Add QWinRegistryKey::name() and debug operator

Helps debugging to know which key you're working with, if
all you have is a QWinRegistryKey instance.

Change-Id: I09aa2d997871ff46c455ee0d1a566d858163d19e
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/CMakeLists.txt

@@ -620,6 +620,7 @@ qt_internal_extend_target(Core CONDITION WIN32
         text/qlatin1stringmatcher.cpp
         text/qunicodetools.cpp
         tools/qhash.cpp # Q_DECL_INIT_PRIORITY
+        kernel/qwinregistry.cpp # ntstatus.h clashes
 )
 
 qt_internal_extend_target(Core CONDITION GCC AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS "13"

src/corelib/kernel/qwinregistry.cpp

@@ -1,13 +1,25 @@
 // Copyright (C) 2019 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
 
+#define UMDF_USING_NTSTATUS // Avoid ntstatus redefinitions
+
 #include "qwinregistry_p.h"
 #include <QtCore/qvarlengtharray.h>
+#include <QtCore/qdebug.h>
 #include <QtCore/qendian.h>
 #include <QtCore/qlist.h>
 
+#include <ntstatus.h>
+
+// User mode version of ZwQueryKey, as per:
+// https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/nf-wdm-zwquerykey
+extern "C" NTSTATUS NTSYSCALLAPI NtQueryKey(HANDLE KeyHandle, int KeyInformationClass,
+    PVOID KeyInformation, ULONG Length, PULONG ResultLength);
+
 QT_BEGIN_NAMESPACE
 
+using namespace Qt::StringLiterals;
+
 QWinRegistryKey::QWinRegistryKey()
 {
 }
@@ -36,6 +48,39 @@ void QWinRegistryKey::close()
     }
 }
 
+QString QWinRegistryKey::name() const
+{
+    if (!isValid())
+        return {};
+
+    // https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntddk/ns-ntddk-_key_name_information
+    constexpr int kKeyNameInformation = 3;
+    struct KeyNameInformation { ULONG length = 0; WCHAR name[1] = {}; };
+
+    // Resolve name of key iteratively by first computing the needed size,
+    // and then querying the name, accounting for the possibility that the
+    // name length changes behind our back a few times.
+    DWORD keyInformationSize = 0;
+    for (int i = 0; i < 5; ++i) {
+        QByteArray buffer(keyInformationSize, 0u);
+        auto *keyNameInformation = reinterpret_cast<KeyNameInformation *>(buffer.data());
+        switch (NtQueryKey(m_key, kKeyNameInformation, keyNameInformation,
+            keyInformationSize, &keyInformationSize)) {
+        case STATUS_BUFFER_TOO_SMALL:
+        case STATUS_BUFFER_OVERFLOW:
+            continue;
+        case STATUS_SUCCESS: {
+            return QString::fromWCharArray(keyNameInformation->name,
+                keyNameInformation->length / sizeof(wchar_t));
+        }
+        default:
+            return {};
+        }
+    }
+
+    return {};
+}
+
 QVariant QWinRegistryKey::value(QStringView subKey) const
 {
     // NOTE: Empty value name is allowed in Windows registry, it means the default
@@ -129,4 +174,17 @@ QString QWinRegistryKey::stringValue(QStringView subKey) const
     return value<QString>(subKey).value_or(QString());
 }
 
+#ifndef QT_NO_DEBUG_STREAM
+QDebug operator<<(QDebug debug, const QWinRegistryKey &key)
+{
+    QDebugStateSaver saver(debug);
+    debug.nospace();
+    debug << "QWinRegistryKey(";
+    if (key.isValid())
+        debug << key.name();
+    debug << ')';
+    return debug;
+}
+#endif
+
 QT_END_NAMESPACE

src/corelib/kernel/qwinregistry_p.h

@@ -46,6 +46,8 @@ public:
 
     void close();
 
+    QString name() const;
+
     [[nodiscard]] QVariant value(QStringView subKey) const;
     template<typename T>
     [[nodiscard]] std::optional<T> value(QStringView subKey) const
@@ -58,6 +60,10 @@ public:
 
