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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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package java.nio.file;

import java.nio.file.attribute.*;
import java.nio.channels.SeekableByteChannel;
import java.util.Set;
import java.io.IOException;

/**
 * A {@code DirectoryStream} that defines operations on files that are located
 * relative to an open directory. A {@code SecureDirectoryStream} is intended
 * for use by sophisticated or security sensitive applications requiring to
 * traverse file trees or otherwise operate on directories in a race-free manner.
 * Race conditions can arise when a sequence of file operations cannot be
 * carried out in isolation. Each of the file operations defined by this
 * interface specify a relative path. All access to the file is relative
 * to the open directory irrespective of if the directory is moved or replaced
 * by an attacker while the directory is open. A {@code SecureDirectoryStream}
 * may also be used as a virtual <em>working directory</em>.
 *
 * <p> A {@code SecureDirectoryStream} requires corresponding support from the
 * underlying operating system. Where an implementation supports this features
 * then the {@code DirectoryStream} returned by the {@link Path#newDirectoryStream
 * newDirectoryStream} method will be a {@code SecureDirectoryStream} and must
 * be cast to that type in order to invoke the methods defined by this interface.
 *
 * <p> As specified by {@code DirectoryStream}, the iterator's {@link
 * java.util.Iterator#remove() remove} method removes the directory entry for
 * the last element returned by the iterator. In the case of a {@code
 * SecureDirectoryStream} the {@code remove} method behaves as if by invoking
 * the {@link #deleteFile deleteFile} or {@link #deleteDirectory deleteDirectory}
 * methods defined by this interface. The {@code remove} may require to examine
 * the file to determine if the file is a directory, and consequently, it may
 * not be atomic with respect to other file system operations.
 *
 * <p> In the case of the default {@link java.nio.file.spi.FileSystemProvider
 * provider}, and a security manager is set, then the permission checks are
 * performed using the path obtained by resolving the given relative path
 * against the <i>original path</i> of the directory (irrespective of if the
 * directory is moved since it was opened).
 *
 * @since   1.7
 */

public abstract class SecureDirectoryStream<T>
    implements DirectoryStream<T>
{
    /**
     * Initialize a new instance of this class.
     */
    protected SecureDirectoryStream() { }

    /**
     * Opens the directory identified by the given path, returning a {@code
     * SecureDirectoryStream} to iterate over the entries in the directory.
     *
     * <p> This method works in exactly the manner specified by the {@link
     * Path#newDirectoryStream() newDirectoryStream} method for the case that
     * the {@code path} parameter is an {@link Path#isAbsolute absolute} path.
     * When the parameter is a relative path then the directory to open is
     * relative to this open directory. The {@link
     * LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} option may be used to
     * ensure that this method fails if the file is a symbolic link.
     *
     * <p> The new directory stream, once created, is not dependent upon the
     * directory stream used to create it. Closing this directory stream has no
     * effect upon newly created directory stream.
     *
     * @param   path
     *          the path to the directory to open
     * @param   options
     *          options indicating how symbolic links are handled
     *
     * @return  a new and open {@code SecureDirectoryStream} object
     *
     * @throws  ClosedDirectoryStreamException
     *          if the directory stream is closed
     * @throws  NotDirectoryException
     *          if the file could not otherwise be opened because it is not
     *          a directory <i>(optional specific exception)</i>
     * @throws  IOException
     *          if an I/O error occurs
     * @throws  SecurityException
     *          In the case of the default provider, and a security manager is
     *          installed, the {@link SecurityManager#checkRead(String) checkRead}
     *          method is invoked to check read access to the directory.
     */
    public abstract SecureDirectoryStream<T> newDirectoryStream(T path,
                                                                LinkOption... options)
        throws IOException;

