<u8, E>>, { reader .take(n) .map(|r| r.map_err(Into::into)) .unwrap_or(Err(Error::UnexpectedEof)) }