/****************************************************************************
**
** Copyright (C) 2018 Intel Corporation.
** Copyright (C) 2016 The Qt Company Ltd.
** Copyright (C) 2013 Samuel Gaist <samuel.gaist@edeltech.ch>
** Contact: https://www.qt.io/licensing/
**
** This file is part of the QtCore module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see https://www.qt.io/terms-conditions. For further
** information use the contact form at https://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 3 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL3 included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 3 requirements
** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 2.0 or (at your option) the GNU General
** Public license version 3 or any later version approved by the KDE Free
** Qt Foundation. The licenses are as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
** included in the packaging of this file. Please review the following
** information to ensure the GNU General Public License requirements will
** be met: https://www.gnu.org/licenses/gpl-2.0.html and
** https://www.gnu.org/licenses/gpl-3.0.html.
**
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qplatformdefs.h"
#include "qfilesystemengine_p.h"
#include "qfile.h"

#include <QtCore/qoperatingsystemversion.h>
#include <QtCore/private/qcore_unix_p.h>
#include <QtCore/qvarlengtharray.h>

#include <pwd.h>
#include <stdlib.h> // for realpath()
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <errno.h>

#if __has_include(<paths.h>)
# include <paths.h>
#endif
#ifndef _PATH_TMP           // from <paths.h>
# define _PATH_TMP          "/tmp"
#endif

#if defined(Q_OS_MAC)
# include <QtCore/private/qcore_mac_p.h>
# include <CoreFoundation/CFBundle.h>
#endif

#ifdef Q_OS_OSX
#include <CoreServices/CoreServices.h>
#endif

#if defined(QT_PLATFORM_UIKIT)
#include <MobileCoreServices/MobileCoreServices.h>
#endif

#if defined(Q_OS_DARWIN)
# include <sys/clonefile.h>
# include <copyfile.h>
// We cannot include <Foundation/Foundation.h> (it's an Objective-C header), but
// we need these declarations:
Q_FORWARD_DECLARE_OBJC_CLASS(NSString);
extern "C" NSString *NSTemporaryDirectory();
#endif

#if defined(Q_OS_LINUX)
#  include <sys/ioctl.h>
#  include <sys/sendfile.h>
#  include <linux/fs.h>

// in case linux/fs.h is too old and doesn't define it:
#ifndef FICLONE
#  define FICLONE       _IOW(0x94, 9, int)
#endif
#endif

#if defined(Q_OS_ANDROID)
// statx() is disabled on Android because quite a few systems
// come with sandboxes that kill applications that make system calls outside a
// whitelist and several Android vendors can't be bothered to update the list.
#  undef STATX_BASIC_STATS
#endif

#ifndef STATX_ALL
struct statx { mode_t stx_mode; };      // dummy
#endif

QT_BEGIN_NAMESPACE

enum {
#ifdef Q_OS_ANDROID
    // On Android, the link(2) system call has been observed to always fail
    // with EACCES, regardless of whether there are permission problems or not.
    SupportsHardlinking = false
#else
    SupportsHardlinking = true
#endif
};

#if defined(Q_OS_DARWIN)
static inline bool hasResourcePropertyFlag(const QFileSystemMetaData &data,
                                           const QFileSystemEntry &entry,
                                           CFStringRef key)
{
    QCFString path = CFStringCreateWithFileSystemRepresentation(0,
        entry.nativeFilePath().constData());
    if (!path)
        return false;

    QCFType<CFURLRef> url = CFURLCreateWithFileSystemPath(0, path, kCFURLPOSIXPathStyle,
        data.hasFlags(QFileSystemMetaData::DirectoryType));
    if (!url)
        return false;

    CFBooleanRef value;
    if (CFURLCopyResourcePropertyForKey(url, key, &value, NULL)) {
        if (value == kCFBooleanTrue)
            return true;
    }

    return false;
}

static bool isPackage(const QFileSystemMetaData &data, const QFileSystemEntry &entry)
{
    if (!data.isDirectory())
        return false;

    QFileInfo info(entry.filePath());
    QString suffix = info.suffix();

    if (suffix.length() > 0) {
        // First step: is the extension known ?
        QCFType<CFStringRef> extensionRef = suffix.toCFString();
        QCFType<CFStringRef> uniformTypeIdentifier = UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension, extensionRef, NULL);
        if (UTTypeConformsTo(uniformTypeIdentifier, kUTTypeBundle))
            return true;

        // Second step: check if an application knows the package type
        QCFType<CFStringRef> path = entry.filePath().toCFString();
        QCFType<CFURLRef> url = CFURLCreateWithFileSystemPath(0, path, kCFURLPOSIXPathStyle, true);

        UInt32 type, creator;
        // Well created packages have the PkgInfo file
        if (CFBundleGetPackageInfoInDirectory(url, &type, &creator))
            return true;

#ifdef Q_OS_MACOS
        // Find if an application other than Finder claims to know how to handle the package
        QCFType<CFURLRef> application = LSCopyDefaultApplicationURLForURL(url,
            kLSRolesEditor | kLSRolesViewer, nullptr);

        if (application) {
            QCFType<CFBundleRef> bundle = CFBundleCreate(kCFAllocatorDefault, application);
            CFStringRef identifier = CFBundleGetIdentifier(bundle);
            QString applicationId = QString::fromCFString(identifier);
            if (applicationId != QLatin1String("com.apple.finder"))
                return true;
        }
#endif
    }

    // Third step: check if the directory has the package bit set
    return hasResourcePropertyFlag(data, entry, kCFURLIsPackageKey);
}
#endif

namespace {
namespace GetFileTimes {
#if !QT_CONFIG(futimens) && (QT_CONFIG(futimes))
template <typename T>
static inline typename QtPrivate::QEnableIf<(&T::st_atim, &T::st_mtim, true)>::Type get(const T *p, struct timeval *access, struct timeval *modification)
{
    access->tv_sec = p->st_atim.tv_sec;
    access->tv_usec = p->st_atim.tv_nsec / 1000;

    modification->tv_sec = p->st_mtim.tv_sec;
    modification->tv_usec = p->st_mtim.tv_nsec / 1000;
}

template <typename T>
static inline typename QtPrivate::QEnableIf<(&T::st_atimespec, &T::st_mtimespec, true)>::Type get(const T *p, struct timeval *access, struct timeval *modification)
{
    access->tv_sec = p->st_atimespec.tv_sec;
    access->tv_usec = p->st_atimespec.tv_nsec / 1000;

    modification->tv_sec = p->st_mtimespec.tv_sec;
    modification->tv_usec = p->st_mtimespec.tv_nsec / 1000;
}

#  ifndef st_atimensec
// if "st_atimensec" is defined, this would expand to invalid C++
template <typename T>
static inline typename QtPrivate::QEnableIf<(&T::st_atimensec, &T::st_mtimensec, true)>::Type get(const T *p, struct timeval *access, struct timeval *modification)
{
    access->tv_sec = p->st_atime;
    access->tv_usec = p->st_atimensec / 1000;

    modification->tv_sec = p->st_mtime;
    modification->tv_usec = p->st_mtimensec / 1000;
}
#  endif
#endif

qint64 timespecToMSecs(const timespec &spec)
{
    return (qint64(spec.tv_sec) * 1000) + (spec.tv_nsec / 1000000);
}

