Subversion Repositories QNX 8.QNX8 LLVM/Clang compiler suite

//===- llvm/Support/FileSystem.h - File System OS Concept -------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file declares the llvm::sys::fs namespace. It is designed after

// TR2/boost filesystem (v3), but modified to remove exception handling and the

// path class.

//

// All functions return an error_code and their actual work via the last out

// argument. The out argument is defined if and only if errc::success is

// returned. A function may return any error code in the generic or system

// category. However, they shall be equivalent to any error conditions listed

// in each functions respective documentation if the condition applies. [ note:

// this does not guarantee that error_code will be in the set of explicitly

// listed codes, but it does guarantee that if any of the explicitly listed

// errors occur, the correct error_code will be used ]. All functions may

// return errc::not_enough_memory if there is not enough memory to complete the

// operation.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_SUPPORT_FILESYSTEM_H

#define LLVM_SUPPORT_FILESYSTEM_H

#include "llvm/ADT/SmallString.h"

#include "llvm/ADT/StringRef.h"

#include "llvm/ADT/Twine.h"

#include "llvm/Config/llvm-config.h"

#include "llvm/Support/Chrono.h"

#include "llvm/Support/Error.h"

#include "llvm/Support/ErrorHandling.h"

#include "llvm/Support/ErrorOr.h"

#include "llvm/Support/FileSystem/UniqueID.h"

#include "llvm/Support/MD5.h"

#include <cassert>

#include <cstdint>

#include <ctime>

#include <memory>

#include <stack>

#include <string>

#include <system_error>

#include <vector>

#ifdef HAVE_SYS_STAT_H

#include <sys/stat.h>

#endif

namespace llvm {

namespace sys {

namespace fs {

#if defined(_WIN32)

// A Win32 HANDLE is a typedef of void*

using file_t = void *;

#else

using file_t = int;

#endif

extern const file_t kInvalidFile;

/// An enumeration for the file system's view of the type.

enum class file_type {

  status_error,

  file_not_found,

  regular_file,

  directory_file,

  symlink_file,

  block_file,

  character_file,

  fifo_file,

  socket_file,

  type_unknown

};

/// space_info - Self explanatory.

struct space_info {

  uint64_t capacity;

  uint64_t free;

  uint64_t available;

};

enum perms {

  no_perms = 0,

  owner_read = 0400,

  owner_write = 0200,

  owner_exe = 0100,

  owner_all = owner_read | owner_write | owner_exe,

  group_read = 040,

  group_write = 020,

  group_exe = 010,

  group_all = group_read | group_write | group_exe,

  others_read = 04,

  others_write = 02,

  others_exe = 01,

  others_all = others_read | others_write | others_exe,

  all_read = owner_read | group_read | others_read,

  all_write = owner_write | group_write | others_write,

  all_exe = owner_exe | group_exe | others_exe,

  all_all = owner_all | group_all | others_all,

  set_uid_on_exe = 04000,

  set_gid_on_exe = 02000,

  sticky_bit = 01000,

  all_perms = all_all | set_uid_on_exe | set_gid_on_exe | sticky_bit,

  perms_not_known = 0xFFFF

};

// Helper functions so that you can use & and | to manipulate perms bits:

inline perms operator|(perms l, perms r) {

  return static_cast<perms>(static_cast<unsigned short>(l) |

                            static_cast<unsigned short>(r));

}

inline perms operator&(perms l, perms r) {

  return static_cast<perms>(static_cast<unsigned short>(l) &

                            static_cast<unsigned short>(r));

}

inline perms &operator|=(perms &l, perms r) {

  l = l | r;

  return l;

}

inline perms &operator&=(perms &l, perms r) {

  l = l & r;

  return l;

}

inline perms operator~(perms x) {

  // Avoid UB by explicitly truncating the (unsigned) ~ result.

  return static_cast<perms>(

      static_cast<unsigned short>(~static_cast<unsigned short>(x)));

}

/// Represents the result of a call to directory_iterator::status(). This is a

/// subset of the information returned by a regular sys::fs::status() call, and

/// represents the information provided by Windows FileFirstFile/FindNextFile.

class basic_file_status {

protected:

  #if defined(LLVM_ON_UNIX)

  time_t fs_st_atime = 0;

  time_t fs_st_mtime = 0;

  uint32_t fs_st_atime_nsec = 0;

  uint32_t fs_st_mtime_nsec = 0;

  uid_t fs_st_uid = 0;

  gid_t fs_st_gid = 0;

  off_t fs_st_size = 0;

