Coverage Report

Coverage Report - org.apache.myfaces.util.FilenameUtils

Classes in this File
Line Coverage
Branch Coverage
Complexity
FilenameUtils
0/195
0/188
6.308
 /*
  * 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 org.apache.myfaces.util;
 
 import java.io.File;
 
 /**
  * General filename and filepath manipulation utilities.
  * <p>
  * 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.
  * <p>
  * <b>NOTE</b>: 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)}.
  * <p>
  * 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.
  * <p>
  * Most methods recognise both separators (forward and back), and both
  * sets of prefixes. See the javadoc of each method for details.
  * <p>
  * This class defines six components within a filename
  * (example C:\dev\project\file.txt):
  * <ul>
  * <li>the prefix - C:\</li>
  * <li>the path - dev\project\</li>
  * <li>the full path - C:\dev\project\</li>
  * <li>the name - file.txt</li>
  * <li>the base name - file</li>
  * <li>the extension - txt</li>
  * </ul>
  * 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.
  * <p>
  * This class only supports Unix and Windows style names.
  * Prefixes are matched as follows:
  * <pre>
  * 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)
  * </pre>
  * Both prefix styles are matched always, irrespective of the machine that you are
  * currently running on.
  * <p>
  * Origin of code: Excalibur, Alexandria, Tomcat, Commons-Utils.
  * 
  * NOTE: Taken from Commons-IO package
  *
  * @version $Id$
  * @since 1.1
  */
 public class FilenameUtils
 {
 
     /**
      * The extension separator character.
      *
      * @since 1.4
      */
     public static final char EXTENSION_SEPARATOR = '.';
 
     /**
      * The extension separator String.
      *
      * @since 1.4
      */
     public static final String EXTENSION_SEPARATOR_STR = Character.toString(EXTENSION_SEPARATOR);
 
     /**
      * The Unix separator character.
      */
     private static final char UNIX_SEPARATOR = '/';
 
     /**
      * The Windows separator character.
      */
     private static final char WINDOWS_SEPARATOR = '\\';
 
     /**
      * The system separator character.
      */
     private static final char SYSTEM_SEPARATOR = File.separatorChar;
 
     /**
      * The separator character that is the opposite of the system separator.
      */
     private static final char OTHER_SEPARATOR;
 
     static
     {
         if (isSystemWindows())
         {
             OTHER_SEPARATOR = UNIX_SEPARATOR;
         }
         else
         {
             OTHER_SEPARATOR = WINDOWS_SEPARATOR;
         }
     }
 
     /**
      * Instances should NOT be constructed in standard programming.
      */
     public FilenameUtils()
     {
         super();
     }
 
     //-----------------------------------------------------------------------
     /**
      * Determines if Windows file system is in use.
      *
      * @return true if the system is Windows
      */
     static boolean isSystemWindows()
     {
         return SYSTEM_SEPARATOR == WINDOWS_SEPARATOR;
     }
 
     //-----------------------------------------------------------------------
     /**
      * Checks if the character is a separator.
      *
      * @param ch the character to check
      * @return true if it is a separator character
      */
     private static boolean isSeparator(final char ch)
     {
         return ch == UNIX_SEPARATOR || ch == WINDOWS_SEPARATOR;
     }
 
     //-----------------------------------------------------------------------
     /**
      * Normalizes a path, removing double and single dot path steps.
      * <p>
      * This method normalizes a path to a standard format.
      * The input may contain separators in either Unix or Windows format.
      * The output will contain separators in the format of the system.
      * <p>
      * A trailing slash will be retained.
      * A double slash will be merged to a single slash (but UNC names are handled).
      * A single dot path segment will be removed.
      * A double dot will cause that path segment and the one before to be removed.
      * If the double dot has no parent path segment to work with, {@code null}
      * is returned.
      * <p>
      * The output will be the same on both Unix and Windows except
      * for the separator character.
      * <pre>
      * /foo//               -->   /foo/
      * /foo/./              -->   /foo/
      * /foo/../bar          -->   /bar
      * /foo/../bar/         -->   /bar/
      * /foo/../bar/../baz   -->   /baz
      * //foo//./bar         -->   /foo/bar
      * /../                 -->   null
      * ../foo               -->   null
      * foo/bar/..           -->   foo/
      * foo/../../bar        -->   null
      * foo/../bar           -->   bar
      * //server/foo/../bar  -->   //server/bar
      * //server/../bar      -->   null
      * C:\foo\..\bar        -->   C:\bar
      * C:\..\bar            -->   null
      * ~/foo/../bar/        -->   ~/bar/
      * ~/../bar             -->   null
      * </pre>
      * (Note the file separator returned will be correct for Windows/Unix)
      *
      * @param filename  the filename to normalize, null returns null
      * @return the normalized filename, or null if invalid
      */
     public static String normalize(final String filename)
     {
         return doNormalize(filename, SYSTEM_SEPARATOR, true);
     }
 
