src/java.base/share/classes/sun/misc/JarIndex.java

*** 23,36 ****
   * questions.
   */
  
  package sun.misc;
  
! import java.io.*;
! import java.util.*;
! import java.util.jar.*;
! import java.util.zip.*;
  
  /**
   * This class is used to maintain mappings from packages, classes
   * and resources to their enclosing JAR files. Mappings are kept
   * at the package level except for class or resource files that
--- 23,52 ----
   * questions.
   */
  
  package sun.misc;
  
! import java.io.BufferedReader;
! import java.io.BufferedWriter;
! import java.io.ByteArrayInputStream;
! import java.io.File;
! import java.io.IOException;
! import java.io.InputStream;
! import java.io.InputStreamReader;
! import java.io.OutputStream;
! import java.io.OutputStreamWriter;
! import java.nio.ByteBuffer;
! import java.util.Enumeration;
! import java.util.HashMap;
! import java.util.Iterator;
! import java.util.LinkedList;
! import java.util.Map;
! import java.util.Vector;
! import java.util.jar.JarEntry;
! import java.util.jar.JarFile;
! import java.util.zip.ZipEntry;
! import java.util.zip.ZipFile;
  
  /**
   * This class is used to maintain mappings from packages, classes
   * and resources to their enclosing JAR files. Mappings are kept
   * at the package level except for class or resource files that
*** 72,81 ****
--- 88,100 ----
       * be added to the index. Otherwise, just the directory names are added.
       */
      private static final boolean metaInfFilenames =
          "true".equals(System.getProperty("sun.misc.JarIndex.metaInfFilenames"));
  
+     private static final sun.misc.JavaUtilZipFileAccess zipAccess
+             = sun.misc.SharedSecrets.getJavaUtilZipFileAccess();
+ 
      /**
       * Constructs a new, empty jar index.
       */
      public JarIndex() {
          indexMap = new HashMap<>();
*** 132,143 ****
--- 151,171 ----
              return null;
          }
          JarEntry e = jar.getJarEntry(INDEX_NAME);
          // if found, then load the index
          if (e != null) {
+             long size = e.getSize();
+             if (size > 0 && size < 512 * 1024) {
+                 byte[] bytes = new byte[(int) size];
+                 ByteBuffer bb = ByteBuffer.wrap(bytes);
+                 zipAccess.fillByteBuffer(jar, e, bb);
+                 index = new JarIndex(new ByteArrayInputStream(bytes, 0, bb.position()));
+             } else {
+                 // Unknown or too large ZipEntry size to use a array
                  index = new JarIndex(jar.getInputStream(e));
              }
+         }
          return index;
      }
  
      /**
       * Returns the jar files that are defined in this index.