Index: java/util/zip/ZipFile.java
===================================================================
RCS file: /cvsroot/classpath/classpath/java/util/zip/ZipFile.java,v
retrieving revision 1.20
diff -u -r1.20 ZipFile.java
--- java/util/zip/ZipFile.java	12 Dec 2004 19:10:29 -0000	1.20
+++ java/util/zip/ZipFile.java	27 Jan 2005 15:50:14 -0000
@@ -1,5 +1,6 @@
 /* ZipFile.java --
-   Copyright (C) 2001, 2002, 2003, 2004  Free Software Foundation, Inc.
+   Copyright (C) 2001, 2002, 2003, 2004, 2005
+   Free Software Foundation, Inc.
 
 This file is part of GNU Classpath.
 
@@ -38,6 +39,8 @@
 
 package java.util.zip;
 
+import gnu.java.util.EmptyEnumeration;
+
 import java.io.BufferedInputStream;
 import java.io.DataInput;
 import java.io.EOFException;
@@ -62,6 +65,7 @@
  */
 public class ZipFile implements ZipConstants
 {
+  private static final int ZIP_MAGIC = 0x4b50;
 
   /**
    * Mode flag to open a zip file for reading.
@@ -94,6 +98,7 @@
   {
     this.raf = new RandomAccessFile(name, "r");
     this.name = name;
+    checkZipFile();
   }
 
   /**
@@ -106,6 +111,7 @@
   {
     this.raf = new RandomAccessFile(file, "r");
     this.name = file.getPath();
+    checkZipFile();
   }
 
   /**
@@ -135,6 +141,30 @@
       }
     this.raf = new RandomAccessFile(file, "r");
     this.name = file.getPath();
+    checkZipFile();
+  }
+
+  private void checkZipFile() throws IOException, ZipException
+  {
+    byte[] magic = new byte[2];
+    long position = raf.getFilePointer();
+    raf.read(magic);
+    raf.seek(position);
+
+    if (((((int) magic[1]) << 8) + ((int) magic[0])) != ZIP_MAGIC)
+      {
+	raf.close();
+	throw new ZipException("Not a valid zip file");
+      }
+  }
+
+  /**
+   * Checks if file is closed and throws an exception.
+   */
+  private void checkClosed()
+  {
+    if (closed)
+      throw new IllegalStateException("ZipFile has closed: " + name);
   }
 
   /**
@@ -312,16 +342,20 @@
 
   /**
    * Returns an enumeration of all Zip entries in this Zip file.
+   *
+   * @exception IllegalStateException when the ZipFile has already been closed
    */
   public Enumeration entries()
   {
+    checkClosed();
+    
     try
       {
 	return new ZipEntryEnumeration(getEntries().values().iterator());
       }
     catch (IOException ioe)
       {
-	return null;
+	return EmptyEnumeration.getInstance();
       }
   }
 
@@ -335,8 +369,7 @@
   {
     synchronized(raf)
       {
-	if (closed)
-	  throw new IllegalStateException("ZipFile has closed: " + name);
+	checkClosed();
 
 	if (entries == null)
 	  readEntries();
@@ -351,9 +384,13 @@
    * @param the name. May contain directory components separated by
    * slashes ('/').
    * @return the zip entry, or null if no entry with that name exists.
+   *
+   * @exception IllegalStateException when the ZipFile has already been closed
    */
   public ZipEntry getEntry(String name)
   {
+    checkClosed();
+
     try
       {
 	HashMap entries = getEntries();
@@ -423,11 +460,14 @@
    * @param entry the entry to create an InputStream for.
    * @return the input stream, or null if the requested entry does not exist.
    *
+   * @exception IllegalStateException when the ZipFile has already been closed
    * @exception IOException if a i/o error occured.
    * @exception ZipException if the Zip archive is malformed.  
    */
   public InputStream getInputStream(ZipEntry entry) throws IOException
   {
+    checkClosed();
+
     HashMap entries = getEntries();
     String name = entry.getName();
     ZipEntry zipEntry = (ZipEntry) entries.get(name);
@@ -459,9 +499,13 @@
 
   /**
    * Returns the number of entries in this zip file.
+   *
+   * @exception IllegalStateException when the ZipFile has already been closed
    */
   public int size()
   {
+    checkClosed();
+    
     try
       {
 	return getEntries().size();