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+@* Unit information.
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+
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+\noindent As unit information is required in several places, the enumeration
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+listing these is moved to an external class. This derives from QObject only to
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+take advantage of the meta-object system. There are no data members, however
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+there are some convenience methods for working with unit data.
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+
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+@(units.h@>=
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+class Units: public QObject
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+{
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+ Q_OBJECT
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+ Q_ENUMS(Units)
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+ public:
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+ enum Units
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+ {
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+ Fahrenheit = 10144,
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+ Celsius = 10143,
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+ Kelvin = 10325,
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+ Rankine = 10145
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+ };
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+ double convertTemperature(double value, Unit fromUnit, Unit toUnit);
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+ bool isTemperatureUnit(Unit unit);
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+}
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+
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+@ Methods are implemented in a separate file.
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+
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+@(units.cpp@>=
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+#inculde "units.h"
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+#include "moc_units.cpp"
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+
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+@ The |isTemperatureUnit()| method may seem counter-intuitive while the enum
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+only contains represenations of temperature measurements, but there are plans
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+to extend this later to extend hardware support to devices that do not directly
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+measure temperature values and also to support the measurement of properties
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+that cannot sensibly be represented as temperatures such as fuel pressure and
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+control settings.
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+
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+@(units.cpp@>=
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+bool Units::isTemperatureUnit(Unit unit)
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+{
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+ if(unit == Fahrenheit ||
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+ unit == Celsius ||
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+ unit == Kelvin ||
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+ unit == Rankine)
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+ {
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+ return true;
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+ }
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+ return false;
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+}
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+
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+@ Temperature conversions can be performed by the |Units| class and should
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+eliminate the need to have conversion code in multiple places. This method
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+takes the measurement value, the unit that value is in, and the unit that we
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+would like to have the measurement converted into. It returns the value as it
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+would be expressed after unit conversion. A value of 0 is presently returned
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+if either or both of the units to convert are not temperature units, however
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+that behavior may change in the future. Any code activating that branch should
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+be considered flawed.
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+
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+@(units.cpp@>=
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+double Units::convertTemperature(double value, Unit fromUnit, Unit toUnit)
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+{
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+ if(isTemperatureUnit(fromUnit) && isTemperatureUnit(toUnit) == false)
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+ {
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+ return 0;
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+ }
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+ switch(fromUnit)
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+ {
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+ case Fahrenheit:
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+ switch(toUnit)
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+ {
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+ case Fahrenheit:
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+ return value;
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+ break;
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+ case Celsius:
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+ return (value - 32) * 5 / 9;
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+ break;
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+ case Kelvin:
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+ return (value + 459.67) * 5 / 9;
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+ break;
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+ case Rankine:
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+ return value + 459.67;
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+ break;
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+ }
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+ break;
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+ case Celsius:
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+ switch(toUnit)
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+ {
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+ case Fahrenheit:
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+ return value * 9 / 5 + 32;
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+ break;
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+ case Celsius:
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+ return value;
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+ break;
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+ case Kelvin:
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+ return value + 273.15;
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+ break;
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+ case Rankine:
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+ return (value + 273.15) * 9 / 5;
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+ break;
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+ }
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+ break;
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+ case Kelvin:
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+ switch(toUnit)
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+ {
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+ case Fahrenheit:
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+ return value * 5 / 9 - 459.67;
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+ break;
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+ case Celsius:
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+ return value - 273.15;
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+ break;
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+ case Kelvin:
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+ return value;
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+ break;
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+ case Rankine:
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+ return value * 9 / 5;
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+ break;
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+ }
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+ break;
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+ case Rankine:
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+ switch(toUnit)
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+ {
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+ case Fahrenheit:
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+ return value - 457.67;
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+ break;
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+ case Celsius:
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+ return (value - 491.67) * 5 / 9;
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+ break;
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+ case Kelvin:
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+ return value * 5 / 9;
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+ break;
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+ case Rankine:
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+ return value;
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+ break;
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+ }
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+ break;
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+ default:
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+ return 0;
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+ break;
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+ }
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+ return 0;
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+}
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