  #elif defined (_WIN32)

  uint32_t LastAccessedTimeHigh = 0;

  uint32_t LastAccessedTimeLow = 0;

  uint32_t LastWriteTimeHigh = 0;

  uint32_t LastWriteTimeLow = 0;

  uint32_t FileSizeHigh = 0;

  uint32_t FileSizeLow = 0;

  #endif

  file_type Type = file_type::status_error;

  perms Perms = perms_not_known;

public:

  basic_file_status() = default;

  explicit basic_file_status(file_type Type) : Type(Type) {}

  #if defined(LLVM_ON_UNIX)

  basic_file_status(file_type Type, perms Perms, time_t ATime,

                    uint32_t ATimeNSec, time_t MTime, uint32_t MTimeNSec,

                    uid_t UID, gid_t GID, off_t Size)

      : fs_st_atime(ATime), fs_st_mtime(MTime),

        fs_st_atime_nsec(ATimeNSec), fs_st_mtime_nsec(MTimeNSec),

        fs_st_uid(UID), fs_st_gid(GID),

        fs_st_size(Size), Type(Type), Perms(Perms) {}

#elif defined(_WIN32)

  basic_file_status(file_type Type, perms Perms, uint32_t LastAccessTimeHigh,

                    uint32_t LastAccessTimeLow, uint32_t LastWriteTimeHigh,

                    uint32_t LastWriteTimeLow, uint32_t FileSizeHigh,

                    uint32_t FileSizeLow)

      : LastAccessedTimeHigh(LastAccessTimeHigh),

        LastAccessedTimeLow(LastAccessTimeLow),

        LastWriteTimeHigh(LastWriteTimeHigh),

        LastWriteTimeLow(LastWriteTimeLow), FileSizeHigh(FileSizeHigh),

        FileSizeLow(FileSizeLow), Type(Type), Perms(Perms) {}

  #endif

  // getters

  file_type type() const { return Type; }

  perms permissions() const { return Perms; }

  /// The file access time as reported from the underlying file system.

  ///

  /// Also see comments on \c getLastModificationTime() related to the precision

  /// of the returned value.

  TimePoint<> getLastAccessedTime() const;

  /// The file modification time as reported from the underlying file system.

  ///

  /// The returned value allows for nanosecond precision but the actual

  /// resolution is an implementation detail of the underlying file system.

  /// There is no guarantee for what kind of resolution you can expect, the

  /// resolution can differ across platforms and even across mountpoints on the

  /// same machine.

  TimePoint<> getLastModificationTime() const;

  #if defined(LLVM_ON_UNIX)

  uint32_t getUser() const { return fs_st_uid; }

  uint32_t getGroup() const { return fs_st_gid; }

  uint64_t getSize() const { return fs_st_size; }

  #elif defined (_WIN32)

  uint32_t getUser() const {

    return 9999; // Not applicable to Windows, so...

  }

  uint32_t getGroup() const {

    return 9999; // Not applicable to Windows, so...

  }

  uint64_t getSize() const {

    return (uint64_t(FileSizeHigh) << 32) + FileSizeLow;

  }

  #endif

  // setters

  void type(file_type v) { Type = v; }

  void permissions(perms p) { Perms = p; }

};

/// Represents the result of a call to sys::fs::status().

class file_status : public basic_file_status {

  friend bool equivalent(file_status A, file_status B);

  #if defined(LLVM_ON_UNIX)

  dev_t fs_st_dev = 0;

  nlink_t fs_st_nlinks = 0;

  ino_t fs_st_ino = 0;

  #elif defined (_WIN32)

  uint32_t NumLinks = 0;

  uint32_t VolumeSerialNumber = 0;

  uint32_t FileIndexHigh = 0;

  uint32_t FileIndexLow = 0;

  #endif

public:

  file_status() = default;

  explicit file_status(file_type Type) : basic_file_status(Type) {}

  #if defined(LLVM_ON_UNIX)

  file_status(file_type Type, perms Perms, dev_t Dev, nlink_t Links, ino_t Ino,

              time_t ATime, uint32_t ATimeNSec,

              time_t MTime, uint32_t MTimeNSec,

              uid_t UID, gid_t GID, off_t Size)