    /**
     * Opens or creates a file in this directory, returning a seekable byte
     * channel to access the file.
     *
     * <p> This method works in exactly the manner specified by the {@link
     * Path#newByteChannel Path.newByteChannel} method for the
     * case that the {@code path} parameter is an {@link Path#isAbsolute absolute}
     * path. When the parameter is a relative path then the file to open or
     * create is relative to this open directory. In addition to the options
     * defined by the {@code Path.newByteChannel} method, the {@link
     * LinkOption#NOFOLLOW_LINKS NOFOLLOW_LINKS} option may be used to
     * ensure that this method fails if the file is a symbolic link.
     *
     * <p> The channel, once created, is not dependent upon the directory stream
     * used to create it. Closing this directory stream has no effect upon the
     * channel.
     *
     * @param   path
     *          the path of the file to open open or create
     * @param   options
     *          options specifying how the file is opened
     * @param   attrs
     *          an optional list of attributes to set atomically when creating
     *          the file
     *
     * @throws  ClosedDirectoryStreamException
     *          if the directory stream is closed
     * @throws  IllegalArgumentException
     *          if the set contains an invalid combination of options
     * @throws  UnsupportedOperationException
     *          if an unsupported open option is specified or the array contains
     *          attributes that cannot be set atomically when creating the file
     * @throws  FileAlreadyExistsException
     *          if a file of that name already exists and the {@link
     *          StandardOpenOption#CREATE_NEW CREATE_NEW} option is specified
     *          <i>(optional specific exception)</i>
     * @throws  IOException
     *          if an I/O error occurs
     * @throws  SecurityException
     *          In the case of the default provider, and a security manager is
     *          installed, the {@link SecurityManager#checkRead(String) checkRead}
     *          method is invoked to check read access to the path if the file
     *          is opened for reading. The {@link SecurityManager#checkWrite(String)
     *          checkWrite} method is invoked to check write access to the path
     *          if the file is opened for writing.
     */
    public abstract SeekableByteChannel newByteChannel(T path,
                                                       Set<? extends OpenOption> options,
                                                       FileAttribute<?>... attrs)
        throws IOException;

    /**
     * Deletes a file.
     *
     * <p> Unlike the {@link Path#delete delete()} method, this method does
     * not first examine the file to determine if the file is a directory.
     * Whether a directory is deleted by this method is system dependent and
     * therefore not specified. If the file is a symbolic link, then the link
     * itself, not the final target of the link, is deleted. When the
     * parameter is a relative path then the file to delete is relative to
     * this open directory.
     *
     * @param   path
     *          the path of the file to delete
     *
     * @throws  ClosedDirectoryStreamException
     *          if the directory stream is closed
     * @throws  NoSuchFileException
     *          if the file does not exist <i>(optional specific exception)</i>
     * @throws  IOException
     *          if an I/O error occurs
     * @throws  SecurityException
     *          In the case of the default provider, and a security manager is
     *          installed, the {@link SecurityManager#checkDelete(String) checkDelete}
     *          method is invoked to check delete access to the file
     */
    public abstract void deleteFile(T path) throws IOException;

    /**
     * Deletes a directory.
     *
     * <p> Unlike the {@link Path#delete delete()} method, this method
     * does not first examine the file to determine if the file is a directory.
     * Whether non-directories are deleted by this method is system dependent and
     * therefore not specified. When the parameter is a relative path then the
     * directory to delete is relative to this open directory.
     *
     * @param   path
     *          the path of the directory to delete
     *
     * @throws  ClosedDirectoryStreamException
     *          if the directory stream is closed
     * @throws  NoSuchFileException
     *          if the directory does not exist <i>(optional specific exception)</i>
     * @throws  DirectoryNotEmptyException
     *          if the directory could not otherwise be deleted because it is
     *          not empty <i>(optional specific exception)</i>
     * @throws  IOException
     *          if an I/O error occurs
     * @throws  SecurityException
     *          In the case of the default provider, and a security manager is
     *          installed, the {@link SecurityManager#checkDelete(String) checkDelete}
     *          method is invoked to check delete access to the directory
     */
    public abstract void deleteDirectory(T path) throws IOException;

