text: 
  // FilePath is a container for pathnames stored in a platform's native string
  // type, providing containers for manipulation in according with the
  // platform's conventions for pathnames.  It supports the following path
  // types:
  //
  //                   POSIX            Windows
  //                   ---------------  ----------------------------------
  // Fundamental type  char[]           wchar_t[]
  // Encoding          unspecified*     UTF-16
  // Separator         /                \, tolerant of /
  // Drive letters     no               case-insensitive A-Z followed by :
  // Alternate root    // (surprise!)   \\, for UNC paths
  //
  // * The encoding need not be specified on POSIX systems, although some
  //   POSIX-compliant systems do specify an encoding.  Mac OS X uses UTF-8.
  //   Linux does not specify an encoding, but in practice, the locale's
  //   character set may be used.
  //
  // For more arcane bits of path trivia, see below.
  //
  // FilePath objects are intended to be used anywhere paths are.  An
  // application may pass FilePath objects around internally, masking the
  // underlying differences between systems, only differing in implementation
  // where interfacing directly with the system.  For example, a single
  // OpenFile(const FilePath &) function may be made available, allowing all
  // callers to operate without regard to the underlying implementation.  On
  // POSIX-like platforms, OpenFile might wrap fopen, and on Windows, it might
  // wrap _wfopen_s, perhaps both by calling file_path.value().c_str().  This
  // allows each platform to pass pathnames around without requiring conversions
  // between encodings, which has an impact on performance, but more imporantly,
  // has an impact on correctness on platforms that do not have well-defined
  // encodings for pathnames.
  //
  // Several methods are available to perform common operations on a FilePath
  // object, such as determining the parent directory (DirName), isolating the
  // final path component (BaseName), and appending a relative pathname string
  // to an existing FilePath object (Append).  These methods are highly
  // recommended over attempting to split and concatenate strings directly.
  // These methods are based purely on string manipulation and knowledge of
  // platform-specific pathname conventions, and do not consult the filesystem
  // at all, making them safe to use without fear of blocking on I/O operations.
  // These methods do not function as mutators but instead return distinct
  // instances of FilePath objects, and are therefore safe to use on const
  // objects.  The objects themselves are safe to share between threads.
  //
  // To aid in initialization of FilePath objects from string literals, a
  // FILE_PATH_LITERAL macro is provided, which accounts for the difference
  // between char[]-based pathnames on POSIX systems and wchar_t[]-based
  // pathnames on Windows.
  //
  // Because a FilePath object should not be instantiated at the global scope,
  // instead, use a FilePath::CharType[] and initialize it with
  // FILE_PATH_LITERAL.  At runtime, a FilePath object can be created from the
  // character array.  Example:
  //
  // | const FilePath::CharType kLogFileName[] = FILE_PATH_LITERAL("log.txt");
  // |
  // | void Function() {
  // |   FilePath log_file_path(kLogFileName);
  // |   [...]
  // | }
  //
  // WARNING: FilePaths should ALWAYS be displayed with LTR directionality, even
  // when the UI language is RTL. This means you always need to pass filepaths
  // through base::i18n::WrapPathWithLTRFormatting() before displaying it in the
  // RTL UI.
  //
  // This is a very common source of bugs, please try to keep this in mind.
  //
  // ARCANE BITS OF PATH TRIVIA
  //
  //  - A double leading slash is actually part of the POSIX standard.  Systems
  //    are allowed to treat // as an alternate root, as Windows does for UNC
  //    (network share) paths.  Most POSIX systems don't do anything special
  //    with two leading slashes, but FilePath handles this case properly
  //    in case it ever comes across such a system.  FilePath needs this support
  //    for Windows UNC paths, anyway.
  //    References:
  //    The Open Group Base Specifications Issue 7, sections 3.266 ("Pathname")
  //    and 4.12 ("Pathname Resolution"), available at:
  //    http://www.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_266
  //    http://www.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_12
  //
  //  - Windows treats c:\\ the same way it treats \\.  This was intended to
  //    allow older applications that require drive letters to support UNC paths
  //    like \\server\share\path, by permitting c:\\server\share\path as an
  //    equivalent.  Since the OS treats these paths specially, FilePath needs
  //    to do the same.  Since Windows can use either / or \ as the separator,
  //    FilePath treats c://, c:\\, //, and \\ all equivalently.
  //    Reference:
  //    The Old New Thing, "Why is a drive letter permitted in front of UNC
  //    paths (sometimes)?", available at:
  //    http://blogs.msdn.com/oldnewthing/archive/2005/11/22/495740.aspx
  
  #ifndef __base_file_path_h__
  #define __base_file_path_h__
  
  #pragma once
  
  #include <hash_set>
  #include <vector>
  
  #include "string_piece.h" // For implicit conversions.
  #include "string16.h"
  
  class Pickle;
  
  // An abstraction to isolate users from the differences between native
  // pathnames on different platforms.
  class FilePath
  {
  public:
      // On Windows, for Unicode-aware applications, native pathnames are wchar_t
      // arrays encoded in UTF-16.
      typedef std::wstring StringType;
  
      typedef StringType::value_type CharType;
  
