qsettings_win.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:significant reason:trusted-data-only
 
#include "qsettings.h"
 
#include "qsettings_p.h"
#include "qlist.h"
#include "qmap.h"
#include "qdebug.h"
#include "qscopeguard.h"
#include <QtCore/private/wcharhelpers_win_p.h>
 
#include <qt_windows.h>
 
// See "Accessing an Alternate Registry View" at:
// http://msdn.microsoft.com/en-us/library/aa384129%28VS.85%29.aspx
#ifndef KEY_WOW64_64KEY
   // Access a 32-bit key from either a 32-bit or 64-bit application.
#  define KEY_WOW64_64KEY 0x0100
#endif
 
#ifndef KEY_WOW64_32KEY
   // Access a 64-bit key from either a 32-bit or 64-bit application.
#  define KEY_WOW64_32KEY 0x0200
#endif
 
QT_BEGIN_NAMESPACE
 
using namespace Qt::StringLiterals;
 
/*  Keys are stored in QStrings. If the variable name starts with 'u', this is a "user"
    key, ie. "foo/bar/alpha/beta". If the variable name starts with 'r', this is a "registry"
    key, ie. "\foo\bar\alpha\beta". */
 
/*******************************************************************************
** Some convenience functions
*/
 
/*
  We don't use KEY_ALL_ACCESS because it gives more rights than what we
  need. See task 199061.
 */
static const REGSAM registryPermissions = KEY_READ | KEY_WRITE;
 
static QString keyPath(const QString &rKey)
{
    int idx = rKey.lastIndexOf(u'\\');
    if (idx == -1)
        return QString();
    return rKey.left(idx + 1);
}
 
static QString keyName(const QString &rKey)
{
    int idx = rKey.lastIndexOf(u'\\');
 
    QString res;
    if (idx == -1)
        res = rKey;
    else
        res = rKey.mid(idx + 1);
 
    if (res == "Default"_L1 || res == "."_L1)
        res = ""_L1;
 
    return res;
}
 
static QString escapedKey(QString uKey)
{
    QChar *data = uKey.data();
    int l = uKey.length();
    for (int i = 0; i < l; ++i) {
        auto &ucs = data[i].unicode();
        if (ucs == '\\')
            ucs = '/';
        else if (ucs == '/')
            ucs = '\\';
    }
    return uKey;
}
 
static QString unescapedKey(QString rKey)
{
    return escapedKey(rKey);
}
 
typedef QMap<QString, QString> NameSet;
 
static void mergeKeySets(NameSet *dest, const NameSet &src)
{
    NameSet::const_iterator it = src.constBegin();
    for (; it != src.constEnd(); ++it)
        dest->insert(unescapedKey(it.key()), QString());
}
 
static void mergeKeySets(NameSet *dest, const QStringList &src)
{
    QStringList::const_iterator it = src.constBegin();
    for (; it != src.constEnd(); ++it)
        dest->insert(unescapedKey(*it), QString());
}
 
/*******************************************************************************
** Wrappers for the insane windows registry API
*/
 
// ### Qt 6: Use new helpers from qwinregistry.cpp (once bootstrap builds are obsolete)
 
// Open a key with the specified "perms".
// "access" is to explicitly use the 32- or 64-bit branch.
static HKEY openKey(HKEY parentHandle, REGSAM perms, const QString &rSubKey, REGSAM access = 0)
{
    HKEY resultHandle = 0;
    LONG res = RegOpenKeyEx(parentHandle, reinterpret_cast<const wchar_t *>(rSubKey.utf16()),
                            0, perms | access, &resultHandle);
 
    if (res == ERROR_SUCCESS)
        return resultHandle;
 
    return 0;
}
 
// Open a key with the specified "perms", create it if it does not exist.
// "access" is to explicitly use the 32- or 64-bit branch.
static HKEY createOrOpenKey(HKEY parentHandle, REGSAM perms, const QString &rSubKey, REGSAM access = 0)
{
    // try to open it
    HKEY resultHandle = openKey(parentHandle, perms, rSubKey, access);
    if (resultHandle != 0)
        return resultHandle;
 
