system76-edk2/MdeModulePkg/Universal/Disk/UdfDxe/FileName.c

/** @file
  Helper functions for mangling file names in UDF/ECMA-167 file systems.

  Copyright (C) 2014-2017 Paulo Alcantara <pcacjr@zytor.com>

  This program and the accompanying materials are licensed and made available
  under the terms and conditions of the BSD License which accompanies this
  distribution.  The full text of the license may be found at
  http://opensource.org/licenses/bsd-license.php

  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, WITHOUT
  WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
**/

#include "Udf.h"

/**
  Trim the leading and trailing spaces for a give Unicode string.

  @param[in]  String              The Unicode string to trim.

  @return  A pointer to the trimmed string.

**/
CHAR16 *
TrimString (
  IN CHAR16    *String
  )
{
  CHAR16       *TempString;

  for ( ; *String != L'\0' && *String == L' '; String++) {
    ;
  }

  TempString = String + StrLen (String) - 1;
  while ((TempString >= String) && (*TempString == L' ')) {
    TempString--;
  }

  *(TempString + 1) = L'\0';

  return String;
}

/**
  Replace the content of a Unicode string with the content of another Unicode
  string.

  @param[in]  Destination         A pointer to a Unicode string.
  @param[in]  Source              A pointer to a Unicode string.

**/
VOID
ReplaceLeft (
  IN CHAR16         *Destination,
  IN CONST CHAR16   *Source
  )
{
  CONST CHAR16      *EndString;

  EndString = Source + StrLen (Source);
  while (Source <= EndString) {
    *Destination++ = *Source++;
  }
}

/**
  Remove one or more consecutive backslashes starting from the second character
  of a given Unicode string.

  @param[in]  String              A pointer to a Unicode string.

  @return  A pointer to the modified string.

**/
CHAR16 *
ExcludeTrailingBackslashes (
  IN CHAR16                    *String
  )
{
  CHAR16                       *TempString;

  switch (*(String + 1)) {
  case L'\\':
    break;
  case L'\0':
  default:
    String++;
    goto Exit;
  }

  TempString = String;
  while (*TempString != L'\0' && *TempString == L'\\') {
    TempString++;
  }

  if (TempString - 1 > String) {
    ReplaceLeft (String + 1, TempString);
  }

  String++;

Exit:
  return String;
}

/**
  Mangle a filename by cutting off trailing whitespaces, "\\", "." and "..".

  @param[in] FileName Filename.

  @retval The mangled Filename.

**/
CHAR16 *
MangleFileName (
  IN CHAR16        *FileName
  )
{
  CHAR16           *FileNameSavedPointer;
  CHAR16           *TempFileName;
  UINTN            BackslashesNo;

  if (FileName == NULL || *FileName == L'\0') {
    FileName = NULL;
    goto Exit;
  }

  FileName = TrimString (FileName);
  if (*FileName == L'\0') {
    goto Exit;
  }

  if ((StrLen (FileName) > 1) && (FileName[StrLen (FileName) - 1] == L'\\')) {
    FileName[StrLen (FileName) - 1] = L'\0';
  }

  FileNameSavedPointer = FileName;

  if (FileName[0] == L'.') {
    if (FileName[1] == L'.') {
      if (FileName[2] == L'\0') {
        goto Exit;
      } else {
        FileName += 2;
      }
    } else if (FileName[1] == L'\0') {
      goto Exit;
    }
  }

  while (*FileName != L'\0') {
    if (*FileName == L'\\') {
      FileName = ExcludeTrailingBackslashes (FileName);
    } else if (*FileName == L'.') {
      switch (*(FileName + 1)) {
      case L'\0':
        *FileName = L'\0';
        break;
      case L'\\':
        TempFileName = FileName + 1;
        TempFileName = ExcludeTrailingBackslashes (TempFileName);
        ReplaceLeft (FileName, TempFileName);
        break;
      case '.':
        if ((*(FileName - 1) != L'\\') && ((*(FileName + 2) != L'\\') ||
                                           (*(FileName + 2) != L'\0'))) {
          FileName++;
          continue;
        }

        BackslashesNo = 0;
        TempFileName = FileName - 1;
        while (TempFileName >= FileNameSavedPointer) {
          if (*TempFileName == L'\\') {
            if (++BackslashesNo == 2) {
              break;
            }
          }

          TempFileName--;
        }

        TempFileName++;

        if ((*TempFileName == L'.') && (*(TempFileName + 1) == L'.')) {
          FileName += 2;
        } else {
          if (*(FileName + 2) != L'\0') {
            ReplaceLeft (TempFileName, FileName + 3);
            if (*(TempFileName - 1) == L'\\') {
              FileName = TempFileName;
              ExcludeTrailingBackslashes (TempFileName - 1);
              TempFileName = FileName;
            }
          } else {
            *TempFileName = L'\0';
          }

          FileName = TempFileName;
        }

        break;
      default:
        FileName++;
      }
    } else {
      FileName++;
    }
  }

  FileName = FileNameSavedPointer;
  if ((StrLen (FileName) > 1) && (FileName [StrLen (FileName) - 1] == L'\\')) {
    FileName [StrLen (FileName) - 1] = L'\0';
  }

Exit:
  return FileName;
}