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- #include <stdio.h>
- // Some definitions for calculation
- #define SEC_PER_MIN 60UL
- #define SEC_PER_HOUR 3600UL
- #define SEC_PER_DAY 86400UL
- #define SEC_PER_YEAR (SEC_PER_DAY*365)
- // extracts 1..4 characters from a string and interprets it as a decimal value
- #define CONV_STR2DEC_1(str, i) (str[i]>'0'?str[i]-'0':0)
- #define CONV_STR2DEC_2(str, i) (CONV_STR2DEC_1(str, i)*10 + str[i+1]-'0')
- #define CONV_STR2DEC_3(str, i) (CONV_STR2DEC_2(str, i)*10 + str[i+2]-'0')
- #define CONV_STR2DEC_4(str, i) (CONV_STR2DEC_3(str, i)*10 + str[i+3]-'0')
- // Custom "glue logic" to convert the month name to a usable number
- #define GET_MONTH(str, i) (str[i]=='J' && str[i+1]=='a' && str[i+2]=='n' ? 1 : \
- str[i]=='F' && str[i+1]=='e' && str[i+2]=='b' ? 2 : \
- str[i]=='M' && str[i+1]=='a' && str[i+2]=='r' ? 3 : \
- str[i]=='A' && str[i+1]=='p' && str[i+2]=='r' ? 4 : \
- str[i]=='M' && str[i+1]=='a' && str[i+2]=='y' ? 5 : \
- str[i]=='J' && str[i+1]=='u' && str[i+2]=='n' ? 6 : \
- str[i]=='J' && str[i+1]=='u' && str[i+2]=='l' ? 7 : \
- str[i]=='A' && str[i+1]=='u' && str[i+2]=='g' ? 8 : \
- str[i]=='S' && str[i+1]=='e' && str[i+2]=='p' ? 9 : \
- str[i]=='O' && str[i+1]=='c' && str[i+2]=='t' ? 10 : \
- str[i]=='N' && str[i+1]=='o' && str[i+2]=='v' ? 11 : \
- str[i]=='D' && str[i+1]=='e' && str[i+2]=='c' ? 12 : 0)
- // extract the information from the time string given by __TIME__ and __DATE__
- #define __TIME_SECONDS__ CONV_STR2DEC_2(__TIME__, 6)
- #define __TIME_MINUTES__ CONV_STR2DEC_2(__TIME__, 3)
- #define __TIME_HOURS__ CONV_STR2DEC_2(__TIME__, 0)
- #define __TIME_DAYS__ CONV_STR2DEC_2(__DATE__, 4)
- #define __TIME_MONTH__ GET_MONTH(__DATE__, 0)
- #define __TIME_YEARS__ CONV_STR2DEC_4(__DATE__, 7)
- // Days in February
- #define _UNIX_TIMESTAMP_FDAY(year) \
- (((year) % 400) == 0UL ? 29UL : \
- (((year) % 100) == 0UL ? 28UL : \
- (((year) % 4) == 0UL ? 29UL : \
- 28UL)))
- // Days in the year
- #define _UNIX_TIMESTAMP_YDAY(year, month, day) \
- ( \
- /* January */ day \
- /* February */ + (month >= 2 ? 31UL : 0UL) \
- /* March */ + (month >= 3 ? _UNIX_TIMESTAMP_FDAY(year) : 0UL) \
- /* April */ + (month >= 4 ? 31UL : 0UL) \
- /* May */ + (month >= 5 ? 30UL : 0UL) \
- /* June */ + (month >= 6 ? 31UL : 0UL) \
- /* July */ + (month >= 7 ? 30UL : 0UL) \
- /* August */ + (month >= 8 ? 31UL : 0UL) \
- /* September */+ (month >= 9 ? 31UL : 0UL) \
- /* October */ + (month >= 10 ? 30UL : 0UL) \
- /* November */ + (month >= 11 ? 31UL : 0UL) \
- /* December */ + (month >= 12 ? 30UL : 0UL) \
- )
- // get the UNIX timestamp from a digits representation
- #define _UNIX_TIMESTAMP(year, month, day, hour, minute, second) \
- ( /* time */ second \
- + minute * SEC_PER_MIN \
- + hour * SEC_PER_HOUR \
- + /* year day (month + day) */ (_UNIX_TIMESTAMP_YDAY(year, month, day) - 1) * SEC_PER_DAY \
- + /* year */ (year - 1970UL) * SEC_PER_YEAR \
- + ((year - 1969UL) / 4UL) * SEC_PER_DAY \
- - ((year - 1901UL) / 100UL) * SEC_PER_DAY \
- + ((year - 1601UL) / 400UL) * SEC_PER_DAY \
- )
- // the UNIX timestamp
- #define UNIX_TIMESTAMP (_UNIX_TIMESTAMP(__TIME_YEARS__, __TIME_MONTH__, __TIME_DAYS__, __TIME_HOURS__, __TIME_MINUTES__, __TIME_SECONDS__))
- // Current UTC day of week--0 is Sunday
- #define DAY_OF_WEEK ((UNIX_TIMESTAMP / 86400) + 4) % 7
- // Type your code here, or load an example.
- int main(int argc, char **argv) {
- static_assert(DAY_OF_WEEK != 1);
- printf("It is not Monday\n");
- }
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