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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// 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.
// Chrome OS also 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.
// Paths can't contain NULs as a precaution agaist premature truncation.
// 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.
// - 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:
// - 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:
#include <stddef.h>
#include <string>
#include <vector>
#include "base/base_export.h"
#include "base/compiler_specific.h"
#include "base/hash_tables.h"
#include "base/string16.h"
#include "base/string_piece.h" // For implicit conversions.
#include "build/build_config.h"
class Pickle;
class PickleIterator;
// An abstraction to isolate users from the differences between native
// pathnames on different platforms.
class BASE_EXPORT FilePath {
#if defined(OS_POSIX) || defined(OS_STARBOARD)
// On most platforms, native pathnames are char arrays, and the encoding
// may or may not be specified. On Mac OS X, native pathnames are encoded
// in UTF-8.
typedef std::string StringType;
#elif defined(OS_WIN)
// On Windows, for Unicode-aware applications, native pathnames are wchar_t
// arrays encoded in UTF-16.
typedef std::wstring StringType;
#endif // OS_WIN
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(const FilePath& that);
explicit FilePath(const StringType& path);
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);
// 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 WARN_UNUSED_RESULT;
// 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 WARN_UNUSED_RESULT;
// 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 WARN_UNUSED_RESULT;
// 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 WARN_UNUSED_RESULT;
FilePath InsertBeforeExtensionASCII(
const base::StringPiece& suffix) const WARN_UNUSED_RESULT;
// Adds |extension| to |file_name|. Returns the current FilePath if
// |extension| is empty. Returns "" if BaseName() == "." or "..".
FilePath AddExtension(
const StringType& extension) const WARN_UNUSED_RESULT;
// Replaces the extension of |file_name| with |extension|. If |file_name|
// does not have an extension, then |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 WARN_UNUSED_RESULT;
// 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 WARN_UNUSED_RESULT;
FilePath Append(const FilePath& component) const WARN_UNUSED_RESULT;
// 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)
// 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 WARN_UNUSED_RESULT;
// 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;
// Return the path as UTF-8.
// This function is *unsafe* as there is no way to tell what encoding is
// used in file names on POSIX systems other than Mac and Chrome OS,
// although UTF-8 is practically used everywhere these days. To mitigate
// the encoding issue, this function internally calls
// SysNativeMBToWide() on POSIX systems other than Mac and Chrome OS,
// per assumption that the current locale's encoding is used in file
// names, but this isn't a perfect solution.
// Once it becomes safe to to stop caring about non-UTF-8 file names,
// the SysNativeMBToWide() hack will be removed from the code, along
// with "Unsafe" in the function name.
std::string AsUTF8Unsafe() 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.
// 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);
// Returns a FilePath object from a path name in UTF-8. This function
// should only be used for cases where you are sure that the input
// string is UTF-8.
// Like AsUTF8Unsafe(), this function is unsafe. This function
// internally calls SysWideToNativeMB() on POSIX systems other than Mac
// and Chrome OS, to mitigate the encoding issue. See the comment at
// AsUTF8Unsafe() for details.
static FilePath FromUTF8Unsafe(const std::string& utf8);
void WriteToPickle(Pickle* pickle) const;
bool ReadFromPickle(PickleIterator* iter);
// Normalize all path separators to backslash on Windows
// (if FILE_PATH_USES_WIN_SEPARATORS is true), or do nothing on POSIX systems.
FilePath NormalizePathSeparators() 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;
#if defined(OS_MACOSX)
// Returns the string in the special canonical decomposed form as defined for
// HFS, which is close to, but not quite, decomposition form D. See
// for further comments.
// Returns the epmty string if the conversion failed.
static StringType GetHFSDecomposedForm(const FilePath::StringType& string);
// Special UTF-8 version of FastUnicodeCompare. Cf:
// IMPORTANT: The input strings must be in the special HFS decomposed form!
// (cf. above GetHFSDecomposedForm method)
static int HFSFastUnicodeCompare(const StringType& string1,
const StringType& string2);
// 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_;
// This is required by googletest to print a readable output on test failures.
BASE_EXPORT extern void PrintTo(const FilePath& path, std::ostream* out);
// Macros for string literal initialization of FilePath::CharType[], and for
// using a FilePath::CharType[] in a printf-style format string.
#if defined(OS_POSIX) || defined(OS_STARBOARD)
#define FILE_PATH_LITERAL(x) x
#define PRFilePath "s"
#define PRFilePathLiteral "%s"
#elif defined(OS_WIN)
#define FILE_PATH_LITERAL(x) L ## x
#define PRFilePath "ls"
#define PRFilePathLiteral L"%ls"
#endif // OS_WIN
// Provide a hash function so that hash_sets and maps can contain FilePath
// objects.
struct hash<FilePath> {
size_t operator()(const FilePath& f) const {
return hash<FilePath::StringType>()(f.value());
inline size_t hash_value(const FilePath& f) {
return hash_value(f.value());
#endif // defined(BASE_HASH_USE_HASH_STRUCT)
} // namespace BASE_HASH_NAMESPACE
#endif // BASE_FILE_PATH_H_