      : basic_file_status(Type, Perms, ATime, ATimeNSec, MTime, MTimeNSec,

                          UID, GID, Size),

        fs_st_dev(Dev), fs_st_nlinks(Links), fs_st_ino(Ino) {}

  #elif defined(_WIN32)

  file_status(file_type Type, perms Perms, uint32_t LinkCount,

              uint32_t LastAccessTimeHigh, uint32_t LastAccessTimeLow,

              uint32_t LastWriteTimeHigh, uint32_t LastWriteTimeLow,

              uint32_t VolumeSerialNumber, uint32_t FileSizeHigh,

              uint32_t FileSizeLow, uint32_t FileIndexHigh,

              uint32_t FileIndexLow)

      : basic_file_status(Type, Perms, LastAccessTimeHigh, LastAccessTimeLow,

                          LastWriteTimeHigh, LastWriteTimeLow, FileSizeHigh,

                          FileSizeLow),

        NumLinks(LinkCount), VolumeSerialNumber(VolumeSerialNumber),

        FileIndexHigh(FileIndexHigh), FileIndexLow(FileIndexLow) {}

  #endif

  UniqueID getUniqueID() const;

  uint32_t getLinkCount() const;

};

/// @}

/// @name Physical Operators

/// @{

/// Make \a path an absolute path.

///

/// Makes \a path absolute using the \a current_directory if it is not already.

/// An empty \a path will result in the \a current_directory.

///

/// /absolute/path   => /absolute/path

/// relative/../path => <current-directory>/relative/../path

///

/// @param path A path that is modified to be an absolute path.

void make_absolute(const Twine &current_directory, SmallVectorImpl<char> &path);

/// Make \a path an absolute path.

///

/// Makes \a path absolute using the current directory if it is not already. An

/// empty \a path will result in the current directory.

///

/// /absolute/path   => /absolute/path

/// relative/../path => <current-directory>/relative/../path

///

/// @param path A path that is modified to be an absolute path.

/// @returns errc::success if \a path has been made absolute, otherwise a

///          platform-specific error_code.

std::error_code make_absolute(SmallVectorImpl<char> &path);

/// Create all the non-existent directories in path.

///

/// @param path Directories to create.

/// @returns errc::success if is_directory(path), otherwise a platform

///          specific error_code. If IgnoreExisting is false, also returns

///          error if the directory already existed.

std::error_code create_directories(const Twine &path,

                                   bool IgnoreExisting = true,

                                   perms Perms = owner_all | group_all);

/// Create the directory in path.

///

/// @param path Directory to create.

/// @returns errc::success if is_directory(path), otherwise a platform

///          specific error_code. If IgnoreExisting is false, also returns

///          error if the directory already existed.

std::error_code create_directory(const Twine &path, bool IgnoreExisting = true,

                                 perms Perms = owner_all | group_all);

/// Create a link from \a from to \a to.

///

/// The link may be a soft or a hard link, depending on the platform. The caller

/// may not assume which one. Currently on windows it creates a hard link since

/// soft links require extra privileges. On unix, it creates a soft link since

/// hard links don't work on SMB file systems.

///

/// @param to The path to hard link to.

/// @param from The path to hard link from. This is created.

/// @returns errc::success if the link was created, otherwise a platform

/// specific error_code.

std::error_code create_link(const Twine &to, const Twine &from);

/// Create a hard link from \a from to \a to, or return an error.

///

/// @param to The path to hard link to.

/// @param from The path to hard link from. This is created.

/// @returns errc::success if the link was created, otherwise a platform

/// specific error_code.

std::error_code create_hard_link(const Twine &to, const Twine &from);

/// Collapse all . and .. patterns, resolve all symlinks, and optionally

///        expand ~ expressions to the user's home directory.

///

/// @param path The path to resolve.

/// @param output The location to store the resolved path.

/// @param expand_tilde If true, resolves ~ expressions to the user's home

///                     directory.

std::error_code real_path(const Twine &path, SmallVectorImpl<char> &output,

                          bool expand_tilde = false);

/// Expands ~ expressions to the user's home directory. On Unix ~user

/// directories are resolved as well.

///

/// @param path The path to resolve.

void expand_tilde(const Twine &path, SmallVectorImpl<char> &output);

/// Get the current path.

///

/// @param result Holds the current path on return.

/// @returns errc::success if the current path has been stored in result,

///          otherwise a platform-specific error_code.

std::error_code current_path(SmallVectorImpl<char> &result);

/// Set the current path.

