text: // 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.
  
  // This file contains utility functions for dealing with the local
  // filesystem.
  
  #ifndef BASE_FILES_FILE_UTIL_H_
  #define BASE_FILES_FILE_UTIL_H_
  
  #include <stddef.h>
  #include <stdint.h>
  #include <stdio.h>
  
  #include <limits>
  #include <set>
  #include <string>
  #include <vector>
  
  #if defined(OS_POSIX) || defined(OS_FUCHSIA)
  #include <sys/stat.h>
  #include <unistd.h>
  #endif
  
  #include "base/base_export.h"
  #include "base/callback_forward.h"
  #include "base/containers/span.h"
  #include "base/files/file.h"
  #include "base/files/file_path.h"
  #include "base/files/scoped_file.h"
  #include "base/strings/string16.h"
  #include "build/build_config.h"
  
  #if defined(OS_WIN)
  #include "base/win/windows_types.h"
  #elif defined(OS_POSIX) || defined(OS_FUCHSIA)
  #include "base/file_descriptor_posix.h"
  #include "base/posix/eintr_wrapper.h"
  #endif
  
  namespace base {
  
  class Environment;
  class Time;
  
  //-----------------------------------------------------------------------------
  // Functions that involve filesystem access or modification:
  
  // Returns an absolute version of a relative path. Returns an empty path on
  // error. On POSIX, this function fails if the path does not exist. This
  // function can result in I/O so it can be slow.
  BASE_EXPORT FilePath MakeAbsoluteFilePath(const FilePath& input);
  
  // Returns the total number of bytes used by all the files under |root_path|.
  // If the path does not exist the function returns 0.
  //
  // This function is implemented using the FileEnumerator class so it is not
  // particularly speedy in any platform.
  BASE_EXPORT int64_t ComputeDirectorySize(const FilePath& root_path);
  
  // Deletes the given path, whether it's a file or a directory.
  // If it's a directory, it's perfectly happy to delete all of the directory's
  // contents, but it will not recursively delete subdirectories and their
  // contents.
  // Returns true if successful, false otherwise. It is considered successful to
  // attempt to delete a file that does not exist.
  //
  // In POSIX environment and if |path| is a symbolic link, this deletes only
  // the symlink. (even if the symlink points to a non-existent file)
  BASE_EXPORT bool DeleteFile(const FilePath& path);
  
  // Deletes the given path, whether it's a file or a directory.
  // If it's a directory, it's perfectly happy to delete all of the
  // directory's contents, including subdirectories and their contents.
  // Returns true if successful, false otherwise. It is considered successful
  // to attempt to delete a file that does not exist.
  //
  // In POSIX environment and if |path| is a symbolic link, this deletes only
  // the symlink. (even if the symlink points to a non-existent file)
  //
  // WARNING: USING THIS EQUIVALENT TO "rm -rf", SO USE WITH CAUTION.
  // TODO(thestig): Rename to DeletePathRecursively().
  BASE_EXPORT bool DeleteFileRecursively(const FilePath& path);
  
  // DEPRECATED. Please use the functions immediately above.
  // https://crbug.com/1009837
  //
  // Deletes the given path, whether it's a file or a directory.
  // If it's a directory, it's perfectly happy to delete all of the
  // directory's contents.  Passing true to recursively delete
  // subdirectories and their contents as well.
  // Returns true if successful, false otherwise. It is considered successful
  // to attempt to delete a file that does not exist.
  //
  // In POSIX environment and if |path| is a symbolic link, this deletes only
  // the symlink. (even if the symlink points to a non-existent file)
  //
  // WARNING: USING THIS WITH recursive==true IS EQUIVALENT
  //          TO "rm -rf", SO USE WITH CAUTION.
  BASE_EXPORT bool DeleteFile(const FilePath& path, bool recursive);
  
  // Simplified way to get a callback to do DeleteFile(path) and ignore the
  // DeleteFile() result.
  BASE_EXPORT OnceCallback<void(const FilePath&)> GetDeleteFileCallback();
  
  // Simplified way to get a callback to do DeleteFileRecursively(path) and ignore
  // the DeleteFileRecursively() result.
  BASE_EXPORT OnceCallback<void(const FilePath&)>
  GetDeletePathRecursivelyCallback();
  