     QString stringValue(QStringView subKey) const;
 
+#ifndef QT_NO_DEBUG_STREAM
+    friend Q_CORE_EXPORT QDebug operator<<(QDebug dbg, const QWinRegistryKey &);
+#endif
+
 private:
     HKEY m_key = nullptr;
 };

tests/auto/corelib/kernel/qwinregistrykey/tst_qwinregistrykey.cpp

@@ -98,6 +98,7 @@ private Q_SLOTS:
     void initTestCase();
     void cleanupTestCase();
     void qwinregistrykey();
+    void name();
 
 private:
     bool m_available = false;
@@ -136,16 +137,7 @@ void tst_qwinregistrykey::cleanupTestCase()
     const LONG ret = RegOpenKeyExW(HKEY_CURRENT_USER, TEST_KEY, 0, KEY_READ | KEY_WRITE, &key);
     if (ret != ERROR_SUCCESS)
         return;
-    #define C_STR(View) reinterpret_cast<const wchar_t *>(View.utf16())
-    RegDeleteValueW(key, C_STR(TEST_STRING.first));
-    RegDeleteValueW(key, C_STR(TEST_STRING_NULL.first));
-    RegDeleteValueW(key, C_STR(TEST_STRINGLIST.first));
-    RegDeleteValueW(key, C_STR(TEST_STRINGLIST_NULL.first));
-    RegDeleteValueW(key, C_STR(TEST_DWORD.first));
-    RegDeleteValueW(key, C_STR(TEST_QWORD.first));
-    RegDeleteValueW(key, C_STR(TEST_BINARY.first));
-    RegDeleteValueW(key, C_STR(TEST_DEFAULT.first));
-    #undef C_STR
+    RegDeleteTree(key, nullptr);
     RegDeleteKeyW(HKEY_CURRENT_USER, TEST_KEY);
     RegCloseKey(key);
 }
@@ -236,6 +228,44 @@ void tst_qwinregistrykey::qwinregistrykey()
     }
 }
 
+void tst_qwinregistrykey::name()
+{
+    if (!m_available)
+        QSKIP("The test data is not ready.");
+
+    QWinRegistryKey testKey(HKEY_CURRENT_USER, TEST_KEY);
+    QVERIFY(testKey.isValid());
+
+    // In practice: "\\REGISTRY\\USER\\S-1-5-21-4156955479-607706614-2054699034-1000\\Software\\tst_qwinregistrykey",
+    //          or: "\\REGISTRY\\USER\\S-1-5-21-4156955479-607706614-2054699034-1000\\SOFTWARE\\tst_qwinregistrykey".
+    QVERIFY(testKey.name().toLower().endsWith("software\\tst_qwinregistrykey"));
+
+    // Check that we can report the name of a key with a deep path
+    HKEY baseKey = testKey.handle();
+    constexpr auto kKeyDepth = 500;
+    for (int i = 0; i < kKeyDepth; ++i) {
+        constexpr auto kChildKeyName = LR"(childKey)";
+
+        HKEY childKey = nullptr;
+        auto ret = RegCreateKeyEx(baseKey, kChildKeyName, 0, nullptr, 0,
+            KEY_READ | KEY_WRITE, nullptr, &childKey, nullptr);
+        QVERIFY(ret == ERROR_SUCCESS);
+
+        if (i == kKeyDepth - 1) {
+            RegCloseKey(childKey);
+            QWinRegistryKey leafKey(baseKey, kChildKeyName);
+            QVERIFY(leafKey.isValid());
+            const QString keyName = leafKey.name();
+            QVERIFY(keyName.size() > 1000);
+            QVERIFY(keyName.endsWith("childKey\\childKey\\childKey"));
+        } else {
+            if (baseKey != testKey.handle())
+                RegCloseKey(baseKey);
+            baseKey = childKey;
+        }
+    }
+}
+
 QTEST_MAIN(tst_qwinregistrykey)
 
 #include "tst_qwinregistrykey.moc"