    // try to create it
    LONG res = RegCreateKeyEx(parentHandle, reinterpret_cast<const wchar_t *>(rSubKey.utf16()), 0, 0,
                              REG_OPTION_NON_VOLATILE, perms | access, 0, &resultHandle, 0);
 
    if (res == ERROR_SUCCESS)
        return resultHandle;
 
    //qErrnoWarning(int(res), "QSettings: Failed to create subkey \"%ls\"",
    //              qUtf16Printable(rSubKey));
 
    return 0;
}
 
// Open or create a key in read-write mode if possible, otherwise read-only.
// "access" is to explicitly use the 32- or 64-bit branch.
static HKEY createOrOpenKey(HKEY parentHandle, const QString &rSubKey, bool *readOnly, REGSAM access = 0)
{
    // try to open or create it read/write
    HKEY resultHandle = createOrOpenKey(parentHandle, registryPermissions, rSubKey, access);
    if (resultHandle != 0) {
        if (readOnly != 0)
            *readOnly = false;
        return resultHandle;
    }
 
    // try to open or create it read/only
    resultHandle = createOrOpenKey(parentHandle, KEY_READ, rSubKey, access);
    if (resultHandle != 0) {
        if (readOnly != 0)
            *readOnly = true;
        return resultHandle;
    }
    return 0;
}
 
static QStringList childKeysOrGroups(HKEY parentHandle, QSettingsPrivate::ChildSpec spec)
{
    QStringList result;
    DWORD numKeys;
    DWORD maxKeySize;
    DWORD numSubgroups;
    DWORD maxSubgroupSize;
 
    // Find the number of keys and subgroups, as well as the max of their lengths.
    LONG res = RegQueryInfoKey(parentHandle, 0, 0, 0, &numSubgroups, &maxSubgroupSize, 0,
                               &numKeys, &maxKeySize, 0, 0, 0);
 
    if (res != ERROR_SUCCESS) {
        qErrnoWarning(int(res), "QSettings: RegQueryInfoKey() failed");
        return result;
    }
 
    ++maxSubgroupSize;
    ++maxKeySize;
 
    int n;
    int m;
    if (spec == QSettingsPrivate::ChildKeys) {
        n = numKeys;
        m = maxKeySize;
    } else {
        n = numSubgroups;
        m = maxSubgroupSize;
    }
 
    /* The size does not include the terminating null character. */
    ++m;
 
    // Get the list
    QByteArray buff(m * sizeof(wchar_t), 0);
    for (int i = 0; i < n; ++i) {
        QString item;
        DWORD l = DWORD(buff.size()) / DWORD(sizeof(wchar_t));
        if (spec == QSettingsPrivate::ChildKeys) {
            res = RegEnumValue(parentHandle, i, reinterpret_cast<wchar_t *>(buff.data()), &l, 0, 0, 0, 0);
        } else {
            res = RegEnumKeyEx(parentHandle, i, reinterpret_cast<wchar_t *>(buff.data()), &l, 0, 0, 0, 0);
        }
        if (res == ERROR_SUCCESS)
            item = QString::fromWCharArray((const wchar_t *)buff.constData(), l);
 
        if (res != ERROR_SUCCESS) {
            qErrnoWarning(int(res), "QSettings: RegEnumValue failed");
            continue;
        }
        if (item.isEmpty())
            item = "."_L1;
        result.append(item);
    }
    return result;
}
 
static void allKeys(HKEY parentHandle, const QString &rSubKey, NameSet *result, REGSAM access = 0)
{
    HKEY handle = openKey(parentHandle, KEY_READ, rSubKey, access);
    if (handle == 0)
        return;
 
