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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 // FilePath is a container for pathnames stored in a platform's native string
6 // type, providing containers for manipulation in according with the
7 // platform's conventions for pathnames.  It supports the following path
8 // types:
9 //
10 //                   POSIX            Windows
11 //                   ---------------  ----------------------------------
12 // Fundamental type  char[]           wchar_t[]
13 // Encoding          unspecified*     UTF-16
14 // Separator         /                \, tolerant of /
15 // Drive letters     no               case-insensitive A-Z followed by :
16 // Alternate root    // (surprise!)   \\, for UNC paths
17 //
18 // * The encoding need not be specified on POSIX systems, although some
19 //   POSIX-compliant systems do specify an encoding.  Mac OS X uses UTF-8.
20 //   Chrome OS also uses UTF-8.
21 //   Linux does not specify an encoding, but in practice, the locale's
22 //   character set may be used.
23 //
24 // For more arcane bits of path trivia, see below.
25 //
26 // FilePath objects are intended to be used anywhere paths are.  An
27 // application may pass FilePath objects around internally, masking the
28 // underlying differences between systems, only differing in implementation
29 // where interfacing directly with the system.  For example, a single
30 // OpenFile(const FilePath &) function may be made available, allowing all
31 // callers to operate without regard to the underlying implementation.  On
32 // POSIX-like platforms, OpenFile might wrap fopen, and on Windows, it might
33 // wrap _wfopen_s, perhaps both by calling file_path.value().c_str().  This
34 // allows each platform to pass pathnames around without requiring conversions
35 // between encodings, which has an impact on performance, but more imporantly,
36 // has an impact on correctness on platforms that do not have well-defined
37 // encodings for pathnames.
38 //
39 // Several methods are available to perform common operations on a FilePath
40 // object, such as determining the parent directory (DirName), isolating the
41 // final path component (BaseName), and appending a relative pathname string
42 // to an existing FilePath object (Append).  These methods are highly
43 // recommended over attempting to split and concatenate strings directly.
44 // These methods are based purely on string manipulation and knowledge of
45 // platform-specific pathname conventions, and do not consult the filesystem
46 // at all, making them safe to use without fear of blocking on I/O operations.
47 // These methods do not function as mutators but instead return distinct
48 // instances of FilePath objects, and are therefore safe to use on const
49 // objects.  The objects themselves are safe to share between threads.
50 //
51 // To aid in initialization of FilePath objects from string literals, a
52 // FILE_PATH_LITERAL macro is provided, which accounts for the difference
53 // between char[]-based pathnames on POSIX systems and wchar_t[]-based
54 // pathnames on Windows.
55 //
56 // Paths can't contain NULs as a precaution agaist premature truncation.
57 //
58 // Because a FilePath object should not be instantiated at the global scope,
59 // instead, use a FilePath::CharType[] and initialize it with
60 // FILE_PATH_LITERAL.  At runtime, a FilePath object can be created from the
61 // character array.  Example:
62 //
63 // | const FilePath::CharType kLogFileName[] = FILE_PATH_LITERAL("log.txt");
64 // |
65 // | void Function() {
66 // |   FilePath log_file_path(kLogFileName);
67 // |   [...]
68 // | }
69 //
70 // WARNING: FilePaths should ALWAYS be displayed with LTR directionality, even
71 // when the UI language is RTL. This means you always need to pass filepaths
72 // through base::i18n::WrapPathWithLTRFormatting() before displaying it in the
73 // RTL UI.
74 //
75 // This is a very common source of bugs, please try to keep this in mind.
76 //
77 // ARCANE BITS OF PATH TRIVIA
78 //
79 //  - A double leading slash is actually part of the POSIX standard.  Systems
80 //    are allowed to treat // as an alternate root, as Windows does for UNC
81 //    (network share) paths.  Most POSIX systems don't do anything special
82 //    with two leading slashes, but FilePath handles this case properly
83 //    in case it ever comes across such a system.  FilePath needs this support
84 //    for Windows UNC paths, anyway.
85 //    References:
86 //    The Open Group Base Specifications Issue 7, sections 3.266 ("Pathname")
87 //    and 4.12 ("Pathname Resolution"), available at:
88 //    http://www.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_266
89 //    http://www.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_12
90 //
91 //  - Windows treats c:\\ the same way it treats \\.  This was intended to
92 //    allow older applications that require drive letters to support UNC paths
93 //    like \\server\share\path, by permitting c:\\server\share\path as an
94 //    equivalent.  Since the OS treats these paths specially, FilePath needs
95 //    to do the same.  Since Windows can use either / or \ as the separator,
96 //    FilePath treats c://, c:\\, //, and \\ all equivalently.