  #if defined(OS_WIN)
  // Schedules to delete the given path, whether it's a file or a directory, until
  // the operating system is restarted.
  // Note:
  // 1) The file/directory to be deleted should exist in a temp folder.
  // 2) The directory to be deleted must be empty.
  BASE_EXPORT bool DeleteFileAfterReboot(const FilePath& path);
  #endif
  
  // Moves the given path, whether it's a file or a directory.
  // If a simple rename is not possible, such as in the case where the paths are
  // on different volumes, this will attempt to copy and delete. Returns
  // true for success.
  // This function fails if either path contains traversal components ('..').
  BASE_EXPORT bool Move(const FilePath& from_path, const FilePath& to_path);
  
  // Renames file |from_path| to |to_path|. Both paths must be on the same
  // volume, or the function will fail. Destination file will be created
  // if it doesn't exist. Prefer this function over Move when dealing with
  // temporary files. On Windows it preserves attributes of the target file.
  // Returns true on success, leaving *error unchanged.
  // Returns false on failure and sets *error appropriately, if it is non-NULL.
  BASE_EXPORT bool ReplaceFile(const FilePath& from_path,
                               const FilePath& to_path,
                               File::Error* error);
  
  // Copies a single file. Use CopyDirectory() to copy directories.
  // This function fails if either path contains traversal components ('..').
  // This function also fails if |to_path| is a directory.
  //
  // On POSIX, if |to_path| is a symlink, CopyFile() will follow the symlink. This
  // may have security implications. Use with care.
  //
  // If |to_path| already exists and is a regular file, it will be overwritten,
  // though its permissions will stay the same.
  //
  // If |to_path| does not exist, it will be created. The new file's permissions
  // varies per platform:
  //
  // - This function keeps the metadata on Windows. The read only bit is not kept.
  // - On Mac and iOS, |to_path| retains |from_path|'s permissions, except user
  //   read/write permissions are always set.
  // - On Linux and Android, |to_path| has user read/write permissions only. i.e.
  //   Always 0600.
  // - On ChromeOS, |to_path| has user read/write permissions and group/others
  //   read permissions. i.e. Always 0644.
  BASE_EXPORT bool CopyFile(const FilePath& from_path, const FilePath& to_path);
  
  // Copies the given path, and optionally all subdirectories and their contents
  // as well.
  //
  // If there are files existing under to_path, always overwrite. Returns true
  // if successful, false otherwise. Wildcards on the names are not supported.
  //
  // This function has the same metadata behavior as CopyFile().
  //
  // If you only need to copy a file use CopyFile, it's faster.
  BASE_EXPORT bool CopyDirectory(const FilePath& from_path,
                                 const FilePath& to_path,
                                 bool recursive);
  
  // Like CopyDirectory() except trying to overwrite an existing file will not
  // work and will return false.
  BASE_EXPORT bool CopyDirectoryExcl(const FilePath& from_path,
                                     const FilePath& to_path,
                                     bool recursive);
  
  // Returns true if the given path exists on the local filesystem,
  // false otherwise.
  BASE_EXPORT bool PathExists(const FilePath& path);
  
  // Returns true if the given path is writable by the user, false otherwise.
  BASE_EXPORT bool PathIsWritable(const FilePath& path);
  
  // Returns true if the given path exists and is a directory, false otherwise.
  BASE_EXPORT bool DirectoryExists(const FilePath& path);
  
  // Returns true if the contents of the two files given are equal, false
  // otherwise.  If either file can't be read, returns false.
  BASE_EXPORT bool ContentsEqual(const FilePath& filename1,
                                 const FilePath& filename2);
  
  // Returns true if the contents of the two text files given are equal, false
  // otherwise.  This routine treats "\r\n" and "\n" as equivalent.
  BASE_EXPORT bool TextContentsEqual(const FilePath& filename1,
                                     const FilePath& filename2);
  
  // Reads the file at |path| into |contents| and returns true on success and
  // false on error.  For security reasons, a |path| containing path traversal
  // components ('..') is treated as a read error and |contents| is set to empty.
  // In case of I/O error, |contents| holds the data that could be read from the
  // file before the error occurred.
  // |contents| may be NULL, in which case this function is useful for its side
  // effect of priming the disk cache (could be used for unit tests).
  BASE_EXPORT bool ReadFileToString(const FilePath& path, std::string* contents);
  
