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use std::mem;
use bytes::Buf;
use criterion::{Criterion, Throughput};
use prost::encoding::{decode_varint, encode_varint, encoded_len_varint};
use rand::{rngs::StdRng, seq::SliceRandom, SeedableRng};
fn benchmark_varint(criterion: &mut Criterion, name: &str, mut values: Vec<u64>) {
// Shuffle the values in a stable order.
values.shuffle(&mut StdRng::seed_from_u64(0));
let name = format!("varint/{}", name);
let encoded_len = values
.iter()
.cloned()
.map(encoded_len_varint)
.sum::<usize>() as u64;
let decoded_len = (values.len() * mem::size_of::<u64>()) as u64;
criterion
.benchmark_group(&name)
.bench_function("encode", {
let encode_values = values.clone();
move |b| {
let mut buf = Vec::<u8>::with_capacity(encode_values.len() * 10);
b.iter(|| {
buf.clear();
for &value in &encode_values {
encode_varint(value, &mut buf);
}
criterion::black_box(&buf);
})
}
})
.throughput(Throughput::Bytes(encoded_len));
criterion
.benchmark_group(&name)
.bench_function("decode", {
let decode_values = values.clone();
move |b| {
let mut buf = Vec::with_capacity(decode_values.len() * 10);
for &value in &decode_values {
encode_varint(value, &mut buf);
}
b.iter(|| {
let mut buf = &mut buf.as_slice();
while buf.has_remaining() {
let result = decode_varint(&mut buf);
debug_assert!(result.is_ok());
criterion::black_box(&result);
}
})
}
})
.throughput(Throughput::Bytes(decoded_len));
criterion
.benchmark_group(&name)
.bench_function("encoded_len", move |b| {
b.iter(|| {
let mut sum = 0;
for &value in &values {
sum += encoded_len_varint(value);
}
criterion::black_box(sum);
})
})
.throughput(Throughput::Bytes(decoded_len));
}
fn main() {
let mut criterion = Criterion::default().configure_from_args();
// Benchmark encoding and decoding 100 small (1 byte) varints.
benchmark_varint(&mut criterion, "small", (0..100).collect());
// Benchmark encoding and decoding 100 medium (5 byte) varints.
benchmark_varint(&mut criterion, "medium", (1 << 28..).take(100).collect());
// Benchmark encoding and decoding 100 large (10 byte) varints.
benchmark_varint(&mut criterion, "large", (1 << 63..).take(100).collect());
// Benchmark encoding and decoding 100 varints of mixed width (average 5.5 bytes).
benchmark_varint(
&mut criterion,
"mixed",
(0..10)
.flat_map(move |width| {
let exponent = width * 7;
(0..10).map(move |offset| offset + (1 << exponent))
})
.collect(),
);
criterion.final_summary();
}