/*

 * Copyright 2008-2009 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * 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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.nio.fs;

import java.util.*;

import java.io.IOException;

/**

 * Linux implementation of FileStore

 */

class LinuxFileStore

    extends UnixFileStore

{

    // used when checking if extended attributes are enabled or not

    private volatile boolean xattrChecked;

    private volatile boolean xattrEnabled;

    LinuxFileStore(UnixPath file) throws IOException {

        super(file);

    }

    LinuxFileStore(UnixFileSystem fs, UnixMountEntry entry) throws IOException {

        super(fs, entry);

    }

    /**

     * Finds, and returns, the mount entry for the file system where the file

     * resides.

     */

    @Override

    UnixMountEntry findMountEntry() throws IOException {

        UnixFileSystem fs = file().getFileSystem();

        // step 1: get realpath

        UnixPath path = null;

        try {

            byte[] rp = UnixNativeDispatcher.realpath(file());

            path = new UnixPath(fs, rp);

        } catch (UnixException x) {

            x.rethrowAsIOException(file());

        }

        // step 2: find mount point

        UnixPath parent = path.getParent();

        while (parent != null) {

            UnixFileAttributes attrs = null;

            try {

                attrs = UnixFileAttributes.get(parent, true);

            } catch (UnixException x) {

                x.rethrowAsIOException(parent);

            }

            if (attrs.dev() != dev())

                break;

            path = parent;

            parent = parent.getParent();

        }

        // step 3: lookup mounted file systems

        byte[] dir = path.asByteArray();

        for (UnixMountEntry entry: fs.getMountEntries()) {

            if (Arrays.equals(dir, entry.dir()))

                return entry;

        }

        throw new IOException("Mount point not found in mtab");

    }

    // returns true if extended attributes enabled on file system where given

    // file resides, returns false if disabled or unable to determine.

    private boolean isExtendedAttributesEnabled(UnixPath path) {

        try {

            int fd = path.openForAttributeAccess(false);

            try {

                // fgetxattr returns size if called with size==0

                LinuxNativeDispatcher.fgetxattr(fd, "user.java".getBytes(), 0L, 0);

                return true;

            } catch (UnixException e) {

                // attribute does not exist

                if (e.errno() == UnixConstants.ENODATA)

                    return true;

            } finally {

                UnixNativeDispatcher.close(fd);

            }

        } catch (IOException ignore) {

            // nothing we can do

        }

        return false;

    }

    @Override

    public boolean supportsFileAttributeView(String name) {

        // support DosFileAttributeView and NamedAttributeView if extended

        // attributes enabled

        if (name.equals("dos") || name.equals("xattr")) {

            // lookup fstypes.properties

            FeatureStatus status = checkIfFeaturePresent("user_xattr");

            if (status == FeatureStatus.PRESENT)

                return true;

            if (status == FeatureStatus.NOT_PRESENT)

                return false;

            // if file system is mounted with user_xattr option then assume

            // extended attributes are enabled

            if ((entry().hasOption("user_xattr")))

                return true;

            // user_xattr option not present but we special-case ext3/4 as we

            // know that extended attributes are not enabled by default.

            if (entry().fstype().equals("ext3") || entry().fstype().equals("ext4"))

                return false;

            // not ext3/4 so probe mount point

            if (!xattrChecked) {

                UnixPath dir = new UnixPath(file().getFileSystem(), entry().dir());

                xattrEnabled = isExtendedAttributesEnabled(dir);

                xattrChecked = true;

            }

            return xattrEnabled;

        }

        return super.supportsFileAttributeView(name);

    }

    @Override

    boolean isLoopback() {

        return false;

    }

}