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https://github.com/tokio-rs/bytes
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Optimize Bytes::slice(n, n) (#123)
Return empty `Bytes` object Bench for `slice_empty` difference is ``` 55 ns/iter (+/- 1) # before this patch 17 ns/iter (+/- 5) # with this patch ``` Bench for `slice_not_empty` is ``` 25,058 ns/iter (+/- 1,099) # before this patch 25,072 ns/iter (+/- 1,593) # with this patch ```
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@ -4,7 +4,7 @@ extern crate bytes;
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extern crate test;
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use test::Bencher;
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use bytes::{BytesMut, BufMut};
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use bytes::{Bytes, BytesMut, BufMut};
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#[bench]
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fn alloc_small(b: &mut Bencher) {
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@ -126,3 +126,23 @@ fn drain_write_drain(b: &mut Bencher) {
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test::black_box(parts);
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})
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}
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#[bench]
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fn slice_empty(b: &mut Bencher) {
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b.iter(|| {
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// Use empty vec to avoid measure of allocation/deallocation
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let bytes = Bytes::from(Vec::new());
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(bytes.slice(0, 0), bytes)
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})
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}
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#[bench]
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fn slice_not_empty(b: &mut Bencher) {
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b.iter(|| {
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let b = Bytes::from(b"aabbccddeeffgghh".to_vec());
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for _ in 0..1024 {
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test::black_box(b.slice(3, 5));
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test::black_box(&b);
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}
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})
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}
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@ -464,6 +464,11 @@ impl Bytes {
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/// Requires that `begin <= end` and `end <= self.len()`, otherwise slicing
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/// will panic.
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pub fn slice(&self, begin: usize, end: usize) -> Bytes {
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if begin == end {
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assert!(begin <= self.len());
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return Bytes::new();
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}
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let mut ret = self.clone();
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unsafe {
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@ -79,6 +79,15 @@ fn slice() {
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let b = a.slice(3, 5);
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assert_eq!(b, b"lo"[..]);
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let b = a.slice(0, 0);
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assert_eq!(b, b""[..]);
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let b = a.slice(3, 3);
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assert_eq!(b, b""[..]);
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let b = a.slice(a.len(), a.len());
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assert_eq!(b, b""[..]);
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let b = a.slice_to(5);
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assert_eq!(b, b"hello"[..]);
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