97 //    Reference:
98 //    The Old New Thing, "Why is a drive letter permitted in front of UNC
99 //    paths (sometimes)?", available at:
100 //    http://blogs.msdn.com/oldnewthing/archive/2005/11/22/495740.aspx
101 
102 #ifndef BASE_FILES_FILE_PATH_H_
103 #define BASE_FILES_FILE_PATH_H_
104 
105 #include <stddef.h>
106 #include <string>
107 #include <vector>
108 
109 #include "base/base_export.h"
110 #include "base/compiler_specific.h"
111 #include "base/containers/hash_tables.h"
112 #include "base/strings/string16.h"
113 #include "base/strings/string_piece.h"  // For implicit conversions.
114 #include "build/build_config.h"
115 
116 // Windows-style drive letter support and pathname separator characters can be
117 // enabled and disabled independently, to aid testing.  These #defines are
118 // here so that the same setting can be used in both the implementation and
119 // in the unit test.
120 #if defined(OS_WIN)
121 #define FILE_PATH_USES_DRIVE_LETTERS
122 #define FILE_PATH_USES_WIN_SEPARATORS
123 #endif  // OS_WIN
124 
125 class Pickle;
126 class PickleIterator;
127 
128 namespace base {
129 
130 // An abstraction to isolate users from the differences between native
131 // pathnames on different platforms.
132 class BASE_EXPORT FilePath {
133  public:
134 #if defined(OS_POSIX)
135   // On most platforms, native pathnames are char arrays, and the encoding
136   // may or may not be specified.  On Mac OS X, native pathnames are encoded
137   // in UTF-8.
138   typedef std::string StringType;
139 #elif defined(OS_WIN)
140   // On Windows, for Unicode-aware applications, native pathnames are wchar_t
141   // arrays encoded in UTF-16.
142   typedef std::wstring StringType;
143 #endif  // OS_WIN
144 
145   typedef StringType::value_type CharType;
146 
147   // Null-terminated array of separators used to separate components in
148   // hierarchical paths.  Each character in this array is a valid separator,
149   // but kSeparators[0] is treated as the canonical separator and will be used
150   // when composing pathnames.
151   static const CharType kSeparators[];
152 
153   // arraysize(kSeparators).
154   static const size_t kSeparatorsLength;
155 
156   // A special path component meaning "this directory."
157   static const CharType kCurrentDirectory[];
158 
159   // A special path component meaning "the parent directory."
160   static const CharType kParentDirectory[];
161 
162   // The character used to identify a file extension.
163   static const CharType kExtensionSeparator;
164 
165   FilePath();
166   FilePath(const FilePath& that);
167   explicit FilePath(const StringType& path);
168   ~FilePath();
169   FilePath& operator=(const FilePath& that);
170 
171   bool operator==(const FilePath& that) const;
172 
173   bool operator!=(const FilePath& that) const;
174 
175   // Required for some STL containers and operations
176   bool operator<(const FilePath& that) const {
177     return path_ < that.path_;
178   }
179 
value()180   const StringType& value() const { return path_; }
181 
empty()182   bool empty() const { return path_.empty(); }
183 
clear()184   void clear() { path_.clear(); }
185 
186   // Returns true if |character| is in kSeparators.
187   static bool IsSeparator(CharType character);
188 
189   // Returns a vector of all of the components of the provided path. It is
190   // equivalent to calling DirName().value() on the path's root component,
191   // and BaseName().value() on each child component.
192   //
193   // To make sure this is lossless so we can differentiate absolute and
194   // relative paths, the root slash will be included even though no other
195   // slashes will be. The precise behavior is:
196   //
197   // Posix:  "/foo/bar"  ->  [ "/", "foo", "bar" ]
198   // Windows:  "C:\foo\bar"  ->  [ "C:", "\\", "foo", "bar" ]
199   void GetComponents(std::vector<FilePath::StringType>* components) const;
200 
201   // Returns true if this FilePath is a strict parent of the |child|. Absolute
202   // and relative paths are accepted i.e. is /foo parent to /foo/bar and
203   // is foo parent to foo/bar. Does not convert paths to absolute, follow
204   // symlinks or directory navigation (e.g. ".."). A path is *NOT* its own
205   // parent.