// fallback set
Q_DECL_UNUSED qint64 atime(const QT_STATBUF &statBuffer, ulong) { return qint64(statBuffer.st_atime) * 1000; }
Q_DECL_UNUSED qint64 birthtime(const QT_STATBUF &, ulong)       { return Q_INT64_C(0); }
Q_DECL_UNUSED qint64 ctime(const QT_STATBUF &statBuffer, ulong) { return qint64(statBuffer.st_ctime) * 1000; }
Q_DECL_UNUSED qint64 mtime(const QT_STATBUF &statBuffer, ulong) { return qint64(statBuffer.st_mtime) * 1000; }

// Xtim, POSIX.1-2008
template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_atim, true), qint64>::type
atime(const T &statBuffer, int)
{ return timespecToMSecs(statBuffer.st_atim); }

template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_birthtim, true), qint64>::type
birthtime(const T &statBuffer, int)
{ return timespecToMSecs(statBuffer.st_birthtim); }

template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_ctim, true), qint64>::type
ctime(const T &statBuffer, int)
{ return timespecToMSecs(statBuffer.st_ctim); }

template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_mtim, true), qint64>::type
mtime(const T &statBuffer, int)
{ return timespecToMSecs(statBuffer.st_mtim); }

#ifndef st_mtimespec
// Xtimespec
template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_atimespec, true), qint64>::type
atime(const T &statBuffer, int)
{ return timespecToMSecs(statBuffer.st_atimespec); }

template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_birthtimespec, true), qint64>::type
birthtime(const T &statBuffer, int)
{ return timespecToMSecs(statBuffer.st_birthtimespec); }

template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_ctimespec, true), qint64>::type
ctime(const T &statBuffer, int)
{ return timespecToMSecs(statBuffer.st_ctimespec); }

template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_mtimespec, true), qint64>::type
mtime(const T &statBuffer, int)
{ return timespecToMSecs(statBuffer.st_mtimespec); }
#endif

#if !defined(st_mtimensec) && !defined(__alpha__)
// Xtimensec
template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_atimensec, true), qint64>::type
atime(const T &statBuffer, int)
{ return statBuffer.st_atime * Q_INT64_C(1000) + statBuffer.st_atimensec / 1000000; }

template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_birthtimensec, true), qint64>::type
birthtime(const T &statBuffer, int)
{ return statBuffer.st_birthtime * Q_INT64_C(1000) + statBuffer.st_birthtimensec / 1000000; }

template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_ctimensec, true), qint64>::type
ctime(const T &statBuffer, int)
{ return statBuffer.st_ctime * Q_INT64_C(1000) + statBuffer.st_ctimensec / 1000000; }

template <typename T>
Q_DECL_UNUSED static typename std::enable_if<(&T::st_mtimensec, true), qint64>::type
mtime(const T &statBuffer, int)
{ return statBuffer.st_mtime * Q_INT64_C(1000) + statBuffer.st_mtimensec / 1000000; }
#endif
} // namespace GetFileTimes
} // unnamed namespace

#ifdef STATX_BASIC_STATS
static int qt_real_statx(int fd, const char *pathname, int flags, struct statx *statxBuffer)
{
    unsigned mask = STATX_BASIC_STATS | STATX_BTIME;
    int ret = statx(fd, pathname, flags, mask, statxBuffer);
    return ret == -1 ? -errno : 0;
}

static int qt_statx(const char *pathname, struct statx *statxBuffer)
{
    return qt_real_statx(AT_FDCWD, pathname, 0, statxBuffer);
}

static int qt_lstatx(const char *pathname, struct statx *statxBuffer)
{
    return qt_real_statx(AT_FDCWD, pathname, AT_SYMLINK_NOFOLLOW, statxBuffer);
}

static int qt_fstatx(int fd, struct statx *statxBuffer)
{
    return qt_real_statx(fd, "", AT_EMPTY_PATH, statxBuffer);
}

inline void QFileSystemMetaData::fillFromStatxBuf(const struct statx &statxBuffer)
{
    // Permissions
    if (statxBuffer.stx_mode & S_IRUSR)
        entryFlags |= QFileSystemMetaData::OwnerReadPermission;
    if (statxBuffer.stx_mode & S_IWUSR)
        entryFlags |= QFileSystemMetaData::OwnerWritePermission;
    if (statxBuffer.stx_mode & S_IXUSR)
        entryFlags |= QFileSystemMetaData::OwnerExecutePermission;

    if (statxBuffer.stx_mode & S_IRGRP)
        entryFlags |= QFileSystemMetaData::GroupReadPermission;
    if (statxBuffer.stx_mode & S_IWGRP)
        entryFlags |= QFileSystemMetaData::GroupWritePermission;
    if (statxBuffer.stx_mode & S_IXGRP)
        entryFlags |= QFileSystemMetaData::GroupExecutePermission;

    if (statxBuffer.stx_mode & S_IROTH)
        entryFlags |= QFileSystemMetaData::OtherReadPermission;
    if (statxBuffer.stx_mode & S_IWOTH)
        entryFlags |= QFileSystemMetaData::OtherWritePermission;
    if (statxBuffer.stx_mode & S_IXOTH)
        entryFlags |= QFileSystemMetaData::OtherExecutePermission;

    // Type
    if (S_ISLNK(statxBuffer.stx_mode))
        entryFlags |= QFileSystemMetaData::LinkType;
    if ((statxBuffer.stx_mode & S_IFMT) == S_IFREG)
        entryFlags |= QFileSystemMetaData::FileType;
    else if ((statxBuffer.stx_mode & S_IFMT) == S_IFDIR)
        entryFlags |= QFileSystemMetaData::DirectoryType;
    else if ((statxBuffer.stx_mode & S_IFMT) != S_IFBLK)
        entryFlags |= QFileSystemMetaData::SequentialType;

    // Attributes
    entryFlags |= QFileSystemMetaData::ExistsAttribute; // inode exists
    if (statxBuffer.stx_nlink == 0)
        entryFlags |= QFileSystemMetaData::WasDeletedAttribute;
    size_ = qint64(statxBuffer.stx_size);

    // Times
    auto toMSecs = [](struct statx_timestamp ts)
    {
        return qint64(ts.tv_sec) * 1000 + (ts.tv_nsec / 1000000);
    };
    accessTime_ = toMSecs(statxBuffer.stx_atime);
    metadataChangeTime_ = toMSecs(statxBuffer.stx_ctime);
    modificationTime_ = toMSecs(statxBuffer.stx_mtime);
    if (statxBuffer.stx_mask & STATX_BTIME)
        birthTime_ = toMSecs(statxBuffer.stx_btime);
    else
        birthTime_ = 0;

    userId_ = statxBuffer.stx_uid;
    groupId_ = statxBuffer.stx_gid;
}
#else
static int qt_statx(const char *, struct statx *)
{ return -ENOSYS; }

static int qt_lstatx(const char *, struct statx *)
{ return -ENOSYS; }

static int qt_fstatx(int, struct statx *)
{ return -ENOSYS; }

inline void QFileSystemMetaData::fillFromStatxBuf(const struct statx &)
{ }
#endif

