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Merged
404Setup merged 1 commit into from
Feb 18, 2026
Merged

Optimize Sequence packing to avoid table lookup in write loop #234

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34 changes: 0 additions & 34 deletions bench_result.txt
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32 changes: 32 additions & 0 deletions examples/manual_bench.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
use libdeflate::Compressor;
use std::time::Instant;

fn main() {
let size = 256 * 1024;
let mut data = Vec::with_capacity(size);
for i in 0..size {
data.push((i % 256) as u8);
}

let mut compressor = Compressor::new(6).unwrap();
let bound = compressor.deflate_compress_bound(size);
let mut out_buf = vec![0u8; bound];

// Warmup
for _ in 0..10 {
compressor.compress_deflate_into(&data, &mut out_buf).unwrap();
}

let start = Instant::now();
let iterations = 2000;
let mut total_bytes = 0;
for _ in 0..iterations {
let size = compressor.compress_deflate_into(&data, &mut out_buf).unwrap();
total_bytes += size;
}
let duration = start.elapsed();

println!("Compressed {} iterations of {} bytes", iterations, size);
println!("Total time: {:?}", duration);
println!("Throughput: {:.2} GiB/s", (iterations as f64 * size as f64) / duration.as_secs_f64() / 1024.0 / 1024.0 / 1024.0);
}
121 changes: 71 additions & 50 deletions src/compress/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -100,6 +100,27 @@ struct Sequence {
offset: u16,
}

impl Sequence {
#[inline(always)]
fn new(litrunlen: u32, len: u16, offset: u16, off_slot: u8) -> Self {
Self {
litrunlen,
length: len | ((off_slot as u16) << 9),
offset,
}
}

#[inline(always)]
fn len(&self) -> u16 {
self.length & 0x1FF
}

#[inline(always)]
fn off_slot(&self) -> usize {
(self.length >> 9) as usize
}
}

#[derive(Clone, Copy)]
struct DPNode {
cost: u32,
Expand Down Expand Up @@ -1067,14 +1088,16 @@ impl Compressor {
}
}

self.sequences.push(Sequence {
let off_slot = self.get_offset_slot(offset);
self.sequences.push(Sequence::new(
litrunlen,
length: len as u16,
offset: offset as u16,
});
len as u16,
offset as u16,
off_slot as u8,
));
self.split_stats.observe_match(len, offset);
self.litlen_freqs[257 + self.get_length_slot(len)] += 1;
self.offset_freqs[self.get_offset_slot(offset)] += 1;
self.offset_freqs[off_slot] += 1;
litrunlen = 0;
if len - 1 > skipped {
mf.skip_positions(
Expand All @@ -1092,11 +1115,7 @@ impl Compressor {
in_idx += 1;
}
}
self.sequences.push(Sequence {
litrunlen,
length: 0,
offset: 0,
});
self.sequences.push(Sequence::new(litrunlen, 0, 0, 0));
self.litlen_freqs[256] += 1;
in_idx - start_pos
}
Expand Down Expand Up @@ -1149,15 +1168,18 @@ impl Compressor {
}
}
}
if seq.length >= 3 {
let len = seq.len();
if len >= 3 {
let offset = seq.offset as usize;
let off_slot = seq.off_slot();
if bs.out_idx + 16 < bs.output.len() {
unsafe {
self.write_match_fast(bs, seq.length as usize, seq.offset as usize);
self.write_match_fast(bs, len as usize, offset, off_slot);
}
} else if !self.write_match(bs, seq.length as usize, seq.offset as usize) {
} else if !self.write_match(bs, len as usize, offset, off_slot) {
return false;
}
in_pos += seq.length as usize;
in_pos += len as usize;
}
}
if !self.write_sym(bs, 256) {
Expand Down Expand Up @@ -1275,11 +1297,12 @@ impl Compressor {
while in_idx < input.len() {
let (len, offset) = mf.find_match(input, in_idx, self.max_search_depth);
if len >= 3 {
self.sequences.push(Sequence {
self.sequences.push(Sequence::new(
litrunlen,
length: len as u16,
offset: offset as u16,
});
len as u16,
offset as u16,
self.get_offset_slot(offset) as u8,
));
litrunlen = 0;
mf.skip_positions(input, in_idx + 1, len - 1, self.max_search_depth);
in_idx += len;
Expand All @@ -1300,11 +1323,12 @@ impl Compressor {
let (len, offset) = mf.find_match(input, in_idx, self.max_search_depth);
if len >= 3 {
self.split_stats.observe_match(len, offset);
self.sequences.push(Sequence {
self.sequences.push(Sequence::new(
litrunlen,
length: len as u16,
offset: offset as u16,
});
len as u16,
offset as u16,
self.get_offset_slot(offset) as u8,
));
litrunlen = 0;
mf.skip_positions(input, in_idx + 1, len - 1, self.max_search_depth);
in_idx += len;
Expand All @@ -1315,11 +1339,7 @@ impl Compressor {
}
}
}
self.sequences.push(Sequence {
litrunlen,
length: 0,
offset: 0,
});
self.sequences.push(Sequence::new(litrunlen, 0, 0, 0));

