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// 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
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