///

/// @param path The path to set.

/// @returns errc::success if the current path was successfully set,

///          otherwise a platform-specific error_code.

std::error_code set_current_path(const Twine &path);

/// Remove path. Equivalent to POSIX remove().

///

/// @param path Input path.

/// @returns errc::success if path has been removed or didn't exist, otherwise a

///          platform-specific error code. If IgnoreNonExisting is false, also

///          returns error if the file didn't exist.

std::error_code remove(const Twine &path, bool IgnoreNonExisting = true);

/// Recursively delete a directory.

///

/// @param path Input path.

/// @returns errc::success if path has been removed or didn't exist, otherwise a

///          platform-specific error code.

std::error_code remove_directories(const Twine &path, bool IgnoreErrors = true);

/// Rename \a from to \a to.

///

/// Files are renamed as if by POSIX rename(), except that on Windows there may

/// be a short interval of time during which the destination file does not

/// exist.

///

/// @param from The path to rename from.

/// @param to The path to rename to. This is created.

std::error_code rename(const Twine &from, const Twine &to);

/// Copy the contents of \a From to \a To.

///

/// @param From The path to copy from.

/// @param To The path to copy to. This is created.

std::error_code copy_file(const Twine &From, const Twine &To);

/// Copy the contents of \a From to \a To.

///

/// @param From The path to copy from.

/// @param ToFD The open file descriptor of the destination file.

std::error_code copy_file(const Twine &From, int ToFD);

/// Resize path to size. File is resized as if by POSIX truncate().

///

/// @param FD Input file descriptor.

/// @param Size Size to resize to.

/// @returns errc::success if \a path has been resized to \a size, otherwise a

///          platform-specific error_code.

std::error_code resize_file(int FD, uint64_t Size);

/// Resize \p FD to \p Size before mapping \a mapped_file_region::readwrite. On

/// non-Windows, this calls \a resize_file(). On Windows, this is a no-op,

/// since the subsequent mapping (via \c CreateFileMapping) automatically

/// extends the file.

inline std::error_code resize_file_before_mapping_readwrite(int FD,

                                                            uint64_t Size) {

#ifdef _WIN32

  (void)FD;

  (void)Size;

  return std::error_code();

#else

  return resize_file(FD, Size);

#endif

}

/// Compute an MD5 hash of a file's contents.

///

/// @param FD Input file descriptor.

/// @returns An MD5Result with the hash computed, if successful, otherwise a

///          std::error_code.

ErrorOr<MD5::MD5Result> md5_contents(int FD);

/// Version of compute_md5 that doesn't require an open file descriptor.

ErrorOr<MD5::MD5Result> md5_contents(const Twine &Path);

/// @}

/// @name Physical Observers

/// @{

/// Does file exist?

///

/// @param status A basic_file_status previously returned from stat.

/// @returns True if the file represented by status exists, false if it does

///          not.

bool exists(const basic_file_status &status);

enum class AccessMode { Exist, Write, Execute };

/// Can the file be accessed?

///

/// @param Path Input path.

/// @returns errc::success if the path can be accessed, otherwise a

///          platform-specific error_code.

std::error_code access(const Twine &Path, AccessMode Mode);

/// Does file exist?

///

/// @param Path Input path.

/// @returns True if it exists, false otherwise.

inline bool exists(const Twine &Path) {

  return !access(Path, AccessMode::Exist);

}

/// Can we execute this file?

///

/// @param Path Input path.

/// @returns True if we can execute it, false otherwise.

bool can_execute(const Twine &Path);

/// Can we write this file?

///

/// @param Path Input path.

/// @returns True if we can write to it, false otherwise.

inline bool can_write(const Twine &Path) {

  return !access(Path, AccessMode::Write);

}

/// Do file_status's represent the same thing?

///

/// @param A Input file_status.

/// @param B Input file_status.

///

/// assert(status_known(A) || status_known(B));

///

/// @returns True if A and B both represent the same file system entity, false

///          otherwise.

bool equivalent(file_status A, file_status B);

/// Do paths represent the same thing?

///

/// assert(status_known(A) || status_known(B));

///

/// @param A Input path A.

/// @param B Input path B.

/// @param result Set to true if stat(A) and stat(B) have the same device and

///               inode (or equivalent).