//static
bool QFileSystemEngine::fillMetaData(int fd, QFileSystemMetaData &data)
{
    data.entryFlags &= ~QFileSystemMetaData::PosixStatFlags;
    data.knownFlagsMask |= QFileSystemMetaData::PosixStatFlags;

    union {
        struct statx statxBuffer;
        QT_STATBUF statBuffer;
    };

    int ret = qt_fstatx(fd, &statxBuffer);
    if (ret != -ENOSYS) {
        if (ret == 0) {
            data.fillFromStatxBuf(statxBuffer);
            return true;
        }
        return false;
    }

    if (QT_FSTAT(fd, &statBuffer) == 0) {
        data.fillFromStatBuf(statBuffer);
        return true;
    }

    return false;
}

#if defined(_DEXTRA_FIRST)
static void fillStat64fromStat32(struct stat64 *statBuf64, const struct stat &statBuf32)
{
    statBuf64->st_mode = statBuf32.st_mode;
    statBuf64->st_size = statBuf32.st_size;
#if _POSIX_VERSION >= 200809L
    statBuf64->st_ctim = statBuf32.st_ctim;
    statBuf64->st_mtim = statBuf32.st_mtim;
    statBuf64->st_atim = statBuf32.st_atim;
#else
    statBuf64->st_ctime = statBuf32.st_ctime;
    statBuf64->st_mtime = statBuf32.st_mtime;
    statBuf64->st_atime = statBuf32.st_atime;
#endif
    statBuf64->st_uid = statBuf32.st_uid;
    statBuf64->st_gid = statBuf32.st_gid;
}
#endif

void QFileSystemMetaData::fillFromStatBuf(const QT_STATBUF &statBuffer)
{
    // Permissions
    if (statBuffer.st_mode & S_IRUSR)
        entryFlags |= QFileSystemMetaData::OwnerReadPermission;
    if (statBuffer.st_mode & S_IWUSR)
        entryFlags |= QFileSystemMetaData::OwnerWritePermission;
    if (statBuffer.st_mode & S_IXUSR)
        entryFlags |= QFileSystemMetaData::OwnerExecutePermission;

    if (statBuffer.st_mode & S_IRGRP)
        entryFlags |= QFileSystemMetaData::GroupReadPermission;
    if (statBuffer.st_mode & S_IWGRP)
        entryFlags |= QFileSystemMetaData::GroupWritePermission;
    if (statBuffer.st_mode & S_IXGRP)
        entryFlags |= QFileSystemMetaData::GroupExecutePermission;

    if (statBuffer.st_mode & S_IROTH)
        entryFlags |= QFileSystemMetaData::OtherReadPermission;
    if (statBuffer.st_mode & S_IWOTH)
        entryFlags |= QFileSystemMetaData::OtherWritePermission;
    if (statBuffer.st_mode & S_IXOTH)
        entryFlags |= QFileSystemMetaData::OtherExecutePermission;

    // Type
    if ((statBuffer.st_mode & S_IFMT) == S_IFREG)
        entryFlags |= QFileSystemMetaData::FileType;
    else if ((statBuffer.st_mode & S_IFMT) == S_IFDIR)
        entryFlags |= QFileSystemMetaData::DirectoryType;
    else if ((statBuffer.st_mode & S_IFMT) != S_IFBLK)
        entryFlags |= QFileSystemMetaData::SequentialType;

    // Attributes
    entryFlags |= QFileSystemMetaData::ExistsAttribute; // inode exists
    if (statBuffer.st_nlink == 0)
        entryFlags |= QFileSystemMetaData::WasDeletedAttribute;
    size_ = statBuffer.st_size;
#ifdef UF_HIDDEN
    if (statBuffer.st_flags & UF_HIDDEN) {
        entryFlags |= QFileSystemMetaData::HiddenAttribute;
        knownFlagsMask |= QFileSystemMetaData::HiddenAttribute;
    }
#endif

    // Times
    accessTime_ = GetFileTimes::atime(statBuffer, 0);
    birthTime_ = GetFileTimes::birthtime(statBuffer, 0);
    metadataChangeTime_ = GetFileTimes::ctime(statBuffer, 0);
    modificationTime_ = GetFileTimes::mtime(statBuffer, 0);

    userId_ = statBuffer.st_uid;
    groupId_ = statBuffer.st_gid;
}

void QFileSystemMetaData::fillFromDirEnt(const QT_DIRENT &entry)
{
#if defined(_DEXTRA_FIRST)
    knownFlagsMask = 0;
    entryFlags = 0;
    for (dirent_extra *extra = _DEXTRA_FIRST(&entry); _DEXTRA_VALID(extra, &entry);
         extra = _DEXTRA_NEXT(extra)) {
        if (extra->d_type == _DTYPE_STAT || extra->d_type == _DTYPE_LSTAT) {

            const struct dirent_extra_stat * const extra_stat =
                    reinterpret_cast<struct dirent_extra_stat *>(extra);

            // Remember whether this was a link or not, this saves an lstat() call later.
            if (extra->d_type == _DTYPE_LSTAT) {
                knownFlagsMask |= QFileSystemMetaData::LinkType;
                if (S_ISLNK(extra_stat->d_stat.st_mode))
                    entryFlags |= QFileSystemMetaData::LinkType;
            }

            // For symlinks, the extra type _DTYPE_LSTAT doesn't work for filling out the meta data,
            // as we need the stat() information there, not the lstat() information.
            // In this case, don't use the extra information.
            // Unfortunately, readdir() never seems to return extra info of type _DTYPE_STAT, so for
            // symlinks, we always incur the cost of an extra stat() call later.
            if (S_ISLNK(extra_stat->d_stat.st_mode) && extra->d_type == _DTYPE_LSTAT)
                continue;

#if defined(QT_USE_XOPEN_LFS_EXTENSIONS) && defined(QT_LARGEFILE_SUPPORT)
            // Even with large file support, d_stat is always of type struct stat, not struct stat64,
            // so it needs to be converted
            struct stat64 statBuf;
            fillStat64fromStat32(&statBuf, extra_stat->d_stat);
            fillFromStatBuf(statBuf);
#else
            fillFromStatBuf(extra_stat->d_stat);
#endif
            knownFlagsMask |= QFileSystemMetaData::PosixStatFlags;
            if (!S_ISLNK(extra_stat->d_stat.st_mode)) {
                knownFlagsMask |= QFileSystemMetaData::ExistsAttribute;
                entryFlags |= QFileSystemMetaData::ExistsAttribute;
            }
        }
    }
#elif defined(_DIRENT_HAVE_D_TYPE) || defined(Q_OS_BSD4)
    // BSD4 includes OS X and iOS

