1 files changed, 120 insertions, 0 deletions
diff --git a/src/qml/common/qjsnumbercoercion.h b/src/qml/common/qjsnumbercoercion.h
new file mode 100644
index 0000000000..0023bff6e8
--- /dev/null
+++ b/src/qml/common/qjsnumbercoercion.h
@@ -0,0 +1,120 @@
+// Copyright (C) 2020 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
+
+#ifndef QJSNUMBERCOERCION_H
+#define QJSNUMBERCOERCION_H
+
+#include <QtCore/qglobal.h>
+#include <cstring>
+
+QT_BEGIN_NAMESPACE
+
+class QJSNumberCoercion
+{
+public:
+
+    static constexpr bool isInteger(double d)
+    {
+        // Comparing d with itself checks for NaN and comparing d with the min and max values
+        // for int also covers infinities.
+        if (!equals(d, d) || d < (std::numeric_limits<int>::min)()
+            || d > (std::numeric_limits<int>::max)()) {
+            return false;
+        }
+
+        return equals(static_cast<int>(d), d);
+    }
+
+    static constexpr bool isArrayIndex(double d)
+    {
+        return d >= 0
+                && equals(d, d)
+                && d <= (std::numeric_limits<uint>::max)()
+                && equals(static_cast<uint>(d), d);
+    }
+
+    static constexpr bool isArrayIndex(qint64 i)
+    {
+        return i >= 0 && i <= (std::numeric_limits<uint>::max)();
+    }
+
+    static constexpr bool isArrayIndex(quint64 i)
+    {
+        return i <= (std::numeric_limits<uint>::max)();
+    }
+
+    static constexpr int toInteger(double d) {
+        // Check for NaN
+        if (!equals(d, d))
+            return 0;
+
+        if (d >= (std::numeric_limits<int>::min)() && d <= (std::numeric_limits<int>::max)()) {
+            const int i = static_cast<int>(d);
+            if (equals(i, d))
+                return i;
+        }
+
+        return QJSNumberCoercion(d).toInteger();
+    }
+
+    static constexpr bool equals(double lhs, double rhs)
+    {
+        QT_WARNING_PUSH
+        QT_WARNING_DISABLE_FLOAT_COMPARE
+        return lhs == rhs;
+        QT_WARNING_POP
+    }
+
+private:
+    constexpr QJSNumberCoercion(double dbl)
+    {
+        // the dbl == 0 path is guaranteed constexpr. The other one may or may not be, depending
+        // on whether and how the compiler inlines the memcpy.
+        // In order to declare the ctor constexpr we need one guaranteed constexpr path.
+        if (!equals(dbl, 0))
+            memcpy(&d, &dbl, sizeof(double));
+    }
+
+    constexpr int sign() const
+    {
+        return (d >> 63) ? -1 : 1;
+    }
+
+    constexpr bool isDenormal() const
+    {
+        return static_cast<int>((d << 1) >> 53) == 0;
+    }
+
+    constexpr int exponent() const
+    {
+        return static_cast<int>((d << 1) >> 53) - 1023;
+    }
+
+    constexpr quint64 significant() const
+    {
+        quint64 m = (d << 12) >> 12;
+        if (!isDenormal())
+            m |= (static_cast<quint64>(1) << 52);
+        return m;
+    }
+
+    constexpr int toInteger()
+    {
+        int e = exponent() - 52;
+        if (e < 0) {
+            if (e <= -53)
+                return 0;
+            return sign() * static_cast<int>(significant() >> -e);
+        } else {
+            if (e > 31)
+                return 0;
+            return sign() * (static_cast<int>(significant()) << e);
+        }
+    }
+
+    quint64 d = 0;
+};
+
+QT_END_NAMESPACE
+
+#endif // QJSNUMBERCOERCION_H