     /**
      * Normalizes a path, removing double and single dot path steps.
      * <p>
      * This method normalizes a path to a standard format.
      * The input may contain separators in either Unix or Windows format.
      * The output will contain separators in the format specified.
      * <p>
      * A trailing slash will be retained.
      * A double slash will be merged to a single slash (but UNC names are handled).
      * A single dot path segment will be removed.
      * A double dot will cause that path segment and the one before to be removed.
      * If the double dot has no parent path segment to work with, {@code null}
      * is returned.
      * <p>
      * The output will be the same on both Unix and Windows except
      * for the separator character.
      * <pre>
      * /foo//               -->   /foo/
      * /foo/./              -->   /foo/
      * /foo/../bar          -->   /bar
      * /foo/../bar/         -->   /bar/
      * /foo/../bar/../baz   -->   /baz
      * //foo//./bar         -->   /foo/bar
      * /../                 -->   null
      * ../foo               -->   null
      * foo/bar/..           -->   foo/
      * foo/../../bar        -->   null
      * foo/../bar           -->   bar
      * //server/foo/../bar  -->   //server/bar
      * //server/../bar      -->   null
      * C:\foo\..\bar        -->   C:\bar
      * C:\..\bar            -->   null
      * ~/foo/../bar/        -->   ~/bar/
      * ~/../bar             -->   null
      * </pre>
      * The output will be the same on both Unix and Windows including
      * the separator character.
      *
      * @param filename  the filename to normalize, null returns null
      * @param unixSeparator {@code true} if a unix separator should
      * be used or {@code false} if a windows separator should be used.
      * @return the normalized filename, or null if invalid
      * @since 2.0
      */
     public static String normalize(final String filename, final boolean unixSeparator)
     {
         final char separator = unixSeparator ? UNIX_SEPARATOR : WINDOWS_SEPARATOR;
         return doNormalize(filename, separator, true);
     }
 
     //-----------------------------------------------------------------------
     /**
      * Normalizes a path, removing double and single dot path steps,
      * and removing any final directory separator.
      * <p>
      * This method normalizes a path to a standard format.
      * The input may contain separators in either Unix or Windows format.
      * The output will contain separators in the format of the system.
      * <p>
      * A trailing slash will be removed.
      * A double slash will be merged to a single slash (but UNC names are handled).
      * A single dot path segment will be removed.
      * A double dot will cause that path segment and the one before to be removed.
      * If the double dot has no parent path segment to work with, {@code null}
      * is returned.
      * <p>
      * The output will be the same on both Unix and Windows except
      * for the separator character.
      * <pre>
      * /foo//               -->   /foo
      * /foo/./              -->   /foo
      * /foo/../bar          -->   /bar
      * /foo/../bar/         -->   /bar
      * /foo/../bar/../baz   -->   /baz
      * //foo//./bar         -->   /foo/bar
      * /../                 -->   null
      * ../foo               -->   null
      * foo/bar/..           -->   foo
      * foo/../../bar        -->   null
      * foo/../bar           -->   bar
      * //server/foo/../bar  -->   //server/bar
      * //server/../bar      -->   null
      * C:\foo\..\bar        -->   C:\bar
      * C:\..\bar            -->   null
      * ~/foo/../bar/        -->   ~/bar
      * ~/../bar             -->   null
      * </pre>
      * (Note the file separator returned will be correct for Windows/Unix)
      *
      * @param filename  the filename to normalize, null returns null
      * @return the normalized filename, or null if invalid
      */
     public static String normalizeNoEndSeparator(final String filename)
     {
         return doNormalize(filename, SYSTEM_SEPARATOR, false);
     }
 