206   bool IsParent(const FilePath& child) const;
207 
208   // If IsParent(child) holds, appends to path (if non-NULL) the
209   // relative path to child and returns true.  For example, if parent
210   // holds "/Users/johndoe/Library/Application Support", child holds
211   // "/Users/johndoe/Library/Application Support/Google/Chrome/Default", and
212   // *path holds "/Users/johndoe/Library/Caches", then after
213   // parent.AppendRelativePath(child, path) is called *path will hold
214   // "/Users/johndoe/Library/Caches/Google/Chrome/Default".  Otherwise,
215   // returns false.
216   bool AppendRelativePath(const FilePath& child, FilePath* path) const;
217 
218   // Returns a FilePath corresponding to the directory containing the path
219   // named by this object, stripping away the file component.  If this object
220   // only contains one component, returns a FilePath identifying
221   // kCurrentDirectory.  If this object already refers to the root directory,
222   // returns a FilePath identifying the root directory.
223   FilePath DirName() const WARN_UNUSED_RESULT;
224 
225   // Returns a FilePath corresponding to the last path component of this
226   // object, either a file or a directory.  If this object already refers to
227   // the root directory, returns a FilePath identifying the root directory;
228   // this is the only situation in which BaseName will return an absolute path.
229   FilePath BaseName() const WARN_UNUSED_RESULT;
230 
231   // Returns ".jpg" for path "C:\pics\jojo.jpg", or an empty string if
232   // the file has no extension.  If non-empty, Extension() will always start
233   // with precisely one ".".  The following code should always work regardless
234   // of the value of path.  For common double-extensions like .tar.gz and
235   // .user.js, this method returns the combined extension.  For a single
236   // component, use FinalExtension().
237   // new_path = path.RemoveExtension().value().append(path.Extension());
238   // ASSERT(new_path == path.value());
239   // NOTE: this is different from the original file_util implementation which
240   // returned the extension without a leading "." ("jpg" instead of ".jpg")
241   StringType Extension() const;
242 
243   // Returns the path's file extension, as in Extension(), but will
244   // never return a double extension.
245   //
246   // TODO(davidben): Check all our extension-sensitive code to see if
247   // we can rename this to Extension() and the other to something like
248   // LongExtension(), defaulting to short extensions and leaving the
249   // long "extensions" to logic like base::GetUniquePathNumber().
250   StringType FinalExtension() const;
251 
252   // Returns "C:\pics\jojo" for path "C:\pics\jojo.jpg"
253   // NOTE: this is slightly different from the similar file_util implementation
254   // which returned simply 'jojo'.
255   FilePath RemoveExtension() const WARN_UNUSED_RESULT;
256 
257   // Removes the path's file extension, as in RemoveExtension(), but
258   // ignores double extensions.
259   FilePath RemoveFinalExtension() const WARN_UNUSED_RESULT;
260 
261   // Inserts |suffix| after the file name portion of |path| but before the
262   // extension.  Returns "" if BaseName() == "." or "..".
263   // Examples:
264   // path == "C:\pics\jojo.jpg" suffix == " (1)", returns "C:\pics\jojo (1).jpg"
265   // path == "jojo.jpg"         suffix == " (1)", returns "jojo (1).jpg"
266   // path == "C:\pics\jojo"     suffix == " (1)", returns "C:\pics\jojo (1)"
267   // path == "C:\pics.old\jojo" suffix == " (1)", returns "C:\pics.old\jojo (1)"
268   FilePath InsertBeforeExtension(
269       const StringType& suffix) const WARN_UNUSED_RESULT;
270   FilePath InsertBeforeExtensionASCII(
271       const base::StringPiece& suffix) const WARN_UNUSED_RESULT;
272 
273   // Adds |extension| to |file_name|. Returns the current FilePath if
274   // |extension| is empty. Returns "" if BaseName() == "." or "..".
275   FilePath AddExtension(
276       const StringType& extension) const WARN_UNUSED_RESULT;
277 
278   // Replaces the extension of |file_name| with |extension|.  If |file_name|
279   // does not have an extension, then |extension| is added.  If |extension| is
280   // empty, then the extension is removed from |file_name|.
281   // Returns "" if BaseName() == "." or "..".
282   FilePath ReplaceExtension(
283       const StringType& extension) const WARN_UNUSED_RESULT;
284 
285   // Returns true if the file path matches the specified extension. The test is
286   // case insensitive. Don't forget the leading period if appropriate.
