Source/WTF/wtf/FileSystem.h - WebKit - Git at Google

 /*
  * Copyright (C) 2007-2017 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Collabora, Ltd. All rights reserved.
  * Copyright (C) 2015 Canon Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
  *     documentation and/or other materials provided with the distribution.
  * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
  *     its contributors may be used to endorse or promote products derived
  *     from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #pragma once

 #include <time.h>
 #include <utility>
 #include <wtf/Forward.h>
 #include <wtf/OptionSet.h>
 #include <wtf/Span.h>
 #include <wtf/Vector.h>
 #include <wtf/WallTime.h>
 #include <wtf/text/WTFString.h>

 #if USE(CF)
 #include <wtf/RetainPtr.h>
 #endif

 #if USE(CF)
 typedef const struct __CFData* CFDataRef;
 #endif

 OBJC_CLASS NSString;

 #if OS(WINDOWS)
 typedef void *HANDLE;
 #endif

 #if USE(GLIB)
 typedef struct _GFileIOStream GFileIOStream;
 #endif

 namespace WTF {

 namespace FileSystemImpl {

 // PlatformFileHandle
 #if USE(GLIB) && !OS(WINDOWS)
 typedef GFileIOStream* PlatformFileHandle;
 const PlatformFileHandle invalidPlatformFileHandle = 0;
 #elif OS(WINDOWS)
 typedef HANDLE PlatformFileHandle;
 // FIXME: -1 is INVALID_HANDLE_VALUE, defined in <winbase.h>. Chromium tries to
 // avoid using Windows headers in headers. We'd rather move this into the .cpp.
 const PlatformFileHandle invalidPlatformFileHandle = reinterpret_cast<HANDLE>(-1);
 #else
 typedef int PlatformFileHandle;
 const PlatformFileHandle invalidPlatformFileHandle = -1;
 #endif

 enum class FileOpenMode {
     Read,
     Write,
     ReadWrite,
 #if OS(DARWIN)
     EventsOnly,
 #endif
 };

 enum class FileAccessPermission : bool {
     User,
     All
 };

 enum class FileSeekOrigin {
     Beginning,
     Current,
     End,
 };

 enum class FileLockMode {
     Shared = 1 << 0,
     Exclusive = 1 << 1,
     Nonblocking = 1 << 2,
 };

 enum class MappedFileMode {
     Shared,
     Private,
 };

 WTF_EXPORT_PRIVATE bool fileExists(const String&);
 WTF_EXPORT_PRIVATE bool deleteFile(const String&);
 WTF_EXPORT_PRIVATE bool deleteEmptyDirectory(const String&);
 WTF_EXPORT_PRIVATE bool moveFile(const String& oldPath, const String& newPath);
 WTF_EXPORT_PRIVATE std::optional<uint64_t> fileSize(const String&); // Follows symlinks.
 WTF_EXPORT_PRIVATE std::optional<uint64_t> fileSize(PlatformFileHandle);
 WTF_EXPORT_PRIVATE std::optional<WallTime> fileModificationTime(const String&);
 WTF_EXPORT_PRIVATE bool updateFileModificationTime(const String& path); // Sets modification time to now.
 WTF_EXPORT_PRIVATE std::optional<WallTime> fileCreationTime(const String&); // Not all platforms store file creation time.
 WTF_EXPORT_PRIVATE bool isHiddenFile(const String&);
 WTF_EXPORT_PRIVATE String pathByAppendingComponent(const String& path, const String& component);
 WTF_EXPORT_PRIVATE String pathByAppendingComponents(StringView path, const Vector<StringView>& components);
 WTF_EXPORT_PRIVATE String lastComponentOfPathIgnoringTrailingSlash(const String& path);
 WTF_EXPORT_PRIVATE bool makeAllDirectories(const String& path);
 WTF_EXPORT_PRIVATE String pathFileName(const String&);
 WTF_EXPORT_PRIVATE String parentPath(const String&);
 WTF_EXPORT_PRIVATE std::optional<uint64_t> volumeFreeSpace(const String&);
 WTF_EXPORT_PRIVATE std::optional<uint32_t> volumeFileBlockSize(const String&);
 WTF_EXPORT_PRIVATE std::optional<int32_t> getFileDeviceId(const CString&);
 WTF_EXPORT_PRIVATE bool createSymbolicLink(const String& targetPath, const String& symbolicLinkPath);
 WTF_EXPORT_PRIVATE String createTemporaryZipArchive(const String& directory);

 enum class FileType { Regular, Directory, SymbolicLink };
 WTF_EXPORT_PRIVATE std::optional<FileType> fileType(const String&);
 WTF_EXPORT_PRIVATE std::optional<FileType> fileTypeFollowingSymlinks(const String&);