     /**
      * Normalizes a path, removing double and single dot path steps,
      * and removing any final directory separator.
      * <p>
      * This method normalizes a path to a standard format.
      * The input may contain separators in either Unix or Windows format.
      * The output will contain separators in the format specified.
      * <p>
      * A trailing slash will be removed.
      * A double slash will be merged to a single slash (but UNC names are handled).
      * A single dot path segment will be removed.
      * A double dot will cause that path segment and the one before to be removed.
      * If the double dot has no parent path segment to work with, {@code null}
      * is returned.
      * <p>
      * The output will be the same on both Unix and Windows including
      * the separator character.
      * <pre>
      * /foo//               -->   /foo
      * /foo/./              -->   /foo
      * /foo/../bar          -->   /bar
      * /foo/../bar/         -->   /bar
      * /foo/../bar/../baz   -->   /baz
      * //foo//./bar         -->   /foo/bar
      * /../                 -->   null
      * ../foo               -->   null
      * foo/bar/..           -->   foo
      * foo/../../bar        -->   null
      * foo/../bar           -->   bar
      * //server/foo/../bar  -->   //server/bar
      * //server/../bar      -->   null
      * C:\foo\..\bar        -->   C:\bar
      * C:\..\bar            -->   null
      * ~/foo/../bar/        -->   ~/bar
      * ~/../bar             -->   null
      * </pre>
      *
      * @param filename  the filename to normalize, null returns null
      * @param unixSeparator {@code true} if a unix separator should
      * be used or {@code false} if a windows separtor should be used.
      * @return the normalized filename, or null if invalid
      * @since 2.0
      */
     public static String normalizeNoEndSeparator(final String filename, final boolean unixSeparator)
     {
         final char separator = unixSeparator ? UNIX_SEPARATOR : WINDOWS_SEPARATOR;
         return doNormalize(filename, separator, false);
     }
 
     /**
      * Internal method to perform the normalization.
      *
      * @param filename  the filename
      * @param separator The separator character to use
      * @param keepSeparator  true to keep the final separator
      * @return the normalized filename
      */
     private static String doNormalize(final String filename, final char separator, final boolean keepSeparator)
     {
         if (filename == null)
         {
             return null;
         }
         int size = filename.length();
         if (size == 0)
         {
             return filename;
         }
         final int prefix = getPrefixLength(filename);
         if (prefix < 0)
         {
             return null;
         }
 
         final char[] array = new char[size + 2];  // +1 for possible extra slash, +2 for arraycopy
         filename.getChars(0, filename.length(), array, 0);
 
         // fix separators throughout
         final char otherSeparator = separator == SYSTEM_SEPARATOR ? OTHER_SEPARATOR : SYSTEM_SEPARATOR;
         for (int i = 0; i < array.length; i++)
         {
             if (array[i] == otherSeparator)
             {
                 array[i] = separator;
             }
         }
 
         // add extra separator on the end to simplify code below
         boolean lastIsDirectory = true;
         if (array[size - 1] != separator)
         {
             array[size++] = separator;
             lastIsDirectory = false;
         }
 
         // adjoining slashes
         for (int i = prefix + 1; i < size; i++)
         {
             if (array[i] == separator && array[i - 1] == separator)
             {
                 System.arraycopy(array, i, array, i - 1, size - i);
                 size--;
                 i--;
             }
         }
 
         // dot slash
         for (int i = prefix + 1; i < size; i++)
         {
             if (array[i] == separator && array[i - 1] == '.'
                     && (i == prefix + 1 || array[i - 2] == separator))
             {
                 if (i == size - 1)
                 {
                     lastIsDirectory = true;
                 }
                 System.arraycopy(array, i + 1, array, i - 1, size - i);
                 size -= 2;
                 i--;
             }
         }
 