  // Reads the file at |path| into |contents| and returns true on success and
  // false on error.  For security reasons, a |path| containing path traversal
  // components ('..') is treated as a read error and |contents| is set to empty.
  // In case of I/O error, |contents| holds the data that could be read from the
  // file before the error occurred.  When the file size exceeds |max_size|, the
  // function returns false with |contents| holding the file truncated to
  // |max_size|.
  // |contents| may be NULL, in which case this function is useful for its side
  // effect of priming the disk cache (could be used for unit tests).
  BASE_EXPORT bool ReadFileToStringWithMaxSize(const FilePath& path,
                                               std::string* contents,
                                               size_t max_size);
  
  // As ReadFileToString, but reading from an open stream after seeking to its
  // start (if supported by the stream).
  BASE_EXPORT bool ReadStreamToString(FILE* stream, std::string* contents);
  
  // As ReadFileToStringWithMaxSize, but reading from an open stream after seeking
  // to its start (if supported by the stream).
  BASE_EXPORT bool ReadStreamToStringWithMaxSize(FILE* stream,
                                                 size_t max_size,
                                                 std::string* contents);
  
  #if defined(OS_POSIX) || defined(OS_FUCHSIA)
  
  // Read exactly |bytes| bytes from file descriptor |fd|, storing the result
  // in |buffer|. This function is protected against EINTR and partial reads.
  // Returns true iff |bytes| bytes have been successfully read from |fd|.
  BASE_EXPORT bool ReadFromFD(int fd, char* buffer, size_t bytes);
  
  // Performs the same function as CreateAndOpenTemporaryStreamInDir(), but
  // returns the file-descriptor wrapped in a ScopedFD, rather than the stream
  // wrapped in a ScopedFILE.
  BASE_EXPORT ScopedFD CreateAndOpenFdForTemporaryFileInDir(const FilePath& dir,
                                                            FilePath* path);
  
  #endif  // defined(OS_POSIX) || defined(OS_FUCHSIA)
  
  #if defined(OS_POSIX)
  
  // ReadFileToStringNonBlocking is identical to ReadFileToString except it
  // guarantees that it will not block. This guarantee is provided on POSIX by
  // opening the file as O_NONBLOCK. This variant should only be used on files
  // which are guaranteed not to block (such as kernel files). Or in situations
  // where a partial read would be acceptable because the backing store returned
  // EWOULDBLOCK.
  BASE_EXPORT bool ReadFileToStringNonBlocking(const base::FilePath& file,
                                               std::string* ret);
  
  // Creates a symbolic link at |symlink| pointing to |target|.  Returns
  // false on failure.
  BASE_EXPORT bool CreateSymbolicLink(const FilePath& target,
                                      const FilePath& symlink);
  
  // Reads the given |symlink| and returns where it points to in |target|.
  // Returns false upon failure.
  BASE_EXPORT bool ReadSymbolicLink(const FilePath& symlink, FilePath* target);
  
  // Bits and masks of the file permission.
  enum FilePermissionBits {
    FILE_PERMISSION_MASK              = S_IRWXU | S_IRWXG | S_IRWXO,
    FILE_PERMISSION_USER_MASK         = S_IRWXU,
    FILE_PERMISSION_GROUP_MASK        = S_IRWXG,
    FILE_PERMISSION_OTHERS_MASK       = S_IRWXO,
  
    FILE_PERMISSION_READ_BY_USER      = S_IRUSR,
    FILE_PERMISSION_WRITE_BY_USER     = S_IWUSR,
    FILE_PERMISSION_EXECUTE_BY_USER   = S_IXUSR,
    FILE_PERMISSION_READ_BY_GROUP     = S_IRGRP,
    FILE_PERMISSION_WRITE_BY_GROUP    = S_IWGRP,
    FILE_PERMISSION_EXECUTE_BY_GROUP  = S_IXGRP,
    FILE_PERMISSION_READ_BY_OTHERS    = S_IROTH,
    FILE_PERMISSION_WRITE_BY_OTHERS   = S_IWOTH,
    FILE_PERMISSION_EXECUTE_BY_OTHERS = S_IXOTH,
  };
  