    // ### This will clear all entry flags and knownFlagsMask
    switch (entry.d_type)
    {
    case DT_DIR:
        knownFlagsMask = QFileSystemMetaData::LinkType
            | QFileSystemMetaData::FileType
            | QFileSystemMetaData::DirectoryType
            | QFileSystemMetaData::SequentialType
            | QFileSystemMetaData::ExistsAttribute;

        entryFlags = QFileSystemMetaData::DirectoryType
            | QFileSystemMetaData::ExistsAttribute;

        break;

    case DT_BLK:
        knownFlagsMask = QFileSystemMetaData::LinkType
            | QFileSystemMetaData::FileType
            | QFileSystemMetaData::DirectoryType
            | QFileSystemMetaData::BundleType
            | QFileSystemMetaData::AliasType
            | QFileSystemMetaData::SequentialType
            | QFileSystemMetaData::ExistsAttribute;

        entryFlags = QFileSystemMetaData::ExistsAttribute;

        break;

    case DT_CHR:
    case DT_FIFO:
    case DT_SOCK:
        // ### System attribute
        knownFlagsMask = QFileSystemMetaData::LinkType
            | QFileSystemMetaData::FileType
            | QFileSystemMetaData::DirectoryType
            | QFileSystemMetaData::BundleType
            | QFileSystemMetaData::AliasType
            | QFileSystemMetaData::SequentialType
            | QFileSystemMetaData::ExistsAttribute;

        entryFlags = QFileSystemMetaData::SequentialType
            | QFileSystemMetaData::ExistsAttribute;

        break;

    case DT_LNK:
        knownFlagsMask = QFileSystemMetaData::LinkType;
        entryFlags = QFileSystemMetaData::LinkType;
        break;

    case DT_REG:
        knownFlagsMask = QFileSystemMetaData::LinkType
            | QFileSystemMetaData::FileType
            | QFileSystemMetaData::DirectoryType
            | QFileSystemMetaData::BundleType
            | QFileSystemMetaData::SequentialType
            | QFileSystemMetaData::ExistsAttribute;

        entryFlags = QFileSystemMetaData::FileType
            | QFileSystemMetaData::ExistsAttribute;

        break;

    case DT_UNKNOWN:
    default:
        clear();
    }
#else
    Q_UNUSED(entry)
#endif
}

//static
QFileSystemEntry QFileSystemEngine::getLinkTarget(const QFileSystemEntry &link, QFileSystemMetaData &data)
{
    Q_CHECK_FILE_NAME(link, link);

    QByteArray s = qt_readlink(link.nativeFilePath().constData());
    if (s.length() > 0) {
        QString ret;
        if (!data.hasFlags(QFileSystemMetaData::DirectoryType))
            fillMetaData(link, data, QFileSystemMetaData::DirectoryType);
        if (data.isDirectory() && s[0] != '/') {
            QDir parent(link.filePath());
            parent.cdUp();
            ret = parent.path();
            if (!ret.isEmpty() && !ret.endsWith(QLatin1Char('/')))
                ret += QLatin1Char('/');
        }
        ret += QFile::decodeName(s);

        if (!ret.startsWith(QLatin1Char('/')))
            ret.prepend(absoluteName(link).path() + QLatin1Char('/'));
        ret = QDir::cleanPath(ret);
        if (ret.size() > 1 && ret.endsWith(QLatin1Char('/')))
            ret.chop(1);
        return QFileSystemEntry(ret);
    }
#if defined(Q_OS_DARWIN)
    {
        QCFString path = CFStringCreateWithFileSystemRepresentation(0,
            QFile::encodeName(QDir::cleanPath(link.filePath())).data());
        if (!path)
            return QFileSystemEntry();

        QCFType<CFURLRef> url = CFURLCreateWithFileSystemPath(0, path, kCFURLPOSIXPathStyle,
            data.hasFlags(QFileSystemMetaData::DirectoryType));
        if (!url)
            return QFileSystemEntry();

        QCFType<CFDataRef> bookmarkData = CFURLCreateBookmarkDataFromFile(0, url, NULL);
        if (!bookmarkData)
            return QFileSystemEntry();

        QCFType<CFURLRef> resolvedUrl = CFURLCreateByResolvingBookmarkData(0,
            bookmarkData,
            (CFURLBookmarkResolutionOptions)(kCFBookmarkResolutionWithoutUIMask
                | kCFBookmarkResolutionWithoutMountingMask), NULL, NULL, NULL, NULL);
        if (!resolvedUrl)
            return QFileSystemEntry();

        QCFString cfstr(CFURLCopyFileSystemPath(resolvedUrl, kCFURLPOSIXPathStyle));
        if (!cfstr)
            return QFileSystemEntry();

        return QFileSystemEntry(QString::fromCFString(cfstr));
    }
#endif
    return QFileSystemEntry();
}

//static
QFileSystemEntry QFileSystemEngine::canonicalName(const QFileSystemEntry &entry, QFileSystemMetaData &data)
{
    Q_CHECK_FILE_NAME(entry, entry);

#if !defined(Q_OS_MAC) && !defined(Q_OS_QNX) && !defined(Q_OS_ANDROID) && !defined(Q_OS_HAIKU) && _POSIX_VERSION < 200809L
    // realpath(X,0) is not supported
    Q_UNUSED(data);
    return QFileSystemEntry(slowCanonicalized(absoluteName(entry).filePath()));
#else
    char stack_result[PATH_MAX+1];
    char *resolved_name = nullptr;
# if defined(Q_OS_DARWIN) || defined(Q_OS_ANDROID)
    // On some Android and macOS versions, realpath() will return a path even if
    // it does not exist. To work around this, we check existence in advance.
    if (!data.hasFlags(QFileSystemMetaData::ExistsAttribute))
        fillMetaData(entry, data, QFileSystemMetaData::ExistsAttribute);

    if (!data.exists()) {
        errno = ENOENT;
    } else {
        resolved_name = stack_result;
    }
    if (resolved_name && realpath(entry.nativeFilePath().constData(), resolved_name) == nullptr)
        resolved_name = nullptr;
# else
#  if _POSIX_VERSION >= 200801L // ask realpath to allocate memory
    resolved_name = realpath(entry.nativeFilePath().constData(), nullptr);
#  else
    resolved_name = stack_result;
    if (realpath(entry.nativeFilePath().constData(), resolved_name) == nullptr)
        resolved_name = nullptr;
#  endif
# endif
    if (resolved_name) {
        data.knownFlagsMask |= QFileSystemMetaData::ExistsAttribute;
        data.entryFlags |= QFileSystemMetaData::ExistsAttribute;
        QString canonicalPath = QDir::cleanPath(QFile::decodeName(resolved_name));
        if (resolved_name != stack_result)
            free(resolved_name);
        return QFileSystemEntry(canonicalPath);
    } else if (errno == ENOENT || errno == ENOTDIR) { // file doesn't exist
        data.knownFlagsMask |= QFileSystemMetaData::ExistsAttribute;
        data.entryFlags &= ~(QFileSystemMetaData::ExistsAttribute);
        return QFileSystemEntry();
    }
    return entry;
#endif
}

//static
QFileSystemEntry QFileSystemEngine::absoluteName(const QFileSystemEntry &entry)
{
    Q_CHECK_FILE_NAME(entry, entry);

    if (entry.isAbsolute() && entry.isClean())
        return entry;

