diff options
Diffstat (limited to 'contrib/ntp/libntp/ntp_calendar.c')
| -rw-r--r-- | contrib/ntp/libntp/ntp_calendar.c | 85 |
1 files changed, 56 insertions, 29 deletions
diff --git a/contrib/ntp/libntp/ntp_calendar.c b/contrib/ntp/libntp/ntp_calendar.c index ff6ead364e5a..4bfb0e723c01 100644 --- a/contrib/ntp/libntp/ntp_calendar.c +++ b/contrib/ntp/libntp/ntp_calendar.c @@ -91,7 +91,7 @@ /* *--------------------------------------------------------------------- * replacing the 'time()' function - * -------------------------------------------------------------------- + *--------------------------------------------------------------------- */ static systime_func_ptr systime_func = &time; @@ -395,7 +395,7 @@ ntpcal_get_build_date( /* *--------------------------------------------------------------------- * basic calendar stuff - * -------------------------------------------------------------------- + *--------------------------------------------------------------------- */ /* month table for a year starting with March,1st */ @@ -443,11 +443,11 @@ static const uint16_t real_month_table[2][13] = { */ /* - * ================================================================== + * ==================================================================== * * General algorithmic stuff * - * ================================================================== + * ==================================================================== */ /* @@ -495,7 +495,7 @@ static const uint16_t real_month_table[2][13] = { * 32/16bit divisions and is still performant is a bit more * difficult. Since most usecases can be coded in a way that does only * require the 32-bit version a 64bit version is NOT provided here. - * --------------------------------------------------------------------- + *--------------------------------------------------------------------- */ int32_t ntpcal_periodic_extend( @@ -542,8 +542,35 @@ ntpcal_periodic_extend( return pivot; } +/*--------------------------------------------------------------------- + * Note to the casual reader + * + * In the next two functions you will find (or would have found...) + * the expression + * + * res.Q_s -= 0x80000000; + * + * There was some ruckus about a possible programming error due to + * integer overflow and sign propagation. + * + * This assumption is based on a lack of understanding of the C + * standard. (Though this is admittedly not one of the most 'natural' + * aspects of the 'C' language and easily to get wrong.) + * + * see + * http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf + * "ISO/IEC 9899:201x Committee Draft — April 12, 2011" + * 6.4.4.1 Integer constants, clause 5 + * + * why there is no sign extension/overflow problem here. + * + * But to ease the minds of the doubtful, I added back the 'u' qualifiers + * that somehow got lost over the last years. + */ + + /* - *------------------------------------------------------------------- + *--------------------------------------------------------------------- * Convert a timestamp in NTP scale to a 64bit seconds value in the UN*X * scale with proper epoch unfolding around a given pivot or the current * system time. This function happily accepts negative pivot values as @@ -553,7 +580,7 @@ ntpcal_periodic_extend( * This is also a periodic extension, but since the cycle is 2^32 and * the shift is 2^31, we can do some *very* fast math without explicit * divisions. - *------------------------------------------------------------------- + *--------------------------------------------------------------------- */ vint64 ntpcal_ntp_to_time( @@ -568,7 +595,7 @@ ntpcal_ntp_to_time( res.q_s = (pivot != NULL) ? *pivot : now(); - res.Q_s -= 0x80000000; /* unshift of half range */ + res.Q_s -= 0x80000000u; /* unshift of half range */ ntp -= (uint32_t)JAN_1970; /* warp into UN*X domain */ ntp -= res.D_s.lo; /* cycle difference */ res.Q_s += (uint64_t)ntp; /* get expanded time */ @@ -581,7 +608,7 @@ ntpcal_ntp_to_time( ? *pivot : now(); res = time_to_vint64(&tmp); - M_SUB(res.D_s.hi, res.D_s.lo, 0, 0x80000000); + M_SUB(res.D_s.hi, res.D_s.lo, 0, 0x80000000u); ntp -= (uint32_t)JAN_1970; /* warp into UN*X domain */ ntp -= res.D_s.lo; /* cycle difference */ M_ADD(res.D_s.hi, res.D_s.lo, 0, ntp); @@ -592,7 +619,7 @@ ntpcal_ntp_to_time( } /* - *------------------------------------------------------------------- + *--------------------------------------------------------------------- * Convert a timestamp in NTP scale to a 64bit seconds value in the NTP * scale with proper epoch unfolding around a given pivot or the current * system time. @@ -602,7 +629,7 @@ ntpcal_ntp_to_time( * This is also a periodic extension, but since