 WTF_EXPORT_PRIVATE void setMetadataURL(const String& path, const String& urlString, const String& referrer = { });

 bool canExcludeFromBackup(); // Returns true if any file can ever be excluded from backup.
 bool excludeFromBackup(const String&); // Returns true if successful.

 WTF_EXPORT_PRIVATE Vector<String> listDirectory(const String& path); // Returns file names, not full paths.

 WTF_EXPORT_PRIVATE CString fileSystemRepresentation(const String&);
 WTF_EXPORT_PRIVATE String stringFromFileSystemRepresentation(const char*);

 inline bool isHandleValid(const PlatformFileHandle& handle) { return handle != invalidPlatformFileHandle; }

 using Salt = std::array<uint8_t, 8>;
 WTF_EXPORT_PRIVATE std::optional<Salt> readOrMakeSalt(const String& path);

 // Prefix is what the filename should be prefixed with, not the full path.
 WTF_EXPORT_PRIVATE String openTemporaryFile(const String& prefix, PlatformFileHandle&, const String& suffix = { });
 WTF_EXPORT_PRIVATE PlatformFileHandle openFile(const String& path, FileOpenMode, FileAccessPermission = FileAccessPermission::All, bool failIfFileExists = false);
 WTF_EXPORT_PRIVATE void closeFile(PlatformFileHandle&);
 // Returns the resulting offset from the beginning of the file if successful, -1 otherwise.
 WTF_EXPORT_PRIVATE long long seekFile(PlatformFileHandle, long long offset, FileSeekOrigin);
 WTF_EXPORT_PRIVATE bool truncateFile(PlatformFileHandle, long long offset);
 WTF_EXPORT_PRIVATE bool flushFile(PlatformFileHandle);
 // Returns number of bytes actually read if successful, -1 otherwise.
 WTF_EXPORT_PRIVATE int writeToFile(PlatformFileHandle, const void* data, int length);
 // Returns number of bytes actually written if successful, -1 otherwise.
 WTF_EXPORT_PRIVATE int readFromFile(PlatformFileHandle, void* data, int length);

 WTF_EXPORT_PRIVATE PlatformFileHandle openAndLockFile(const String&, FileOpenMode, OptionSet<FileLockMode> = FileLockMode::Exclusive);
 WTF_EXPORT_PRIVATE void unlockAndCloseFile(PlatformFileHandle);

 // Appends the contents of the file found at 'path' to the open PlatformFileHandle.
 // Returns true if the write was successful, false if it was not.
 WTF_EXPORT_PRIVATE bool appendFileContentsToFileHandle(const String& path, PlatformFileHandle&);

 WTF_EXPORT_PRIVATE bool hardLink(const String& targetPath, const String& linkPath);
 // Hard links a file if possible, copies it if not.
 WTF_EXPORT_PRIVATE bool hardLinkOrCopyFile(const String& targetPath, const String& linkPath);
 WTF_EXPORT_PRIVATE std::optional<uint64_t> hardLinkCount(const String& path);

 #if USE(FILE_LOCK)
 WTF_EXPORT_PRIVATE bool lockFile(PlatformFileHandle, OptionSet<FileLockMode>);
 WTF_EXPORT_PRIVATE bool unlockFile(PlatformFileHandle);
 #endif

 // Encode a string for use within a file name.
 WTF_EXPORT_PRIVATE String encodeForFileName(const String&);
 WTF_EXPORT_PRIVATE String decodeFromFilename(const String&);

 WTF_EXPORT_PRIVATE bool filesHaveSameVolume(const String&, const String&);

 #if USE(CF)
 WTF_EXPORT_PRIVATE RetainPtr<CFURLRef> pathAsURL(const String&);
 #endif

 #if USE(GLIB)
 WTF_EXPORT_PRIVATE String filenameForDisplay(const String&);
 WTF_EXPORT_PRIVATE CString currentExecutablePath();
 WTF_EXPORT_PRIVATE CString currentExecutableName();
 #endif

