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Merged
mdsteele merged 5 commits into from
Feb 4, 2026
Merged

feat: dynamic stream buffer #79

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4bdfbdf
feat: dynamic stream buffer
francisdb Feb 2, 2026
78c402a
feat: improve benchmark
francisdb Feb 2, 2026
d0357f5
api cleanup, tried to stay close to initial api before I introduced s…
francisdb Feb 2, 2026
69a8c72
Aggressively grow buffer on the read side.
francisdb Feb 3, 2026
0ee2dae
bench: add a 10000x0B case
francisdb Feb 4, 2026
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236 changes: 73 additions & 163 deletions benches/benchmark.rs
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Original file line number Diff line number Diff line change
@@ -1,46 +1,28 @@
use cfb::{CompoundFile, CreateStreamOptions};
use criterion::{
criterion_group, criterion_main, BenchmarkId, Criterion, Throughput,
};
use cfb::CompoundFile;
use criterion::{criterion_group, criterion_main, Criterion, Throughput};
use std::fs::OpenOptions;
use std::hint::black_box;
use std::io::Cursor;
use std::io::Read;
use std::io::Write;
use tempfile::NamedTempFile;

fn write_many_streams(
n: usize,
size: usize,
stream_buffer_size: Option<usize>,
) -> Vec<u8> {
fn write_many_streams(n: usize, size: usize) -> Vec<u8> {
let mut buff = Vec::new();
{
let mut test_comp =
CompoundFile::create(Cursor::new(&mut buff)).unwrap();
let data = vec![0; size];
for i in 0..n {
let name = format!("test{i}");
let mut stream = match stream_buffer_size {
Some(buf_size) => {
let options =
CreateStreamOptions::new().buffer_size(buf_size);
test_comp
.create_stream_with_options(name, options)
.unwrap()
}
None => test_comp.create_stream(name).unwrap(),
};
let mut stream = test_comp.create_stream(name).unwrap();
stream.write_all(&data).unwrap();
}
}
buff
}

fn write_many_streams_disk(
n: usize,
size: usize,
stream_buffer_size: Option<usize>,
) {
fn write_many_streams_disk(n: usize, size: usize) {
let tmpfile = NamedTempFile::new().unwrap();
{
let mut test_comp = CompoundFile::create(
Expand All @@ -54,159 +36,87 @@ fn write_many_streams_disk(
let data = vec![0; size];
for i in 0..n {
let name = format!("test{i}");
let mut stream = match stream_buffer_size {
Some(buf_size) => {
let options =
CreateStreamOptions::new().buffer_size(buf_size);
test_comp
.create_stream_with_options(name, options)
.unwrap()
}
None => test_comp.create_stream(name).unwrap(),
};
let mut stream = test_comp.create_stream(name).unwrap();
stream.write_all(&data).unwrap();
}
}
// File is deleted when tmpfile is dropped
}

fn criterion_benchmark(c: &mut Criterion) {
// Buffer sizes to compare (in bytes). `None` means the default internal
// stream buffer size.
let buffer_sizes: &[(Option<usize>, &str)] = &[
(None, "default"),
(Some(8 * 1024), "buffer=8192"),
(Some(64 * 1024), "buffer=65536"),
(Some(256 * 1024), "buffer=262144"),
(Some(1024 * 1024), "buffer=1048576"),
];

// many small streams with throughput reporting
let mut small = c.benchmark_group("write many smaller streams");
let size = 64usize;
let n = 1000;
let total_bytes = (n * size) as u64;
small.sample_size(10);
small.throughput(Throughput::Bytes(total_bytes));

for (buf, label) in buffer_sizes {
small.bench_with_input(
BenchmarkId::new("total", *label),
&size,
|b, &s| {
b.iter(|| {
let out = write_many_streams(
black_box(n),
black_box(s),
buf.map(black_box),
);
black_box(out);
})
},
);
fn read_many_streams(buff: &[u8], n: usize) {
let mut test_comp = CompoundFile::open(Cursor::new(buff)).unwrap();
for i in 0..n {
let name = format!("test{i}");
let mut stream = test_comp.open_stream(name).unwrap();
let mut sink = Vec::new();
stream.read_to_end(&mut sink).unwrap();
black_box(sink);
}
small.finish();

// streams just below the MiniFAT cutoff
let mut cutoff = c.benchmark_group("write MiniFAT max streams");
let size = (4 * 1024) - 1;
let n = 500;
let total_bytes = (n * size) as u64;
cutoff.sample_size(10);
cutoff.throughput(Throughput::Bytes(total_bytes));

for (buf, label) in buffer_sizes {
cutoff.bench_with_input(
BenchmarkId::new("total", *label),
&size,
|b, &s| {
b.iter(|| {
let out = write_many_streams(
black_box(n),
black_box(s),
buf.map(black_box),
);
black_box(out);
})
},
);
}
cutoff.finish();
}