/// @returns errc::success if result has been successfully set, otherwise a

///          platform-specific error_code.

std::error_code equivalent(const Twine &A, const Twine &B, bool &result);

/// Simpler version of equivalent for clients that don't need to

///        differentiate between an error and false.

inline bool equivalent(const Twine &A, const Twine &B) {

  bool result;

  return !equivalent(A, B, result) && result;

}

/// Is the file mounted on a local filesystem?

///

/// @param path Input path.

/// @param result Set to true if \a path is on fixed media such as a hard disk,

///               false if it is not.

/// @returns errc::success if result has been successfully set, otherwise a

///          platform specific error_code.

std::error_code is_local(const Twine &path, bool &result);

/// Version of is_local accepting an open file descriptor.

std::error_code is_local(int FD, bool &result);

/// Simpler version of is_local for clients that don't need to

///        differentiate between an error and false.

inline bool is_local(const Twine &Path) {

  bool Result;

  return !is_local(Path, Result) && Result;

}

/// Simpler version of is_local accepting an open file descriptor for

///        clients that don't need to differentiate between an error and false.

inline bool is_local(int FD) {

  bool Result;

  return !is_local(FD, Result) && Result;

}

/// Does status represent a directory?

///

/// @param Path The path to get the type of.

/// @param Follow For symbolic links, indicates whether to return the file type

///               of the link itself, or of the target.

/// @returns A value from the file_type enumeration indicating the type of file.

file_type get_file_type(const Twine &Path, bool Follow = true);

/// Does status represent a directory?

///

/// @param status A basic_file_status previously returned from status.

/// @returns status.type() == file_type::directory_file.

bool is_directory(const basic_file_status &status);

/// Is path a directory?

///

/// @param path Input path.

/// @param result Set to true if \a path is a directory (after following

///               symlinks, false if it is not. Undefined otherwise.

/// @returns errc::success if result has been successfully set, otherwise a

///          platform-specific error_code.

std::error_code is_directory(const Twine &path, bool &result);

/// Simpler version of is_directory for clients that don't need to

///        differentiate between an error and false.

inline bool is_directory(const Twine &Path) {

  bool Result;

  return !is_directory(Path, Result) && Result;

}

/// Does status represent a regular file?

///

/// @param status A basic_file_status previously returned from status.

/// @returns status_known(status) && status.type() == file_type::regular_file.

bool is_regular_file(const basic_file_status &status);

/// Is path a regular file?

///

/// @param path Input path.

/// @param result Set to true if \a path is a regular file (after following

///               symlinks), false if it is not. Undefined otherwise.

/// @returns errc::success if result has been successfully set, otherwise a

///          platform-specific error_code.

std::error_code is_regular_file(const Twine &path, bool &result);

/// Simpler version of is_regular_file for clients that don't need to

///        differentiate between an error and false.

inline bool is_regular_file(const Twine &Path) {

  bool Result;

  if (is_regular_file(Path, Result))

    return false;

  return Result;

}

/// Does status represent a symlink file?

///

/// @param status A basic_file_status previously returned from status.

/// @returns status_known(status) && status.type() == file_type::symlink_file.

bool is_symlink_file(const basic_file_status &status);

/// Is path a symlink file?

///

/// @param path Input path.

/// @param result Set to true if \a path is a symlink file, false if it is not.

///               Undefined otherwise.

/// @returns errc::success if result has been successfully set, otherwise a

///          platform-specific error_code.

std::error_code is_symlink_file(const Twine &path, bool &result);

/// Simpler version of is_symlink_file for clients that don't need to

///        differentiate between an error and false.

inline bool is_symlink_file(const Twine &Path) {

  bool Result;

  if (is_symlink_file(Path, Result))

    return false;

  return Result;

}

/// Does this status represent something that exists but is not a

///        directory or regular file?

///

/// @param status A basic_file_status previously returned from status.

/// @returns exists(s) && !is_regular_file(s) && !is_directory(s)

bool is_other(const basic_file_status &status);

/// Is path something that exists but is not a directory,

///        regular file, or symlink?

///

/// @param path Input path.

/// @param result Set to true if \a path exists, but is not a directory, regular

///               file, or a symlink, false if it does not. Undefined otherwise.

/// @returns errc::success if result has been successfully set, otherwise a

///          platform-specific error_code.

std::error_code is_other(const Twine &path, bool &result);

/// Get file status as if by POSIX stat().

///

/// @param path Input path.