 #if OS(WINDOWS)
 WTF_EXPORT_PRIVATE String localUserSpecificStorageDirectory();
 WTF_EXPORT_PRIVATE String roamingUserSpecificStorageDirectory();
 WTF_EXPORT_PRIVATE String createTemporaryDirectory();
 #endif

 #if PLATFORM(COCOA)
 WTF_EXPORT_PRIVATE NSString *createTemporaryDirectory(NSString *directoryPrefix);

 // Allow reading cloud files with no local copy.
 enum class PolicyScope : uint8_t { Process, Thread };
 WTF_EXPORT_PRIVATE bool setAllowsMaterializingDatalessFiles(bool, PolicyScope);
 WTF_EXPORT_PRIVATE std::optional<bool> allowsMaterializingDatalessFiles(PolicyScope);
 #endif

 WTF_EXPORT_PRIVATE bool deleteNonEmptyDirectory(const String&);

 WTF_EXPORT_PRIVATE String realPath(const String&);

 WTF_EXPORT_PRIVATE bool isSafeToUseMemoryMapForPath(const String&);
 WTF_EXPORT_PRIVATE void makeSafeToUseMemoryMapForPath(const String&);

 class MappedFileData {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     MappedFileData() { }
     MappedFileData(MappedFileData&&);
     WTF_EXPORT_PRIVATE MappedFileData(const String& filePath, MappedFileMode, bool& success);
     WTF_EXPORT_PRIVATE MappedFileData(PlatformFileHandle, MappedFileMode, bool& success);
     WTF_EXPORT_PRIVATE MappedFileData(PlatformFileHandle, FileOpenMode, MappedFileMode, bool& success);
     WTF_EXPORT_PRIVATE ~MappedFileData();
     MappedFileData& operator=(MappedFileData&&);

     explicit operator bool() const { return !!m_fileData; }
     const void* data() const { return m_fileData; }
     unsigned size() const { return m_fileSize; }

 #if PLATFORM(COCOA)
     void* leakHandle() { return std::exchange(m_fileData, nullptr); }
 #endif
 #if OS(WINDOWS)
     HANDLE fileMapping() const { return m_fileMapping; }
 #endif

 private:
     WTF_EXPORT_PRIVATE bool mapFileHandle(PlatformFileHandle, FileOpenMode, MappedFileMode);

     void* m_fileData { nullptr };
     unsigned m_fileSize { 0 };
 #if OS(WINDOWS)
     HANDLE m_fileMapping { nullptr };
 #endif
 };

 inline MappedFileData::MappedFileData(PlatformFileHandle handle, MappedFileMode mapMode, bool& success)
 {
     success = mapFileHandle(handle, FileOpenMode::Read, mapMode);
 }

 inline MappedFileData::MappedFileData(PlatformFileHandle handle, FileOpenMode openMode, MappedFileMode mapMode, bool& success)
 {
     success = mapFileHandle(handle, openMode, mapMode);
 }

 inline MappedFileData::MappedFileData(MappedFileData&& other)
     : m_fileData(std::exchange(other.m_fileData, nullptr))
     , m_fileSize(std::exchange(other.m_fileSize, 0))
 #if OS(WINDOWS)
     , m_fileMapping(std::exchange(other.m_fileMapping, nullptr))
 #endif
 {
 }

 inline MappedFileData& MappedFileData::operator=(MappedFileData&& other)
 {
     m_fileData = std::exchange(other.m_fileData, nullptr);
     m_fileSize = std::exchange(other.m_fileSize, 0);
 #if OS(WINDOWS)
     m_fileMapping = std::exchange(other.m_fileMapping, nullptr);
 #endif
     return *this;
 }

 // This creates the destination file, maps it, write the provided data to it and returns the mapped file.
 // This function fails if there is already a file at the destination path.
 WTF_EXPORT_PRIVATE MappedFileData mapToFile(const String& path, size_t bytesSize, Function<void(const Function<bool(Span<const uint8_t>)>&)>&& apply, PlatformFileHandle* = nullptr);