the cycle is 2^32 and * the shift is 2^31, we can do some *very* fast math without explicit * divisions. - *------------------------------------------------------------------- + *--------------------------------------------------------------------- */ vint64 ntpcal_ntp_to_ntp( @@ -617,7 +644,7 @@ ntpcal_ntp_to_ntp( res.q_s = (pivot) ? *pivot : now(); - res.Q_s -= 0x80000000; /* unshift of half range */ + res.Q_s -= 0x80000000u; /* unshift of half range */ res.Q_s += (uint32_t)JAN_1970; /* warp into NTP domain */ ntp -= res.D_s.lo; /* cycle difference */ res.Q_s += (uint64_t)ntp; /* get expanded time */ @@ -642,20 +669,20 @@ ntpcal_ntp_to_ntp( /* - * ================================================================== + * ==================================================================== * * Splitting values to composite entities * - * ================================================================== + * ==================================================================== */ /* - *------------------------------------------------------------------- + *--------------------------------------------------------------------- * Split a 64bit seconds value into elapsed days in 'res.hi' and * elapsed seconds since midnight in 'res.lo' using explicit floor * division. This function happily accepts negative time values as * timestamps before the respective epoch start. - * ------------------------------------------------------------------- + *--------------------------------------------------------------------- */ ntpcal_split ntpcal_daysplit( @@ -736,11 +763,11 @@ ntpcal_daysplit( } /* - *------------------------------------------------------------------- + *--------------------------------------------------------------------- * Split a 32bit seconds value into h/m/s and excessive days. This * function happily accepts negative time values as timestamps before * midnight. - * ------------------------------------------------------------------- + *--------------------------------------------------------------------- */ static int32_t priv_timesplit( @@ -773,7 +800,7 @@ priv_timesplit( } /* - * --------------------------------------------------------------------- + *--------------------------------------------------------------------- * Given the number of elapsed days in the calendar era, split this * number into the number of elapsed years in 'res.hi' and the number * of elapsed days of that year in 'res.lo'. @@ -1053,11 +1080,11 @@ ntpcal_time_to_date( /* - * ================================================================== + * ==================================================================== * * merging composite entities * - * ================================================================== + * ==================================================================== */ /* @@ -1251,8 +1278,8 @@ ntpcal_edate_to_eradays( * Convert ELAPSED years/months/days of gregorian calendar to elapsed * days in year. * - * Note: This will give the true difference to the start of the given year, - * even if months & days are off-scale. + * Note: This will give the true difference to the start of the given + * year, even if months & days are off-scale. *--------------------------------------------------------------------- */ int32_t @@ -1434,11 +1461,11 @@ ntpcal_date_to_time( /* - * ================================================================== + * ==================================================================== * * extended and unchecked variants of caljulian/caltontp * - * ================================================================== + * ==================================================================== */ int ntpcal_ntp64_to_date( @@ -1500,11 +1527,11 @@ ntpcal_date_to_ntp( /* - * ================================================================== + * ==================================================================== * * day-of-week calculations * - * ================================================================== + * ==================================================================== */ /* * Given a RataDie and a day-of-week, calculate a RDN that is reater-than, @@ -1557,7 +1584,7 @@ ntpcal_weekday_lt( } /* - * ================================================================== + * ==================================================================== * * ISO week-calendar conversions * @@ -1601,7 +1628,7 @@ ntpcal_weekday_lt( * smallest possible powers of two, so the division can be implemented * as shifts if the optimiser chooses to do so. * - * ================================================================== + * ==================================================================== */ /* |