/// @param result Set to the file status.

/// @param follow When true, follows symlinks.  Otherwise, the symlink itself is

///               statted.

/// @returns errc::success if result has been successfully set, otherwise a

///          platform-specific error_code.

std::error_code status(const Twine &path, file_status &result,

                       bool follow = true);

/// A version for when a file descriptor is already available.

std::error_code status(int FD, file_status &Result);

#ifdef _WIN32

/// A version for when a file descriptor is already available.

std::error_code status(file_t FD, file_status &Result);

#endif

/// Get file creation mode mask of the process.

///

/// @returns Mask reported by umask(2)

/// @note There is no umask on Windows. This function returns 0 always

///       on Windows. This function does not return an error_code because

///       umask(2) never fails. It is not thread safe.

unsigned getUmask();

/// Set file permissions.

///

/// @param Path File to set permissions on.

/// @param Permissions New file permissions.

/// @returns errc::success if the permissions were successfully set, otherwise

///          a platform-specific error_code.

/// @note On Windows, all permissions except *_write are ignored. Using any of

///       owner_write, group_write, or all_write will make the file writable.

///       Otherwise, the file will be marked as read-only.

std::error_code setPermissions(const Twine &Path, perms Permissions);

/// Vesion of setPermissions accepting a file descriptor.

/// TODO Delete the path based overload once we implement the FD based overload

/// on Windows.

std::error_code setPermissions(int FD, perms Permissions);

/// Get file permissions.

///

/// @param Path File to get permissions from.

/// @returns the permissions if they were successfully retrieved, otherwise a

///          platform-specific error_code.

/// @note On Windows, if the file does not have the FILE_ATTRIBUTE_READONLY

///       attribute, all_all will be returned. Otherwise, all_read | all_exe

///       will be returned.

ErrorOr<perms> getPermissions(const Twine &Path);

/// Get file size.

///

/// @param Path Input path.

/// @param Result Set to the size of the file in \a Path.

/// @returns errc::success if result has been successfully set, otherwise a

///          platform-specific error_code.

inline std::error_code file_size(const Twine &Path, uint64_t &Result) {

  file_status Status;

  std::error_code EC = status(Path, Status);

  if (EC)

    return EC;

  Result = Status.getSize();

  return std::error_code();

}

/// Set the file modification and access time.

///

/// @returns errc::success if the file times were successfully set, otherwise a

///          platform-specific error_code or errc::function_not_supported on

///          platforms where the functionality isn't available.

std::error_code setLastAccessAndModificationTime(int FD, TimePoint<> AccessTime,

                                                 TimePoint<> ModificationTime);

/// Simpler version that sets both file modification and access time to the same

/// time.

inline std::error_code setLastAccessAndModificationTime(int FD,

                                                        TimePoint<> Time) {

  return setLastAccessAndModificationTime(FD, Time, Time);

}

/// Is status available?

///

/// @param s Input file status.

/// @returns True if status() != status_error.

bool status_known(const basic_file_status &s);

/// Is status available?

///

/// @param path Input path.

/// @param result Set to true if status() != status_error.

/// @returns errc::success if result has been successfully set, otherwise a

///          platform-specific error_code.

std::error_code status_known(const Twine &path, bool &result);

enum CreationDisposition : unsigned {

  /// CD_CreateAlways - When opening a file:

  ///   * If it already exists, truncate it.

  ///   * If it does not already exist, create a new file.

  CD_CreateAlways = 0,

  /// CD_CreateNew - When opening a file:

  ///   * If it already exists, fail.

  ///   * If it does not already exist, create a new file.

  CD_CreateNew = 1,

  /// CD_OpenExisting - When opening a file:

  ///   * If it already exists, open the file with the offset set to 0.

  ///   * If it does not already exist, fail.

  CD_OpenExisting = 2,

  /// CD_OpenAlways - When opening a file:

  ///   * If it already exists, open the file with the offset set to 0.

  ///   * If it does not already exist, create a new file.

  CD_OpenAlways = 3,

};

enum FileAccess : unsigned {

  FA_Read = 1,

  FA_Write = 2,

};

enum OpenFlags : unsigned {

  OF_None = 0,

  /// The file should be opened in text mode on platforms like z/OS that make

  /// this distinction.

  OF_Text = 1,

  /// The file should use a carriage linefeed '\r\n'. This flag should only be

  /// used with OF_Text. Only makes a difference on Windows.

