Optimize StringView substring search

builtin/string_find_bench_test.mbt

@@ -0,0 +1,127 @@
+// Copyright 2026 International Digital Economy Academy
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+///|
+let string_find_bench_len : Int = 4096
+
+///|
+fn make_string_find_single_miss() -> String {
+  String::make(string_find_bench_len, 'a')
+}
+
+///|
+fn make_string_find_single_hit_end() -> String {
+  String::make(string_find_bench_len - 1, 'a') + "Z"
+}
+
+///|
+fn make_string_find_single_hit_start() -> String {
+  "Z" + String::make(string_find_bench_len - 1, 'a')
+}
+
+///|
+fn make_string_find_substring_hit_end() -> String {
+  String::make(string_find_bench_len - 4, 'a') + "Zabc"
+}
+
+///|
+fn make_string_find_substring_hit_start() -> String {
+  "Zabc" + String::make(string_find_bench_len - 4, 'a')
+}
+
+///|
+fn make_string_find_view_substring_hit_end() -> String {
+  "prefix-" + String::make(string_find_bench_len - 4, 'a') + "Zabc" + "-suffix"
+}
+
+///|
+fn make_string_find_view_substring_hit_start() -> String {
+  "prefix-" + "Zabc" + String::make(string_find_bench_len - 4, 'a') + "-suffix"
+}
+
+///|
+test "bench StringView::find single code unit hit end n=4096" (it : @bench.T) {
+  let data = make_string_find_single_hit_end()
+  let view = data[:]
+  it.bench(fn() { it.keep(view.find("Z")) })
+}
+
+///|
+test "bench StringView::find single code unit miss n=4096" (it : @bench.T) {
+  let data = make_string_find_single_miss()
+  let view = data[:]
+  it.bench(fn() { it.keep(view.find("Z")) })
+}
+
+///|
+test "bench StringView::find substring rare hit end n=4096" (it : @bench.T) {
+  let data = make_string_find_substring_hit_end()
+  let view = data[:]
+  it.bench(fn() { it.keep(view.find("Zabc")) })
+}
+
+///|
+test "bench StringView::find substring dense miss n=4096" (it : @bench.T) {
+  let data = make_string_find_single_miss()
+  let view = data[:]
+  it.bench(fn() { it.keep(view.find("aaaaZ")) })
+}
+
+///|
+test "bench StringView::find offset view rare hit end n=4096" (it : @bench.T) {
+  let data = make_string_find_view_substring_hit_end()
+  let view = data[7:string_find_bench_len + 7]
+  it.bench(fn() { it.keep(view.find("Zabc")) })
+}
+
+///|
+test "bench StringView::rev_find single code unit hit start n=4096" (
+  it : @bench.T,
+) {
+  let data = make_string_find_single_hit_start()
+  let view = data[:]
+  it.bench(fn() { it.keep(view.rev_find("Z")) })
+}
+
+///|
+test "bench StringView::rev_find single code unit miss n=4096" (it : @bench.T) {
+  let data = make_string_find_single_miss()
+  let view = data[:]
+  it.bench(fn() { it.keep(view.rev_find("Z")) })
+}
+
+///|
+test "bench StringView::rev_find substring rare hit start n=4096" (
+  it : @bench.T,
+) {
+  let data = make_string_find_substring_hit_start()
+  let view = data[:]
+  it.bench(fn() { it.keep(view.rev_find("Zabc")) })
+}
+
+///|
+test "bench StringView::rev_find substring dense miss n=4096" (it : @bench.T) {
+  let data = make_string_find_single_miss()
+  let view = data[:]
+  it.bench(fn() { it.keep(view.rev_find("aaaaZ")) })
+}
+
+///|
+test "bench StringView::rev_find offset view rare hit start n=4096" (
+  it : @bench.T,
+) {
+  let data = make_string_find_view_substring_hit_start()
+  let view = data[7:string_find_bench_len + 7]
+  it.bench(fn() { it.keep(view.rev_find("Zabc")) })
+}