      // Null-terminated array of separators used to separate components in
      // hierarchical paths.  Each character in this array is a valid separator,
      // but kSeparators[0] is treated as the canonical separator and will be used
      // when composing pathnames.
      static const CharType kSeparators[];
  
      // A special path component meaning "this directory."
      static const CharType kCurrentDirectory[];
  
      // A special path component meaning "the parent directory."
      static const CharType kParentDirectory[];
  
      // The character used to identify a file extension.
      static const CharType kExtensionSeparator;
  
      FilePath();
      FilePath(const FilePath& that);
      explicit FilePath(const StringType& path);
      ~FilePath();
      FilePath& operator=(const FilePath& that);
  
      bool operator==(const FilePath& that) const;
  
      bool operator!=(const FilePath& that) const;
  
      // Required for some STL containers and operations
      bool operator<(const FilePath& that) const
      {
          return path_ < that.path_;
      }
  
      const StringType& value() const { return path_; }
  
      bool empty() const { return path_.empty(); }
  
      void clear() { path_.clear(); }
  
      // Returns true if |character| is in kSeparators.
      static bool IsSeparator(CharType character);
  
  	bool FilePath::EndsWithSeparator() const {
  	  if (empty())
  		return false;
  	  return IsSeparator(path_[path_.size() - 1]);
  	}
  
      // Returns a vector of all of the components of the provided path. It is
      // equivalent to calling DirName().value() on the path's root component,
      // and BaseName().value() on each child component.
      void GetComponents(std::vector<FilePath::StringType>* components) const;
  
      // Returns true if this FilePath is a strict parent of the |child|. Absolute
      // and relative paths are accepted i.e. is /foo parent to /foo/bar and
      // is foo parent to foo/bar. Does not convert paths to absolute, follow
      // symlinks or directory navigation (e.g. ".."). A path is *NOT* its own
      // parent.
      bool IsParent(const FilePath& child) const;
  
      // If IsParent(child) holds, appends to path (if non-NULL) the
      // relative path to child and returns true.  For example, if parent
      // holds "/Users/johndoe/Library/Application Support", child holds
      // "/Users/johndoe/Library/Application Support/Google/Chrome/Default", and
      // *path holds "/Users/johndoe/Library/Caches", then after
      // parent.AppendRelativePath(child, path) is called *path will hold
      // "/Users/johndoe/Library/Caches/Google/Chrome/Default".  Otherwise,
      // returns false.
      bool AppendRelativePath(const FilePath& child, FilePath* path) const;
  
      // Returns a FilePath corresponding to the directory containing the path
      // named by this object, stripping away the file component.  If this object
      // only contains one component, returns a FilePath identifying
      // kCurrentDirectory.  If this object already refers to the root directory,
      // returns a FilePath identifying the root directory.
      FilePath DirName() const;
  
      // Returns a FilePath corresponding to the last path component of this
      // object, either a file or a directory.  If this object already refers to
      // the root directory, returns a FilePath identifying the root directory;
      // this is the only situation in which BaseName will return an absolute path.
      FilePath BaseName() const;
  
      // Returns ".jpg" for path "C:\pics\jojo.jpg", or an empty string if
      // the file has no extension.  If non-empty, Extension() will always start
      // with precisely one ".".  The following code should always work regardless
      // of the value of path.
      // new_path = path.RemoveExtension().value().append(path.Extension());
      // ASSERT(new_path == path.value());
      // NOTE: this is different from the original file_util implementation which
      // returned the extension without a leading "." ("jpg" instead of ".jpg")
      StringType Extension() const;
  
      // Returns "C:\pics\jojo" for path "C:\pics\jojo.jpg"
      // NOTE: this is slightly different from the similar file_util implementation
      // which returned simply 'jojo'.
      FilePath RemoveExtension() const;
  
      // Inserts |suffix| after the file name portion of |path| but before the
      // extension.  Returns "" if BaseName() == "." or "..".
      // Examples:
      // path == "C:\pics\jojo.jpg" suffix == " (1)", returns "C:\pics\jojo (1).jpg"
      // path == "jojo.jpg"         suffix == " (1)", returns "jojo (1).jpg"
      // path == "C:\pics\jojo"     suffix == " (1)", returns "C:\pics\jojo (1)"
      // path == "C:\pics.old\jojo" suffix == " (1)", returns "C:\pics.old\jojo (1)"
      FilePath InsertBeforeExtension(const StringType& suffix) const;
      FilePath InsertBeforeExtensionASCII(const base::StringPiece& suffix) const;
  
      // Replaces the extension of |file_name| with |extension|.  If |file_name|
      // does not have an extension, them |extension| is added.  If |extension| is
      // empty, then the extension is removed from |file_name|.
      // Returns "" if BaseName() == "." or "..".
      FilePath ReplaceExtension(const StringType& extension) const;
  
      // Returns true if the file path matches the specified extension. The test is
      // case insensitive. Don't forget the leading period if appropriate.
      bool MatchesExtension(const StringType& extension) const;
  