    QStringList childKeys = childKeysOrGroups(handle, QSettingsPrivate::ChildKeys);
    QStringList childGroups = childKeysOrGroups(handle, QSettingsPrivate::ChildGroups);
    RegCloseKey(handle);
 
    for (int i = 0; i < childKeys.size(); ++i) {
        QString s = rSubKey;
        if (!s.isEmpty())
            s += u'\\';
        s += childKeys.at(i);
        result->insert(s, QString());
    }
 
    for (int i = 0; i < childGroups.size(); ++i) {
        QString s = rSubKey;
        if (!s.isEmpty())
            s += u'\\';
        s += childGroups.at(i);
        allKeys(parentHandle, s, result, access);
    }
}
 
static void deleteChildGroups(HKEY parentHandle, REGSAM access = 0)
{
    QStringList childGroups = childKeysOrGroups(parentHandle, QSettingsPrivate::ChildGroups);
 
    for (int i = 0; i < childGroups.size(); ++i) {
        QString group = childGroups.at(i);
 
        // delete subgroups in group
        HKEY childGroupHandle = openKey(parentHandle, registryPermissions, group, access);
        if (childGroupHandle == 0)
            continue;
        deleteChildGroups(childGroupHandle, access);
        RegCloseKey(childGroupHandle);
 
        // delete group itself
        LONG res = RegDeleteKey(parentHandle, qt_castToWchar(group));
        if (res != ERROR_SUCCESS) {
            qErrnoWarning(int(res), "QSettings: RegDeleteKey failed on subkey \"%ls\"",
                          qUtf16Printable(group));
            return;
        }
    }
}
 
/*******************************************************************************
** class RegistryKey
*/
 
class RegistryKey
{
public:
    RegistryKey(HKEY parent_handle = 0, const QString &key = QString(), bool read_only = true, REGSAM access = 0);
    QString key() const;
    HKEY handle() const;
    HKEY parentHandle() const;
    bool readOnly() const;
    void close();
private:
    HKEY m_parent_handle;
    mutable HKEY m_handle;
    QString m_key;
    mutable bool m_read_only;
    REGSAM m_access;
};
 
RegistryKey::RegistryKey(HKEY parent_handle, const QString &key, bool read_only, REGSAM access)
    : m_parent_handle(parent_handle),
      m_handle(0),
      m_key(key),
      m_read_only(read_only),
      m_access(access)
{
}
 
QString RegistryKey::key() const
{
    return m_key;
}
 
HKEY RegistryKey::handle() const
{
    if (m_handle != 0)
        return m_handle;
 
    if (m_read_only)
        m_handle = openKey(m_parent_handle, KEY_READ, m_key, m_access);
    else
        m_handle = createOrOpenKey(m_parent_handle, m_key, &m_read_only, m_access);
 
    return m_handle;
}
 
HKEY RegistryKey::parentHandle() const
{
    return m_parent_handle;
}
 
bool RegistryKey::readOnly() const
{
    return m_read_only;
}
 
void RegistryKey::close()
{
    if (m_handle != 0)
        RegCloseKey(m_handle);
    m_handle = 0;
}
 
typedef QList<RegistryKey> RegistryKeyList;
 
/*******************************************************************************
** class QWinSettingsPrivate
*/
 
class QWinSettingsPrivate : public QSettingsPrivate
{
    Q_DISABLE_COPY(QWinSettingsPrivate)
public:
    QWinSettingsPrivate(QSettings::Scope scope, const QString &organization,
                        const QString &application, REGSAM access = 0);
    QWinSettingsPrivate(QString rKey, REGSAM access = 0);
    ~QWinSettingsPrivate() override;
 
    void remove(const QString &uKey) override;
    void set(const QString &uKey, const QVariant &value) override;
    std::optional<QVariant> get(const QString &uKey) const override;
    QStringList children(const QString &uKey, ChildSpec spec) const override;
    void clear() override;
    void sync() override;
    void flush() override;
    bool isWritable() const override;
    HKEY writeHandle() const;
    std::optional<QVariant> readKey(HKEY parentHandle, const QString &rSubKey) const;
    QString fileName() const override;
 
private:
    RegistryKeyList regList; // list of registry locations to search for keys
    bool deleteWriteHandleOnExit;
    REGSAM access;
};
 