  // Reads the permission of the given |path|, storing the file permission
  // bits in |mode|. If |path| is symbolic link, |mode| is the permission of
  // a file which the symlink points to.
  BASE_EXPORT bool GetPosixFilePermissions(const FilePath& path, int* mode);
  // Sets the permission of the given |path|. If |path| is symbolic link, sets
  // the permission of a file which the symlink points to.
  BASE_EXPORT bool SetPosixFilePermissions(const FilePath& path, int mode);
  
  // Returns true iff |executable| can be found in any directory specified by the
  // environment variable in |env|.
  BASE_EXPORT bool ExecutableExistsInPath(Environment* env,
                                          const FilePath::StringType& executable);
  
  #if defined(OS_LINUX) || defined(OS_AIX)
  // Determine if files under a given |path| can be mapped and then mprotect'd
  // PROT_EXEC. This depends on the mount options used for |path|, which vary
  // among different Linux distributions and possibly local configuration. It also
  // depends on details of kernel--ChromeOS uses the noexec option for /dev/shm
  // but its kernel allows mprotect with PROT_EXEC anyway.
  BASE_EXPORT bool IsPathExecutable(const FilePath& path);
  #endif  // OS_LINUX || OS_AIX
  
  #endif  // OS_POSIX
  
  // Returns true if the given directory is empty
  BASE_EXPORT bool IsDirectoryEmpty(const FilePath& dir_path);
  
  // Get the temporary directory provided by the system.
  //
  // WARNING: In general, you should use CreateTemporaryFile variants below
  // instead of this function. Those variants will ensure that the proper
  // permissions are set so that other users on the system can't edit them while
  // they're open (which can lead to security issues).
  BASE_EXPORT bool GetTempDir(FilePath* path);
  
  // Get the home directory. This is more complicated than just getenv("HOME")
  // as it knows to fall back on getpwent() etc.
  //
  // You should not generally call this directly. Instead use DIR_HOME with the
  // path service which will use this function but cache the value.
  // Path service may also override DIR_HOME.
  BASE_EXPORT FilePath GetHomeDir();
  
  // Returns a new temporary file in |dir| with a unique name. The file is opened
  // for exclusive read, write, and delete access (note: exclusivity is unique to
  // Windows). On Windows, the returned file supports File::DeleteOnClose.
  // On success, |temp_file| is populated with the full path to the created file.
  BASE_EXPORT File CreateAndOpenTemporaryFileInDir(const FilePath& dir,
                                                   FilePath* temp_file);
  
  // Creates a temporary file. The full path is placed in |path|, and the
  // function returns true if was successful in creating the file. The file will
  // be empty and all handles closed after this function returns.
  BASE_EXPORT bool CreateTemporaryFile(FilePath* path);
  
  // Same as CreateTemporaryFile but the file is created in |dir|.
  BASE_EXPORT bool CreateTemporaryFileInDir(const FilePath& dir,
                                            FilePath* temp_file);
  
  // Create and open a temporary file stream for exclusive read, write, and delete
  // access (note: exclusivity is unique to Windows). The full path is placed in
  // |path|. Returns the opened file stream, or null in case of error.
  BASE_EXPORT ScopedFILE CreateAndOpenTemporaryStream(FilePath* path);
  
  // Similar to CreateAndOpenTemporaryStream, but the file is created in |dir|.
  BASE_EXPORT ScopedFILE CreateAndOpenTemporaryStreamInDir(const FilePath& dir,
                                                           FilePath* path);
  
  // Create a new directory. If prefix is provided, the new directory name is in
  // the format of prefixyyyy.
  // NOTE: prefix is ignored in the POSIX implementation.
  // If success, return true and output the full path of the directory created.
  BASE_EXPORT bool CreateNewTempDirectory(const FilePath::StringType& prefix,
                                          FilePath* new_temp_path);
  
  // Create a directory within another directory.
  // Extra characters will be appended to |prefix| to ensure that the
  // new directory does not have the same name as an existing directory.
  BASE_EXPORT bool CreateTemporaryDirInDir(const FilePath& base_dir,
                                           const FilePath::StringType& prefix,
                                           FilePath* new_dir);
  
  // Creates a directory, as well as creating any parent directories, if they
  // don't exist. Returns 'true' on successful creation, or if the directory
  // already exists.  The directory is only readable by the current user.
  // Returns true on success, leaving *error unchanged.
  // Returns false on failure and sets *error appropriately, if it is non-NULL.
  BASE_EXPORT bool CreateDirectoryAndGetError(const FilePath& full_path,
                                              File::Error* error);
  
