Introduce a PropertyKey class that inherits from Value

This will replace Identifier over the next few commits.

The advantage of PropertyKey is that it can be stored on
the JS stack, so that a GC run won't accidentally clean
up the string/symbol referenced by the key.

Change-Id: Ib4daa4616bcfa537e6d371ef7c7740bc7727a50d
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 120 insertions, 0 deletions

diff --git a/src/qml/jsruntime/qv4propertykey_p.h b/src/qml/jsruntime/qv4propertykey_p.h
new file mode 100644
index 0000000000..2e33562514
--- /dev/null
+++ b/src/qml/jsruntime/qv4propertykey_p.h
@@ -0,0 +1,120 @@
+/****************************************************************************
+**
+** Copyright (C) 2018 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the QtQml 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
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+** 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 QV4PROPERTYKEY_H
+#define QV4PROPERTYKEY_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 <private/qv4value_p.h>
+#include <private/qv4identifier_p.h>
+
+QT_BEGIN_NAMESPACE
+
+class QString;
+
+namespace QV4 {
+
+struct PropertyKey : private Value
+{
+    // Property keys are Strings, Symbols or unsigned integers.
+    // For convenience we derive them from Values, allowing us to store them
+    // on the JS stack
+    //
+    // They do however behave somewhat different than a Value:
+    // * If the key is a String, the pointer to the string is stored in the identifier
+    // table and thus unique.
+    // * If the key is a Symbol it simply points to the referenced symbol object
+    // * if the key is an array index (a uint < UINT_MAX), it's encoded as an
+    // integer value
+    int id;
+
+    static PropertyKey invalid() { PropertyKey key; key.setRawValue(0); return key; }
+    static PropertyKey fromArrayIndex(uint idx) { PropertyKey key; key.setInt_32(static_cast<int>(idx)); return key; }
+    bool isStringOrSymbol() const { return isManaged(); }
+    uint asArrayIndex() const { return isManaged() ? std::numeric_limits<uint>::max() : value(); }
+    uint isArrayIndex() const { return !isManaged(); }
+    static PropertyKey fromStringOrSymbol(Heap::StringOrSymbol *b)
+    { PropertyKey key; key.setM(reinterpret_cast<Heap::Base *>(b)); return key; }
+    Heap::StringOrSymbol *asStringOrSymbol() const { return reinterpret_cast<Heap::StringOrSymbol *>(heapObject()); }
+
+    bool isString() const {
+        Heap::Base *s = heapObject();
+        return s && s->internalClass->vtable->isString;
+    }
+
+    bool isSymbol() const {
+        Heap::Base *s = heapObject();
+        return s && s->internalClass->vtable->isString && s->internalClass->vtable->isStringOrSymbol;
+    }
+
+    // ### temporary until we transitioned Identifier to PropertyKey
+    static PropertyKey fromIdentifier(Identifier id) {
+        if (id.isArrayIndex())
+            return PropertyKey::fromArrayIndex(id.asArrayIndex());
+        return PropertyKey::fromStringOrSymbol(id.asStringOrSymbol());
+    }
+
+    Identifier toIdentifier() const {
+        if (isArrayIndex())
+            return Identifier::fromArrayIndex(asArrayIndex());
+        return Identifier::fromStringOrSymbol(asStringOrSymbol());
+    }
+
+    Q_QML_EXPORT QString toQString() const;
+    Heap::StringOrSymbol *toStringOrSymbol(ExecutionEngine *e);
+
+    bool operator ==(const PropertyKey &other) const { return id == other.id; }
+    bool operator !=(const PropertyKey &other) const { return id != other.id; }
+    bool operator <(const PropertyKey &other) const { return id < other.id; }
+};
+
+}
+
+QT_END_NAMESPACE
+
+#endif