The current versions of defineClass require that the class data be copied to a java byte array. But in many cases, the class data is copied from a C buffer to a Java array and back to a C buffer in defineClass0(), without being examined by Java code.

By adding a version of defineClass that accepts a java.nio.ByteBuffer instead of a byte array, redundant copying can be avoided.

This change, plus a change to enhance support for mapped zip/jar files via ByteBuffers, will allow application-level class loaders to eliminate copying data in uncompressed jar files.

Propsed API:

   /**
     * Converts a {@link java.nio.ByteBuffer <tt>ByteBuffer</tt>}
     * into an instance of class <tt>Class</tt>. The new class will use a default
     * {@link java.security.ProtectionDomain <tt>ProtectionDomain</tt>} as
     * specified in the documentation for {@link #defineClass(String, byte[],
     * int, int)}.
     * Before the <tt>Class</tt> can be used it must be resolved.
     *
     * <p> An invocation of this method of the form
     * <i>cl</i><tt>.defineClass(</tt><i>name</i><tt>,</tt> <i>bBuffer</i><tt>)</tt>
     * yields exactly the same result as the expression
     *
     * <blockquote><tt>
     * {@link #defineClass(String, java.nio.ByteBuffer,
     * ProtectionDomain)}(</tt><i>name</i><tt>,</tt><i>bBuffer</i><tt>,
     * null)</tt></blockquote>
     *
     * @param name
     * The expected name of the class, or <tt>null</tt>
     * if not known, using '<tt>.</tt>' and not '<tt>/</tt>' as the
     * separator and without a trailing <tt>.class</tt> suffix.
     *
     * @param b
     * The bytes that make up the class data.
     *
     * @return The <tt>Class</tt> object that was created from the specified
     * class data.
     *
     * @throws ClassFormatError
     * If the data did not contain a valid class
     *
     * @throws SecurityException
     * If an attempt is made to add this class to a package that
     * contains classes that were signed by a different set of
     * certificates than this class (which is unsigned), or if the
     * class name begins with "<tt>java.</tt>".
     *
     * @see #defineClass(String, java.nio.ByteBuffer,
     * ProtectionDomain)
     * @see #loadClass(String, boolean)
     * @see #resolveClass(Class)
     * @see java.nio.ByteBuffer
     *
     * @since 1.5
     */
   protected final Class defineClass(String name, java.nio.ByteBuffer b)
throws ClassFormatError

    /**
     * Converts a {@link java.nio.ByteBuffer <tt>ByteBuffer</tt>}
     * into an instance of class <tt>Class</tt>,
     * with an optional <tt>ProtectionDomain</tt>. If the domain is
     * <tt>null</tt>, then a default domain will be assigned to the class as
     * specified in the documentation for {@link #defineClass(String, byte[],
     * int, int)}. Before the class can be used it must be resolved.
     *
     * <p> An invocation of this method of the form
     * <i>cl</i><tt>.defineClass(</tt><i>name</i><tt>,</tt> <i>bBuffer</i><tt>,</tt> <i>pd</i><tt>)</tt>
     * yields exactly the same result as the statements
     *
     * <blockquote><tt>
     * {
     * byte[] temp = new byte[</tt><i>bBuffer</i><tt>.{@link java.nio.ByteBuffer#len
     * len}()];
     * </tt><i>bBuffer</i><tt>.{@link java.nio.ByteBuffer#get(byte[])
     * get}(temp);
     * return {@link #defineClass(String, byte[], int, int, ProtectionDomain)
     * defineClass}(</tt><i>name</i><tt>, temp, 0, temp.length, </tt><i>pd</i><tt>);
     * }
     * </tt></blockquote>
     *
     * @param name
     * The expected name of the class, or <tt>null</tt> if not known,
     * using '<tt>.</tt>' and not '<tt>/</tt>' as the separator and
     * without a trailing "<tt>.class</tt>" suffix.
     *
     * @param b
     * The bytes that make up the class data. The bytes from positions
     * <tt>b.position()</tt> through <tt>b.position() + b.limit() -1 </tt>
     * should have the format of a valid class file as defined by the <a
     * href="http://java.sun.com/docs/books/vmspec/">Java Virtual
     * Machine Specification</a>.
     *
     * @param protectionDomain
     * The ProtectionDomain of the class, or <tt>null</tt>.
     *
     * @return The <tt>Class</tt> object created from the data,
     * and optional <tt>ProtectionDomain</tt>.
     *
     * @throws ClassFormatError
     * If the data did not contain a valid class.
     *
     * @throws NoClassDefFoundError
     * If <tt>name</tt> is not equal to the name of the class
     * specified by <tt>bbuffer</tt>
     *
     * @throws NoClassDefFoundError
     * If <tt>name</tt> is not equal to the name of the class
     * specified by <tt>bbuffer</tt>
     *
     * @throws SecurityException
     * If an attempt is made to add this class to a package that
     * contains classes that were signed by a different set of
     * certificates than this class, or if the class name begins with
     * "<tt>java.</tt>".
     *
     * see #defineClass(String, byte[], int, int, ProtectionDomain)
     *
     * @since 1.5
     */
 protected final Class defineClass(String name, java.nio.ByteBuffer b,
ProtectionDomain protectionDomain)