/* * timetoa.h -- time_t related string formatting * * Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project. * The contents of 'html/copyright.html' apply. * * Printing a 'time_t' has some portability pitfalls, due to it's opaque * base type. The only requirement imposed by the standard is that it * must be a numeric type. For all practical purposes it's a signed int, * and 32 bits are common. * * Since the UN*X time epoch will cause a signed integer overflow for * 32-bit signed int values in the year 2038, implementations slowly * move to 64bit base types for time_t, even in 32-bit environments. In * such an environment sizeof(time_t) could be bigger than sizeof(long) * and the commonly used idiom of casting to long leads to truncation. * * As the printf() family has no standardised type specifier for time_t, * guessing the right output format specifier is a bit troublesome and * best done with the help of the preprocessor and "config.h". */ #ifndef TIMETOA_H #define TIMETOA_H #include "ntp_fp.h" #include "ntp_stdlib.h" #include "ntp_unixtime.h" /* * Given the size of time_t, guess what can be used as an unsigned value * to hold a time_t and the printf() format specifcation. * * These should be used with the string constant concatenation feature * of the compiler like this: * * printf("a time stamp: %" TIME_FORMAT " and more\n", a_time_t_value); * * It's not exactly nice, but there's not much leeway once we want to * use the printf() family on time_t values. */ #if SIZEOF_TIME_T <= SIZEOF_INT typedef unsigned int u_time; #define TIME_FORMAT "d" #define UTIME_FORMAT "u" #elif SIZEOF_TIME_T <= SIZEOF_LONG typedef unsigned long u_time; #define TIME_FORMAT "ld" #define UTIME_FORMAT "lu" #elif defined(SIZEOF_LONG_LONG) && SIZEOF_TIME_T <= SIZEOF_LONG_LONG typedef unsigned long long u_time; #define TIME_FORMAT "lld" #define UTIME_FORMAT "llu" #else #include "GRONK: what size has a time_t here?" #endif /* * general fractional time stamp formatting. * * secs - integral seconds of time stamp * frac - fractional units * prec - log10 of units per second (3=milliseconds, 6=microseconds,..) * or in other words: the count of decimal digits required. * If prec is < 0, abs(prec) is taken for the precision and secs * is treated as an unsigned value. * * The function will eventually normalise the fraction and adjust the * seconds accordingly. * * This function uses the string buffer library for the return value, * so do not keep the resulting pointers around. */ extern const char * format_time_fraction(time_t secs, long frac, int prec); #endif /* !defined(TIMETOA_H) */