 } // namespace FileSystemImpl
 } // namespace WTF

 namespace FileSystem = WTF::FileSystemImpl;
	/*
	* Copyright (C) 2007-2017 Apple Inc. All rights reserved.
	* Copyright (C) 2008 Collabora, Ltd. All rights reserved.
	* Copyright (C) 2015 Canon Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. Neither the name of Apple Inc. ("Apple") nor the names of
	* its contributors may be used to endorse or promote products derived
	* from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
	* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
	* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
	* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
	* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#pragma once

	#include <time.h>
	#include <utility>
	#include <wtf/Forward.h>
	#include <wtf/OptionSet.h>
	#include <wtf/Span.h>
	#include <wtf/Vector.h>
	#include <wtf/WallTime.h>
	#include <wtf/text/WTFString.h>

	#if USE(CF)
	#include <wtf/RetainPtr.h>
	#endif

	#if USE(CF)
	typedef const struct __CFData* CFDataRef;
	#endif

	OBJC_CLASS NSString;

	#if OS(WINDOWS)
	typedef void *HANDLE;
	#endif

	#if USE(GLIB)
	typedef struct _GFileIOStream GFileIOStream;
	#endif

	namespace WTF {

	namespace FileSystemImpl {

	// PlatformFileHandle
	#if USE(GLIB) && !OS(WINDOWS)
	typedef GFileIOStream* PlatformFileHandle;
	const PlatformFileHandle invalidPlatformFileHandle = 0;
	#elif OS(WINDOWS)
	typedef HANDLE PlatformFileHandle;
	// FIXME: -1 is INVALID_HANDLE_VALUE, defined in <winbase.h>. Chromium tries to
	// avoid using Windows headers in headers. We'd rather move this into the .cpp.
	const PlatformFileHandle invalidPlatformFileHandle = reinterpret_cast<HANDLE>(-1);
	#else
	typedef int PlatformFileHandle;
	const PlatformFileHandle invalidPlatformFileHandle = -1;
	#endif

	enum class FileOpenMode {
	Read,
	Write,
	ReadWrite,
	#if OS(DARWIN)
	EventsOnly,
	#endif
	};

	enum class FileAccessPermission : bool {
	User,
	All
	};

	enum class FileSeekOrigin {
	Beginning,
	Current,
	End,
	};

	enum class FileLockMode {
	Shared = 1 << 0,
	Exclusive = 1 << 1,
	Nonblocking = 1 << 2,
	};

	enum class MappedFileMode {
	Shared,
	Private,
	};

	WTF_EXPORT_PRIVATE bool fileExists(const String&);
	WTF_EXPORT_PRIVATE bool deleteFile(const String&);
	WTF_EXPORT_PRIVATE bool deleteEmptyDirectory(const String&);
	WTF_EXPORT_PRIVATE bool moveFile(const String& oldPath, const String& newPath);
	WTF_EXPORT_PRIVATE std::optional<uint64_t> fileSize(const String&); // Follows symlinks.
	WTF_EXPORT_PRIVATE std::optional<uint64_t> fileSize(PlatformFileHandle);
	WTF_EXPORT_PRIVATE std::optional<WallTime> fileModificationTime(const String&);
	WTF_EXPORT_PRIVATE bool updateFileModificationTime(const String& path); // Sets modification time to now.
	WTF_EXPORT_PRIVATE std::optional<WallTime> fileCreationTime(const String&); // Not all platforms store file creation time.
	WTF_EXPORT_PRIVATE bool isHiddenFile(const String&);
	WTF_EXPORT_PRIVATE String pathByAppendingComponent(const String& path, const String& component);
	WTF_EXPORT_PRIVATE String pathByAppendingComponents(StringView path, const Vector<StringView>& components);
	WTF_EXPORT_PRIVATE String lastComponentOfPathIgnoringTrailingSlash(const String& path);
	WTF_EXPORT_PRIVATE bool makeAllDirectories(const String& path);
	WTF_EXPORT_PRIVATE String pathFileName(const String&);
	WTF_EXPORT_PRIVATE String parentPath(const String&);
	WTF_EXPORT_PRIVATE std::optional<uint64_t> volumeFreeSpace(const String&);
	WTF_EXPORT_PRIVATE std::optional<uint32_t> volumeFileBlockSize(const String&);
	WTF_EXPORT_PRIVATE std::optional<int32_t> getFileDeviceId(const CString&);
	WTF_EXPORT_PRIVATE bool createSymbolicLink(const String& targetPath, const String& symbolicLinkPath);
	WTF_EXPORT_PRIVATE String createTemporaryZipArchive(const String& directory);

	enum class FileType { Regular, Directory, SymbolicLink };
	WTF_EXPORT_PRIVATE std::optional<FileType> fileType(const String&);
	WTF_EXPORT_PRIVATE std::optional<FileType> fileTypeFollowingSymlinks(const String&);

