Win32: Consolidate registry code

Add a RAII class for registry keys and use it throughout
the code base.

Change-Id: I666b2fbb790f83436443101d6bc1e3c0525e78df
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

3 files changed, 213 insertions, 2 deletions

diff --git a/src/corelib/kernel/kernel.pri b/src/corelib/kernel/kernel.pri
index 789bcb7927..bd3cabc01a 100644
--- a/src/corelib/kernel/kernel.pri
+++ b/src/corelib/kernel/kernel.pri
@@ -88,8 +88,10 @@ win32 {
             SOURCES += kernel/qeventdispatcher_winrt.cpp
             HEADERS += kernel/qeventdispatcher_winrt_p.h
         } else {
-            SOURCES += kernel/qeventdispatcher_win.cpp
-            HEADERS += kernel/qeventdispatcher_win_p.h
+            SOURCES += kernel/qeventdispatcher_win.cpp \
+                       kernel/qwinregistry.cpp
+            HEADERS += kernel/qeventdispatcher_win_p.h \
+                       kernel/qwinregistry_p.h
         }
 
         !winrt: LIBS_PRIVATE += -lversion
diff --git a/src/corelib/kernel/qwinregistry.cpp b/src/corelib/kernel/qwinregistry.cpp
new file mode 100644
index 0000000000..6566dd3c76
--- /dev/null
+++ b/src/corelib/kernel/qwinregistry.cpp
@@ -0,0 +1,120 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** 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 "qwinregistry_p.h"
+
+#include <QtCore/qvarlengtharray.h>
+
+#include <algorithm>
+
+QT_BEGIN_NAMESPACE
+
+QWinRegistryKey::QWinRegistryKey() :
+    m_key(nullptr)
+{
+}
+
+// Open a key with the specified permissions (KEY_READ/KEY_WRITE).
+// "access" is to explicitly use the 32- or 64-bit branch.
+QWinRegistryKey::QWinRegistryKey(HKEY parentHandle, QStringView subKey,
+                                 REGSAM permissions, REGSAM access)
+{
+    if (RegOpenKeyEx(parentHandle, reinterpret_cast<const wchar_t *>(subKey.utf16()),
+                     0, permissions | access, &m_key) != ERROR_SUCCESS) {
+        m_key = nullptr;
+    }
+}
+
+QWinRegistryKey::~QWinRegistryKey()
+{
+    close();
+}
+
+void QWinRegistryKey::close()
+{
+    if (isValid()) {
+        RegCloseKey(m_key);
+        m_key = nullptr;
+    }
+}
+
+QString QWinRegistryKey::stringValue(QStringView subKey) const
+{
+    QString result;
+    if (!isValid())
+        return result;
+    DWORD type;
+    DWORD size;
+    auto subKeyC = reinterpret_cast<const wchar_t *>(subKey.utf16());
+    if (RegQueryValueEx(m_key, subKeyC, nullptr, &type, nullptr, &size) != ERROR_SUCCESS
+        || (type != REG_SZ && type != REG_EXPAND_SZ) || size <= 2) {
+        return result;
+    }
+    // Reserve more for rare cases where trailing '\0' are missing in registry,
+    // otherwise chop off the '\0' received.
+    QString buffer(int(size / sizeof(wchar_t)), Qt::Uninitialized);
+    if (RegQueryValueEx(m_key, subKeyC, nullptr, &type,
+                        reinterpret_cast<LPBYTE>(buffer.data()), &size) == ERROR_SUCCESS) {
+        if (buffer.endsWith(QChar::Null))
+            buffer.chop(1);
+    } else {
+        buffer.clear();
+    }
+    return buffer;
+}
+
+QPair<DWORD, bool> QWinRegistryKey::dwordValue(QStringView subKey) const
+{
+    if (!isValid())
+        return qMakePair(0, false);
+    DWORD type;
+    auto subKeyC = reinterpret_cast<const wchar_t *>(subKey.utf16());
+    if (RegQueryValueEx(m_key, subKeyC, nullptr, &type, nullptr, nullptr) != ERROR_SUCCESS
+        || type != REG_DWORD) {
+        return qMakePair(0, false);
+    }
+    DWORD value = 0;
+    DWORD size = sizeof(value);
+    const bool ok =
+        RegQueryValueEx(m_key, subKeyC, nullptr, nullptr,
+                        reinterpret_cast<unsigned char *>(&value), &size) == ERROR_SUCCESS;
+    return qMakePair(value, ok);
+}
+
+QT_END_NAMESPACE
diff --git a/src/corelib/kernel/qwinregistry_p.h b/src/corelib/kernel/qwinregistry_p.h
new file mode 100644
index 0000000000..d249a97988
--- /dev/null
+++ b/src/corelib/kernel/qwinregistry_p.h
@@ -0,0 +1,89 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** 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.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QWINREGISTRY_H
+#define QWINREGISTRY_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API. It exists purely as an
+// implementation detail. This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtCore/qpair.h>
+#include <QtCore/qstring.h>
+#include <QtCore/qstringview.h>
+#include <QtCore/qt_windows.h>
+
+QT_BEGIN_NAMESPACE
+
+class Q_CORE_EXPORT QWinRegistryKey
+{
+public:
+    Q_DISABLE_COPY(QWinRegistryKey)
+
+    QWinRegistryKey();
+    explicit QWinRegistryKey(HKEY parentHandle, QStringView subKey,
+                             REGSAM permissions = KEY_READ, REGSAM access = 0);
+    ~QWinRegistryKey();
+
+    QWinRegistryKey(QWinRegistryKey &&other) noexcept { swap(other); }
+    QWinRegistryKey &operator=(QWinRegistryKey &&other) noexcept { swap(other); return *this; }
+
+    void swap(QWinRegistryKey &other) noexcept { qSwap(m_key, other.m_key); }
+
+    bool isValid() const { return m_key != nullptr; }
+    operator HKEY() const { return m_key; }
+    void close();
+
+    QString stringValue(QStringView subKey) const;
+    QPair<DWORD, bool> dwordValue(QStringView subKey) const;
+
+private:
+    HKEY m_key;
+};
+
+QT_END_NAMESPACE
+
+#endif // QWINREGISTRY_H