QWinSettingsPrivate::QWinSettingsPrivate(QSettings::Scope scope, const QString &organization,
                                         const QString &application, REGSAM access)
    : QSettingsPrivate(QSettings::NativeFormat, scope, organization, application),
      access(access)
{
    deleteWriteHandleOnExit = false;
 
    if (!organization.isEmpty()) {
        QString prefix = "Software\\"_L1 + organization;
        QString orgPrefix = prefix + "\\OrganizationDefaults"_L1;
        QString appPrefix = prefix + u'\\' + application;
 
        if (scope == QSettings::UserScope) {
            if (!application.isEmpty())
                regList.append(RegistryKey(HKEY_CURRENT_USER, appPrefix, !regList.isEmpty(), access));
 
            regList.append(RegistryKey(HKEY_CURRENT_USER, orgPrefix, !regList.isEmpty(), access));
        }
 
        if (!application.isEmpty())
            regList.append(RegistryKey(HKEY_LOCAL_MACHINE, appPrefix, !regList.isEmpty(), access));
 
        regList.append(RegistryKey(HKEY_LOCAL_MACHINE, orgPrefix, !regList.isEmpty(), access));
    }
 
    if (regList.isEmpty())
        setStatus(QSettings::AccessError);
}
 
QWinSettingsPrivate::QWinSettingsPrivate(QString rPath, REGSAM access)
    : QSettingsPrivate(QSettings::NativeFormat),
      access(access)
{
    deleteWriteHandleOnExit = false;
 
    if (rPath.startsWith(u'\\'))
        rPath.remove(0, 1);
 
    int keyLength;
    HKEY keyName;
 
    if (rPath.startsWith("HKEY_CURRENT_USER"_L1)) {
        keyLength = 17;
        keyName = HKEY_CURRENT_USER;
    } else if (rPath.startsWith("HKCU"_L1)) {
        keyLength = 4;
        keyName = HKEY_CURRENT_USER;
    } else if (rPath.startsWith("HKEY_LOCAL_MACHINE"_L1)) {
        keyLength = 18;
        keyName = HKEY_LOCAL_MACHINE;
    } else if (rPath.startsWith("HKLM"_L1)) {
        keyLength = 4;
        keyName = HKEY_LOCAL_MACHINE;
    } else if (rPath.startsWith("HKEY_CLASSES_ROOT"_L1)) {
        keyLength = 17;
        keyName = HKEY_CLASSES_ROOT;
    } else if (rPath.startsWith("HKCR"_L1)) {
        keyLength = 4;
        keyName = HKEY_CLASSES_ROOT;
    } else if (rPath.startsWith("HKEY_USERS"_L1)) {
        keyLength = 10;
        keyName = HKEY_USERS;
    } else if (rPath.startsWith("HKU"_L1)) {
        keyLength = 3;
        keyName = HKEY_USERS;
    } else {
        return;
    }
 
    if (rPath.length() == keyLength)
        regList.append(RegistryKey(keyName, QString(), false, access));
    else if (rPath[keyLength] == u'\\')
        regList.append(RegistryKey(keyName, rPath.mid(keyLength+1), false, access));
}
 
std::optional<QVariant> QWinSettingsPrivate::readKey(HKEY parentHandle, const QString &rSubKey) const
{
    QString rSubkeyName = keyName(rSubKey);
    QString rSubkeyPath = keyPath(rSubKey);
 
    // open a handle on the subkey
    HKEY handle = openKey(parentHandle, KEY_READ, rSubkeyPath, access);
    if (handle == 0)
        return std::nullopt;
 
    const auto closeKey = qScopeGuard([handle] { RegCloseKey(handle); });
 