    /**
     * Move a file from this directory to another directory.
     *
     * <p> This method works in a similar manner to {@link Path#moveTo moveTo}
     * method when the {@link StandardCopyOption#ATOMIC_MOVE ATOMIC_MOVE} option
     * is specified. That is, this method moves a file as an atomic file system
     * operation. If the {@code srcpath} parameter is an {@link Path#isAbsolute
     * absolute} path then it locates the source file. If the parameter is a
     * relative path then it is located relative to this open directory. If
     * the {@code targetpath} parameter is absolute then it locates the target
     * file (the {@code targetdir} parameter is ignored). If the parameter is
     * a relative path it is located relative to the open directory identified
     * by the {@code targetdir} parameter. In all cases, if the target file
     * exists then it is implementation specific if it is replaced or this
     * method fails.
     *
     * @param   srcpath
     *          the name of the file to move
     * @param   targetdir
     *          the destination directory
     * @param   targetpath
     *          the name to give the file in the destination directory
     *
     * @throws  ClosedDirectoryStreamException
     *          if this or the target directory stream is closed
     * @throws  FileAlreadyExistsException
     *          if the file already exists in the target directory and cannot
     *          be replaced <i>(optional specific exception)</i>
     * @throws  AtomicMoveNotSupportedException
     *          if the file cannot be moved as an atomic file system operation
     * @throws  IOException
     *          if an I/O error occurs
     * @throws  SecurityException
     *          In the case of the default provider, and a security manager is
     *          installed, the {@link SecurityManager#checkWrite(String) checkWrite}
     *          method is invoked to check write access to both the source and
     *          target file.
     */
    public abstract void move(T srcpath, SecureDirectoryStream<T> targetdir, T targetpath)
        throws IOException;

    /**
     * Returns a new file attribute view to access the file attributes of this
     * directory.
     *
     * <p> The resulting file attribute view can be used to read or update the
     * attributes of this (open) directory. The {@code type} parameter specifies
     * the type of the attribute view and the method returns an instance of that
     * type if supported. Invoking this method to obtain a {@link
     * BasicFileAttributeView} always returns an instance of that class that is
     * bound to this open directory.
     *
     * <p> The state of resulting file attribute view is intimately connected
     * to this directory stream. Once the directory stream is {@link #close closed},
     * then all methods to read or update attributes will throw {@link
     * ClosedDirectoryStreamException ClosedDirectoryStreamException}.
     *
     * @param   type
     *          the {@code Class} object corresponding to the file attribute view
     *
     * @return  a new file attribute view of the specified type bound to
     *          this directory stream, or {@code null} if the attribute view
     *          type is not available
     */
    public abstract <V extends FileAttributeView> V getFileAttributeView(Class<V> type);

    /**
     * Returns a new file attribute view to access the file attributes of a file
     * in this directory.
     *
     * <p> The resulting file attribute view can be used to read or update the
     * attributes of file in this directory. The {@code type} parameter specifies
     * the type of the attribute view and the method returns an instance of that
     * type if supported. Invoking this method to obtain a {@link
     * BasicFileAttributeView} always returns an instance of that class that is
     * bound to the file in the directory.
     *
     * <p> The state of resulting file attribute view is intimately connected
     * to this directory stream. Once the directory stream {@link #close closed},
     * then all methods to read or update attributes will throw {@link
     * ClosedDirectoryStreamException ClosedDirectoryStreamException}. The
     * file is not required to exist at the time that the file attribute view
     * is created but methods to read or update attributes of the file will
     * fail when invoked and the file does not exist.
     *
     * @param   path
     *          the path of the file
     * @param   type
     *          the {@code Class} object corresponding to the file attribute view
     * @param   options
     *          options indicating how symbolic links are handled
     *
     * @return  a new file attribute view of the specified type bound to a
     *          this directory stream, or {@code null} if the attribute view
     *          type is not available
     *
     */
    public abstract <V extends FileAttributeView> V getFileAttributeView(T path,
                                                                         Class<V> type,
                                                                         LinkOption... options);
}