filesystem.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 248 行

/*
 * @(#)FileSystem.java	1.14 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.  
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
 *   
 * This program 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.   
 *   
 * This program 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 at /legal/license.txt).   
 *   
 * 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 or visit www.sun.com if you need additional  
 * information or have any questions. 
 *
 */

package java.io;


/**
 * Package-private abstract class for the local filesystem abstraction.
 */

abstract class FileSystem {

    /**
     * Return the FileSystem object representing this platform's local
     * filesystem.
     */
    public static native FileSystem getFileSystem();


    /* -- Normalization and construction -- */

    /**
     * Return the local filesystem's name-separator character.
     */
    public abstract char getSeparator();

    /**
     * Return the local filesystem's path-separator character.
     */
    public abstract char getPathSeparator();

    /**
     * Convert the given pathname string to normal form.  If the string is
     * already in normal form then it is simply returned.
     */
    public abstract String normalize(String path);

    /**
     * Compute the length of this pathname string's prefix.  The pathname
     * string must be in normal form.
     */
    public abstract int prefixLength(String path);

    /**
     * Resolve the child pathname string against the parent.
     * Both strings must be in normal form, and the result
     * will be in normal form.
     */
    public abstract String resolve(String parent, String child);

    /**
     * Return the parent pathname string to be used when the parent-directory
     * argument in one of the two-argument File constructors is the empty
     * pathname.
     */
    public abstract String getDefaultParent();

    /**
     * Post-process the given URI path string if necessary.  This is used on
     * win32, e.g., to transform "/c:/foo" into "c:/foo".  The path string
     * still has slash separators; code in the File class will translate them
     * after this method returns.
     */
    public abstract String fromURIPath(String path);


    /* -- Path operations -- */

    /**
     * Tell whether or not the given abstract pathname is absolute.
     */
    public abstract boolean isAbsolute(File f);

    /**
     * Resolve the given abstract pathname into absolute form.  Invoked by the
     * getAbsolutePath and getCanonicalPath methods in the File class.
     */
    public abstract String resolve(File f);

    public abstract String canonicalize(String path) throws IOException;


    /* -- Attribute accessors -- */

    /* Constants for simple boolean attributes */
    public static final int BA_EXISTS    = 0x01;
    public static final int BA_REGULAR   = 0x02;
    public static final int BA_DIRECTORY = 0x04;
    public static final int BA_HIDDEN    = 0x08;

    /**
     * Return the simple boolean attributes for the file or directory denoted
     * by the given abstract pathname, or zero if it does not exist or some
     * other I/O error occurs.
     */
    public abstract int getBooleanAttributes(File f);

    /**
     * Check whether the file or directory denoted by the given abstract
     * pathname may be accessed by this process.  If the second argument is
     * <code>false</code>, then a check for read access is made; if the second
     * argument is <code>true</code>, then a check for write (not read-write)
     * access is made.  Return false if access is denied or an I/O error
     * occurs.
     */
    public abstract boolean checkAccess(File f, boolean write);

    /**
     * Return the time at which the file or directory denoted by the given
     * abstract pathname was last modified, or zero if it does not exist or
     * some other I/O error occurs.
     */
    public abstract long getLastModifiedTime(File f);

    /**
     * Return the length in bytes of the file denoted by the given abstract
     * pathname, or zero if it does not exist, is a directory, or some other
     * I/O error occurs.
     */
    public abstract long getLength(File f);


    /* -- File operations -- */

    /**
     * Create a new empty file with the given pathname.  Return
     * <code>true</code> if the file was created and <code>false</code> if a
     * file or directory with the given pathname already exists.  Throw an
     * IOException if an I/O error occurs.
     */
    public abstract boolean createFileExclusively(String pathname)
	throws IOException;

    /**
     * Delete the file or directory denoted by the given abstract pathname,
     * returning <code>true</code> if and only if the operation succeeds.
     */
    public abstract boolean delete(File f);

    /**
     * Arrange for the file or directory denoted by the given abstract
     * pathname to be deleted when the VM exits, returning <code>true</code> if
     * and only if the operation succeeds.
     */
    public abstract boolean deleteOnExit(File f);

    /**
     * List the elements of the directory denoted by the given abstract
     * pathname.  Return an array of strings naming the elements of the
     * directory if successful; otherwise, return <code>null</code>.
     */
    public abstract String[] list(File f);

    /**
     * Create a new directory denoted by the given abstract pathname,
     * returning <code>true</code> if and only if the operation succeeds.
     */
    public abstract boolean createDirectory(File f);

    /**
     * Rename the file or directory denoted by the first abstract pathname to
     * the second abstract pathname, returning <code>true</code> if and only if
     * the operation succeeds.
     */
    public abstract boolean rename(File f1, File f2);

    /**
     * Set the last-modified time of the file or directory denoted by the
     * given abstract pathname, returning <code>true</code> if and only if the
     * operation succeeds.
     */
    public abstract boolean setLastModifiedTime(File f, long time);

    /**
     * Mark the file or directory denoted by the given abstract pathname as
     * read-only, returning <code>true</code> if and only if the operation
     * succeeds.
     */
    public abstract boolean setReadOnly(File f);


    /* -- Filesystem interface -- */

    /**
     * List the available filesystem roots.
     */
    public abstract File[] listRoots();


    /* -- Basic infrastructure -- */

    /**
     * Compare two abstract pathnames lexicographically.
     */
    public abstract int compare(File f1, File f2);

    /**
     * Compute the hash code of an abstract pathname.
     */
    public abstract int hashCode(File f);

    // Flags for enabling/disabling performance optimizations for file
    // name canonicalization
    static boolean useCanonCaches      = true;
    static boolean useCanonPrefixCache = true;

    private static boolean getBooleanProperty(String prop, boolean defaultVal) {
        String val = System.getProperty("sun.io.useCanonCaches");
        if (val == null) return defaultVal;
        if (val.equalsIgnoreCase("true")) {
            return true;
        } else {
            return false;
        }
    }

    static {
        useCanonCaches      = getBooleanProperty("sun.io.useCanonCaches",
                                                 useCanonCaches);
        useCanonPrefixCache = getBooleanProperty("sun.io.useCanonPrefixCache",
                                                 useCanonPrefixCache);
    }
}