         // double dot slash
         outer:
         for (int i = prefix + 2; i < size; i++)
         {
             if (array[i] == separator && array[i - 1] == '.' && array[i - 2] == '.'
                     && (i == prefix + 2 || array[i - 3] == separator))
             {
                 if (i == prefix + 2)
                 {
                     return null;
                 }
                 if (i == size - 1)
                 {
                     lastIsDirectory = true;
                 }
                 int j;
                 for (j = i - 4; j >= prefix; j--)
                 {
                     if (array[j] == separator)
                     {
                         // remove b/../ from a/b/../c
                         System.arraycopy(array, i + 1, array, j + 1, size - i);
                         size -= i - j;
                         i = j + 1;
                         continue outer;
                     }
                 }
                 // remove a/../ from a/../c
                 System.arraycopy(array, i + 1, array, prefix, size - i);
                 size -= i + 1 - prefix;
                 i = prefix + 1;
             }
         }
 
         if (size <= 0)
         {  // should never be less than 0
             return "";
         }
         if (size <= prefix)
         {  // should never be less than prefix
             return new String(array, 0, size);
         }
         if (lastIsDirectory && keepSeparator)
         {
             return new String(array, 0, size);  // keep trailing separator
         }
         return new String(array, 0, size - 1);  // lose trailing separator
     }
 
     //-----------------------------------------------------------------------
     /**
      * Concatenates a filename to a base path using normal command line style rules.
      * <p>
      * The effect is equivalent to resultant directory after changing
      * directory to the first argument, followed by changing directory to
      * the second argument.
      * <p>
      * The first argument is the base path, the second is the path to concatenate.
      * The returned path is always normalized via {@link #normalize(String)},
      * thus <code>..</code> is handled.
      * <p>
      * If <code>pathToAdd</code> is absolute (has an absolute prefix), then
      * it will be normalized and returned.
      * Otherwise, the paths will be joined, normalized and returned.
      * <p>
      * The output will be the same on both Unix and Windows except
      * for the separator character.
      * <pre>
      * /foo/ + bar          -->   /foo/bar
      * /foo + bar           -->   /foo/bar
      * /foo + /bar          -->   /bar
      * /foo + C:/bar        -->   C:/bar
      * /foo + C:bar         -->   C:bar (*)
      * /foo/a/ + ../bar     -->   foo/bar
      * /foo/ + ../../bar    -->   null
      * /foo/ + /bar         -->   /bar
      * /foo/.. + /bar       -->   /bar
      * /foo + bar/c.txt     -->   /foo/bar/c.txt
      * /foo/c.txt + bar     -->   /foo/c.txt/bar (!)
      * </pre>
      * (*) Note that the Windows relative drive prefix is unreliable when
      * used with this method.
      * (!) Note that the first parameter must be a path. If it ends with a name, then
      * the name will be built into the concatenated path. If this might be a problem,
      * use {@link #getFullPath(String)} on the base path argument.
      *
      * @param basePath  the base path to attach to, always treated as a path
      * @param fullFilenameToAdd  the filename (or path) to attach to the base
      * @return the concatenated path, or null if invalid
      */
     public static String concat(final String basePath, final String fullFilenameToAdd)
     {
         final int prefix = getPrefixLength(fullFilenameToAdd);
         if (prefix < 0)
         {
             return null;
         }
         if (prefix > 0)
         {
             return normalize(fullFilenameToAdd);
         }
         if (basePath == null)
         {
             return null;
         }
         final int len = basePath.length();
         if (len == 0)
         {
             return normalize(fullFilenameToAdd);
         }
         final char ch = basePath.charAt(len - 1);
         if (isSeparator(ch))
         {
             return normalize(basePath + fullFilenameToAdd);
         }
         else
         {
             return normalize(basePath + '/' + fullFilenameToAdd);
         }
     }
 
     //-----------------------------------------------------------------------
     /**
      * Converts all separators to the Unix separator of forward slash.
      *
      * @param path the path to be changed, null ignored
      * @return the updated path
      */
     public static String separatorsToUnix(final String path)
     {
         if (path == null || path.indexOf(WINDOWS_SEPARATOR) == -1)
         {
             return path;
         }
         return path.replace(WINDOWS_SEPARATOR, UNIX_SEPARATOR);
     }
 
