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T73 Flyweight pattern based on pimpl, to reduce CMeasurementUnit memory usage.

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* All members of CMeasurementUnit moved into nested pimpl class Data.
* CMeasurementUnit has only one member: a pointer to a const Data.
* Static const CMeasurementUnits replaced with static const Datas.
* Each CMeasurementUnit singleton method returns by-value a CMeasurementUnit containing a pointer to a static const Data.
* Means CMeasurementUnit is trivial to copy because we never copy the pimpl members.
** Works because the available units are fixed at compile time so we never need to create novel units at runtime.
This commit is contained in:
Mathew Sutcliffe
2017-04-21 16:11:58 +01:00
parent fef2bc528e
commit c8d78ada65
3 changed files with 172 additions and 235 deletions
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78
src/blackmisc/pq/measurementunit.h
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@@ -204,15 +204,29 @@ namespace BlackMisc
};
//! @}
private:
QLatin1String m_name; //!< name, e.g. "meter"
QLatin1String m_symbol; //!< unit name, e.g. "m"
double m_epsilon = 0.0; //!< values with differences below epsilon are the equal
int m_displayDigits = 0; //!< standard rounding for string conversions
ConverterFunction m_toDefault = nullptr; //!< convert from this unit to default unit
ConverterFunction m_fromDefault = nullptr; //!< convert to this unit from default unit
protected:
//! Pimpl class
struct Data
{
//! Construct a unit with custom conversion
template <class Converter>
Q_DECL_CONSTEXPR Data(QLatin1String name, QLatin1String symbol, Converter, int displayDigits = 2, double epsilon = 1e-9)
: m_name(name), m_symbol(symbol), m_epsilon(epsilon), m_displayDigits(displayDigits), m_toDefault(Converter::toDefault), m_fromDefault(Converter::fromDefault)
{}
//! Construct a null unit
Q_DECL_CONSTEXPR Data(QLatin1String name, QLatin1String symbol)
: m_name(name), m_symbol(symbol)
{}
QLatin1String m_name; //!< name, e.g. "meter"
QLatin1String m_symbol; //!< unit name, e.g. "m"
double m_epsilon = 0.0; //!< values with differences below epsilon are the equal
int m_displayDigits = 0; //!< standard rounding for string conversions
ConverterFunction m_toDefault = nullptr; //!< convert from this unit to default unit
ConverterFunction m_fromDefault = nullptr; //!< convert to this unit from default unit
};
//! Workaround to constant-initialize QLatin1String on platforms without constexpr strlen.
template <size_t N>
static Q_DECL_CONSTEXPR QLatin1String constQLatin1(const char (&str)[N])
@@ -220,27 +234,18 @@ namespace BlackMisc
return QLatin1String(str, N - 1); // -1 because N includes the null terminator
}
//! Workaround because std::nullptr_t might not be a literal type.
struct NullType {};
//! Constructor
CMeasurementUnit(const Data &data) : m_data(&data) {}
/*!
* Construct a unit with custom conversion
*/
template <class Converter>
Q_DECL_CONSTEXPR CMeasurementUnit(QLatin1String name, QLatin1String symbol, Converter, int displayDigits, double epsilon)
: m_name(name), m_symbol(symbol), m_epsilon(epsilon), m_displayDigits(displayDigits), m_toDefault(Converter::toDefault), m_fromDefault(Converter::fromDefault)
{}
/*!
* Construct a null unit
*/
Q_DECL_CONSTEXPR CMeasurementUnit(QLatin1String name, QLatin1String symbol, NullType)
: m_name(name), m_symbol(symbol)
{}
//! Constructor saves the address of its argument, so forbid rvalues
CMeasurementUnit(const Data &&) = delete;
//! Destructor
~CMeasurementUnit() = default;
private:
const Data *m_data = (throw std::logic_error("Uninitialized pimpl"), nullptr);
public:
//! \copydoc BlackMisc::Mixin::String::toQString
QString convertToQString(bool i18n = false) const
@@ -251,7 +256,7 @@ namespace BlackMisc
//! \copydoc BlackMisc::Mixin::DBusByMetaClass::marshallToDbus
void marshallToDbus(QDBusArgument &argument) const
{
argument << this->m_symbol;
argument << this->m_data->m_symbol;
}
//! \copydoc BlackMisc::Mixin::DBusByMetaClass::unmarshallFromDbus
@@ -262,11 +267,6 @@ namespace BlackMisc
(*this) = CMeasurementUnit::None();
}
//! Default constructor for meta system
//! \remarks Only public because the need, to use this with the metasystem
CMeasurementUnit() : m_name("none")
{}
//! Equal operator ==
bool operator == (const CMeasurementUnit &other) const;
@@ -282,13 +282,13 @@ namespace BlackMisc
//! Name such as "meter"
QString getName(bool i18n = false) const
{
return i18n ? QCoreApplication::translate("CMeasurementUnit", this->m_name.latin1()) : this->m_name;
return i18n ? QCoreApplication::translate("CMeasurementUnit", this->m_data->m_name.latin1()) : this->m_data->m_name;
}
//! Unit name such as "m"
QString getSymbol(bool i18n = false) const
{
return i18n ? QCoreApplication::translate("CMeasurementUnit", this->m_symbol.latin1()) : this->m_symbol;
return i18n ? QCoreApplication::translate("CMeasurementUnit", this->m_data->m_symbol.latin1()) : this->m_data->m_symbol;
}
//! Rounded value
@@ -303,13 +303,13 @@ namespace BlackMisc
//! Threshold for rounding
double getEpsilon() const
{
return this->m_epsilon;
return this->m_data->m_epsilon;
}
//! Display digits
int getDisplayDigits() const
{
return this->m_displayDigits;
return this->m_data->m_displayDigits;
}
//! Convert from other unit to this unit.
@@ -320,13 +320,13 @@ namespace BlackMisc
{
if (this->isNull()) return false;
if (value == 0) return true;
return std::abs(value) <= this->m_epsilon;
return std::abs(value) <= this->m_data->m_epsilon;
}
//! Is unit null?
bool isNull() const
{
return this->m_toDefault == nullptr;
return this->m_data->m_toDefault == nullptr;
}
// --------------------------------------------------------------------
@@ -338,7 +338,7 @@ namespace BlackMisc
* \param symbol must be a valid unit symbol (without i18n) or empty string (empty means default unit)
* \param strict strict check means if unit is not found, program terminates
*/
template <class U> static const U &unitFromSymbol(const QString &symbol, bool strict = true)
template <class U> static U unitFromSymbol(const QString &symbol, bool strict = true)
{
if (symbol.isEmpty()) return U::defaultUnit();
const QList<U> &units = U::allUnits();
@@ -368,9 +368,9 @@ namespace BlackMisc
}
//! Dimensionless unit
static const CMeasurementUnit &None()
static CMeasurementUnit None()
{
static Q_CONSTEXPR CMeasurementUnit none(constQLatin1("none"), constQLatin1(""), NilConverter(), 0, 0);
static Q_CONSTEXPR CMeasurementUnit::Data none(constQLatin1("none"), constQLatin1(""), NilConverter(), 0, 0);
return none;
}
};