Generate JNI signature strings at compile time

Introduce an internal QtJniTypes namespace with types that allow us to
concatenate string literals at compile time. This makes it possible to
generate arbitrary strings based on types, which we can then use as
signatures to JNI method calls.

Move some of the private members of QJniObject into the QtJniTypes
namespace for consistency, and to allow further template specialization
by user code to make other types and their JNI signature string known.
Remove the "Jni" prefix from names.

Use the compile-time generated string in QJniObject methods that created
the signature string at runtime, which involved a temporary memory
allocation.

Treat 'void' as a primitive type (with signature string 'V'), and
remove redundant template specializations.

Add a test case to verify the the strings are constructed correctly
at compile time.

Change-Id: I5e3895a97f7dc1b86961f7a7855b899d9203037d
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>
Reviewed-by: Marc Mutz <marc.mutz@qt.io>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

3 files changed, 123 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/CMakeLists.txt b/tests/auto/corelib/kernel/CMakeLists.txt
index 18f20bfadc..3083652945 100644
--- a/tests/auto/corelib/kernel/CMakeLists.txt
+++ b/tests/auto/corelib/kernel/CMakeLists.txt
@@ -49,4 +49,5 @@ endif()
 if(ANDROID)
     add_subdirectory(qjnienvironment)
     add_subdirectory(qjniobject)
+    add_subdirectory(qjnitypes)
 endif()
diff --git a/tests/auto/corelib/kernel/qjnitypes/CMakeLists.txt b/tests/auto/corelib/kernel/qjnitypes/CMakeLists.txt
new file mode 100644
index 0000000000..8184e91a11
--- /dev/null
+++ b/tests/auto/corelib/kernel/qjnitypes/CMakeLists.txt
@@ -0,0 +1,4 @@
+qt_internal_add_test(tst_qjnitypes
+    SOURCES
+    tst_qjnitypes.cpp
+)
diff --git a/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp b/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp
new file mode 100644
index 0000000000..559fcd47c9
--- /dev/null
+++ b/tests/auto/corelib/kernel/qjnitypes/tst_qjnitypes.cpp
@@ -0,0 +1,118 @@
+/****************************************************************************
+**
+** Copyright (C) 2022 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:GPL-EXCEPT$
+** 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 General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 3 as published by the Free Software
+** Foundation with exceptions as appearing in the file LICENSE.GPL3-EXCEPT
+** 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-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <QtTest>
+
+#include <QtCore/qjnitypes.h>
+
+class tst_QJniTypes : public QObject
+{
+    Q_OBJECT
+
+public:
+    tst_QJniTypes() = default;
+
+private slots:
+    void initTestCase();
+};
+
+struct QtJavaWrapper {};
+template<>
+constexpr auto QtJniTypes::typeSignature<QtJavaWrapper>()
+{
+    return QtJniTypes::String("Lorg/qtproject/qt/android/QtJavaWrapper;");
+}
+
+template<>
+constexpr auto QtJniTypes::typeSignature<QJniObject>()
+{
+    return QtJniTypes::String("Ljava/lang/Object;");
+}
+
+struct QtCustomJniObject : QJniObject {};
+template<>
+constexpr auto QtJniTypes::typeSignature<QtCustomJniObject>()
+{
+    return QtJniTypes::String("Lorg/qtproject/qt/android/QtCustomJniObject;");
+}
+
+static_assert(QtJniTypes::typeSignature<QtJavaWrapper>() == "Lorg/qtproject/qt/android/QtJavaWrapper;");
+static_assert(QtJniTypes::typeSignature<QtJavaWrapper>() != "Ljava/lang/Object;");
+static_assert(!(QtJniTypes::typeSignature<QtJavaWrapper>() == "X"));
+
+static_assert(QtJniTypes::fieldSignature<jint>() == "I");
+static_assert(QtJniTypes::fieldSignature<jint>() != "X");
+static_assert(QtJniTypes::fieldSignature<jint>() != "Ljava/lang/Object;");
+static_assert(QtJniTypes::fieldSignature<jlong>() == "J");
+static_assert(QtJniTypes::fieldSignature<jstring>() == "Ljava/lang/String;");
+static_assert(QtJniTypes::fieldSignature<jobject>() == "Ljava/lang/Object;");
+static_assert(QtJniTypes::fieldSignature<jobjectArray>() == "[Ljava/lang/Object;");
+static_assert(QtJniTypes::fieldSignature<QJniObject>() == "Ljava/lang/Object;");
+static_assert(QtJniTypes::fieldSignature<QtJavaWrapper>() == "Lorg/qtproject/qt/android/QtJavaWrapper;");
+static_assert(QtJniTypes::fieldSignature<QtCustomJniObject>() == "Lorg/qtproject/qt/android/QtCustomJniObject;");
+
+static_assert(QtJniTypes::methodSignature<void>() == "()V");
+static_assert(QtJniTypes::methodSignature<void>() != "()X");
+static_assert(QtJniTypes::methodSignature<void, jint>() == "(I)V");
+static_assert(QtJniTypes::methodSignature<void, jint, jstring>() == "(ILjava/lang/String;)V");
+static_assert(QtJniTypes::methodSignature<jlong, jint, jclass>() == "(ILjava/lang/Class;)J");
+static_assert(QtJniTypes::methodSignature<jobject, jint, jstring>() == "(ILjava/lang/String;)Ljava/lang/Object;");
+
+static_assert(QtJniTypes::isPrimitiveType<jint>());
+static_assert(QtJniTypes::isPrimitiveType<void>());
+static_assert(!QtJniTypes::isPrimitiveType<jobject>());
+static_assert(!QtJniTypes::isPrimitiveType<QtCustomJniObject>());
+
+static_assert(!QtJniTypes::isObjectType<jint>());
+static_assert(!QtJniTypes::isObjectType<void>());
+static_assert(QtJniTypes::isObjectType<jobject>());
+static_assert(QtJniTypes::isObjectType<QtCustomJniObject>());
+
+static_assert(QtJniTypes::String("ABCDE").startsWith("ABC"));
+static_assert(QtJniTypes::String("ABCDE").startsWith("A"));
+static_assert(QtJniTypes::String("ABCDE").startsWith("ABCDE"));
+static_assert(!QtJniTypes::String("ABCDE").startsWith("ABCDEF"));
+static_assert(!QtJniTypes::String("ABCDE").startsWith("9AB"));
+static_assert(QtJniTypes::String("ABCDE").startsWith('A'));
+static_assert(!QtJniTypes::String("ABCDE").startsWith('B'));
+
+static_assert(QtJniTypes::String("ABCDE").endsWith("CDE"));
+static_assert(QtJniTypes::String("ABCDE").endsWith("E"));
+static_assert(QtJniTypes::String("ABCDE").endsWith("ABCDE"));
+static_assert(!QtJniTypes::String("ABCDE").endsWith("DEF"));
+static_assert(!QtJniTypes::String("ABCDE").endsWith("ABCDEF"));
+static_assert(QtJniTypes::String("ABCDE").endsWith('E'));
+static_assert(!QtJniTypes::String("ABCDE").endsWith('F'));
+
+void tst_QJniTypes::initTestCase()
+{
+}
+
+QTEST_MAIN(tst_QJniTypes)
+
+#include "tst_qjnitypes.moc"