    QByteArray orig = entry.nativeFilePath();
    QByteArray result;
    if (orig.isEmpty() || !orig.startsWith('/')) {
        QFileSystemEntry cur(currentPath());
        result = cur.nativeFilePath();
    }
    if (!orig.isEmpty() && !(orig.length() == 1 && orig[0] == '.')) {
        if (!result.isEmpty() && !result.endsWith('/'))
            result.append('/');
        result.append(orig);
    }

    if (result.length() == 1 && result[0] == '/')
        return QFileSystemEntry(result, QFileSystemEntry::FromNativePath());
    const bool isDir = result.endsWith('/');

    /* as long as QDir::cleanPath() operates on a QString we have to convert to a string here.
     * ideally we never convert to a string since that loses information. Please fix after
     * we get a QByteArray version of QDir::cleanPath()
     */
    QFileSystemEntry resultingEntry(result, QFileSystemEntry::FromNativePath());
    QString stringVersion = QDir::cleanPath(resultingEntry.filePath());
    if (isDir)
        stringVersion.append(QLatin1Char('/'));
    return QFileSystemEntry(stringVersion);
}

//static
QByteArray QFileSystemEngine::id(const QFileSystemEntry &entry)
{
    Q_CHECK_FILE_NAME(entry, QByteArray());

    QT_STATBUF statResult;
    if (QT_STAT(entry.nativeFilePath().constData(), &statResult)) {
        if (errno != ENOENT)
            qErrnoWarning("stat() failed for '%s'", entry.nativeFilePath().constData());
        return QByteArray();
    }
    QByteArray result = QByteArray::number(quint64(statResult.st_dev), 16);
    result += ':';
    result += QByteArray::number(quint64(statResult.st_ino));
    return result;
}

//static
QByteArray QFileSystemEngine::id(int fd)
{
    QT_STATBUF statResult;
    if (QT_FSTAT(fd, &statResult)) {
        qErrnoWarning("fstat() failed for fd %d", fd);
        return QByteArray();
    }
    QByteArray result = QByteArray::number(quint64(statResult.st_dev), 16);
    result += ':';
    result += QByteArray::number(quint64(statResult.st_ino));
    return result;
}

//static
QString QFileSystemEngine::resolveUserName(uint userId)
{
#if QT_CONFIG(thread) && defined(_POSIX_THREAD_SAFE_FUNCTIONS) && !defined(Q_OS_OPENBSD)
    int size_max = sysconf(_SC_GETPW_R_SIZE_MAX);
    if (size_max == -1)
        size_max = 1024;
    QVarLengthArray<char, 1024> buf(size_max);
#endif

#if !defined(Q_OS_INTEGRITY) && !defined(Q_OS_WASM)
    struct passwd *pw = nullptr;
#if QT_CONFIG(thread) && defined(_POSIX_THREAD_SAFE_FUNCTIONS) && !defined(Q_OS_OPENBSD) && !defined(Q_OS_VXWORKS)
    struct passwd entry;
    getpwuid_r(userId, &entry, buf.data(), buf.size(), &pw);
#else
    pw = getpwuid(userId);
#endif
    if (pw)
        return QFile::decodeName(QByteArray(pw->pw_name));
#else // Integrity || WASM
    Q_UNUSED(userId);
#endif
    return QString();
}

//static
QString QFileSystemEngine::resolveGroupName(uint groupId)
{
#if QT_CONFIG(thread) && defined(_POSIX_THREAD_SAFE_FUNCTIONS) && !defined(Q_OS_OPENBSD)
    int size_max = sysconf(_SC_GETPW_R_SIZE_MAX);
    if (size_max == -1)
        size_max = 1024;
    QVarLengthArray<char, 1024> buf(size_max);
#endif

#if !defined(Q_OS_INTEGRITY) && !defined(Q_OS_WASM)
    struct group *gr = nullptr;
#if QT_CONFIG(thread) && defined(_POSIX_THREAD_SAFE_FUNCTIONS) && !defined(Q_OS_OPENBSD) && !defined(Q_OS_VXWORKS) && (!defined(Q_OS_ANDROID) || defined(Q_OS_ANDROID) && (__ANDROID_API__ >= 24))
    size_max = sysconf(_SC_GETGR_R_SIZE_MAX);
    if (size_max == -1)
        size_max = 1024;
    buf.resize(size_max);
    struct group entry;
    // Some large systems have more members than the POSIX max size
    // Loop over by doubling the buffer size (upper limit 250k)
    for (unsigned size = size_max; size < 256000; size += size)
    {
        buf.resize(size);
        // ERANGE indicates that the buffer was too small
        if (!getgrgid_r(groupId, &entry, buf.data(), buf.size(), &gr)
            || errno != ERANGE)
            break;
    }
#else
    gr = getgrgid(groupId);
#endif
    if (gr)
        return QFile::decodeName(QByteArray(gr->gr_name));
#else // Integrity || WASM
    Q_UNUSED(groupId);
#endif
    return QString();
}

#if defined(Q_OS_DARWIN)
//static
QString QFileSystemEngine::bundleName(const QFileSystemEntry &entry)
{
    QCFType<CFURLRef> url = CFURLCreateWithFileSystemPath(0, QCFString(entry.filePath()),
            kCFURLPOSIXPathStyle, true);
    if (QCFType<CFDictionaryRef> dict = CFBundleCopyInfoDictionaryForURL(url)) {
        if (CFTypeRef name = (CFTypeRef)CFDictionaryGetValue(dict, kCFBundleNameKey)) {
            if (CFGetTypeID(name) == CFStringGetTypeID())
                return QString::fromCFString((CFStringRef)name);
        }
    }
    return QString();
}
#endif

//static
bool QFileSystemEngine::fillMetaData(const QFileSystemEntry &entry, QFileSystemMetaData &data,
        QFileSystemMetaData::MetaDataFlags what)
{
    Q_CHECK_FILE_NAME(entry, false);

#if defined(Q_OS_DARWIN)
    if (what & QFileSystemMetaData::BundleType) {
        if (!data.hasFlags(QFileSystemMetaData::DirectoryType))
            what |= QFileSystemMetaData::DirectoryType;
    }
#endif
#ifdef UF_HIDDEN
    if (what & QFileSystemMetaData::HiddenAttribute) {
        // OS X >= 10.5: st_flags & UF_HIDDEN
        what |= QFileSystemMetaData::PosixStatFlags;
    }
#endif // defined(Q_OS_DARWIN)

    // if we're asking for any of the stat(2) flags, then we're getting them all
    if (what & QFileSystemMetaData::PosixStatFlags)
        what |= QFileSystemMetaData::PosixStatFlags;

    data.entryFlags &= ~what;

    const QByteArray nativeFilePath = entry.nativeFilePath();
    int entryErrno = 0; // innocent until proven otherwise

