feat(s2n-quic-core): add skip functionality to ReceiveBuffer (#2050)

Author: camshaft

Diff for: quic/s2n-quic-bench/src/buffer.rs

@@ -1,24 +1,53 @@
 // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-use criterion::{BenchmarkId, Criterion, Throughput};
+use criterion::{black_box, BenchmarkId, Criterion, Throughput};
 use s2n_quic_core::{buffer::ReceiveBuffer, varint::VarInt};
 
 pub fn benchmarks(c: &mut Criterion) {
     let mut group = c.benchmark_group("buffer");
 
-    for size in [1, 100, 1000, 1450] {
+    for size in [1, 100, 1000, 1450, 8500, 9000] {
         let input = vec![42u8; size];
 
         group.throughput(Throughput::Bytes(input.len() as _));
+
+        group.bench_with_input(BenchmarkId::new("skip", size), &input, |b, _input| {
+            let mut buffer = ReceiveBuffer::new();
+            b.iter(move || {
+                buffer.skip(black_box(size)).unwrap();
+            });
+        });
+
         group.bench_with_input(BenchmarkId::new("write_at", size), &input, |b, input| {
             let mut buffer = ReceiveBuffer::new();
             let mut offset = VarInt::from_u8(0);
             let len = VarInt::new(input.len() as _).unwrap();
             b.iter(move || {
                 buffer.write_at(offset, input).unwrap();
+                while buffer.pop().is_some() {}
                 offset += len;
             });
         });
+
+        // we double the writes in the fragment test
+        group.throughput(Throughput::Bytes((input.len() * 2) as _));
+        group.bench_with_input(
+            BenchmarkId::new("write_at_fragmented", size),
+            &input,
+            |b, input| {
+                let mut buffer = ReceiveBuffer::new();
+                let mut offset = VarInt::from_u8(0);
+                let len = VarInt::new(input.len() as _).unwrap();
+                b.iter(move || {
+                    let first_offset = offset + len;
+                    buffer.write_at(first_offset, input).unwrap();
+                    let second_offset = offset;
+                    buffer.write_at(second_offset, input).unwrap();
+                    while buffer.pop().is_some() {}
+                    offset = first_offset + len;
+                });
+            },
+        );
     }
 }