bench: Add digest overhead benchmarks.

bench/Cargo.toml

@@ -20,6 +20,11 @@ name = "agreement"
 harness = false
 path = "agreement.rs"
 
+[[bench]]
+name = "digest"
+harness = false
+path = "digest.rs"
+
 [[bench]]
 name = "ecdsa"
 harness = false

bench/digest.rs

@@ -0,0 +1,49 @@
+// Copyright 2023 Brian Smith.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHORS DISCLAIM ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
+// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+#![allow(missing_docs)]
+
+use criterion::{black_box, criterion_group, criterion_main, BenchmarkId, Criterion};
+use ring::digest;
+
+static ALGORITHMS: &[(&str, &digest::Algorithm)] = &[
+    ("sha256", &digest::SHA256),
+    ("sha384", &digest::SHA384),
+    ("sha512", &digest::SHA512),
+];
+
+const INPUT_LENGTHS: &[usize] = &[
+    // Benchmark that emphasizes overhead.
+    0,
+];
+
+fn oneshot(c: &mut Criterion) {
+    for &(alg_name, algorithm) in ALGORITHMS {
+        for input_len in INPUT_LENGTHS {
+            c.bench_with_input(
+                BenchmarkId::new(format!("digest::oneshot::{alg_name}"), 0),
+                input_len,
+                |b, &input_len| {
+                    let input = vec![0u8; input_len];
+                    b.iter(|| -> usize {
+                        let digest = digest::digest(algorithm, &input);
+                        black_box(digest.as_ref().len())
+                    })
+                },
+            );
+        }
+    }
+}
+
+criterion_group!(digest, oneshot);
+criterion_main!(digest);