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      1 /*
      2  * Copyright (C) 2012 Google, Inc.
      3  *
      4  * This library is free software; you can redistribute it and/or modify it
      5  * under the terms of the GNU Lesser General Public License as published
      6  * by the Free Software Foundation; either version 2.1 of the License, or
      7  * (at your option) any later version.
      8  *
      9  * This library is distributed in the hope that it will be useful, but
     10  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
     11  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
     12  * License for more details.
     13  *
     14  * You should have received a copy of the GNU Lesser General Public License
     15  * along with this library; If not, write to the Free Software Foundation, Inc.,
     16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
     17  */
     18 
     19 package de.waldheinz.fs.fat;
     20 
     21 import java.security.SecureRandom;
     22 
     23 /**
     24  * Generates dummy 8.3 buffers that are associated with the long names.
     25  *
     26  * @author Daniel Galpin <dgalpin (at) google.com> based upon the work of
     27  *         Andrew Tridgell <tridge (at) samba.org>
     28  */
     29 final class Dummy83BufferGenerator {
     30     final SecureRandom mRandom;
     31 
     32     /**
     33      * Creates a new instance of {@code Dummy83BufferGenerator} that uses
     34      * randomness only to avoid short name collisions.
     35      */
     36     public Dummy83BufferGenerator() {
     37         mRandom = new SecureRandom();
     38     }
     39 
     40     /*
     41      * Its in the DOS manual!(DOS 5: page 72) Valid: A..Z 0..9 _ ^ $ ~ ! # % & - {} () @ ' `
     42      *
     43      * Invalid: spaces/periods,
     44      */
     45     public static boolean validChar(char toTest) {
     46         if (toTest >= 'A' && toTest <= 'Z') return true;
     47         if (toTest >= 'a' && toTest <= 'z') return true;
     48         if (toTest >= '0' && toTest <= '9') return true;
     49         if (toTest == '_' || toTest == '^' || toTest == '$' || toTest == '~' ||
     50                 toTest == '!' || toTest == '#' || toTest == '%' || toTest == '&' ||
     51                 toTest == '-' || toTest == '{' || toTest == '}' || toTest == '(' ||
     52                 toTest == ')' || toTest == '@' || toTest == '\'' || toTest == '`')
     53             return true;
     54 
     55         return false;
     56     }
     57 
     58     public static boolean isSkipChar(char c) {
     59         return (c == '.') || (c == ' ');
     60     }
     61 
     62     public static String tidyString(String dirty) {
     63         final StringBuilder result = new StringBuilder();
     64 
     65         /* epurate it from alien characters */
     66         for (int src=0; src < dirty.length(); src++) {
     67             final char toTest = Character.toUpperCase(dirty.charAt(src));
     68             if (isSkipChar(toTest)) continue;
     69 
     70             if (validChar(toTest)) {
     71                 result.append(toTest);
     72             } else {
     73                 result.append('_');
     74             }
     75         }
     76 
     77         return result.toString();
     78     }
     79 
     80     public static boolean cleanString(String s) {
     81         for (int i=0; i < s.length(); i++) {
     82             if (isSkipChar(s.charAt(i))) return false;
     83             if (!validChar(s.charAt(i))) return false;
     84         }
     85 
     86         return true;
     87     }
     88 
     89     public static String stripLeadingPeriods(String str) {
     90         final StringBuilder sb = new StringBuilder(str.length());
     91 
     92         for (int i=0; i < str.length(); i++) {
     93             if (str.charAt(i) != '.') { //NOI18N
     94                 sb.append(str.substring(i));
     95                 break;
     96             }
     97         }
     98 
     99         return sb.toString();
    100     }    /*
    101      * These characters are all invalid in 8.3 names, plus have been shown to be
    102      * harmless on all tested devices
    103      */
    104     static final private char[] invalidchar = {
    105             (char) 0x01, (char) 0x02, (char) 0x03, (char) 0x04, (char) 0x05, (char) 0x06,
    106             (char) 0x0B,
    107             (char) 0x0C, (char) 0x0E, (char) 0x0F, (char) 0x10, (char) 0x11, (char) 0x12,
    108             (char) 0x13,
    109             (char) 0x14, (char) 0x15, (char) 0x16, (char) 0x17, (char) 0x18, (char) 0x19,
    110             (char) 0x1A,
    111             (char) 0x1B, (char) 0x1C, (char) 0x1D, (char) 0x1E, (char) 0x1F, (char) 0x22,
    112             (char) 0x2a,
    113             (char) 0x3a, (char) 0x3c, (char) 0x3e, (char) 0x3f, (char) 0x5b, (char) 0x5d,
    114             (char) 0x7c
    115     };
    116 
    117     /**
    118      * See original C Linux patch by Andrew Tridgell &lt;tridge (at) samba.org&gt;
    119      * build a 11 byte 8.3 buffer which is not a short filename. We want 11
    120      * bytes which: - will be seen as a constant string to all APIs on Linux and
    121      * Windows - cannot be matched with wildcard patterns - cannot be used to
    122      * access the file - has a low probability of collision within a directory -
    123      * has an invalid 3 byte extension - contains at least one non-space and
    124      * non-nul byte
    125      *
    126      * @param longFullName the long file name to generate the buffer for
    127      * @return the generated 8.3 buffer
    128      */
    129     public ShortName generate83BufferNew(String longFullName)
    130             throws IllegalStateException {
    131 
    132         char[] retBuffer = new char[11];
    133 
    134         boolean hasRealShortName = false;// getRealShortNameInstead(longFullName,
    135                                          // retBuffer);
    136         if (!hasRealShortName) {
    137             int i, tilde_pos, slash_pos;
    138             int randomNumber = Math.abs(mRandom.nextInt());
    139 
    140             /*
    141              * the '/' makes sure that even unpatched Linux systems can't get at
    142              * files by the 8.3 entry.
    143              */
    144 
    145             slash_pos = randomNumber % 8;
    146             randomNumber >>= 3;
    147 
    148             /*
    149              * fill in the first 8 bytes with invalid characters. Note that we
    150              * need to be careful not to run out of randomness. We use the same
    151              * extension for all buffers.
    152              */
    153             for (i = 0; i < 8; i++) {
    154             	if (i == slash_pos)
    155                     retBuffer[i] = '/';
    156                 else {
    157                     retBuffer[i] =
    158                             invalidchar[randomNumber % invalidchar.length];
    159                     randomNumber /= invalidchar.length;
    160                     if (randomNumber < invalidchar.length)
    161                         randomNumber = Math.abs(mRandom.nextInt());
    162                 }
    163             }
    164 
    165             for ( i = 0; i < 8; i ++ ) {
    166                 if (retBuffer[i] == 0xe5) {
    167                     throw new RuntimeException();
    168                 }
    169             }
    170 
    171             retBuffer[8] = 'i';
    172             retBuffer[9] = 'f';
    173             retBuffer[10] = 'l';
    174         }
    175         ShortName retName = new ShortName(retBuffer);
    176         retName.setHasShortNameOnly(hasRealShortName);
    177         return retName;
    178     }
    179 
    180 }
    181