1 /* temphelper.c: aid in converting temperature units
3 * Copyright (C) 2008 Phil Sutter <Phil@nwl.cc>
5 * This library is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 * GNU General Public License for more details.
15 * You should have received a copy of the GNU General Public License
16 * along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301
28 #include <sys/types.h>
29 #include "temphelper.h"
31 /* default to output in celsius */
32 static enum TEMP_UNIT output_unit = TEMP_CELSIUS;
35 fahrenheit_to_celsius(double n)
37 return ((n - 32) * 5 / 9);
41 celsius_to_fahrenheit(double n)
43 return ((n * 9 / 5) + 32);
47 set_temp_output_unit(const char *name)
57 for (i = 0; i < strlen(name); i++)
58 buf[i] = tolower(name[i]);
60 if (!strcmp(buf, "celsius"))
61 output_unit = TEMP_CELSIUS;
62 else if (!strcmp(buf, "fahrenheit"))
63 output_unit = TEMP_FAHRENHEIT;
71 convert_temp_output(double n, enum TEMP_UNIT input_unit)
73 if (input_unit == output_unit)
78 return fahrenheit_to_celsius(n);
80 return celsius_to_fahrenheit(n);
86 int temp_print(char *p, size_t p_max_size, double n, enum TEMP_UNIT input_unit)
90 out = convert_temp_output(n, input_unit);
92 /* Skip decimal for big values but keep padding sane
93 * (i.e. use 4 chars for them)
95 plen = snprintf(p, p_max_size, ((out > 100.0) ?
96 "%4.0lf" : "%2.1lf") , out);
97 return !(plen >= p_max_size);