MdeModulePkg/Universal/Disk/UdfDxe/FileName.c

   1 /** @file
   2   Helper functions for mangling file names in UDF/ECMA-167 file systems.
   3
   4   Copyright (C) 2014-2017 Paulo Alcantara <pcacjr@zytor.com>
   5
   6   SPDX-License-Identifier: BSD-2-Clause-Patent
   7 **/
   8
   9 #include "Udf.h"
  10
  11 /**
  12   Trim the leading and trailing spaces for a give Unicode string.
  13
  14   @param[in]  String              The Unicode string to trim.
  15
  16   @return  A pointer to the trimmed string.
  17
  18 **/
  19 CHAR16 *
  20 TrimString (
  21   IN CHAR16    *String
  22   )
  23 {
  24   CHAR16       *TempString;
  25
  26   for ( ; *String != L'\0' && *String == L' '; String++) {
  27     ;
  28   }
  29
  30   TempString = String + StrLen (String) - 1;
  31   while ((TempString >= String) && (*TempString == L' ')) {
  32     TempString--;
  33   }
  34
  35   *(TempString + 1) = L'\0';
  36
  37   return String;
  38 }
  39
  40 /**
  41   Replace the content of a Unicode string with the content of another Unicode
  42   string.
  43
  44   @param[in]  Destination         A pointer to a Unicode string.
  45   @param[in]  Source              A pointer to a Unicode string.
  46
  47 **/
  48 VOID
  49 ReplaceLeft (
  50   IN CHAR16         *Destination,
  51   IN CONST CHAR16   *Source
  52   )
  53 {
  54   CONST CHAR16      *EndString;
  55
  56   EndString = Source + StrLen (Source);
  57   while (Source <= EndString) {
  58     *Destination++ = *Source++;
  59   }
  60 }
  61
  62 /**
  63   Remove one or more consecutive backslashes starting from the second character
  64   of a given Unicode string.
  65
  66   @param[in]  String              A pointer to a Unicode string.
  67
  68   @return  A pointer to the modified string.
  69
  70 **/
  71 CHAR16 *
  72 ExcludeTrailingBackslashes (
  73   IN CHAR16                    *String
  74   )
  75 {
  76   CHAR16                       *TempString;
  77
  78   switch (*(String + 1)) {
  79   case L'\\':
  80     break;
  81   case L'\0':
  82   default:
  83     String++;
  84     goto Exit;
  85   }
  86
  87   TempString = String;
  88   while (*TempString != L'\0' && *TempString == L'\\') {
  89     TempString++;
  90   }
  91
  92   if (TempString - 1 > String) {
  93     ReplaceLeft (String + 1, TempString);
  94   }
  95
  96   String++;
  97
  98 Exit:
  99   return String;
 100 }
 101
 102 /**
 103   Mangle a filename by cutting off trailing whitespaces, "\\", "." and "..".
 104
 105   @param[in] FileName Filename.
 106
 107   @retval The mangled Filename.
 108
 109 **/
 110 CHAR16 *
 111 MangleFileName (
 112   IN CHAR16        *FileName
 113   )
 114 {
 115   CHAR16           *FileNameSavedPointer;
 116   CHAR16           *TempFileName;
 117   UINTN            BackslashesNo;
 118
 119   if (FileName == NULL || *FileName == L'\0') {
 120     FileName = NULL;
 121     goto Exit;
 122   }
 123
 124   FileName = TrimString (FileName);
 125   if (*FileName == L'\0') {
 126     goto Exit;
 127   }
 128
 129   if ((StrLen (FileName) > 1) && (FileName[StrLen (FileName) - 1] == L'\\')) {
 130     FileName[StrLen (FileName) - 1] = L'\0';
 131   }
 132
 133   FileNameSavedPointer = FileName;
 134
 135   if (FileName[0] == L'.') {
 136     if (FileName[1] == L'.') {
 137       if (FileName[2] == L'\0') {
 138         goto Exit;
 139       } else {
 140         FileName += 2;
 141       }
 142     } else if (FileName[1] == L'\0') {
 143       goto Exit;
 144     }
 145   }
 146
 147   while (*FileName != L'\0') {
 148     if (*FileName == L'\\') {
 149       FileName = ExcludeTrailingBackslashes (FileName);
 150     } else if (*FileName == L'.') {
 151       switch (*(FileName + 1)) {
 152       case L'\0':
 153         *FileName = L'\0';
 154         break;
 155       case L'\\':
 156         TempFileName = FileName + 1;
 157         TempFileName = ExcludeTrailingBackslashes (TempFileName);
 158         ReplaceLeft (FileName, TempFileName);
 159         break;
 160       case '.':
 161         if ((*(FileName - 1) != L'\\') && ((*(FileName + 2) != L'\\') ||
 162                                            (*(FileName + 2) != L'\0'))) {
 163           FileName++;
 164           continue;
 165         }
 166
 167         BackslashesNo = 0;
 168         TempFileName = FileName - 1;
 169         while (TempFileName >= FileNameSavedPointer) {
 170           if (*TempFileName == L'\\') {
 171             if (++BackslashesNo == 2) {
 172               break;
 173             }
 174           }
 175
 176           TempFileName--;
 177         }
 178
 179         TempFileName++;
 180
 181         if ((*TempFileName == L'.') && (*(TempFileName + 1) == L'.')) {
 182           FileName += 2;
 183         } else {
 184           if (*(FileName + 2) != L'\0') {
 185             ReplaceLeft (TempFileName, FileName + 3);
 186             if (*(TempFileName - 1) == L'\\') {
 187               FileName = TempFileName;
 188               ExcludeTrailingBackslashes (TempFileName - 1);
 189               TempFileName = FileName;
 190             }
 191           } else {
 192             *TempFileName = L'\0';
 193           }
 194
 195           FileName = TempFileName;
 196         }
 197
 198         break;
 199       default:
 200         FileName++;
 201       }
 202     } else {
 203       FileName++;
 204     }
 205   }
 206
 207   FileName = FileNameSavedPointer;
 208   if ((StrLen (FileName) > 1) && (FileName [StrLen (FileName) - 1] == L'\\')) {
 209     FileName [StrLen (FileName) - 1] = L'\0';
 210   }
 211
 212 Exit:
 213   return FileName;
 214 }