add benchmark

Cargo.toml

@@ -58,3 +58,7 @@ harness = false
 [[bench]]
 name = "deserialize"
 harness = false
+
+[[bench]]
+name = "sha256_hash"
+harness = false

benches/sha256_hash.rs

@@ -0,0 +1,40 @@
+use criterion::{Criterion, criterion_group, criterion_main};
+
+use clvmr::sha2::Sha256;
+
+const BYTE_LENGTHS: [u8; 6] = [8, 16, 32, 64, 96, 128];
+const MAX_VAL: u8 = 250;
+fn gen_bytes(value: &u8, amount: &u8) -> Vec<u8> {
+    let mut bytes = Vec::new();
+    for _ in 0..*amount {
+        bytes.push(*value);
+    }
+    bytes
+}
+
+fn hash_bytes(bytes: Vec<u8>) -> [u8; 32] {
+    let mut sha256 = Sha256::new();
+    sha256.update(&bytes);
+    sha256.finalize()
+}
+
+fn sha256_hash_benchmark(c: &mut Criterion) {
+    // setup benchmark
+    let mut group = c.benchmark_group("sha256_hash");
+
+    group.bench_function("hash_benchmark", |b| {
+        b.iter(|| { // this figures out how many iterations to run.
+            for val in 0..MAX_VAL {
+                for len in BYTE_LENGTHS {
+                    let bytes = gen_bytes(&val, &len);
+                    hash_bytes(bytes); // purposely not borrowing bytes, as no longer needed.
+                }
+            }
+        })
+    });
+    // create
+    group.finish();
+}
+
+criterion_group!(sha256_hash, sha256_hash_benchmark);
+criterion_main!(sha256_hash);