add Pattern.split benchmark

benchmarks/src/main/java/com/google/re2j/benchmark/BenchmarkSplit.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2021 The Go Authors. All rights reserved.
+ *
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file.
+ */
+package com.google.re2j.benchmark;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.infra.Blackhole;
+
+import java.util.concurrent.TimeUnit;
+
+@OutputTimeUnit(TimeUnit.MICROSECONDS)
+@State(Scope.Benchmark)
+public class BenchmarkSplit {
+  @Param({"JDK", "RE2J"})
+  private Implementations impl;
+
+  private Implementations.Pattern pattern;
+
+  private String input;
+
+  @Setup
+  public void setup() {
+    pattern = Implementations.Pattern.compile(impl, "a");
+
+    StringBuilder b = new StringBuilder();
+    for (int i = 0; i < 100; i++) {
+      b.append("this should be a pretty big string containing a few delimiters to split on");
+    }
+
+    input = b.toString();
+  }
+
+  @Benchmark
+  public void benchmarkSplit(Blackhole bh) {
+    bh.consume(pattern.split(input));
+  }
+}

benchmarks/src/main/java/com/google/re2j/benchmark/Implementations.java

@@ -82,6 +82,8 @@ public static Pattern compile(Implementations impl, String pattern) {
 
     public abstract Matcher matcher(byte[] bytes);
 
+    public abstract String[] split(String str);
+
     public static class JdkPattern extends Pattern {
 
       private final java.util.regex.Pattern pattern;
@@ -99,6 +101,11 @@ public Matcher matcher(String str) {
       public Matcher matcher(byte[] bytes) {
         return new Matcher.JdkMatcher(pattern.matcher(new String(bytes)));
       }
+
+      @Override
+      public String[] split(String str) {
+        return pattern.split(str);
+      }
     }
 
     public static class Re2Pattern extends Pattern {
@@ -118,6 +125,11 @@ public Matcher matcher(String str) {
       public Matcher matcher(byte[] bytes) {
         return new Matcher.Re2Matcher(pattern.matcher(bytes));
       }
+
+      @Override
+      public String[] split(String str) {
+        return pattern.split(str);
+      }
     }
   }
 }