      // Returns a FilePath by appending a separator and the supplied path
      // component to this object's path.  Append takes care to avoid adding
      // excessive separators if this object's path already ends with a separator.
      // If this object's path is kCurrentDirectory, a new FilePath corresponding
      // only to |component| is returned.  |component| must be a relative path;
      // it is an error to pass an absolute path.
      FilePath Append(const StringType& component) const;
      FilePath Append(const FilePath& component) const;
  
      // Although Windows StringType is std::wstring, since the encoding it uses for
      // paths is well defined, it can handle ASCII path components as well.
      // Mac uses UTF8, and since ASCII is a subset of that, it works there as well.
      // On Linux, although it can use any 8-bit encoding for paths, we assume that
      // ASCII is a valid subset, regardless of the encoding, since many operating
      // system paths will always be ASCII.
      FilePath AppendASCII(const base::StringPiece& component) const;
  
      // Returns true if this FilePath contains an absolute path.  On Windows, an
      // absolute path begins with either a drive letter specification followed by
      // a separator character, or with two separator characters.  On POSIX
      // platforms, an absolute path begins with a separator character.
      bool IsAbsolute() const;
  
      // Returns a copy of this FilePath that does not end with a trailing
      // separator.
      FilePath StripTrailingSeparators() const;
  
      // Returns true if this FilePath contains any attempt to reference a parent
      // directory (i.e. has a path component that is ".."
      bool ReferencesParent() const;
  
      // Return a Unicode human-readable version of this path.
      // Warning: you can *not*, in general, go from a display name back to a real
      // path.  Only use this when displaying paths to users, not just when you
      // want to stuff a string16 into some other API.
      string16 LossyDisplayName() const;
  
      // Return the path as ASCII, or the empty string if the path is not ASCII.
      // This should only be used for cases where the FilePath is representing a
      // known-ASCII filename.
      std::string MaybeAsASCII() const;
  
      // Older Chromium code assumes that paths are always wstrings.
      // This function converts wstrings to FilePaths, and is
      // useful to smooth porting that old code to the FilePath API.
      // It has "Hack" its name so people feel bad about using it.
      // http://code.google.com/p/chromium/issues/detail?id=24672
      //
      // If you are trying to be a good citizen and remove these, ask yourself:
      // - Am I interacting with other Chrome code that deals with files?  Then
      //   try to convert the API into using FilePath.
      // - Am I interacting with OS-native calls?  Then use value() to get at an
      //   OS-native string format.
      // - Am I using well-known file names, like "config.ini"?  Then use the
      //   ASCII functions (we require paths to always be supersets of ASCII).
      // - Am I displaying a string to the user in some UI?  Then use the
      //   LossyDisplayName() function, but keep in mind that you can't
      //   ever use the result of that again as a path.
      static FilePath FromWStringHack(const std::wstring& wstring);
  
      // Static helper method to write a StringType to a pickle.
      static void WriteStringTypeToPickle(Pickle* pickle,
          const FilePath::StringType& path);
      static bool ReadStringTypeFromPickle(Pickle* pickle, void** iter,
          FilePath::StringType* path);
  
      void WriteToPickle(Pickle* pickle);
      bool ReadFromPickle(Pickle* pickle, void** iter);
  
      // Normalize all path separators to backslash.
      FilePath NormalizeWindowsPathSeparators() const;
  
      // Compare two strings in the same way the file system does.
      // Note that these always ignore case, even on file systems that are case-
      // sensitive. If case-sensitive comparison is ever needed, add corresponding
      // methods here.
      // The methods are written as a static method so that they can also be used
      // on parts of a file path, e.g., just the extension.
      // CompareIgnoreCase() returns -1, 0 or 1 for less-than, equal-to and
      // greater-than respectively.
      static int CompareIgnoreCase(const StringType& string1,
          const StringType& string2);
      static bool CompareEqualIgnoreCase(const StringType& string1,
          const StringType& string2)
      {
          return CompareIgnoreCase(string1, string2) == 0;
      }
      static bool CompareLessIgnoreCase(const StringType& string1,
          const StringType& string2)
      {
          return CompareIgnoreCase(string1, string2) < 0;
      }
  
  private:
      // Remove trailing separators from this object.  If the path is absolute, it
      // will never be stripped any more than to refer to the absolute root
      // directory, so "////" will become "/", not "".  A leading pair of
      // separators is never stripped, to support alternate roots.  This is used to
      // support UNC paths on Windows.
      void StripTrailingSeparatorsInternal();
  
      StringType path_;
  };
  
  // Macros for string literal initialization of FilePath::CharType[], and for
  // using a FilePath::CharType[] in a printf-style format string.
  #define FILE_PATH_LITERAL(x)    L ## x
  #define PRFilePath              "ls"
  #define PRFilePathLiteral       L"%ls"
  
  namespace stdext
  {
  
      inline size_t hash_value(const FilePath& f)
      {
          return hash_value(f.value());
      }
  
  }
  
  #endif //__base_file_path_h__