287   bool MatchesExtension(const StringType& extension) const;
288 
289   // Returns a FilePath by appending a separator and the supplied path
290   // component to this object's path.  Append takes care to avoid adding
291   // excessive separators if this object's path already ends with a separator.
292   // If this object's path is kCurrentDirectory, a new FilePath corresponding
293   // only to |component| is returned.  |component| must be a relative path;
294   // it is an error to pass an absolute path.
295   FilePath Append(const StringType& component) const WARN_UNUSED_RESULT;
296   FilePath Append(const FilePath& component) const WARN_UNUSED_RESULT;
297 
298   // Although Windows StringType is std::wstring, since the encoding it uses for
299   // paths is well defined, it can handle ASCII path components as well.
300   // Mac uses UTF8, and since ASCII is a subset of that, it works there as well.
301   // On Linux, although it can use any 8-bit encoding for paths, we assume that
302   // ASCII is a valid subset, regardless of the encoding, since many operating
303   // system paths will always be ASCII.
304   FilePath AppendASCII(const base::StringPiece& component)
305       const WARN_UNUSED_RESULT;
306 
307   // Returns true if this FilePath contains an absolute path.  On Windows, an
308   // absolute path begins with either a drive letter specification followed by
309   // a separator character, or with two separator characters.  On POSIX
310   // platforms, an absolute path begins with a separator character.
311   bool IsAbsolute() const;
312 
313   // Returns true if the patch ends with a path separator character.
314   bool EndsWithSeparator() const WARN_UNUSED_RESULT;
315 
316   // Returns a copy of this FilePath that ends with a trailing separator. If
317   // the input path is empty, an empty FilePath will be returned.
318   FilePath AsEndingWithSeparator() const WARN_UNUSED_RESULT;
319 
320   // Returns a copy of this FilePath that does not end with a trailing
321   // separator.
322   FilePath StripTrailingSeparators() const WARN_UNUSED_RESULT;
323 
324   // Returns true if this FilePath contains an attempt to reference a parent
325   // directory (e.g. has a path component that is "..").
326   bool ReferencesParent() const;
327 
328   // Return a Unicode human-readable version of this path.
329   // Warning: you can *not*, in general, go from a display name back to a real
330   // path.  Only use this when displaying paths to users, not just when you
331   // want to stuff a string16 into some other API.
332   string16 LossyDisplayName() const;
333 
334   // Return the path as ASCII, or the empty string if the path is not ASCII.
335   // This should only be used for cases where the FilePath is representing a
336   // known-ASCII filename.
337   std::string MaybeAsASCII() const;
338 
339   // Return the path as UTF-8.
340   //
341   // This function is *unsafe* as there is no way to tell what encoding is
342   // used in file names on POSIX systems other than Mac and Chrome OS,
343   // although UTF-8 is practically used everywhere these days. To mitigate
344   // the encoding issue, this function internally calls
345   // SysNativeMBToWide() on POSIX systems other than Mac and Chrome OS,
346   // per assumption that the current locale's encoding is used in file
347   // names, but this isn't a perfect solution.
348   //
349   // Once it becomes safe to to stop caring about non-UTF-8 file names,
350   // the SysNativeMBToWide() hack will be removed from the code, along
351   // with "Unsafe" in the function name.
352   std::string AsUTF8Unsafe() const;
353 
354   // Similar to AsUTF8Unsafe, but returns UTF-16 instead.
355   string16 AsUTF16Unsafe() const;
356 
357   // Returns a FilePath object from a path name in UTF-8. This function
358   // should only be used for cases where you are sure that the input
359   // string is UTF-8.
360   //
361   // Like AsUTF8Unsafe(), this function is unsafe. This function
362   // internally calls SysWideToNativeMB() on POSIX systems other than Mac
363   // and Chrome OS, to mitigate the encoding issue. See the comment at
364   // AsUTF8Unsafe() for details.
365   static FilePath FromUTF8Unsafe(const std::string& utf8);
366 
367   // Similar to FromUTF8Unsafe, but accepts UTF-16 instead.
368   static FilePath FromUTF16Unsafe(const string16& utf16);
369 
370   void WriteToPickle(Pickle* pickle) const;
371   bool ReadFromPickle(PickleIterator* iter);
372 
373   // Normalize all path separators to backslash on Windows
374   // (if FILE_PATH_USES_WIN_SEPARATORS is true), or do nothing on POSIX systems.
