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#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <getopt.h>
/* Supported units and string conversion */
typedef enum TemperatureUnit { CELSIUS, DELISLE, FARENHEIT, KELVIN, RANKINE } TemperatureUnit;
const TemperatureUnit temperatureUnits[] = { CELSIUS, DELISLE, FARENHEIT, KELVIN, RANKINE };
const char* temperatureUnitNames[] = { "Celsius", "Delisle", "Farenheit", "Kelvin", "Rankine" };
/* Conversion table to kelvin */
const double kelvinMult[] = {1., -2. / 3., 5. / 9., 1, 5. / 9.};
const double kelvinAdd[] = {273.15, 373.15, 255.37, 0, 0};
static int const maxUnitLength = 31; // Maximum Length of members of temperatureUnitNames (not counting trailing \0)
static int const unknownUnit = -1; // Ugh.
void printUsage()
{
printf("usage: temperaturUmrechner {-f|--from} <UNIT> {-t|--to} <UNIT> [<VALUE> [...]]\n"
);
}
TemperatureUnit parseUnit(char str[])
{
char lowerUnit[maxUnitLength + 1];
char lowerStr[maxUnitLength + 1];
memset(lowerStr, '\0', maxUnitLength + 1);
strncpy(lowerStr, str, maxUnitLength);
for (int i = 0; i < maxUnitLength; i++)
{
if (lowerStr[i] == '\0')
break;
lowerStr[i] = tolower(lowerStr[i]);
}
for (int unit = 0; unit < (int)( sizeof(temperatureUnits) / sizeof(TemperatureUnit) ); unit++)
{
memset(lowerUnit, '\0', maxUnitLength + 1);
for (int i = 0; i < maxUnitLength; i++)
{
if (temperatureUnitNames[unit][i] == '\0')
break;
lowerUnit[i] = tolower(temperatureUnitNames[unit][i]);
}
if (strcmp(lowerUnit, lowerStr) == 0)
return temperatureUnits[unit];
}
return unknownUnit;
}
double convert(double value, TemperatureUnit fromUnit, TemperatureUnit toUnit)
{
int fromUnitIndex = -1;
int toUnitIndex = -1;
for (int unit = 0; unit < (int)( sizeof(temperatureUnits) / sizeof(TemperatureUnit) ); unit++)
{
if (temperatureUnits[unit] == fromUnit)
fromUnitIndex = unit;
if (temperatureUnits[unit] == toUnit)
toUnitIndex = unit;
if (fromUnitIndex != -1 && toUnitIndex != -1)
break;
}
if (fromUnitIndex == -1 || toUnitIndex == -1)
abort();
return (value * kelvinMult[fromUnitIndex] + kelvinAdd[fromUnitIndex]) / kelvinMult[toUnitIndex] - kelvinAdd[toUnitIndex];
}
void main(int argc, char* argv[])
{
TemperatureUnit fromUnit = unknownUnit;
TemperatureUnit toUnit = unknownUnit;
while (1) {
int c;
int optionIndex = 0;
static struct option longOptions[] = {
{"from", required_argument, 0, 'f'},
{"to", required_argument, 0, 't'},
{"help", no_argument, 0, 'h'},
{0, 0, 0, 0}
};
c = getopt_long(argc, argv, "f:t:h", longOptions, &optionIndex);
if (c == -1)
break;
switch (c)
{
case 'f':
fromUnit = parseUnit(optarg);
break;
case 't':
toUnit = parseUnit(optarg);
break;
case 'h':
printUsage();
exit(0);
break;
default:
printUsage();
}
}
if (fromUnit == unknownUnit)
fprintf(stderr, "Unknown (or unset) unit to convert from\n");
if (toUnit == unknownUnit)
fprintf(stderr, "Unknown (or unset) unit to convert to\n");
if (toUnit == unknownUnit || fromUnit == unknownUnit)
{
printUsage();
exit(2);
}
for (double value;optind < argc;optind++)
{
sscanf(argv[optind], "%lf", &value);
printf("%.3g\n", convert(value, fromUnit, toUnit));
}
exit(0);
}
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