    // first, we may try lstat(2). Possible outcomes:
    //  - success and is a symlink: filesystem entry exists, but we need stat(2)
    //    -> statResult = -1;
    //  - success and is not a symlink: filesystem entry exists and we're done
    //    -> statResult = 0
    //  - failure: really non-existent filesystem entry
    //    -> entryExists = false; statResult = 0;
    //    both stat(2) and lstat(2) may generate a number of different errno
    //    conditions, but of those, the only ones that could happen and the
    //    entry still exist are EACCES, EFAULT, ENOMEM and EOVERFLOW. If we get
    //    EACCES or ENOMEM, then we have no choice on how to proceed, so we may
    //    as well conclude it doesn't exist; EFAULT can't happen and EOVERFLOW
    //    shouldn't happen because we build in _LARGEFIE64.
    union {
        QT_STATBUF statBuffer;
        struct statx statxBuffer;
    };
    int statResult = -1;
    if (what & QFileSystemMetaData::LinkType) {
        mode_t mode = 0;
        statResult = qt_lstatx(nativeFilePath, &statxBuffer);
        if (statResult == -ENOSYS) {
            // use lstst(2)
            statResult = QT_LSTAT(nativeFilePath, &statBuffer);
            if (statResult == 0)
                mode = statBuffer.st_mode;
        } else if (statResult == 0) {
            statResult = 1; // record it was statx(2) that succeeded
            mode = statxBuffer.stx_mode;
        }

        if (statResult >= 0) {
            if (S_ISLNK(mode)) {
               // it's a symlink, we don't know if the file "exists"
                data.entryFlags |= QFileSystemMetaData::LinkType;
                statResult = -1;    // force stat(2) below
            } else {
                // it's a reagular file and it exists
                if (statResult)
                    data.fillFromStatxBuf(statxBuffer);
                else
                    data.fillFromStatBuf(statBuffer);
                data.knownFlagsMask |= QFileSystemMetaData::PosixStatFlags
                        | QFileSystemMetaData::ExistsAttribute;
                data.entryFlags |= QFileSystemMetaData::ExistsAttribute;
            }
        } else {
            // it doesn't exist
            entryErrno = errno;
            data.knownFlagsMask |= QFileSystemMetaData::ExistsAttribute;
        }

        data.knownFlagsMask |= QFileSystemMetaData::LinkType;
    }

    // second, we try a regular stat(2)
    if (statResult == -1 && (what & QFileSystemMetaData::PosixStatFlags)) {
        if (entryErrno == 0 && statResult == -1) {
            data.entryFlags &= ~QFileSystemMetaData::PosixStatFlags;
            statResult = qt_statx(nativeFilePath, &statxBuffer);
            if (statResult == -ENOSYS) {
                // use stat(2)
                statResult = QT_STAT(nativeFilePath, &statBuffer);
                if (statResult == 0)
                    data.fillFromStatBuf(statBuffer);
            } else if (statResult == 0) {
                data.fillFromStatxBuf(statxBuffer);
            }
        }

        if (statResult != 0) {
            entryErrno = errno;
            data.birthTime_ = 0;
            data.metadataChangeTime_ = 0;
            data.modificationTime_ = 0;
            data.accessTime_ = 0;
            data.size_ = 0;
            data.userId_ = (uint) -2;
            data.groupId_ = (uint) -2;
        }

        // reset the mask
        data.knownFlagsMask |= QFileSystemMetaData::PosixStatFlags
            | QFileSystemMetaData::ExistsAttribute;
    }

    // third, we try access(2)
    if (what & (QFileSystemMetaData::UserPermissions | QFileSystemMetaData::ExistsAttribute)) {
        // calculate user permissions
        auto checkAccess = [&](QFileSystemMetaData::MetaDataFlag flag, int mode) {
            if (entryErrno != 0 || (what & flag) == 0)
                return;
            if (QT_ACCESS(nativeFilePath, mode) == 0) {
                // access ok (and file exists)
                data.entryFlags |= flag | QFileSystemMetaData::ExistsAttribute;
            } else if (errno != EACCES && errno != EROFS) {
                entryErrno = errno;
            }
        };

        checkAccess(QFileSystemMetaData::UserReadPermission, R_OK);
        checkAccess(QFileSystemMetaData::UserWritePermission, W_OK);
        checkAccess(QFileSystemMetaData::UserExecutePermission, X_OK);

        // if we still haven't found out if the file exists, try F_OK
        if (entryErrno == 0 && (data.entryFlags & QFileSystemMetaData::ExistsAttribute) == 0) {
            if (QT_ACCESS(nativeFilePath, F_OK) == -1)
                entryErrno = errno;
            else
                data.entryFlags |= QFileSystemMetaData::ExistsAttribute;
        }

        data.knownFlagsMask |= (what & QFileSystemMetaData::UserPermissions) |
                QFileSystemMetaData::ExistsAttribute;
    }

#if defined(Q_OS_DARWIN)
    if (what & QFileSystemMetaData::AliasType) {
        if (entryErrno == 0 && hasResourcePropertyFlag(data, entry, kCFURLIsAliasFileKey))
            data.entryFlags |= QFileSystemMetaData::AliasType;
        data.knownFlagsMask |= QFileSystemMetaData::AliasType;
    }

    if (what & QFileSystemMetaData::BundleType) {
        if (entryErrno == 0 && isPackage(data, entry))
            data.entryFlags |= QFileSystemMetaData::BundleType;

        data.knownFlagsMask |= QFileSystemMetaData::BundleType;
    }
#endif

    if (what & QFileSystemMetaData::HiddenAttribute
            && !data.isHidden()) {
        QString fileName = entry.fileName();
        if ((fileName.size() > 0 && fileName.at(0) == QLatin1Char('.'))
#if defined(Q_OS_DARWIN)
                || (entryErrno == 0 && hasResourcePropertyFlag(data, entry, kCFURLIsHiddenKey))
#endif
                )
            data.entryFlags |= QFileSystemMetaData::HiddenAttribute;
        data.knownFlagsMask |= QFileSystemMetaData::HiddenAttribute;
    }

    if (entryErrno != 0) {
        what &= ~QFileSystemMetaData::LinkType; // don't clear link: could be broken symlink
        data.clearFlags(what);
        return false;
    }
    return true;
}

// static
bool QFileSystemEngine::cloneFile(int srcfd, int dstfd, const QFileSystemMetaData &knownData)
{
    QT_STATBUF statBuffer;
    if (knownData.hasFlags(QFileSystemMetaData::PosixStatFlags) &&
            knownData.isFile()) {
        statBuffer.st_mode = S_IFREG;
    } else if (knownData.hasFlags(QFileSystemMetaData::PosixStatFlags) &&
               knownData.isDirectory()) {
        return false;   // fcopyfile(3) returns success on directories
    } else if (QT_FSTAT(srcfd, &statBuffer) == -1) {
        return false;
    } else if (!S_ISREG((statBuffer.st_mode))) {
        // not a regular file, let QFile do the copy
        return false;
    }

#if defined(Q_OS_LINUX)
    // first, try FICLONE (only works on regular files and only on certain fs)
    if (::ioctl(dstfd, FICLONE, srcfd) == 0)
        return true;

    // Second, try sendfile (it can send to some special types too).
    // sendfile(2) is limited in the kernel to 2G - 4k
    const size_t SendfileSize = 0x7ffff000;

    ssize_t n = ::sendfile(dstfd, srcfd, NULL, SendfileSize);
    if (n == -1) {
        // if we got an error here, give up and try at an upper layer
        return false;
    }

    while (n) {
        n = ::sendfile(dstfd, srcfd, NULL, SendfileSize);
        if (n == -1) {
            // uh oh, this is probably a real error (like ENOSPC), but we have
            // no way to notify QFile of partial success, so just erase any work
            // done (hopefully we won't get any errors, because there's nothing
            // we can do about them)
            n = ftruncate(dstfd, 0);
            n = lseek(srcfd, 0, SEEK_SET);
            n = lseek(dstfd, 0, SEEK_SET);
            return false;
        }
    }

    return true;
#elif defined(Q_OS_DARWIN)
    // try fcopyfile
    return fcopyfile(srcfd, dstfd, nullptr, COPYFILE_DATA | COPYFILE_STAT) == 0;
#else
    Q_UNUSED(dstfd);
    return false;
#endif
}

