diff options
| -rw-r--r-- | gifed/src/lzw.rs | 69 |
1 files changed, 55 insertions, 14 deletions
diff --git a/gifed/src/lzw.rs b/gifed/src/lzw.rs index bcf1988..89b43e5 100644 --- a/gifed/src/lzw.rs +++ b/gifed/src/lzw.rs @@ -2,9 +2,14 @@ use std::collections::HashMap; use bitvec::prelude::*; -pub struct LZW {} +pub struct LZW { + minimum_size: u8, + clear_code: u16, + end_of_information_code: u16, + dictionary: HashMap<Vec<u8>, u16>, +} impl LZW { - pub fn encode(minimum_size: u8, indices: &[u8]) -> Vec<u8> { + pub fn new(minimum_size: u8) -> Self { let mut dictionary: HashMap<Vec<u8>, u16> = HashMap::new(); let clear_code = 1 << minimum_size; @@ -17,24 +22,50 @@ impl LZW { dictionary.insert(vec![value as u8], value); } - let mut next_code = end_of_information_code + 1; - let mut code_size = minimum_size + 1; + Self { + minimum_size, + clear_code, + end_of_information_code, + dictionary, + } + } + + pub fn reset(&mut self) { + *self = Self::new(self.minimum_size) + } + + pub fn decode(&mut self, encoded: &[u8]) -> Vec<u8> { + let mut input = BitStream::new(); + for &byte in encoded { + input.push_bits(8, byte as u16); + } + + let mut out = BitStream::new(); + + todo!(); + + out.vec() + } + + pub fn encode(&mut self, indices: &[u8]) -> Vec<u8> { + let mut next_code = self.end_of_information_code + 1; + let mut code_size = self.minimum_size + 1; let mut iter = indices.iter(); let mut out = BitStream::new(); let mut buffer = vec![*iter.next().unwrap()]; - out.push_bits(code_size, clear_code); + out.push_bits(code_size, self.clear_code); for &index in iter { buffer.push(index); - if !dictionary.contains_key(&buffer) { - if let Some(&code) = dictionary.get(&buffer[..buffer.len() - 1]) { + if !self.dictionary.contains_key(&buffer) { + if let Some(&code) = self.dictionary.get(&buffer[..buffer.len() - 1]) { out.push_bits(code_size, code); // add the vec to the dict - dictionary.insert(buffer, next_code); + self.dictionary.insert(buffer, next_code); next_code += 1; // If the next_code can't fit in the code_size, we have to increase it @@ -46,14 +77,14 @@ impl LZW { } else { println!("index is: {index}"); println!("buffer is: {:?}", buffer); - println!("dictionary: {:?}", dictionary); + println!("dictionary: {:?}", self.dictionary); unreachable!() } } } if !buffer.is_empty() { - match dictionary.get(&buffer) { + match self.dictionary.get(&buffer) { Some(&code) => out.push_bits(code_size, code), None => { unreachable!( @@ -62,7 +93,7 @@ impl LZW { } } } - out.push_bits(code_size, end_of_information_code); + out.push_bits(code_size, self.end_of_information_code); out.vec() } @@ -80,7 +111,7 @@ mod lzw_test { let weezl = weezl::encode::Encoder::new(weezl::BitOrder::Lsb, 2) .encode(&indices) .unwrap(); - let us = LZW::encode(2, &indices); + let us = LZW::new(2).encode(&indices); assert_eq!(us.len(), weezl.len()); } @@ -110,7 +141,7 @@ mod lzw_test { let indices = vec![0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0]; let output = vec![0x84, 0x1D, 0x81, 0x7A, 0x50]; - let lzout = LZW::encode(2, &indices); + let lzout = LZW::new(2).encode(&indices); assert_eq!(lzout, output); } @@ -121,7 +152,7 @@ mod lzw_test { let weezl = weezl::encode::Encoder::new(weezl::BitOrder::Lsb, 2) .encode(&indices) .unwrap(); - let us = LZW::encode(2, &indices); + let us = LZW::new(2).encode(&indices); assert_eq!(weezl, us); } @@ -144,6 +175,16 @@ impl BitStream { } } + fn pop_bits(&mut self, count: u8) -> u16 { + let mut out = 0; + for i in (0..count).filter_map(|_| self.formed.pop()) { + out <<= 1; + let int: u16 = i.into(); + out |= int; + } + out + } + fn vec(mut self) -> Vec<u8> { self.formed.set_uninitialized(false); self.formed.into_vec() |