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 <set>
  #include <string>
  #include <vector>
  
  #include "base/base_export.h"
  #include "base/files/file.h"
  #include "base/files/file_path.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)
  #include <sys/stat.h>
  #include <unistd.h>
  #endif
  
  #if defined(OS_POSIX)
  #include "base/file_descriptor_posix.h"
  #include "base/logging.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.  Passing true to recursive deletes
  // 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);
  
  #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);
  
  #if defined(OS_POSIX)
  
  // 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 CreateAndOpenTemporaryFileInDir(), but returns
  // the file-descriptor directly, rather than wrapping it into a FILE. Returns
  // -1 on failure.
  BASE_EXPORT int CreateAndOpenFdForTemporaryFileInDir(const FilePath& dir,
                                                       FilePath* path);
  
  // The following functions use POSIX functionality that isn't supported by
  // Fuchsia.
  #if !defined(OS_FUCHSIA)
  
  // 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);
  
  #endif  // !OS_FUCHSIA
  #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();
  
  // 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.  File is opened for read/write.
  // The full path is placed in |path|.
  // Returns a handle to the opened file or NULL if an error occurred.
  BASE_EXPORT FILE* CreateAndOpenTemporaryFile(FilePath* path);
  
  // Similar to CreateAndOpenTemporaryFile, but the file is created in |dir|.
  BASE_EXPORT FILE* CreateAndOpenTemporaryFileInDir(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 |path| is a junction or symlink that points to an empty file,
  // or 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);
  
  // Given an existing file in |path|, set |real_path| to the path
  // in native NT format, of the form "\Device\HarddiskVolumeXX\..".
  // Returns false if the path can not be found. Empty files cannot
  // be resolved with this function.
  BASE_EXPORT bool NormalizeToNativeFilePath(const FilePath& path,
                                             FilePath* nt_path);
  #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);
  
  // 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.
  BASE_EXPORT int WriteFile(const FilePath& filename, const char* data,
                            int size);
  
  #if defined(OS_POSIX)
  // 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);
  #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);
  
  // Attempts to find a number that can be appended to the |path| to make it
  // unique. If |path| does not exist, 0 is returned.  If it fails to find such
  // a number, -1 is returned. If |suffix| is not empty, also checks the
  // existence of it with the given suffix.
  BASE_EXPORT int GetUniquePathNumber(const FilePath& path,
                                      const FilePath::StringType& suffix);
  
  // 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);
  
  #if defined(OS_POSIX)
  // 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)
  
  #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)
  // 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)
  
  }  // namespace internal
  }  // namespace base
  
  #endif  // BASE_FILES_FILE_UTIL_H_
  