	WTF_EXPORT_PRIVATE void setMetadataURL(const String& path, const String& urlString, const String& referrer = { });

	bool canExcludeFromBackup(); // Returns true if any file can ever be excluded from backup.
	bool excludeFromBackup(const String&); // Returns true if successful.

	WTF_EXPORT_PRIVATE Vector<String> listDirectory(const String& path); // Returns file names, not full paths.

	WTF_EXPORT_PRIVATE CString fileSystemRepresentation(const String&);
	WTF_EXPORT_PRIVATE String stringFromFileSystemRepresentation(const char*);

	inline bool isHandleValid(const PlatformFileHandle& handle) { return handle != invalidPlatformFileHandle; }

	using Salt = std::array<uint8_t, 8>;
	WTF_EXPORT_PRIVATE std::optional<Salt> readOrMakeSalt(const String& path);

	// Prefix is what the filename should be prefixed with, not the full path.
	WTF_EXPORT_PRIVATE String openTemporaryFile(const String& prefix, PlatformFileHandle&, const String& suffix = { });
	WTF_EXPORT_PRIVATE PlatformFileHandle openFile(const String& path, FileOpenMode, FileAccessPermission = FileAccessPermission::All, bool failIfFileExists = false);
	WTF_EXPORT_PRIVATE void closeFile(PlatformFileHandle&);
	// Returns the resulting offset from the beginning of the file if successful, -1 otherwise.
	WTF_EXPORT_PRIVATE long long seekFile(PlatformFileHandle, long long offset, FileSeekOrigin);
	WTF_EXPORT_PRIVATE bool truncateFile(PlatformFileHandle, long long offset);
	WTF_EXPORT_PRIVATE bool flushFile(PlatformFileHandle);
	// Returns number of bytes actually read if successful, -1 otherwise.
	WTF_EXPORT_PRIVATE int writeToFile(PlatformFileHandle, const void* data, int length);
	// Returns number of bytes actually written if successful, -1 otherwise.
	WTF_EXPORT_PRIVATE int readFromFile(PlatformFileHandle, void* data, int length);

	WTF_EXPORT_PRIVATE PlatformFileHandle openAndLockFile(const String&, FileOpenMode, OptionSet<FileLockMode> = FileLockMode::Exclusive);
	WTF_EXPORT_PRIVATE void unlockAndCloseFile(PlatformFileHandle);

	// Appends the contents of the file found at 'path' to the open PlatformFileHandle.
	// Returns true if the write was successful, false if it was not.
	WTF_EXPORT_PRIVATE bool appendFileContentsToFileHandle(const String& path, PlatformFileHandle&);

	WTF_EXPORT_PRIVATE bool hardLink(const String& targetPath, const String& linkPath);
	// Hard links a file if possible, copies it if not.
	WTF_EXPORT_PRIVATE bool hardLinkOrCopyFile(const String& targetPath, const String& linkPath);
	WTF_EXPORT_PRIVATE std::optional<uint64_t> hardLinkCount(const String& path);

	#if USE(FILE_LOCK)
	WTF_EXPORT_PRIVATE bool lockFile(PlatformFileHandle, OptionSet<FileLockMode>);
	WTF_EXPORT_PRIVATE bool unlockFile(PlatformFileHandle);
	#endif

	// Encode a string for use within a file name.
	WTF_EXPORT_PRIVATE String encodeForFileName(const String&);
	WTF_EXPORT_PRIVATE String decodeFromFilename(const String&);

	WTF_EXPORT_PRIVATE bool filesHaveSameVolume(const String&, const String&);

	#if USE(CF)
	WTF_EXPORT_PRIVATE RetainPtr<CFURLRef> pathAsURL(const String&);
	#endif

	#if USE(GLIB)
	WTF_EXPORT_PRIVATE String filenameForDisplay(const String&);
	WTF_EXPORT_PRIVATE CString currentExecutablePath();
	WTF_EXPORT_PRIVATE CString currentExecutableName();
	#endif