     /**
      * Converts all separators to the Windows separator of backslash.
      *
      * @param path the path to be changed, null ignored
      * @return the updated path
      */
     public static String separatorsToWindows(final String path)
     {
         if (path == null || path.indexOf(UNIX_SEPARATOR) == -1)
         {
             return path;
         }
         return path.replace(UNIX_SEPARATOR, WINDOWS_SEPARATOR);
     }
 
     /**
      * Converts all separators to the system separator.
      *
      * @param path the path to be changed, null ignored
      * @return the updated path
      */
     public static String separatorsToSystem(final String path)
     {
         if (path == null)
         {
             return null;
         }
         if (isSystemWindows())
         {
             return separatorsToWindows(path);
         }
         else
         {
             return separatorsToUnix(path);
         }
     }
 
     //-----------------------------------------------------------------------
     /**
      * Returns the length of the filename prefix, such as <code>C:/</code> or <code>~/</code>.
      * <p>
      * This method will handle a file in either Unix or Windows format.
      * <p>
      * The prefix length includes the first slash in the full filename
      * if applicable. Thus, it is possible that the length returned is greater
      * than the length of the input string.
      * <pre>
      * 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
      * \\\a\b\c.txt        -->  error, length = -1
      *
      * 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)
      * //server/a/b/c.txt  --> "//server/"
      * ///a/b/c.txt        --> error, length = -1
      * </pre>
      * <p>
      * The output will be the same irrespective of the machine that the code is running on.
      * ie. both Unix and Windows prefixes are matched regardless.
      *
      * Note that a leading // (or \\) is used to indicate a UNC name on Windows.
      * These must be followed by a server name, so double-slashes are not collapsed
      * to a single slash at the start of the filename.
      *
      * @param filename  the filename to find the prefix in, null returns -1
      * @return the length of the prefix, -1 if invalid or null
      */
     public static int getPrefixLength(final String filename)
     {
         if (filename == null)
         {
             return -1;
         }
         final int len = filename.length();
         if (len == 0)
         {
             return 0;
         }
         char ch0 = filename.charAt(0);
         if (ch0 == ':')
         {
             return -1;
         }
         if (len == 1)
         {
             if (ch0 == '~')
             {
                 return 2;  // return a length greater than the input
             }
             return isSeparator(ch0) ? 1 : 0;
         }
         else
         {
             if (ch0 == '~')
             {
                 int posUnix = filename.indexOf(UNIX_SEPARATOR, 1);
                 int posWin = filename.indexOf(WINDOWS_SEPARATOR, 1);
                 if (posUnix == -1 && posWin == -1)
                 {
                     return len + 1;  // return a length greater than the input
                 }
                 posUnix = posUnix == -1 ? posWin : posUnix;
                 posWin = posWin == -1 ? posUnix : posWin;
                 return Math.min(posUnix, posWin) + 1;
             }
             final char ch1 = filename.charAt(1);
             if (ch1 == ':')
             {
                 ch0 = Character.toUpperCase(ch0);
                 if (ch0 >= 'A' && ch0 <= 'Z')
                 {
                     if (len == 2 || isSeparator(filename.charAt(2)) == false)
                     {
                         return 2;
                     }
                     return 3;
                 }
                 return -1;
 
             }
             else if (isSeparator(ch0) && isSeparator(ch1))
             {
                 int posUnix = filename.indexOf(UNIX_SEPARATOR, 2);
                 int posWin = filename.indexOf(WINDOWS_SEPARATOR, 2);
                 if (posUnix == -1 && posWin == -1 || posUnix == 2 || posWin == 2)
                 {
                     return -1;
                 }
                 posUnix = posUnix == -1 ? posWin : posUnix;
                 posWin = posWin == -1 ? posUnix : posWin;
                 return Math.min(posUnix, posWin) + 1;
             }
             else
             {
                 return isSeparator(ch0) ? 1 : 0;
             }
         }
     }
 
     /**
      * Returns the index of the last directory separator character.
      * <p>
      * This method will handle a file in either Unix or Windows format.
      * The position of the last forward or backslash is returned.
      * <p>
      * 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 -1;
         }
         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.
      * <p>
      * 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.
      * <p>
      * 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 indexOfExtension(final String filename)
     {
         if (filename == null)
         {
             return -1;
         }
         final int extensionPos = filename.lastIndexOf(EXTENSION_SEPARATOR);
         final int lastSeparator = indexOfLastSeparator(filename);
         return lastSeparator > extensionPos ? -1 : extensionPos;
     }
 