  OF_CRLF = 2,

  /// The file should be opened in text mode and use a carriage linefeed '\r\n'.

  /// This flag has the same functionality as OF_Text on z/OS but adds a

  /// carriage linefeed on Windows.

  OF_TextWithCRLF = OF_Text | OF_CRLF,

  /// The file should be opened in append mode.

  OF_Append = 4,

  /// The returned handle can be used for deleting the file. Only makes a

  /// difference on windows.

  OF_Delete = 8,

  /// When a child process is launched, this file should remain open in the

  /// child process.

  OF_ChildInherit = 16,

  /// Force files Atime to be updated on access. Only makes a difference on

  /// Windows.

  OF_UpdateAtime = 32,

};

/// Create a potentially unique file name but does not create it.

///

/// Generates a unique path suitable for a temporary file but does not

/// open or create the file. The name is based on \a Model with '%'

/// replaced by a random char in [0-9a-f]. If \a MakeAbsolute is true

/// then the system's temp directory is prepended first. If \a MakeAbsolute

/// is false the current directory will be used instead.

///

/// This function does not check if the file exists. If you want to be sure

/// that the file does not yet exist, you should use use enough '%' characters

/// in your model to ensure this. Each '%' gives 4-bits of entropy so you can

/// use 32 of them to get 128 bits of entropy.

///

/// Example: clang-%%-%%-%%-%%-%%.s => clang-a0-b1-c2-d3-e4.s

///

/// @param Model Name to base unique path off of.

/// @param ResultPath Set to the file's path.

/// @param MakeAbsolute Whether to use the system temp directory.

void createUniquePath(const Twine &Model, SmallVectorImpl<char> &ResultPath,

                      bool MakeAbsolute);

/// Create a uniquely named file.

///

/// Generates a unique path suitable for a temporary file and then opens it as a

/// file. The name is based on \a Model with '%' replaced by a random char in

/// [0-9a-f]. If \a Model is not an absolute path, the temporary file will be

/// created in the current directory.

///

/// Example: clang-%%-%%-%%-%%-%%.s => clang-a0-b1-c2-d3-e4.s

///

/// This is an atomic operation. Either the file is created and opened, or the

/// file system is left untouched.

///

/// The intended use is for files that are to be kept, possibly after

/// renaming them. For example, when running 'clang -c foo.o', the file can

/// be first created as foo-abc123.o and then renamed.

///

/// @param Model Name to base unique path off of.

/// @param ResultFD Set to the opened file's file descriptor.

/// @param ResultPath Set to the opened file's absolute path.

/// @param Flags Set to the opened file's flags.

/// @param Mode Set to the opened file's permissions.

/// @returns errc::success if Result{FD,Path} have been successfully set,

///          otherwise a platform-specific error_code.

std::error_code createUniqueFile(const Twine &Model, int &ResultFD,

                                 SmallVectorImpl<char> &ResultPath,

                                 OpenFlags Flags = OF_None,

                                 unsigned Mode = all_read | all_write);

/// Simpler version for clients that don't want an open file. An empty

/// file will still be created.

std::error_code createUniqueFile(const Twine &Model,

                                 SmallVectorImpl<char> &ResultPath,

                                 unsigned Mode = all_read | all_write);

/// Represents a temporary file.

///

/// The temporary file must be eventually discarded or given a final name and

/// kept.

///

/// The destructor doesn't implicitly discard because there is no way to

/// properly handle errors in a destructor.

class TempFile {

  bool Done = false;

  TempFile(StringRef Name, int FD);

public:

  /// This creates a temporary file with createUniqueFile and schedules it for

  /// deletion with sys::RemoveFileOnSignal.

  static Expected<TempFile> create(const Twine &Model,

                                   unsigned Mode = all_read | all_write,

                                   OpenFlags ExtraFlags = OF_None);

  TempFile(TempFile &&Other);

  TempFile &operator=(TempFile &&Other);

  // Name of the temporary file.

  std::string TmpName;

  // The open file descriptor.

  int FD = -1;

#ifdef _WIN32

  // Whether we need to manually remove the file on close.

  bool RemoveOnClose = false;

#endif

  // Keep this with the given name.

  Error keep(const Twine &Name);

  // Keep this with the temporary name.

  Error keep();

  // Delete the file.

  Error discard();

  // This checks that keep or delete was called.

  ~TempFile();