    // get the size and type of the value
    DWORD dataType;
    DWORD dataSize;
    LONG res = RegQueryValueEx(handle, reinterpret_cast<const wchar_t *>(rSubkeyName.utf16()), 0, &dataType, 0, &dataSize);
    if (res != ERROR_SUCCESS)
        return std::nullopt;
 
    // workaround for rare cases where trailing '\0' are missing in registry
    if (dataType == REG_SZ || dataType == REG_EXPAND_SZ)
        dataSize += 2;
    else if (dataType == REG_MULTI_SZ)
        dataSize += 4;
 
    // get the value
    QByteArray data(dataSize, 0);
    res = RegQueryValueEx(handle, reinterpret_cast<const wchar_t *>(rSubkeyName.utf16()), 0, 0,
                           reinterpret_cast<unsigned char*>(data.data()), &dataSize);
    if (res != ERROR_SUCCESS)
        return std::nullopt;
 
    switch (dataType) {
        case REG_EXPAND_SZ:
        case REG_SZ: {
            QString s;
            if (dataSize) {
                s = QString::fromWCharArray(reinterpret_cast<const wchar_t *>(data.constData()));
            }
            return stringToVariant(s);
        }
 
        case REG_MULTI_SZ: {
            QStringList l;
            if (dataSize) {
                int i = 0;
                for (;;) {
                    QString s = QString::fromWCharArray(reinterpret_cast<const wchar_t *>(data.constData()) + i);
                    i += s.length() + 1;
 
                    if (s.isEmpty())
                        break;
                    l.append(s);
                }
            }
            return stringListToVariantList(l);
        }
 
        case REG_NONE:
        case REG_BINARY: {
            QString s;
            if (dataSize) {
                s = QString::fromWCharArray(reinterpret_cast<const wchar_t *>(data.constData()), data.size() / 2);
            }
            return stringToVariant(s);
        }
 
        case REG_DWORD_BIG_ENDIAN:
        case REG_DWORD: {
            Q_ASSERT(data.size() == sizeof(int));
            int i;
            memcpy(reinterpret_cast<char*>(&i), data.constData(), sizeof(int));
            return i;
        }
 
        case REG_QWORD: {
            Q_ASSERT(data.size() == sizeof(qint64));
            qint64 i;
            memcpy(reinterpret_cast<char*>(&i), data.constData(), sizeof(qint64));
            return i;
        }
 
        default:
            qWarning("QSettings: Unknown data %d type in Windows registry", static_cast<int>(dataType));
            break;
    }
 
    return std::nullopt;
}
 
HKEY QWinSettingsPrivate::writeHandle() const
{
    if (regList.isEmpty())
        return 0;
    const RegistryKey &key = regList.at(0);
    if (key.handle() == 0 || key.readOnly())
        return 0;
    return key.handle();
}
 
QWinSettingsPrivate::~QWinSettingsPrivate()
{
    if (deleteWriteHandleOnExit && writeHandle() != 0) {
        DWORD res = RegDeleteKey(writeHandle(), L"");
        if (res != ERROR_SUCCESS) {
            qErrnoWarning(int(res), "QSettings: Failed to delete key \"%ls\"",
                          qUtf16Printable(regList.constFirst().key()));
        }
    }
 
    for (int i = 0; i < regList.size(); ++i)
        regList[i].close();
}
 
void QWinSettingsPrivate::remove(const QString &uKey)
{
    if (writeHandle() == 0) {
        setStatus(QSettings::AccessError);
        return;
    }
 
    QString rKey = escapedKey(uKey);
 
    // try to delete value bar in key foo
    LONG res;
    HKEY handle = openKey(writeHandle(), registryPermissions, keyPath(rKey), access);
    if (handle != 0) {
        res = RegDeleteValue(handle, reinterpret_cast<const wchar_t *>(keyName(rKey).utf16()));
        RegCloseKey(handle);
    }
 
