diff --git a/README.md b/README.md new file mode 100644 index 0000000..4f2e5b8 --- /dev/null +++ b/README.md @@ -0,0 +1,10 @@ +# Upkr + +Upkr is a simple general purpose lz packer designed to be used in the [MicroW8](https://github.com/exoticorn/microw8) platform. +The compressed format is base on [Shrinkler](https://github.com/askeksa/Shrinkler) with the main difference being that +Upkr doesn't differnetiate between literals at odd or even addresses. + +At this point, Upkr should be considered unstable - the exact format isn't finalized yet and still subject to change +and only a very simple (but also very fast) greedy compressor is implemented. The compression ratio will be improved +with a more thourough lz parse in the future, although even in the current state is is already similar to the +DEFLATE compression algorithm. \ No newline at end of file diff --git a/src/lib.rs b/src/lib.rs new file mode 100644 index 0000000..cdfe38c --- /dev/null +++ b/src/lib.rs @@ -0,0 +1,8 @@ +mod context_state; +mod greedy_packer; +mod lz; +mod match_finder; +mod range_coder; + +pub use greedy_packer::pack; +pub use lz::unpack; \ No newline at end of file diff --git a/src/lz.rs b/src/lz.rs index f220a28..9c10439 100644 --- a/src/lz.rs +++ b/src/lz.rs @@ -53,7 +53,7 @@ impl LzCoder { assert!(value >= 1); let top_bit = usize::BITS - 1 - value.leading_zeros(); let mut context_index = context_start; - for i in (0..top_bit).rev() { + for i in 0..top_bit { self.bit(true, context_index); self.bit((value >> i) & 1 != 0, context_index + 1); context_index += 2; @@ -78,14 +78,16 @@ pub fn unpack(packed_data: &[u8]) -> Vec { contexts: &mut ContextState, mut context_index: usize, ) -> usize { - let mut length = 1; + let mut length = 0; + let mut bit_pos = 0; while decoder.decode_with_context(&mut contexts.context_mut(context_index)) { - length = (length << 1) - | decoder.decode_with_context(&mut contexts.context_mut(context_index + 1)) - as usize; + length |= (decoder.decode_with_context(&mut contexts.context_mut(context_index + 1)) + as usize) + << bit_pos; + bit_pos += 1; context_index += 2; } - length + length | (1 << bit_pos) } loop { diff --git a/src/main.rs b/src/main.rs index 82705bb..d3a372b 100644 --- a/src/main.rs +++ b/src/main.rs @@ -1,16 +1,10 @@ -mod context_state; -mod greedy_packer; -mod lz; -mod match_finder; -mod range_coder; - fn main() { - let test_data = include_bytes!("../testcases/skipahead.wasm"); + let test_data = include_bytes!("../README.md"); - let packed = greedy_packer::pack(test_data); + let packed = upkr::pack(test_data); dbg!((test_data.len(), packed.len())); - let unpacked = lz::unpack(&packed); + let unpacked = upkr::unpack(&packed); dbg!(unpacked.len()); assert!(test_data == unpacked.as_slice()); } diff --git a/src/match_finder.rs b/src/match_finder.rs index e576019..ae70fd7 100644 --- a/src/match_finder.rs +++ b/src/match_finder.rs @@ -113,7 +113,7 @@ impl<'a> Iterator for Matches<'a> { self.add_to_queue(self.finder.suffixes[self.left_index]); self.move_left(); } - if self.right_length == self.current_length { + if self.right_length == self.current_length && self.matches_left > 0 { self.add_to_queue(self.finder.suffixes[self.right_index]); self.move_right(); }