  // Backward-compatible convenience method for the above.
  BASE_EXPORT bool CreateDirectory(const FilePath& full_path);
  
  // Returns the file size. Returns true on success.
  BASE_EXPORT bool GetFileSize(const FilePath& file_path, int64_t* file_size);
  
  // Sets |real_path| to |path| with symbolic links and junctions expanded.
  // On windows, make sure the path starts with a lettered drive.
  // |path| must reference a file.  Function will fail if |path| points to
  // a directory or to a nonexistent path.  On windows, this function will
  // fail if |real_path| would be longer than MAX_PATH characters.
  BASE_EXPORT bool NormalizeFilePath(const FilePath& path, FilePath* real_path);
  
  #if defined(OS_WIN)
  
  // Given a path in NT native form ("\Device\HarddiskVolumeXX\..."),
  // return in |drive_letter_path| the equivalent path that starts with
  // a drive letter ("C:\...").  Return false if no such path exists.
  BASE_EXPORT bool DevicePathToDriveLetterPath(const FilePath& device_path,
                                               FilePath* drive_letter_path);
  
  // Method that wraps the win32 GetLongPathName API, normalizing the specified
  // path to its long form. An example where this is needed is when comparing
  // temp file paths. If a username isn't a valid 8.3 short file name (even just a
  // lengthy name like "user with long name"), Windows will set the TMP and TEMP
  // environment variables to be 8.3 paths. ::GetTempPath (called in
  // base::GetTempDir) just uses the value specified by TMP or TEMP, and so can
  // return a short path. Returns an empty path on error.
  BASE_EXPORT FilePath MakeLongFilePath(const FilePath& input);
  
  // Creates a hard link named |to_file| to the file |from_file|. Both paths
  // must be on the same volume, and |from_file| may not name a directory.
  // Returns true if the hard link is created, false if it fails.
  BASE_EXPORT bool CreateWinHardLink(const FilePath& to_file,
                                     const FilePath& from_file);
  #endif
  
  // This function will return if the given file is a symlink or not.
  BASE_EXPORT bool IsLink(const FilePath& file_path);
  
  // Returns information about the given file path.
  BASE_EXPORT bool GetFileInfo(const FilePath& file_path, File::Info* info);
  
  // Sets the time of the last access and the time of the last modification.
  BASE_EXPORT bool TouchFile(const FilePath& path,
                             const Time& last_accessed,
                             const Time& last_modified);
  
  // Wrapper for fopen-like calls. Returns non-NULL FILE* on success. The
  // underlying file descriptor (POSIX) or handle (Windows) is unconditionally
  // configured to not be propagated to child processes.
  BASE_EXPORT FILE* OpenFile(const FilePath& filename, const char* mode);
  
  // Closes file opened by OpenFile. Returns true on success.
  BASE_EXPORT bool CloseFile(FILE* file);
  
  // Associates a standard FILE stream with an existing File. Note that this
  // functions take ownership of the existing File.
  BASE_EXPORT FILE* FileToFILE(File file, const char* mode);
  
  // Returns a new handle to the file underlying |file_stream|.
  BASE_EXPORT File FILEToFile(FILE* file_stream);
  
  // Truncates an open file to end at the location of the current file pointer.
  // This is a cross-platform analog to Windows' SetEndOfFile() function.
  BASE_EXPORT bool TruncateFile(FILE* file);
  
  // Reads at most the given number of bytes from the file into the buffer.
  // Returns the number of read bytes, or -1 on error.
  BASE_EXPORT int ReadFile(const FilePath& filename, char* data, int max_size);
  
  // Writes the given buffer into the file, overwriting any data that was
  // previously there.  Returns the number of bytes written, or -1 on error.
  // If file doesn't exist, it gets created with read/write permissions for all.
  // Note that the other variants of WriteFile() below may be easier to use.
  BASE_EXPORT int WriteFile(const FilePath& filename, const char* data,
                            int size);
  
  // Writes |data| into the file, overwriting any data that was previously there.
  // Returns true if and only if all of |data| was written. If the file does not
  // exist, it gets created with read/write permissions for all.
  BASE_EXPORT bool WriteFile(const FilePath& filename, span<const uint8_t> data);
  