    // try to delete key foo/bar and all subkeys
    handle = openKey(writeHandle(), registryPermissions, rKey, access);
    if (handle != 0) {
        deleteChildGroups(handle, access);
 
        if (rKey.isEmpty()) {
            const QStringList childKeys = childKeysOrGroups(handle, QSettingsPrivate::ChildKeys);
 
            for (const QString &group : childKeys) {
                LONG res = RegDeleteValue(handle, qt_castToWchar(group));
                if (res != ERROR_SUCCESS) {
                    qErrnoWarning(int(res), "QSettings: RegDeleteValue failed on subkey \"%ls\"",
                                  qUtf16Printable(group));
                }
            }
        } else {
            res = RegDeleteKey(writeHandle(), reinterpret_cast<const wchar_t *>(rKey.utf16()));
 
            if (res != ERROR_SUCCESS) {
                qErrnoWarning(int(res), "QSettings: RegDeleteKey failed on key \"%ls\"",
                              qUtf16Printable(rKey));
            }
        }
        RegCloseKey(handle);
    }
}
 
void QWinSettingsPrivate::set(const QString &uKey, const QVariant &value)
{
    if (writeHandle() == 0) {
        setStatus(QSettings::AccessError);
        return;
    }
 
    QString rKey = escapedKey(uKey);
 
    HKEY handle = createOrOpenKey(writeHandle(), registryPermissions, keyPath(rKey), access);
    if (handle == 0) {
        setStatus(QSettings::AccessError);
        return;
    }
 
    DWORD type;
    QByteArray regValueBuff;
 
    // Determine the type
    switch (value.typeId()) {
        case QMetaType::QVariantList:
        case QMetaType::QStringList: {
            // If none of the elements contains '\0', we can use REG_MULTI_SZ, the
            // native registry string list type. Otherwise we use REG_BINARY.
            type = REG_MULTI_SZ;
            QStringList l = variantListToStringList(value.toList());
            QStringList::const_iterator it = l.constBegin();
            for (; it != l.constEnd(); ++it) {
                if ((*it).length() == 0 || it->contains(QChar::Null)) {
                    type = REG_BINARY;
                    break;
                }
            }
 
            if (type == REG_BINARY) {
                const QString s = variantToString(value);
                regValueBuff = QByteArray(reinterpret_cast<const char *>(s.data()), s.length() * 2);
            } else {
                QStringList::const_iterator it = l.constBegin();
                for (; it != l.constEnd(); ++it) {
                    const QString &s = *it;
                    regValueBuff += QByteArray(reinterpret_cast<const char*>(s.utf16()), (s.length() + 1) * 2);
                }
                regValueBuff.append((char)0);
                regValueBuff.append((char)0);
            }
            break;
        }
 
        case QMetaType::Int:
        case QMetaType::UInt: {
            type = REG_DWORD;
            qint32 i = value.toInt();
            regValueBuff = QByteArray(reinterpret_cast<const char*>(&i), sizeof(qint32));
            break;
        }
 
        case QMetaType::LongLong:
        case QMetaType::ULongLong: {
            type = REG_QWORD;
            qint64 i = value.toLongLong();
            regValueBuff = QByteArray(reinterpret_cast<const char*>(&i), sizeof(qint64));
            break;
        }
 
        case QMetaType::QByteArray:
            Q_FALLTHROUGH();
 
        default: {
            // If the string does not contain '\0', we can use REG_SZ, the native registry
            // string type. Otherwise we use REG_BINARY.
            QString s = variantToString(value);
            type = s.contains(QChar::Null) ? REG_BINARY : REG_SZ;
            int length = s.length();
            if (type == REG_SZ)
                ++length;
            regValueBuff = QByteArray(reinterpret_cast<const char *>(s.constData()),
                                      int(sizeof(wchar_t)) * length);
            break;
        }
    }
 