     //-----------------------------------------------------------------------
     /**
      * Gets the prefix from a full filename, such as <code>C:/</code>
      * or <code>~/</code>.
      * <p>
      * This method will handle a file in either Unix or Windows format.
      * The prefix includes the first slash in the full filename where applicable.
      * <pre>
      * 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)
      * </pre>
      * <p>
      * The output will be the same irrespective of the machine that the code is running on.
      * ie. both Unix and Windows prefixes are matched regardless.
      *
      * @param filename  the filename to query, null returns null
      * @return the prefix of the file, null if invalid
      */
     public static String getPrefix(final String filename)
     {
         if (filename == null)
         {
             return null;
         }
         final int len = getPrefixLength(filename);
         if (len < 0)
         {
             return null;
         }
         if (len > filename.length())
         {
             return filename + UNIX_SEPARATOR;  // we know this only happens for unix
         }
         return filename.substring(0, len);
     }
 
     /**
      * Gets the path from a full filename, which excludes the prefix.
      * <p>
      * This method will handle a file in either Unix or Windows format.
      * The method is entirely text based, and returns the text before and
      * including the last forward or backslash.
      * <pre>
      * C:\a\b\c.txt --> a\b\
      * ~/a/b/c.txt  --> a/b/
      * a.txt        --> ""
      * a/b/c        --> a/b/
      * a/b/c/       --> a/b/c/
      * </pre>
      * <p>
      * The output will be the same irrespective of the machine that the code is running on.
      * <p>
      * This method drops the prefix from the result.
      * See {@link #getFullPath(String)} for the method that retains the prefix.
      *
      * @param filename  the filename to query, null returns null
      * @return the path of the file, an empty string if none exists, null if invalid
      */
     public static String getPath(final String filename)
     {
         return doGetPath(filename, 1);
     }
 
     /**
      * Gets the path from a full filename, which excludes the prefix, and
      * also excluding the final directory separator.
      * <p>
      * This method will handle a file in either Unix or Windows format.
      * The method is entirely text based, and returns the text before the
      * last forward or backslash.
      * <pre>
      * C:\a\b\c.txt --> a\b
      * ~/a/b/c.txt  --> a/b
      * a.txt        --> ""
      * a/b/c        --> a/b
      * a/b/c/       --> a/b/c
      * </pre>
      * <p>
      * The output will be the same irrespective of the machine that the code is running on.
      * <p>
      * This method drops the prefix from the result.
      * See {@link #getFullPathNoEndSeparator(String)} for the method that retains the prefix.
      *
      * @param filename  the filename to query, null returns null
      * @return the path of the file, an empty string if none exists, null if invalid
      */
     public static String getPathNoEndSeparator(final String filename)
     {
         return doGetPath(filename, 0);
     }
 
     /**
      * Does the work of getting the path.
      *
      * @param filename  the filename
      * @param separatorAdd  0 to omit the end separator, 1 to return it
      * @return the path
      */
     private static String doGetPath(final String filename, final int separatorAdd)
     {
         if (filename == null)
         {
             return null;
         }
         final int prefix = getPrefixLength(filename);
         if (prefix < 0)
         {
             return null;
         }
         final int index = indexOfLastSeparator(filename);
         final int endIndex = index + separatorAdd;
         if (prefix >= filename.length() || index < 0 || prefix >= endIndex)
         {
             return "";
         }
         return filename.substring(prefix, endIndex);
     }
 
     /**
      * Gets the full path from a full filename, which is the prefix + path.
      * <p>
      * This method will handle a file in either Unix or Windows format.
      * The method is entirely text based, and returns the text before and
      * including the last forward or backslash.
      * <pre>
      * C:\a\b\c.txt --> C:\a\b\
      * ~/a/b/c.txt  --> ~/a/b/
      * a.txt        --> ""
      * a/b/c        --> a/b/
      * a/b/c/       --> a/b/c/
      * C:           --> C:
      * C:\          --> C:\
      * ~            --> ~/
      * ~/           --> ~/
      * ~user        --> ~user/
      * ~user/       --> ~user/
      * </pre>
      * <p>
      * 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 path of the file, an empty string if none exists, null if invalid
      */
     public static String getFullPath(final String filename)
     {
         return doGetFullPath(filename, true);
     }
 