375   FilePath NormalizePathSeparators() const;
376 
377   // Normalize all path separattors to given type on Windows
378   // (if FILE_PATH_USES_WIN_SEPARATORS is true), or do nothing on POSIX systems.
379   FilePath NormalizePathSeparatorsTo(CharType separator) const;
380 
381   // Compare two strings in the same way the file system does.
382   // Note that these always ignore case, even on file systems that are case-
383   // sensitive. If case-sensitive comparison is ever needed, add corresponding
384   // methods here.
385   // The methods are written as a static method so that they can also be used
386   // on parts of a file path, e.g., just the extension.
387   // CompareIgnoreCase() returns -1, 0 or 1 for less-than, equal-to and
388   // greater-than respectively.
389   static int CompareIgnoreCase(const StringType& string1,
390                                const StringType& string2);
CompareEqualIgnoreCase(const StringType & string1,const StringType & string2)391   static bool CompareEqualIgnoreCase(const StringType& string1,
392                                      const StringType& string2) {
393     return CompareIgnoreCase(string1, string2) == 0;
394   }
CompareLessIgnoreCase(const StringType & string1,const StringType & string2)395   static bool CompareLessIgnoreCase(const StringType& string1,
396                                     const StringType& string2) {
397     return CompareIgnoreCase(string1, string2) < 0;
398   }
399 
400 #if defined(OS_MACOSX)
401   // Returns the string in the special canonical decomposed form as defined for
402   // HFS, which is close to, but not quite, decomposition form D. See
403   // http://developer.apple.com/mac/library/technotes/tn/tn1150.html#UnicodeSubtleties
404   // for further comments.
405   // Returns the epmty string if the conversion failed.
406   static StringType GetHFSDecomposedForm(const FilePath::StringType& string);
407 
408   // Special UTF-8 version of FastUnicodeCompare. Cf:
409   // http://developer.apple.com/mac/library/technotes/tn/tn1150.html#StringComparisonAlgorithm
410   // IMPORTANT: The input strings must be in the special HFS decomposed form!
411   // (cf. above GetHFSDecomposedForm method)
412   static int HFSFastUnicodeCompare(const StringType& string1,
413                                    const StringType& string2);
414 #endif
415 
416 #if defined(OS_ANDROID)
417   // On android, file selection dialog can return a file with content uri
418   // scheme(starting with content://). Content uri needs to be opened with
419   // ContentResolver to guarantee that the app has appropriate permissions
420   // to access it.
421   // Returns true if the path is a content uri, or false otherwise.
422   bool IsContentUri() const;
423 #endif
424 
425  private:
426   // Remove trailing separators from this object.  If the path is absolute, it
427   // will never be stripped any more than to refer to the absolute root
428   // directory, so "////" will become "/", not "".  A leading pair of
429   // separators is never stripped, to support alternate roots.  This is used to
430   // support UNC paths on Windows.
431   void StripTrailingSeparatorsInternal();
432 
433   StringType path_;
434 };
435 
436 }  // namespace base
437 
438 // This is required by googletest to print a readable output on test failures.
439 BASE_EXPORT extern void PrintTo(const base::FilePath& path, std::ostream* out);
440 
441 // Macros for string literal initialization of FilePath::CharType[], and for
442 // using a FilePath::CharType[] in a printf-style format string.
443 #if defined(OS_POSIX)
444 #define FILE_PATH_LITERAL(x) x
445 #define PRFilePath "s"
446 #define PRFilePathLiteral "%s"
447 #elif defined(OS_WIN)
448 #define FILE_PATH_LITERAL(x) L ## x
449 #define PRFilePath "ls"
450 #define PRFilePathLiteral L"%ls"
451 #endif  // OS_WIN
452 
453 // Provide a hash function so that hash_sets and maps can contain FilePath
454 // objects.
455 namespace BASE_HASH_NAMESPACE {
456 #if defined(COMPILER_GCC)
457 
458 template<>
459 struct hash<base::FilePath> {
460   size_t operator()(const base::FilePath& f) const {
461     return hash<base::FilePath::StringType>()(f.value());
462   }
463 };
464 
465 #elif defined(COMPILER_MSVC)
466 
467 inline size_t hash_value(const base::FilePath& f) {
468   return hash_value(f.value());
469 }
470 
471 #endif  // COMPILER
472 
473 }  // namespace BASE_HASH_NAMESPACE
474 
475 #endif  // BASE_FILES_FILE_PATH_H_
476