feat: Improve benchmark (#222)

Fixes a bug in the benchmark initialization and adds a `toLowerCase` benchmark.

Author: ppkarwasz

src/main/java/com/github/packageurl/PackageURL.java

@@ -642,7 +642,7 @@ private static int toLowerCase(int c) {
         return isUpperCase(c) ? (c ^ 0x20) : c;
     }
 
-    private static String toLowerCase(String s) {
+    static String toLowerCase(String s) {
         int pos = indexOfFirstUpperCaseChar(s);
 
         if (pos == -1) {

src/test/java/com/github/packageurl/PercentEncodingBenchmark.java

@@ -22,6 +22,7 @@
 package com.github.packageurl;
 
 import java.nio.charset.StandardCharsets;
+import java.util.Locale;
 import java.util.Random;
 import java.util.concurrent.TimeUnit;
 import org.openjdk.jmh.annotations.Benchmark;
@@ -30,7 +31,6 @@
 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;
 
@@ -62,14 +62,8 @@ public class PercentEncodingBenchmark {
     @Param({"0", "0.1", "0.5"})
     private double nonAsciiProb;
 
-    private String[] decodedData = createDecodedData();
-    private String[] encodedData = encodeData(decodedData);
-
-    @Setup
-    public void setup() {
-        decodedData = createDecodedData();
-        encodedData = encodeData(encodedData);
-    }
+    private final String[] decodedData = createDecodedData();
+    private final String[] encodedData = encodeData(decodedData);
 
     private String[] createDecodedData() {
         Random random = new Random();
@@ -90,8 +84,11 @@ private String[] createDecodedData() {
 
     private static String[] encodeData(String[] decodedData) {
         String[] encodedData = new String[decodedData.length];
-        for (int i = 0; i < decodedData.length; i++) {
+        for (int i = 0; i < encodedData.length; i++) {
             encodedData[i] = PackageURL.percentEncode(decodedData[i]);
+            if (!PackageURL.percentDecode(encodedData[i]).equals(decodedData[i])) {
+                throw new RuntimeException("Invalid implementation of `percentEncode` and `percentDecode`.");
+            }
         }
         return encodedData;
     }
@@ -100,17 +97,28 @@ private static String[] encodeData(String[] decodedData) {
     public void baseline(Blackhole blackhole) {
         for (int i = 0; i < DATA_COUNT; i++) {
             byte[] buffer = decodedData[i].getBytes(StandardCharsets.UTF_8);
-            // Change the String a little bit
+            // Prevent JIT compiler from assuming the buffer was not modified
             for (int idx = 0; idx < buffer.length; idx++) {
-                byte b = buffer[idx];
-                if ('a' <= b && b <= 'z') {
-                    buffer[idx] = (byte) (b & 0x20);
-                }
+                buffer[idx] ^= 0x20;
             }
             blackhole.consume(new String(buffer, StandardCharsets.UTF_8));
         }
     }
 
+    @Benchmark
+    public void toLowerCaseJre(Blackhole blackhole) {
+        for (int i = 0; i < DATA_COUNT; i++) {
+            blackhole.consume(decodedData[i].toLowerCase(Locale.ROOT));
+        }
+    }
+
+    @Benchmark
+    public void toLowerCase(Blackhole blackhole) {
+        for (int i = 0; i < DATA_COUNT; i++) {
+            blackhole.consume(PackageURL.toLowerCase(decodedData[i]));
+        }
+    }
+
     @Benchmark
     public void percentDecode(final Blackhole blackhole) {
         for (int i = 0; i < DATA_COUNT; i++) {