/*

 * Copyright 2007-2009 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 java.nio.file.spi;

import java.nio.file.FileRef;

import java.io.IOException;

/**

 * A file type detector for probing a file to guess its file type.

 *

 * <p> A file type detector is a concrete implementation of this class, has a

 * zero-argument constructor, and implements the abstract methods specified

 * below.

 *

 * <p> The means by which a file type detector determines the file type is

 * highly implementation specific. A simple implementation might examine the

 * <em>file extension</em> (a convention used in some platforms) and map it to

 * a file type. In other cases, the file type may be stored as a file <a

 * href="../attribute/package-summary.html"> attribute</a> or the bytes in a

 * file may be examined to guess its file type.

 *

 * @see java.nio.file.Files#probeContentType(FileRef)

 *

 * @since 1.7

 */

public abstract class FileTypeDetector {

    private static Void checkPermission() {

        SecurityManager sm = System.getSecurityManager();

        if (sm != null)

            sm.checkPermission(new RuntimePermission("fileTypeDetector"));

        return null;

    }

    private FileTypeDetector(Void ignore) { }

    /**

     * Initializes a new instance of this class.

     *

     * @throws  SecurityException

     *          If a security manager has been installed and it denies

     *          {@link RuntimePermission}<tt>("fileTypeDetector")</tt>

     */

    protected FileTypeDetector() {

        this(checkPermission());

    }

    /**

     * Probes the given file to guess its content type.

     *

     * <p> The means by which this method determines the file type is highly

     * implementation specific. It may simply examine the file name, it may use

     * a file <a href="../attribute/package-summary.html">attribute</a>,

     * or it may examines bytes in the file.

     *

     * <p> The probe result is the string form of the value of a

     * Multipurpose Internet Mail Extension (MIME) content type as

     * defined by <a href="http://www.ietf.org/rfc/rfc2045.txt"><i>RFC&nbsp;2045:

     * Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet

     * Message Bodies</i></a>. The string must be parsable according to the

     * grammar in the RFC 2045.

     *

     * @param   file

     *          The file to probe

     *

     * @return  The content type or {@code null} if the file type is not

     *          recognized

     *

     * @throws  IOException

     *          An I/O error occurs

     * @throws  SecurityException

     *          If the implementation requires to access the file, and a

     *          security manager is installed, and it denies an unspecified

     *          permission required by a file system provider implementation.

     *          If the file reference is associated with the default file system

     *          provider then the {@link SecurityManager#checkRead(String)} method

     *          is invoked to check read access to the file.

     *

     * @see java.nio.file.Files#probeContentType

     */

    public abstract String probeContentType(FileRef file)

        throws IOException;

}