Benchmark hash functions on their own

Quickphf is the quickest of the three hash functions in this benchmark,
then hashify, then phf. This is inconsistent with the previous
benchmarks for `unescape()` and `unescape_attribute()`.

    hash/hashmap        time:   [22.337 ns  22.432 ns  22.548 ns]
    hash/hashify        time:   [13.932 ns  14.036 ns  14.150 ns]
    hash/phf            time:   [23.504 ns  23.601 ns  23.703 ns]
    hash/quickphf       time:   [14.353 ns  14.427 ns  14.520 ns]
    hash/matchgen       time:   [9.0193 ns  9.0741 ns  9.1346 ns]

(The hashmap benchmark uses `std::collections::HashMap` for reference.)

Author: danielparks

Cargo.toml

@@ -73,6 +73,11 @@ name = "unescape"
 harness = false
 required-features = ["bench", "_unescape_either"]
 
+[[bench]]
+name = "hash"
+harness = false
+required-features = ["bench", "unescape", "unescape_phf", "unescape_quick", "unescape_fast"]
+
 [lints]
 workspace = true
 

benches/hash.rs

@@ -0,0 +1,49 @@
+//! Benchmark hashing functions with [`criterion`].
+
+#![allow(clippy::missing_docs_in_private_items, missing_docs)]
+
+use criterion::{criterion_group, criterion_main, Criterion};
+use htmlize::unescape::internal::{Expander, Hashify, PhfMap, QuickPhf};
+use std::collections::HashMap;
+
+// Include function to match entities at the start of an iterator. Used in
+// `match_entity()`.
+//
+// fn entity_matcher<'a, I>(iter: &mut I) -> Option<(bool, &'static [u8])>
+// where
+//     I: Iterator<Item = &'a u8> + Clone,
+include!(concat!(env!("OUT_DIR"), "/matcher.rs"));
+
+fn benchmarks(c: &mut Criterion) {
+    let mut group = c.benchmark_group("hash");
+    let input = &b"&timesbar;"[..];
+
+    let mut map = HashMap::new();
+    for (&key, &value) in &htmlize::ENTITIES {
+        map.insert(key, value);
+    }
+
+    group.bench_with_input("hashmap", input, |b, input| {
+        b.iter(|| map.get(&input));
+    });
+
+    group.bench_with_input("hashify", input, |b, input| {
+        b.iter(|| Hashify::expand(input));
+    });
+
+    group.bench_with_input("phf", input, |b, input| {
+        b.iter(|| PhfMap::expand(input));
+    });
+
+    group.bench_with_input("quickphf", input, |b, input| {
+        b.iter(|| QuickPhf::expand(input));
+    });
+
+    group.bench_with_input("matchgen", input, |b, input| {
+        b.iter(|| entity_matcher(input));
+    });
+    group.finish();
+}
+
+criterion_group!(hash_group, benchmarks);
+criterion_main!(hash_group);