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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.feilong.lib.io;

/**
 * General filename and filepath manipulation utilities.
 * 

* When dealing with filenames you can hit problems when moving from a Windows * based development machine to a Unix based production machine. * This class aims to help avoid those problems. *

* NOTE: You may be able to avoid using this class entirely simply by * using JDK {@link java.io.File File} objects and the two argument constructor * {@link java.io.File#File(java.io.File, java.lang.String) File(File,String)}. *

* Most methods on this class are designed to work the same on both Unix and Windows. * Those that don't include 'System', 'Unix' or 'Windows' in their name. *

* Most methods recognise both separators (forward and back), and both * sets of prefixes. See the javadoc of each method for details. *

* This class defines six components within a filename * (example C:\dev\project\file.txt): *

    *
  • the prefix - C:\
  • *
  • the path - dev\project\
  • *
  • the full path - C:\dev\project\
  • *
  • the name - file.txt
  • *
  • the base name - file
  • *
  • the extension - txt
  • *
* Note that this class works best if directory filenames end with a separator. * If you omit the last separator, it is impossible to determine if the filename * corresponds to a file or a directory. As a result, we have chosen to say * it corresponds to a file. *

* This class only supports Unix and Windows style names. * Prefixes are matched as follows: * *

 * Windows:
 * a\b\c.txt           --> ""          --> relative
 * \a\b\c.txt          --> "\"         --> current drive absolute
 * C:a\b\c.txt         --> "C:"        --> drive relative
 * C:\a\b\c.txt        --> "C:\"       --> absolute
 * \\server\a\b\c.txt  --> "\\server\" --> UNC
 *
 * Unix:
 * a/b/c.txt           --> ""          --> relative
 * /a/b/c.txt          --> "/"         --> absolute
 * ~/a/b/c.txt         --> "~/"        --> current user
 * ~                   --> "~/"        --> current user (slash added)
 * ~user/a/b/c.txt     --> "~user/"    --> named user
 * ~user               --> "~user/"    --> named user (slash added)
 * 
* * Both prefix styles are matched always, irrespective of the machine that you are * currently running on. *

* Origin of code: Excalibur, Alexandria, Tomcat, Commons-Utils. * * @since 1.1 */ public class FilenameUtils{ private static final int NOT_FOUND = -1; /** * The extension separator character. * * @since 1.4 */ public static final char EXTENSION_SEPARATOR = '.'; /** * The Unix separator character. */ private static final char UNIX_SEPARATOR = '/'; /** * The Windows separator character. */ private static final char WINDOWS_SEPARATOR = '\\'; //--------------------------------------------------------------- /** * Returns the index of the last directory separator character. *

* This method will handle a file in either Unix or Windows format. * The position of the last forward or backslash is returned. *

* The output will be the same irrespective of the machine that the code is running on. * * @param filename * the filename to find the last path separator in, null returns -1 * @return the index of the last separator character, or -1 if there * is no such character */ public static int indexOfLastSeparator(final String filename){ if (filename == null){ return NOT_FOUND; } final int lastUnixPos = filename.lastIndexOf(UNIX_SEPARATOR); final int lastWindowsPos = filename.lastIndexOf(WINDOWS_SEPARATOR); return Math.max(lastUnixPos, lastWindowsPos); } /** * Returns the index of the last extension separator character, which is a dot. *

* This method also checks that there is no directory separator after the last dot. To do this it uses * {@link #indexOfLastSeparator(String)} which will handle a file in either Unix or Windows format. *

*

* The output will be the same irrespective of the machine that the code is running on. *

* * @param filename * the filename to find the last extension separator in, null returns -1 * @return the index of the last extension separator character, or -1 if there is no such character */ public static int indexOfExtension(final String filename){ if (filename == null){ return NOT_FOUND; } final int extensionPos = filename.lastIndexOf(EXTENSION_SEPARATOR); final int lastSeparator = indexOfLastSeparator(filename); return lastSeparator > extensionPos ? NOT_FOUND : extensionPos; } /** * Gets the name minus the path from a full filename. *

* This method will handle a file in either Unix or Windows format. * The text after the last forward or backslash is returned. * *

     * a/b/c.txt --> c.txt
     * a.txt     --> a.txt
     * a/b/c     --> c
     * a/b/c/    --> ""
     * 
*

* The output will be the same irrespective of the machine that the code is running on. * * @param filename * the filename to query, null returns null * @return the name of the file without the path, or an empty string if none exists. * Null bytes inside string will be removed */ public static String getName(final String filename){ if (filename == null){ return null; } failIfNullBytePresent(filename); final int index = indexOfLastSeparator(filename); return filename.substring(index + 1); } /** * Check the input for null bytes, a sign of unsanitized data being passed to to file level functions. * * This may be used for poison byte attacks. * * @param path * the path to check */ private static void failIfNullBytePresent(final String path){ final int len = path.length(); for (int i = 0; i < len; i++){ if (path.charAt(i) == 0){ throw new IllegalArgumentException( "Null byte present in file/path name. There are no " + "known legitimate use cases for such data, but several injection attacks may use it"); } } } /** * Gets the extension of a filename. *

* This method returns the textual part of the filename after the last dot. * There must be no directory separator after the dot. * *

     * foo.txt      --> "txt"
     * a/b/c.jpg    --> "jpg"
     * a/b.txt/c    --> ""
     * a/b/c        --> ""
     * 
*

* The output will be the same irrespective of the machine that the code is running on. * * @param filename * the filename to retrieve the extension of. * @return the extension of the file or an empty string if none exists or {@code null} * if the filename is {@code null}. */ public static String getExtension(final String filename){ if (filename == null){ return null; } final int index = indexOfExtension(filename); if (index == NOT_FOUND){ return ""; } return filename.substring(index + 1); } /** * Checks whether the extension of the filename is one of those specified. *

* This method obtains the extension as the textual part of the filename * after the last dot. There must be no directory separator after the dot. * The extension check is case-sensitive on all platforms. * * @param filename * the filename to query, null returns false * @param extensions * the extensions to check for, null checks for no extension * @return true if the filename is one of the extensions * @throws java.lang.IllegalArgumentException * if the supplied filename contains null bytes */ public static boolean isExtension(final String filename,final String...extensions){ if (filename == null){ return false; } failIfNullBytePresent(filename); if (extensions == null || extensions.length == 0){ return indexOfExtension(filename) == NOT_FOUND; } final String fileExt = getExtension(filename); for (final String extension : extensions){ if (fileExt.equals(extension)){ return true; } } return false; } }





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