time_macros.h
Go to the documentation of this file.
/*
*
* Created: 29.03.2018
*
* Authors:
*
* Assembled from the code released on Stackoverflow by:
* Dennis (instructable.com/member/nqtronix) | https://stackoverflow.com/questions/23032002/c-c-how-to-get-integer-unix-timestamp-of-build-time-not-string
* and
* Alexis Wilke | https://stackoverflow.com/questions/10538444/do-you-know-of-a-c-macro-to-compute-unix-time-and-date
*
* Assembled by Jean Rabault
*
* UNIX_TIMESTAMP gives the UNIX timestamp (unsigned long integer of seconds since 1st Jan 1970) of compilation from macros using the compiler defined __TIME__ macro.
* This should include Gregorian calendar leap days, in particular the 29ths of February, 100 and 400 years modulo leaps.
*
* Careful: __TIME__ is the local time of the computer, NOT the UTC time in general!
*
*/
#ifndef COMPILE_TIME_H_
#define COMPILE_TIME_H_
// add offset for pacific standard time
#define PST_OFFSET (8UL)
// 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__)
#define UNIX_TIMESTAMP_UTC (UNIX_TIMESTAMP + (PST_OFFSET*SEC_PER_HOUR))
#endif