  // Another WriteFile() variant that takes a StringPiece so callers don't have to
  // do manual conversions from a char span to a uint8_t span.
  BASE_EXPORT bool WriteFile(const FilePath& filename, StringPiece data);
  
  #if defined(OS_POSIX) || defined(OS_FUCHSIA)
  // Appends |data| to |fd|. Does not close |fd| when done.  Returns true iff
  // |size| bytes of |data| were written to |fd|.
  BASE_EXPORT bool WriteFileDescriptor(const int fd, const char* data, int size);
  
  // Allocates disk space for the file referred to by |fd| for the byte range
  // starting at |offset| and continuing for |size| bytes. The file size will be
  // changed if |offset|+|len| is greater than the file size. Zeros will fill the
  // new space.
  // After a successful call, subsequent writes into the specified range are
  // guaranteed not to fail because of lack of disk space.
  BASE_EXPORT bool AllocateFileRegion(File* file, int64_t offset, size_t size);
  #endif
  
  // Appends |data| to |filename|.  Returns true iff |size| bytes of |data| were
  // written to |filename|.
  BASE_EXPORT bool AppendToFile(const FilePath& filename,
                                const char* data,
                                int size);
  
  // Gets the current working directory for the process.
  BASE_EXPORT bool GetCurrentDirectory(FilePath* path);
  
  // Sets the current working directory for the process.
  BASE_EXPORT bool SetCurrentDirectory(const FilePath& path);
  
  // The largest value attempted by GetUniquePath{Number,}.
  enum { kMaxUniqueFiles = 100 };
  
  // Returns the number N that makes |path| unique when formatted as " (N)" in a
  // suffix to its basename before any file extension, where N is a number between
  // 1 and 100 (inclusive). Returns 0 if |path| does not exist (meaning that it is
  // unique as-is), or -1 if no such number can be found.
  BASE_EXPORT int GetUniquePathNumber(const FilePath& path);
  
  // Returns |path| if it does not exist. Otherwise, returns |path| with the
  // suffix " (N)" appended to its basename before any file extension, where N is
  // a number between 1 and 100 (inclusive). Returns an empty path if no such
  // number can be found.
  BASE_EXPORT FilePath GetUniquePath(const FilePath& path);
  
  // Sets the given |fd| to non-blocking mode.
  // Returns true if it was able to set it in the non-blocking mode, otherwise
  // false.
  BASE_EXPORT bool SetNonBlocking(int fd);
  
  // Hints the OS to prefetch the first |max_bytes| of |file_path| into its cache.
  //
  // If called at the appropriate time, this can reduce the latency incurred by
  // feature code that needs to read the file.
  //
  // |max_bytes| specifies how many bytes should be pre-fetched. It may exceed the
  // file's size. Passing in std::numeric_limits<int64_t>::max() is a convenient
  // way to get the entire file pre-fetched.
  //
  // |is_executable| specifies whether the file is to be prefetched as
  // executable code or as data. Windows treats the file backed pages in RAM
  // differently, and specifying the wrong value results in two copies in RAM.
  //
  // Returns false if prefetching definitely failed. A return value of true does
  // not guarantee that the entire desired range was prefetched.
  //
  // Calling this before using ::LoadLibrary() on Windows is more efficient memory
  // wise, but we must be sure no other threads try to LoadLibrary() the file
  // while we are doing the mapping and prefetching, or the process will get a
  // private copy of the DLL via COW.
  BASE_EXPORT bool PreReadFile(
      const FilePath& file_path,
      bool is_executable,
      int64_t max_bytes = std::numeric_limits<int64_t>::max());
  
  #if defined(OS_POSIX) || defined(OS_FUCHSIA)
  
  // Creates a pipe. Returns true on success, otherwise false.
  // On success, |read_fd| will be set to the fd of the read side, and
  // |write_fd| will be set to the one of write side. If |non_blocking|
  // is set the pipe will be created with O_NONBLOCK|O_CLOEXEC flags set
  // otherwise flag is set to zero (default).
  BASE_EXPORT bool CreatePipe(ScopedFD* read_fd,
                              ScopedFD* write_fd,
                              bool non_blocking = false);
  
  // Creates a non-blocking, close-on-exec pipe.
  // This creates a non-blocking pipe that is not intended to be shared with any
  // child process. This will be done atomically if the operating system supports
  // it. Returns true if it was able to create the pipe, otherwise false.
  BASE_EXPORT bool CreateLocalNonBlockingPipe(int fds[2]);
  
