Add jmh benchmark for StringDecoder

See gh-25915

spring-core/src/jmh/java/org/springframework/core/codec/StringDecoderBenchmark.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2002-2020 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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.
+ */
+package org.springframework.core.codec;
+
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.util.Collections;
+import java.util.List;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Mode;
+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 reactor.core.publisher.Flux;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferFactory;
+import org.springframework.core.io.buffer.DataBufferUtils;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.util.MimeType;
+
+/**
+ * Benchmarks for {@link DataBufferUtils}.
+ *
+ * @author Rossen Stoyanchev
+ */
+@BenchmarkMode(Mode.Throughput)
+public class StringDecoderBenchmark {
+
+	private static final ResolvableType ELEMENT_TYPE = ResolvableType.forClass(String.class);
+
+	@Benchmark
+	public void parseLines(DecodeState state, Blackhole blackhole) {
+		Flux<DataBuffer> input = Flux.fromIterable(state.chunks);
+		MimeType mimeType = state.mimeType;
+		List<String> lines = state.decoder.decode(input, ELEMENT_TYPE, mimeType, Collections.emptyMap())
+				.collectList()
+				.block();
+
+		blackhole.consume(lines);
+	}
+
+	@State(Scope.Benchmark)
+	@SuppressWarnings({"NotNullFieldNotInitialized", "ConstantConditions"})
+	public static class DecodeState {
+
+		private static final Charset CHARSET = StandardCharsets.UTF_8;
+
+		byte[][] delimiterBytes;
+
+		List<DataBuffer> chunks;
+
+		StringDecoder decoder = StringDecoder.textPlainOnly();
+
+		MimeType mimeType = new MimeType("text", "plain", CHARSET);
+
+		@Setup(Level.Trial)
+		public void setup() {
+			this.delimiterBytes = new byte[][] {"\r\n".getBytes(CHARSET), "\n".getBytes(CHARSET)};
+
+			String eventTemplate = "id:$1\n" +
+					"event:some-event\n" +
+					":some-comment-$1-aa\n" +
+					":some-comment-$1-bb\n" +
+					"data:abcdefg-$1-hijklmnop-$1-qrstuvw-$1-xyz-$1\n\n";
+
+			int totalSize = 10 * 1024;
+			int chunkSize = 2000;
+
+			int eventLength = String.format(eventTemplate, String.format("%05d", 1)).length();
+			int eventCount = totalSize / eventLength;
+			DataBufferFactory bufferFactory = new DefaultDataBufferFactory();
+
+			this.chunks = Flux.range(1, eventCount)
+					.map(index -> String.format(eventTemplate, String.format("%05d", index)))
+					.buffer(chunkSize > eventLength ? chunkSize / eventLength : 1)
+					.map(strings -> String.join("", strings))
+					.map(chunk -> {
+						byte[] bytes = chunk.getBytes(CHARSET);
+						DataBuffer buffer = bufferFactory.allocateBuffer(bytes.length);
+						buffer.write(bytes);
+						return buffer;
+					})
+					.collectList()
+					.block();
+		}
+	}
+
+}