// several medium streams with throughput reporting
let mut medium = c.benchmark_group("write several medium streams");
let size = 1024 * 1024usize;
let n = 50;
let total_bytes = (n * size) as u64;
medium.sample_size(10);
medium.throughput(Throughput::Bytes(total_bytes));
fn criterion_benchmark(c: &mut Criterion) {
let stream_benches = [
// (label, stream_size, stream_count)
("n=10000,size=0B", 0, 10000usize),
("n=1000,size=64B", 64usize, 1000usize),
("n=100,size=4KiB-1 (MiniFAT)", 1024 * 4 - 1, 100usize),
("n=100,size=4KiB (FAT)", 1024 * 4, 100usize),
("n=50,size=1MiB", 1024 * 1024usize, 50usize),
("n=1,size=256MiB", 256 * 1024 * 1024usize, 1usize),
];

for (buf, label) in buffer_sizes {
medium.bench_with_input(
BenchmarkId::new("total", *label),
&size,
|b, &s| {
b.iter(|| {
let out = write_many_streams(
black_box(n),
black_box(s),
buf.map(black_box),
);
black_box(out);
})
},
);
let mut group = c.benchmark_group("write_streams_memory");
for (label, stream_size, stream_count) in stream_benches {
let total_bytes = (stream_count * stream_size) as u64;
group.sample_size(10);
if total_bytes > 0 {
group.throughput(Throughput::Bytes(total_bytes));
}
group.bench_function(label, |b| {
b.iter(|| {
let out = write_many_streams(
black_box(stream_count),
black_box(stream_size),
);
black_box(out);
})
});
}
medium.finish();
group.finish();

// single large stream with throughput reporting
let mut group = c.benchmark_group("write large stream");
let size = 256 * 1024 * 1024usize;
let n = 1;
group.sample_size(10);
group.throughput(Throughput::Bytes(size as u64));
for (buf, label) in buffer_sizes {
group.bench_with_input(
BenchmarkId::new("total", *label),
&size,
|b, &s| {
b.iter(|| {
let out = write_many_streams(
black_box(n),
black_box(s),
buf.map(black_box),
);
black_box(out);
})
},
);
let mut disk_group = c.benchmark_group("write_streams_disk");
for (label, stream_size, stream_count) in stream_benches {
let total_bytes = (stream_count * stream_size) as u64;
disk_group.sample_size(10);
if total_bytes > 0 {
disk_group.throughput(Throughput::Bytes(total_bytes));
}
disk_group.bench_function(label, |b| {
b.iter(|| {
write_many_streams_disk(
black_box(stream_count),
black_box(stream_size),
);
})
});
}
group.finish();
disk_group.finish();

// many small streams with throughput reporting (disk)
let mut small_disk =
c.benchmark_group("write many smaller streams (disk)");
let size = 64usize;
let n = 1000;
let total_bytes = (n * size) as u64;
small_disk.sample_size(10);
small_disk.throughput(Throughput::Bytes(total_bytes));
for (buf, label) in buffer_sizes {
small_disk.bench_with_input(
BenchmarkId::new("total", *label),
&size,
|b, &s| {
b.iter(|| {
write_many_streams_disk(
black_box(n),
black_box(s),
buf.map(black_box),
);
})
},
);
let mut read_group = c.benchmark_group("read_streams_memory");
for (label, stream_size, stream_count) in stream_benches {
let total_bytes = (stream_count * stream_size) as u64;
let buff = write_many_streams(stream_count, stream_size);
read_group.sample_size(10);
if total_bytes > 0 {
read_group.throughput(Throughput::Bytes(total_bytes));
}
read_group.bench_function(label, |b| {
b.iter(|| {
read_many_streams(black_box(&buff), black_box(stream_count));
})
});
}
small_disk.finish();
read_group.finish();
}

criterion_group!(benches, criterion_benchmark);
Expand Down
2 changes: 2 additions & 0 deletions src/internal/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ mod objtype;
pub mod path;
mod sector;
mod stream;
mod stream_buffer;
mod timestamp;
mod validate;
mod version;
Expand All @@ -31,6 +32,7 @@ pub use self::minichain::MiniChain;
pub use self::objtype::ObjType;
pub use self::sector::{Sector, SectorInit, Sectors};
pub use self::stream::Stream;
pub(crate) use self::stream_buffer::DEFAULT_STREAM_MAX_BUFFER_SIZE;
pub use self::timestamp::Timestamp;
pub use self::validate::Validation;
pub use self::version::Version;
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