	#if OS(WINDOWS)
	WTF_EXPORT_PRIVATE String localUserSpecificStorageDirectory();
	WTF_EXPORT_PRIVATE String roamingUserSpecificStorageDirectory();
	WTF_EXPORT_PRIVATE String createTemporaryDirectory();
	#endif

	#if PLATFORM(COCOA)
	WTF_EXPORT_PRIVATE NSString createTemporaryDirectory(NSString directoryPrefix);

	// Allow reading cloud files with no local copy.
	enum class PolicyScope : uint8_t { Process, Thread };
	WTF_EXPORT_PRIVATE bool setAllowsMaterializingDatalessFiles(bool, PolicyScope);
	WTF_EXPORT_PRIVATE std::optional<bool> allowsMaterializingDatalessFiles(PolicyScope);
	#endif

	WTF_EXPORT_PRIVATE bool deleteNonEmptyDirectory(const String&);

	WTF_EXPORT_PRIVATE String realPath(const String&);

	WTF_EXPORT_PRIVATE bool isSafeToUseMemoryMapForPath(const String&);
	WTF_EXPORT_PRIVATE void makeSafeToUseMemoryMapForPath(const String&);

	class MappedFileData {
	WTF_MAKE_FAST_ALLOCATED;
	public:
	MappedFileData() { }
	MappedFileData(MappedFileData&&);
	WTF_EXPORT_PRIVATE MappedFileData(const String& filePath, MappedFileMode, bool& success);
	WTF_EXPORT_PRIVATE MappedFileData(PlatformFileHandle, MappedFileMode, bool& success);
	WTF_EXPORT_PRIVATE MappedFileData(PlatformFileHandle, FileOpenMode, MappedFileMode, bool& success);
	WTF_EXPORT_PRIVATE ~MappedFileData();
	MappedFileData& operator=(MappedFileData&&);

	explicit operator bool() const { return !!m_fileData; }
	const void* data() const { return m_fileData; }
	unsigned size() const { return m_fileSize; }

	#if PLATFORM(COCOA)
	void* leakHandle() { return std::exchange(m_fileData, nullptr); }
	#endif
	#if OS(WINDOWS)
	HANDLE fileMapping() const { return m_fileMapping; }
	#endif

	private:
	WTF_EXPORT_PRIVATE bool mapFileHandle(PlatformFileHandle, FileOpenMode, MappedFileMode);

	void* m_fileData { nullptr };
	unsigned m_fileSize { 0 };
	#if OS(WINDOWS)
	HANDLE m_fileMapping { nullptr };
	#endif
	};

	inline MappedFileData::MappedFileData(PlatformFileHandle handle, MappedFileMode mapMode, bool& success)
	{
	success = mapFileHandle(handle, FileOpenMode::Read, mapMode);
	}

	inline MappedFileData::MappedFileData(PlatformFileHandle handle, FileOpenMode openMode, MappedFileMode mapMode, bool& success)
	{
	success = mapFileHandle(handle, openMode, mapMode);
	}

	inline MappedFileData::MappedFileData(MappedFileData&& other)
	: m_fileData(std::exchange(other.m_fileData, nullptr))
	, m_fileSize(std::exchange(other.m_fileSize, 0))
	#if OS(WINDOWS)
	, m_fileMapping(std::exchange(other.m_fileMapping, nullptr))
	#endif
	{
	}

	inline MappedFileData& MappedFileData::operator=(MappedFileData&& other)
	{
	m_fileData = std::exchange(other.m_fileData, nullptr);
	m_fileSize = std::exchange(other.m_fileSize, 0);
	#if OS(WINDOWS)
	m_fileMapping = std::exchange(other.m_fileMapping, nullptr);
	#endif
	return *this;
	}

	// This creates the destination file, maps it, write the provided data to it and returns the mapped file.
	// This function fails if there is already a file at the destination path.
	WTF_EXPORT_PRIVATE MappedFileData mapToFile(const String& path, size_t bytesSize, Function<void(const Function<bool(Span<const uint8_t>)>&)>&& apply, PlatformFileHandle* = nullptr);

	} // namespace FileSystemImpl
	} // namespace WTF

	namespace FileSystem = WTF::FileSystemImpl;