     /**
      * Gets the full path from a full filename, which is the prefix + path,
      * and also excluding the final directory separator.
      * <p>
      * This method will handle a file in either Unix or Windows format.
      * The method is entirely text based, and returns the text before the
      * last forward or backslash.
      * <pre>
      * C:\a\b\c.txt --> C:\a\b
      * ~/a/b/c.txt  --> ~/a/b
      * a.txt        --> ""
      * a/b/c        --> a/b
      * a/b/c/       --> a/b/c
      * C:           --> C:
      * C:\          --> C:\
      * ~            --> ~
      * ~/           --> ~
      * ~user        --> ~user
      * ~user/       --> ~user
      * </pre>
      * <p>
      * 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 path of the file, an empty string if none exists, null if invalid
      */
     public static String getFullPathNoEndSeparator(final String filename)
     {
         return doGetFullPath(filename, false);
     }
 
     /**
      * Does the work of getting the path.
      *
      * @param filename the filename
      * @param includeSeparator true to include the end separator
      * @return the path
      */
     private static String doGetFullPath(final String filename, final boolean includeSeparator)
     {
         if (filename == null)
         {
             return null;
         }
         final int prefix = getPrefixLength(filename);
         if (prefix < 0)
         {
             return null;
         }
         if (prefix >= filename.length())
         {
             if (includeSeparator)
             {
                 return getPrefix(filename);  // add end slash if necessary
             }
             else
             {
                 return filename;
             }
         }
         final int index = indexOfLastSeparator(filename);
         if (index < 0)
         {
             return filename.substring(0, prefix);
         }
         int end = index + (includeSeparator ? 1 : 0);
         if (end == 0)
         {
             end++;
         }
         return filename.substring(0, end);
     }
 
     /**
      * Gets the name minus the path from a full filename.
      * <p>
      * This method will handle a file in either Unix or Windows format.
      * The text after the last forward or backslash is returned.
      * <pre>
      * a/b/c.txt --> c.txt
      * a.txt     --> a.txt
      * a/b/c     --> c
      * a/b/c/    --> ""
      * </pre>
      * <p>
      * 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
      */
     public static String getName(final String filename)
     {
         if (filename == null)
         {
             return null;
         }
         final int index = indexOfLastSeparator(filename);
         return filename.substring(index + 1);
     }
 
     /**
      * Gets the base name, minus the full path and extension, from a full filename.
      * <p>
      * This method will handle a file in either Unix or Windows format.
      * The text after the last forward or backslash and before the last dot is returned.
      * <pre>
      * a/b/c.txt --> c
      * a.txt     --> a
      * a/b/c     --> c
      * a/b/c/    --> ""
      * </pre>
      * <p>
      * 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
      */
     public static String getBaseName(final String filename)
     {
         return removeExtension(getName(filename));
     }
 
     /**
      * Gets the extension of a filename.
      * <p>
      * This method returns the textual part of the filename after the last dot.
      * There must be no directory separator after the dot.
      * <pre>
      * foo.txt      --> "txt"
      * a/b/c.jpg    --> "jpg"
      * a/b.txt/c    --> ""
      * a/b/c        --> ""
      * </pre>
      * <p>
      * 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 == -1)
         {
             return "";
         }
         else
         {
             return filename.substring(index + 1);
         }
     }
 
     //-----------------------------------------------------------------------
     /**
      * Removes the extension from a filename.
      * <p>
      * This method returns the textual part of the filename before the last dot.
      * There must be no directory separator after the dot.
      * <pre>
      * foo.txt    --> foo
      * a\b\c.jpg  --> a\b\c
      * a\b\c      --> a\b\c
      * a.b\c      --> a.b\c
      * </pre>
      * <p>
      * 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 filename minus the extension
      */
     public static String removeExtension(final String filename)
     {
         if (filename == null)
         {
             return null;
         }
         final int index = indexOfExtension(filename);
         if (index == -1)
         {
             return filename;
         }
         else
         {
             return filename.substring(0, index);
         }
     }
 
 }