// Note: if \a shouldMkdirFirst is false, we assume the caller did try to mkdir
// before calling this function.
static bool createDirectoryWithParents(const QByteArray &nativeName, bool shouldMkdirFirst = true)
{
    // helper function to check if a given path is a directory, since mkdir can
    // fail if the dir already exists (it may have been created by another
    // thread or another process)
    const auto isDir = [](const QByteArray &nativeName) {
        QT_STATBUF st;
        return QT_STAT(nativeName.constData(), &st) == 0 && (st.st_mode & S_IFMT) == S_IFDIR;
    };

    if (shouldMkdirFirst && QT_MKDIR(nativeName, 0777) == 0)
        return true;
    if (errno == EEXIST)
        return isDir(nativeName);
    if (errno != ENOENT)
        return false;

    // mkdir failed because the parent dir doesn't exist, so try to create it
    int slash = nativeName.lastIndexOf('/');
    if (slash < 1)
        return false;

    QByteArray parentNativeName = nativeName.left(slash);
    if (!createDirectoryWithParents(parentNativeName))
        return false;

    // try again
    if (QT_MKDIR(nativeName, 0777) == 0)
        return true;
    return errno == EEXIST && isDir(nativeName);
}

//static
bool QFileSystemEngine::createDirectory(const QFileSystemEntry &entry, bool createParents)
{
    QString dirName = entry.filePath();
    Q_CHECK_FILE_NAME(dirName, false);

    // Darwin doesn't support trailing /'s, so remove for everyone
    while (dirName.size() > 1 && dirName.endsWith(QLatin1Char('/')))
        dirName.chop(1);

    // try to mkdir this directory
    QByteArray nativeName = QFile::encodeName(dirName);
    if (QT_MKDIR(nativeName, 0777) == 0)
        return true;
    if (!createParents)
        return false;

    return createDirectoryWithParents(nativeName, false);
}

//static
bool QFileSystemEngine::removeDirectory(const QFileSystemEntry &entry, bool removeEmptyParents)
{
    Q_CHECK_FILE_NAME(entry, false);

    if (removeEmptyParents) {
        QString dirName = QDir::cleanPath(entry.filePath());
        for (int oldslash = 0, slash=dirName.length(); slash > 0; oldslash = slash) {
            const QByteArray chunk = QFile::encodeName(dirName.left(slash));
            QT_STATBUF st;
            if (QT_STAT(chunk.constData(), &st) != -1) {
                if ((st.st_mode & S_IFMT) != S_IFDIR)
                    return false;
                if (::rmdir(chunk.constData()) != 0)
                    return oldslash != 0;
            } else {
                return false;
            }
            slash = dirName.lastIndexOf(QDir::separator(), oldslash-1);
        }
        return true;
    }
    return rmdir(QFile::encodeName(entry.filePath()).constData()) == 0;
}

//static
bool QFileSystemEngine::createLink(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error)
{
    Q_CHECK_FILE_NAME(source, false);
    Q_CHECK_FILE_NAME(target, false);

    if (::symlink(source.nativeFilePath().constData(), target.nativeFilePath().constData()) == 0)
        return true;
    error = QSystemError(errno, QSystemError::StandardLibraryError);
    return false;
}

//static
bool QFileSystemEngine::copyFile(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error)
{
#if defined(Q_OS_DARWIN)
    if (::clonefile(source.nativeFilePath().constData(),
                    target.nativeFilePath().constData(), 0) == 0)
        return true;
    error = QSystemError(errno, QSystemError::StandardLibraryError);
    return false;
#else
    Q_UNUSED(source);
    Q_UNUSED(target);
    error = QSystemError(ENOSYS, QSystemError::StandardLibraryError); //Function not implemented
    return false;
#endif
}

//static
bool QFileSystemEngine::renameFile(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error)
{
    QFileSystemEntry::NativePath srcPath = source.nativeFilePath();
    QFileSystemEntry::NativePath tgtPath = target.nativeFilePath();

    Q_CHECK_FILE_NAME(srcPath, false);
    Q_CHECK_FILE_NAME(tgtPath, false);

#if defined(RENAME_NOREPLACE) && QT_CONFIG(renameat2)
    if (renameat2(AT_FDCWD, srcPath, AT_FDCWD, tgtPath, RENAME_NOREPLACE) == 0)
        return true;

    // We can also get EINVAL for some non-local filesystems.
    if (errno != EINVAL) {
        error = QSystemError(errno, QSystemError::StandardLibraryError);
        return false;
    }
#endif
#if defined(Q_OS_DARWIN) && defined(RENAME_EXCL)
    if (renameatx_np(AT_FDCWD, srcPath, AT_FDCWD, tgtPath, RENAME_EXCL) == 0)
        return true;
    if (errno != ENOTSUP) {
        error = QSystemError(errno, QSystemError::StandardLibraryError);
        return false;
    }
#endif

    if (SupportsHardlinking && ::link(srcPath, tgtPath) == 0) {
        if (::unlink(srcPath) == 0)
            return true;

        // if we managed to link but can't unlink the source, it's likely
        // it's in a directory we don't have write access to; fail the
        // renaming instead
        int savedErrno = errno;

        // this could fail too, but there's nothing we can do about it now
        ::unlink(tgtPath);

        error = QSystemError(savedErrno, QSystemError::StandardLibraryError);
        return false;
    } else if (!SupportsHardlinking) {
        // man 2 link on Linux has:
        // EPERM  The filesystem containing oldpath and newpath does not
        //        support the creation of hard links.
        errno = EPERM;
    }

    switch (errno) {
    case EACCES:
    case EEXIST:
    case ENAMETOOLONG:
    case ENOENT:
    case ENOTDIR:
    case EROFS:
    case EXDEV:
        // accept the error from link(2) (especially EEXIST) and don't retry
        break;

    default:
        // fall back to rename()
        // ### Race condition. If a file is moved in after this, it /will/ be
        // overwritten.
        if (::rename(srcPath, tgtPath) == 0)
            return true;
    }

    error = QSystemError(errno, QSystemError::StandardLibraryError);
    return false;
}

//static
bool QFileSystemEngine::renameOverwriteFile(const QFileSystemEntry &source, const QFileSystemEntry &target, QSystemError &error)
{
    Q_CHECK_FILE_NAME(source, false);
    Q_CHECK_FILE_NAME(target, false);

    if (::rename(source.nativeFilePath().constData(), target.nativeFilePath().constData()) == 0)
        return true;
    error = QSystemError(errno, QSystemError::StandardLibraryError);
    return false;
}

