1275970Scy/* 2275970Scy * timetoa.h -- time_t related string formatting 3275970Scy * 4275970Scy * Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project. 5275970Scy * The contents of 'html/copyright.html' apply. 6275970Scy * 7275970Scy * Printing a 'time_t' has some portability pitfalls, due to it's opaque 8275970Scy * base type. The only requirement imposed by the standard is that it 9275970Scy * must be a numeric type. For all practical purposes it's a signed int, 10275970Scy * and 32 bits are common. 11275970Scy * 12275970Scy * Since the UN*X time epoch will cause a signed integer overflow for 13275970Scy * 32-bit signed int values in the year 2038, implementations slowly 14275970Scy * move to 64bit base types for time_t, even in 32-bit environments. In 15275970Scy * such an environment sizeof(time_t) could be bigger than sizeof(long) 16275970Scy * and the commonly used idiom of casting to long leads to truncation. 17275970Scy * 18275970Scy * As the printf() family has no standardised type specifier for time_t, 19275970Scy * guessing the right output format specifier is a bit troublesome and 20275970Scy * best done with the help of the preprocessor and "config.h". 21275970Scy */ 22275970Scy#ifndef TIMETOA_H 23275970Scy#define TIMETOA_H 24275970Scy 25275970Scy#include "ntp_fp.h" 26275970Scy#include "ntp_stdlib.h" 27275970Scy#include "ntp_unixtime.h" 28275970Scy 29275970Scy/* 30275970Scy * Given the size of time_t, guess what can be used as an unsigned value 31275970Scy * to hold a time_t and the printf() format specifcation. 32275970Scy * 33275970Scy * These should be used with the string constant concatenation feature 34275970Scy * of the compiler like this: 35275970Scy * 36275970Scy * printf("a time stamp: %" TIME_FORMAT " and more\n", a_time_t_value); 37275970Scy * 38275970Scy * It's not exactly nice, but there's not much leeway once we want to 39275970Scy * use the printf() family on time_t values. 40275970Scy */ 41275970Scy 42275970Scy#if SIZEOF_TIME_T <= SIZEOF_INT 43275970Scy 44275970Scytypedef unsigned int u_time; 45275970Scy#define TIME_FORMAT "d" 46275970Scy#define UTIME_FORMAT "u" 47275970Scy 48275970Scy#elif SIZEOF_TIME_T <= SIZEOF_LONG 49275970Scy 50275970Scytypedef unsigned long u_time; 51275970Scy#define TIME_FORMAT "ld" 52275970Scy#define UTIME_FORMAT "lu" 53275970Scy 54275970Scy#elif defined(SIZEOF_LONG_LONG) && SIZEOF_TIME_T <= SIZEOF_LONG_LONG 55275970Scy 56275970Scytypedef unsigned long long u_time; 57275970Scy#define TIME_FORMAT "lld" 58275970Scy#define UTIME_FORMAT "llu" 59275970Scy 60275970Scy#else 61275970Scy#include "GRONK: what size has a time_t here?" 62275970Scy#endif 63275970Scy 64275970Scy/* 65275970Scy * general fractional time stamp formatting. 66275970Scy * 67275970Scy * secs - integral seconds of time stamp 68275970Scy * frac - fractional units 69275970Scy * prec - log10 of units per second (3=milliseconds, 6=microseconds,..) 70275970Scy * or in other words: the count of decimal digits required. 71275970Scy * If prec is < 0, abs(prec) is taken for the precision and secs 72275970Scy * is treated as an unsigned value. 73275970Scy * 74275970Scy * The function will eventually normalise the fraction and adjust the 75275970Scy * seconds accordingly. 76275970Scy * 77275970Scy * This function uses the string buffer library for the return value, 78275970Scy * so do not keep the resulting pointers around. 79275970Scy */ 80275970Scyextern const char * 81275970Scyformat_time_fraction(time_t secs, long frac, int prec); 82275970Scy 83275970Scy#endif /* !defined(TIMETOA_H) */ 84