  // Sets the given |fd| to close-on-exec mode.
  // Returns true if it was able to set it in the close-on-exec mode, otherwise
  // false.
  BASE_EXPORT bool SetCloseOnExec(int fd);
  
  // Test that |path| can only be changed by a given user and members of
  // a given set of groups.
  // Specifically, test that all parts of |path| under (and including) |base|:
  // * Exist.
  // * Are owned by a specific user.
  // * Are not writable by all users.
  // * Are owned by a member of a given set of groups, or are not writable by
  //   their group.
  // * Are not symbolic links.
  // This is useful for checking that a config file is administrator-controlled.
  // |base| must contain |path|.
  BASE_EXPORT bool VerifyPathControlledByUser(const base::FilePath& base,
                                              const base::FilePath& path,
                                              uid_t owner_uid,
                                              const std::set<gid_t>& group_gids);
  #endif  // defined(OS_POSIX) || defined(OS_FUCHSIA)
  
  #if defined(OS_MACOSX) && !defined(OS_IOS)
  // Is |path| writable only by a user with administrator privileges?
  // This function uses Mac OS conventions.  The super user is assumed to have
  // uid 0, and the administrator group is assumed to be named "admin".
  // Testing that |path|, and every parent directory including the root of
  // the filesystem, are owned by the superuser, controlled by the group
  // "admin", are not writable by all users, and contain no symbolic links.
  // Will return false if |path| does not exist.
  BASE_EXPORT bool VerifyPathControlledByAdmin(const base::FilePath& path);
  #endif  // defined(OS_MACOSX) && !defined(OS_IOS)
  
  // Returns the maximum length of path component on the volume containing
  // the directory |path|, in the number of FilePath::CharType, or -1 on failure.
  BASE_EXPORT int GetMaximumPathComponentLength(const base::FilePath& path);
  
  #if defined(OS_LINUX) || defined(OS_AIX)
  // Broad categories of file systems as returned by statfs() on Linux.
  enum FileSystemType {
    FILE_SYSTEM_UNKNOWN,  // statfs failed.
    FILE_SYSTEM_0,        // statfs.f_type == 0 means unknown, may indicate AFS.
    FILE_SYSTEM_ORDINARY,       // on-disk filesystem like ext2
    FILE_SYSTEM_NFS,
    FILE_SYSTEM_SMB,
    FILE_SYSTEM_CODA,
    FILE_SYSTEM_MEMORY,         // in-memory file system
    FILE_SYSTEM_CGROUP,         // cgroup control.
    FILE_SYSTEM_OTHER,          // any other value.
    FILE_SYSTEM_TYPE_COUNT
  };
  
  // Attempts determine the FileSystemType for |path|.
  // Returns false if |path| doesn't exist.
  BASE_EXPORT bool GetFileSystemType(const FilePath& path, FileSystemType* type);
  #endif
  
  #if defined(OS_POSIX) || defined(OS_FUCHSIA)
  // Get a temporary directory for shared memory files. The directory may depend
  // on whether the destination is intended for executable files, which in turn
  // depends on how /dev/shmem was mounted. As a result, you must supply whether
  // you intend to create executable shmem segments so this function can find
  // an appropriate location.
  BASE_EXPORT bool GetShmemTempDir(bool executable, FilePath* path);
  #endif
  
  // Internal --------------------------------------------------------------------
  
  namespace internal {
  
  // Same as Move but allows paths with traversal components.
  // Use only with extreme care.
  BASE_EXPORT bool MoveUnsafe(const FilePath& from_path,
                              const FilePath& to_path);
  
  #if defined(OS_WIN)
  // Copy from_path to to_path recursively and then delete from_path recursively.
  // Returns true if all operations succeed.
  // This function simulates Move(), but unlike Move() it works across volumes.
  // This function is not transactional.
  BASE_EXPORT bool CopyAndDeleteDirectory(const FilePath& from_path,
                                          const FilePath& to_path);
  #endif  // defined(OS_WIN)
  
  // Used by PreReadFile() when no kernel support for prefetching is available.
  bool PreReadFileSlow(const FilePath& file_path, int64_t max_bytes);
  
  }  // namespace internal
  }  // namespace base
  
  #endif  // BASE_FILES_FILE_UTIL_H_
  