let processed = in_idx - start_pos;
let is_final = (start_pos + processed >= input.len()) && final_block;
Expand Down Expand Up @@ -1353,15 +1373,18 @@ impl Compressor {
}
}
}
if seq.length >= 3 {
let len = seq.len();
if len >= 3 {
let offset = seq.offset as usize;
let off_slot = seq.off_slot();
if bs.out_idx + 16 < bs.output.len() {
unsafe {
self.write_match_fast(bs, seq.length as usize, seq.offset as usize);
self.write_match_fast(bs, len as usize, offset, off_slot);
}
} else if !self.write_match(bs, seq.length as usize, seq.offset as usize) {
} else if !self.write_match(bs, len as usize, offset, off_slot) {
return 0;
}
in_pos += seq.length as usize;
in_pos += len as usize;
}
}
if !self.write_sym(bs, 256) {
Expand Down Expand Up @@ -1415,13 +1438,15 @@ impl Compressor {
while cur_in_idx < block_input.len() {
let (len, offset) = mf.find_match(block_input, cur_in_idx, self.max_search_depth);
if len >= 3 {
self.sequences.push(Sequence {
let off_slot = self.get_offset_slot(offset);
self.sequences.push(Sequence::new(
litrunlen,
length: len as u16,
offset: offset as u16,
});
len as u16,
offset as u16,
off_slot as u8,
));
self.litlen_freqs[257 + self.get_length_slot(len)] += 1;
self.offset_freqs[self.get_offset_slot(offset)] += 1;
self.offset_freqs[off_slot] += 1;
litrunlen = 0;
cur_in_idx += len;
for i in 1..len {
Expand Down Expand Up @@ -1519,22 +1544,20 @@ impl Compressor {
litrunlen += 1;
cur_pos += 1;
} else {
self.sequences.push(Sequence {
let off_slot = self.get_offset_slot(node.offset as usize);
self.sequences.push(Sequence::new(
litrunlen,
length: node.length,
offset: node.offset,
});
node.length,
node.offset,
off_slot as u8,
));
self.litlen_freqs[257 + self.get_length_slot(node.length as usize)] += 1;
self.offset_freqs[self.get_offset_slot(node.offset as usize)] += 1;
self.offset_freqs[off_slot] += 1;
litrunlen = 0;
cur_pos += node.length as usize;
}
}
self.sequences.push(Sequence {
litrunlen,
length: 0,
offset: 0,
});
self.sequences.push(Sequence::new(litrunlen, 0, 0, 0));

make_huffman_code(
DEFLATE_NUM_LITLEN_SYMS,
Expand Down Expand Up @@ -1756,7 +1779,7 @@ impl Compressor {
}

#[inline(always)]
unsafe fn write_match_fast(&self, bs: &mut Bitstream, len: usize, offset: usize) {
unsafe fn write_match_fast(&self, bs: &mut Bitstream, len: usize, offset: usize, off_slot: usize) {
let entry = *self.match_len_table.get_unchecked(len);
let code = entry as u16 as u32;
let huff_len = (entry >> 16) as u8 as u32;
Expand All @@ -1768,7 +1791,6 @@ impl Compressor {

bs.write_bits_unchecked_fast(len_val, len_len);

let off_slot = self.get_offset_slot(offset);
let entry = *self.offset_table.get_unchecked(off_slot);
let off_code = entry as u32;
let off_len = (entry >> 32) as u8 as u32;
Expand All @@ -1781,7 +1803,7 @@ impl Compressor {
bs.write_bits_unchecked_fast(off_val, off_len_total);
}

fn write_match(&self, bs: &mut Bitstream, len: usize, offset: usize) -> bool {
fn write_match(&self, bs: &mut Bitstream, len: usize, offset: usize, off_slot: usize) -> bool {
let entry = unsafe { *self.match_len_table.get_unchecked(len) };
let code = entry as u16 as u32;
let huff_len = (entry >> 16) as u8 as u32;
Expand All @@ -1795,7 +1817,6 @@ impl Compressor {
return false;
}

let off_slot = self.get_offset_slot(offset);
let entry = unsafe { *self.offset_table.get_unchecked(off_slot) };
let off_code = entry as u32;
let off_len = (entry >> 32) as u8 as u32;
Expand Down