Move QLocaleData::convertDoubleToFloat to qnumeric_p.h

So others can use it too.

Change-Id: I01ec3c774d9943adb903fffd17b86236d06a948c
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

src/corelib/global/qnumeric_p.h

@@ -51,6 +51,8 @@ QT_END_NAMESPACE
 
 QT_BEGIN_NAMESPACE
 
+class qfloat16;
+
 namespace qnumeric_std_wrapper {
 #if defined(QT_MATH_H_DEFINES_MACROS)
 #  undef QT_MATH_H_DEFINES_MACROS
@@ -145,15 +147,16 @@ namespace {
     it's out of range. If the conversion is successful, the converted value is
     stored in \a value; if it was not successful, \a value will contain the
     minimum or maximum of T, depending on the sign of \a d. If \c T is
-    unsigned, then \a value contains the absolute value of \a v.
+    unsigned, then \a value contains the absolute value of \a v. If \c T is \c
+    float, an underflow is also signalled by returning false and setting \a
+    value to zero.
 
     This function works for v containing infinities, but not NaN. It's the
     caller's responsibility to exclude that possibility before calling it.
 */
-template<typename T>
-static inline bool convertDoubleTo(double v, T *value, bool allow_precision_upgrade = true)
+template <typename T> static inline std::enable_if_t<std::is_integral_v<T>, bool>
+convertDoubleTo(double v, T *value, bool allow_precision_upgrade = true)
 {
-    static_assert(std::numeric_limits<T>::is_integer);
     static_assert(std::is_integral_v<T>);
     constexpr bool TypeIsLarger = std::numeric_limits<T>::digits > std::numeric_limits<double>::digits;
 
@@ -278,6 +281,40 @@ QT_WARNING_DISABLE_FLOAT_COMPARE
 QT_WARNING_POP
 }
 
+template <typename T> static inline
+std::enable_if_t<std::is_floating_point_v<T> || std::is_same_v<T, qfloat16>, bool>
+convertDoubleTo(double v, T *value, bool allow_precision_upgrade = true)
+{
+    Q_UNUSED(allow_precision_upgrade);
+    constexpr T Huge = std::numeric_limits<T>::infinity();
+
+    if constexpr (std::numeric_limits<double>::max_exponent <=
+            std::numeric_limits<T>::max_exponent) {
+        // no UB can happen
+        *value = T(v);
+        return true;
+    }
+    if (!qt_is_finite(v) && std::numeric_limits<T>::has_infinity) {
+        // infinity (or NaN)
+        *value = T(v);
+        return true;
+    }
+
+    // Check for in-range value to ensure the conversion is not UB (see the
+    // comment above for Standard language).
+    if (std::fabs(v) > (std::numeric_limits<T>::max)()) {
+        *value = v < 0 ? -Huge : Huge;
+        return false;
+    }
+
+    *value = T(v);
+    if (v != 0 && *value == 0) {
+        // Underflow through loss of precision
+        return false;
+    }
+    return true;
+}
+
 template <typename T> inline bool add_overflow(T v1, T v2, T *r) { return qAddOverflow(v1, v2, r); }
 template <typename T> inline bool sub_overflow(T v1, T v2, T *r) { return qSubOverflow(v1, v2, r); }
 template <typename T> inline bool mul_overflow(T v1, T v2, T *r) { return qMulOverflow(v1, v2, r); }

src/corelib/text/qlocale_p.h

@@ -18,10 +18,10 @@
 
 #include "qlocale.h"
 
-#include <QtCore/private/qglobal_p.h>
 #include <QtCore/qcalendar.h>
 #include <QtCore/qlist.h>
 #include <QtCore/qnumeric.h>
+#include <QtCore/private/qnumeric_p.h>
 #include <QtCore/qstring.h>
 #include <QtCore/qvariant.h>
 #include <QtCore/qvarlengtharray.h>
@@ -304,23 +304,14 @@ public:
                                               unsigned flags = NoFlags) const;
 
     // this function is meant to be called with the result of stringToDouble or bytearrayToDouble
+    // so *ok must have been properly set (if not null)
     [[nodiscard]] static float convertDoubleToFloat(double d, bool *ok)
     {
-        if (qIsInf(d))
-            return float(d);
-        if (std::fabs(d) > (std::numeric_limits<float>::max)()) {
-            if (ok)
-                *ok = false;
-            const float huge = std::numeric_limits<float>::infinity();
-            return d < 0 ? -huge : huge;
-        }
-        if (d != 0 && float(d) == 0) {
-            // Values that underflow double already failed. Match them:
-            if (ok)
-                *ok = false;
-            return 0;
-        }
-        return float(d);
+        float result;
+        bool b = convertDoubleTo<float>(d, &result);
+        if (ok && *ok)
+            *ok = b;
+        return result;
     }
 
     [[nodiscard]] double stringToDouble(QStringView str, bool *ok,