//static
bool QFileSystemEngine::removeFile(const QFileSystemEntry &entry, QSystemError &error)
{
    Q_CHECK_FILE_NAME(entry, false);
    if (unlink(entry.nativeFilePath().constData()) == 0)
        return true;
    error = QSystemError(errno, QSystemError::StandardLibraryError);
    return false;

}

static mode_t toMode_t(QFile::Permissions permissions)
{
    mode_t mode = 0;
    if (permissions & (QFile::ReadOwner | QFile::ReadUser))
        mode |= S_IRUSR;
    if (permissions & (QFile::WriteOwner | QFile::WriteUser))
        mode |= S_IWUSR;
    if (permissions & (QFile::ExeOwner | QFile::ExeUser))
        mode |= S_IXUSR;
    if (permissions & QFile::ReadGroup)
        mode |= S_IRGRP;
    if (permissions & QFile::WriteGroup)
        mode |= S_IWGRP;
    if (permissions & QFile::ExeGroup)
        mode |= S_IXGRP;
    if (permissions & QFile::ReadOther)
        mode |= S_IROTH;
    if (permissions & QFile::WriteOther)
        mode |= S_IWOTH;
    if (permissions & QFile::ExeOther)
        mode |= S_IXOTH;
    return mode;
}

//static
bool QFileSystemEngine::setPermissions(const QFileSystemEntry &entry, QFile::Permissions permissions, QSystemError &error, QFileSystemMetaData *data)
{
    Q_CHECK_FILE_NAME(entry, false);

    mode_t mode = toMode_t(permissions);
    bool success = ::chmod(entry.nativeFilePath().constData(), mode) == 0;
    if (success && data) {
        data->entryFlags &= ~QFileSystemMetaData::Permissions;
        data->entryFlags |= QFileSystemMetaData::MetaDataFlag(uint(permissions));
        data->knownFlagsMask |= QFileSystemMetaData::Permissions;
    }
    if (!success)
        error = QSystemError(errno, QSystemError::StandardLibraryError);
    return success;
}

//static
bool QFileSystemEngine::setPermissions(int fd, QFile::Permissions permissions, QSystemError &error, QFileSystemMetaData *data)
{
    mode_t mode = toMode_t(permissions);

    bool success = ::fchmod(fd, mode) == 0;
    if (success && data) {
        data->entryFlags &= ~QFileSystemMetaData::Permissions;
        data->entryFlags |= QFileSystemMetaData::MetaDataFlag(uint(permissions));
        data->knownFlagsMask |= QFileSystemMetaData::Permissions;
    }
    if (!success)
        error = QSystemError(errno, QSystemError::StandardLibraryError);
    return success;
}

//static
bool QFileSystemEngine::setFileTime(int fd, const QDateTime &newDate, QAbstractFileEngine::FileTime time, QSystemError &error)
{
    if (!newDate.isValid() || time == QAbstractFileEngine::BirthTime ||
            time == QAbstractFileEngine::MetadataChangeTime) {
        error = QSystemError(EINVAL, QSystemError::StandardLibraryError);
        return false;
    }

#if QT_CONFIG(futimens)
    struct timespec ts[2];

    ts[0].tv_sec = ts[1].tv_sec = 0;
    ts[0].tv_nsec = ts[1].tv_nsec = UTIME_OMIT;

    const qint64 msecs = newDate.toMSecsSinceEpoch();

    if (time == QAbstractFileEngine::AccessTime) {
        ts[0].tv_sec = msecs / 1000;
        ts[0].tv_nsec = (msecs % 1000) * 1000000;
    } else if (time == QAbstractFileEngine::ModificationTime) {
        ts[1].tv_sec = msecs / 1000;
        ts[1].tv_nsec = (msecs % 1000) * 1000000;
    }

    if (futimens(fd, ts) == -1) {
        error = QSystemError(errno, QSystemError::StandardLibraryError);
        return false;
    }

    return true;
#elif QT_CONFIG(futimes)
    struct timeval tv[2];
    QT_STATBUF st;

    if (QT_FSTAT(fd, &st) == -1) {
        error = QSystemError(errno, QSystemError::StandardLibraryError);
        return false;
    }

    GetFileTimes::get(&st, &tv[0], &tv[1]);

    const qint64 msecs = newDate.toMSecsSinceEpoch();

    if (time == QAbstractFileEngine::AccessTime) {
        tv[0].tv_sec = msecs / 1000;
        tv[0].tv_usec = (msecs % 1000) * 1000;
    } else if (time == QAbstractFileEngine::ModificationTime) {
        tv[1].tv_sec = msecs / 1000;
        tv[1].tv_usec = (msecs % 1000) * 1000;
    }

    if (futimes(fd, tv) == -1) {
        error = QSystemError(errno, QSystemError::StandardLibraryError);
        return false;
    }

    return true;
#else
    Q_UNUSED(fd);
    error = QSystemError(ENOSYS, QSystemError::StandardLibraryError);
    return false;
#endif
}

QString QFileSystemEngine::homePath()
{
    QString home = QFile::decodeName(qgetenv("HOME"));
    if (home.isEmpty())
        home = rootPath();
    return QDir::cleanPath(home);
}

QString QFileSystemEngine::rootPath()
{
    return QLatin1String("/");
}

QString QFileSystemEngine::tempPath()
{
#ifdef QT_UNIX_TEMP_PATH_OVERRIDE
    return QLatin1String(QT_UNIX_TEMP_PATH_OVERRIDE);
#else
    QString temp = QFile::decodeName(qgetenv("TMPDIR"));
    if (temp.isEmpty()) {
        if (false) {
#if defined(Q_OS_DARWIN) && !defined(QT_BOOTSTRAPPED)
        } else if (NSString *nsPath = NSTemporaryDirectory()) {
            temp = QString::fromCFString((CFStringRef)nsPath);
#endif
        } else {
            temp = QLatin1String(_PATH_TMP);
        }
    }
    return QDir(QDir::cleanPath(temp)).canonicalPath();
#endif
}

bool QFileSystemEngine::setCurrentPath(const QFileSystemEntry &path)
{
    int r;
    r = QT_CHDIR(path.nativeFilePath().constData());
    return r >= 0;
}

QFileSystemEntry QFileSystemEngine::currentPath()
{
    QFileSystemEntry result;
#if defined(__GLIBC__) && !defined(PATH_MAX)
    char *currentName = ::get_current_dir_name();
    if (currentName) {
        result = QFileSystemEntry(QByteArray(currentName), QFileSystemEntry::FromNativePath());
        ::free(currentName);
    }
#else
    char currentName[PATH_MAX+1];
    if (::getcwd(currentName, PATH_MAX)) {
#if defined(Q_OS_VXWORKS) && defined(VXWORKS_VXSIM)
        QByteArray dir(currentName);
        if (dir.indexOf(':') < dir.indexOf('/'))
            dir.remove(0, dir.indexOf(':')+1);

        qstrncpy(currentName, dir.constData(), PATH_MAX);
#endif
        result = QFileSystemEntry(QByteArray(currentName), QFileSystemEntry::FromNativePath());
    }
# if defined(QT_DEBUG)
    if (result.isEmpty())
        qWarning("QFileSystemEngine::currentPath: getcwd() failed");
# endif
#endif
    return result;
}
QT_END_NAMESPACE