Optimize VirtualZipDataBlock

Add some optimizations to `VirtualZipDataBlock` that help when
sequentially reading the block from a JarInputStream.

Closes gh-40125

spring-boot-project/spring-boot-tools/spring-boot-loader/src/test/java/org/springframework/boot/loader/zip/VirtualZipPerformanceTests.java

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2012-2024 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.boot.loader.zip;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.nio.file.Path;
+import java.util.Random;
+import java.util.concurrent.TimeUnit;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipInputStream;
+import java.util.zip.ZipOutputStream;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+/**
+ * Performance tests for {@link ZipContent} that creates a {@link VirtualZipDataBlock}.
+ *
+ * @author Phillip Webb
+ */
+@Disabled("Only used for manual testing")
+public class VirtualZipPerformanceTests {
+
+	@TempDir
+	Path temp;
+
+	@Test
+	void sequentialReadPerformace() throws IOException {
+		File file = createZipWithLargeEntries();
+		long start = System.nanoTime();
+		try (ZipContent zipContent = ZipContent.open(file.toPath(), "test/")) {
+			try (InputStream in = zipContent.openRawZipData().asInputStream()) {
+				ZipInputStream zip = new ZipInputStream(in);
+				ZipEntry entry = zip.getNextEntry();
+				while (entry != null) {
+					entry = zip.getNextEntry();
+				}
+			}
+		}
+		System.out.println(TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - start));
+	}
+
+	private File createZipWithLargeEntries() throws IOException {
+		byte[] bytes = new byte[1024 * 1024];
+		new Random().nextBytes(bytes);
+		File file = this.temp.resolve("test.zip").toFile();
+		try (ZipOutputStream out = new ZipOutputStream(new FileOutputStream(file))) {
+			out.putNextEntry(new ZipEntry("test/"));
+			out.closeEntry();
+			for (int i = 0; i < 50; i++) {
+				out.putNextEntry(new ZipEntry("test/" + i + ".dat"));
+				out.write(bytes);
+				out.closeEntry();
+			}
+		}
+		return file;
+	}
+
+}