    // set the value
    LONG res = RegSetValueEx(handle, reinterpret_cast<const wchar_t *>(keyName(rKey).utf16()), 0, type,
                             reinterpret_cast<const unsigned char*>(regValueBuff.constData()),
                             regValueBuff.size());
 
    if (res == ERROR_SUCCESS) {
        deleteWriteHandleOnExit = false;
    } else {
        qErrnoWarning(int(res), "QSettings: failed to set subkey \"%ls\"",
                      qUtf16Printable(rKey));
        setStatus(QSettings::AccessError);
    }
 
    RegCloseKey(handle);
}
 
std::optional<QVariant> QWinSettingsPrivate::get(const QString &uKey) const
{
    QString rKey = escapedKey(uKey);
 
    for (const RegistryKey &r : regList) {
        HKEY handle = r.handle();
        if (handle != 0) {
            if (auto result = readKey(handle, rKey))
                return result;
        }
        if (!fallbacks)
            return std::nullopt;
    }
 
    return std::nullopt;
}
 
QStringList QWinSettingsPrivate::children(const QString &uKey, ChildSpec spec) const
{
    NameSet result;
    QString rKey = escapedKey(uKey);
 
    for (const RegistryKey &r : regList) {
        HKEY parent_handle = r.handle();
        if (parent_handle == 0) {
            if (fallbacks)
                continue;
            break;
        }
        HKEY handle = openKey(parent_handle, KEY_READ, rKey, access);
        if (handle == 0) {
            if (fallbacks)
                continue;
            break;
        }
 
        if (spec == AllKeys) {
            NameSet keys;
            allKeys(handle, ""_L1, &keys, access);
            mergeKeySets(&result, keys);
        } else { // ChildGroups or ChildKeys
            QStringList names = childKeysOrGroups(handle, spec);
            mergeKeySets(&result, names);
        }
 
        RegCloseKey(handle);
 
        if (!fallbacks)
            return result.keys();
    }
 
    return result.keys();
}
 
void QWinSettingsPrivate::clear()
{
    remove(QString());
    deleteWriteHandleOnExit = true;
}
 
void QWinSettingsPrivate::sync()
{
    RegFlushKey(writeHandle());
}
 
void QWinSettingsPrivate::flush()
{
    // Windows does this for us.
}
 
QString QWinSettingsPrivate::fileName() const
{
    if (regList.isEmpty())
        return QString();
 
    const RegistryKey &key = regList.at(0);
    QString result;
    if (key.parentHandle() == HKEY_CURRENT_USER)
        result = "\\HKEY_CURRENT_USER\\"_L1;
    else
        result = "\\HKEY_LOCAL_MACHINE\\"_L1;
 
    return result + regList.at(0).key();
}
 
bool QWinSettingsPrivate::isWritable() const
{
    return writeHandle() != 0;
}
 
QSettingsPrivate *QSettingsPrivate::create(QSettings::Format format, QSettings::Scope scope,
                                           const QString &organization, const QString &application)
{
    switch (format) {
    case QSettings::NativeFormat:
        return new QWinSettingsPrivate(scope, organization, application);
    case QSettings::Registry32Format:
        return new QWinSettingsPrivate(scope, organization, application, KEY_WOW64_32KEY);
    case QSettings::Registry64Format:
        return new QWinSettingsPrivate(scope, organization, application, KEY_WOW64_64KEY);
    default:
        break;
    }
    return new QConfFileSettingsPrivate(format, scope, organization, application);
}
 
QSettingsPrivate *QSettingsPrivate::create(const QString &fileName, QSettings::Format format)
{
    switch (format) {
    case QSettings::NativeFormat:
        return new QWinSettingsPrivate(fileName);
    case QSettings::Registry32Format:
        return new QWinSettingsPrivate(fileName, KEY_WOW64_32KEY);
    case QSettings::Registry64Format:
        return new QWinSettingsPrivate(fileName, KEY_WOW64_64KEY);
    default:
        break;
    }
    return new QConfFileSettingsPrivate(fileName, format);
}
 
QT_END_NAMESPACE