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// Copyright 2008 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 <iosfwd>
#include <string>
#include "base/compiler_specific.h"
#include "build/build_config.h"
// Windows-style drive letter support and pathname separator characters can be
// enabled and disabled independently, to aid testing. These #defines are
// here so that the same setting can be used in both the implementation and
// in the unit test.
#if defined(OS_WIN)
#endif // OS_WIN
namespace base {
// An abstraction to isolate users from the differences between native
// pathnames on different platforms.
class FilePath {
#if defined(OS_POSIX)
// 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 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 the path's file extension. This does not have a special case for
// common double extensions, so FinalExtension() of "foo.tar.gz" is simply
// ".gz". If there is no extension, "" will be returned.
StringType FinalExtension() const WARN_UNUSED_RESULT;
// Returns a FilePath with FinalExtension() removed.
FilePath RemoveFinalExtension() const WARN_UNUSED_RESULT;
// 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;
// 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;
// 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_;
} // namespace base
// This is required by googletest to print a readable output on test failures.
extern void PrintTo(const base::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)
#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