From 1b8fa736b3881e2e3a06af8cf105fa91d30f1557 Mon Sep 17 00:00:00 2001 From: "Richard M. Stallman" Date: Mon, 17 Apr 1995 06:10:39 +0000 Subject: [PATCH] (Fencode_time): Rewrite by Naggum. --- src/editfns.c | 121 ++++++++++++++++++++++++++++---------------------- 1 file changed, 69 insertions(+), 52 deletions(-) diff --git a/src/editfns.c b/src/editfns.c index 3685b26e36..de98ee789c 100644 --- a/src/editfns.c +++ b/src/editfns.c @@ -741,15 +741,15 @@ This is the reverse operation of `decode-time', which see. ZONE defaults\n\ to the current time zone and daylight savings time if not specified; if\n\ specified, it can be either a list (as from `current-time-zone') or an\n\ integer (as from `decode-time'), and is applied without consideration for\n\ -daylight savings time. If YEAR is less than 100, values in the range 0 to\n\ -37 are interpreted as in the 21st century, all other values are in the 20th\n\ -century.") +daylight savings time.\n\ +If YEAR is less than 100, values in the range 0 through 69 are treated\n\ +as 2000 through 2069; values 70 through 99 are treated as 1970...1999.") (sec, min, hour, day, month, year, zone) Lisp_Object sec, min, hour, day, month, year, zone; { - double universal; - int fullyear, mon; - static char days[11] = { 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31 }; + time_t time; + int fullyear, mon, days, seconds, tz = 0; + static char days_per_month[11] = { 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 31 }; CHECK_NATNUM (sec, 0); CHECK_NATNUM (min, 1); @@ -761,62 +761,79 @@ century.") fullyear = XINT (year); if (fullyear < 100) { - if (fullyear < 38) /* end of time: 2038-01-19 03:14:08 */ + if (fullyear < 70) /* Epoch is 1970. */ fullyear += 2000; else fullyear += 1900; } - if (NILP (zone)) - zone = Fcurrent_time_zone (Qnil); - if (CONSP (zone)) - zone = Fcar (zone); - - CHECK_NUMBER (zone, 6); - - /* all of these should evaluate to compile-time constants. */ -#define MIN 60.0 /* 60 */ -#define HOUR (60*MIN) /* 3600 */ -#define DAY (24*HOUR) /* 86400 */ -#define YEAR (365*DAY) /* 31536000 */ -#define YEAR4 (4*YEAR+DAY) /* 126230400 */ -#define YEAR100 (25*YEAR4-DAY) /* 3155673600 */ -#define YEAR400 (4*YEAR100+DAY) /* 12622780800 */ -#define YEAR1900 (4*YEAR400+3*YEAR100) /* 59958144000 */ -#define YEAR1970 (YEAR1900+17*YEAR4+2*YEAR) /* 62167132800 */ -#define LEAPBIAS (59*DAY) /* 5097600 */ - - mon = XINT (month) - 1; - fullyear--; - mon += 10; - fullyear += mon/12; + /* Adjust incoming datespec to epoch = March 1, year 0. */ + mon = XINT (month) - 1 + 10; + fullyear += mon/12 - 1; mon %= 12; - universal = XINT (sec) + XINT (min) * MIN + XINT (hour) * HOUR; - while (mon-- > 0) - universal += days[mon] * DAY; - universal += (XINT (day) - 1) * DAY; - universal += YEAR400 * (fullyear/400); + days = XINT (day) - 1; /* day of month */ + while (mon-- > 0) /* day of year */ + days += days_per_month[mon]; + days += 146097 * (fullyear/400); /* 400 years = 146097 days */ fullyear %= 400; - universal += YEAR100 * (fullyear/100); + days += 36524 * (fullyear/100); /* 100 years = 36524 days */ fullyear %= 100; - universal += YEAR4 * (fullyear/4); + days += 1461 * (fullyear/4); /* 4 years = 1461 days */ fullyear %= 4; - universal += YEAR * fullyear; - universal -= YEAR1970 - LEAPBIAS; - - return make_time ((int)(universal - XINT (zone))); - -#undef MIN -#undef HOUR -#undef DAY -#undef YEAR -#undef YEAR4 -#undef YEAR100 -#undef YEAR400 -#undef YEAR1900 -#undef YEAR1970 -#undef LEAPBIAS + days += 365 * fullyear; /* 1 year = 365 days */ + + /* Adjust computed datespec to epoch = January 1, 1970. */ + days += 59; /* March 1 is 59th day. */ + days -= 719527; /* 1970 years = 719527 days */ + + seconds = XINT (sec) + 60 * XINT (min) + 3600 * XINT (hour); + + if (sizeof (time_t) == 4 + && ((days+(seconds/86400) > 24854) || (days+(seconds/86400) < -24854))) + error ("the specified time is outside the representable range"); + + time = days * 86400 + seconds; + + /* We have the correct value for UTC. Adjust for timezones. */ + if (NILP (zone)) + { + struct tm gmt, *t; + time_t adjusted_time; + int adjusted_tz; + /* If the system does not use timezones, gmtime returns 0, and we + already have the correct value, by definition. */ + if ((t = gmtime (&time)) != 0) + { + gmt = *t; + t = localtime (&time); + tz = difftm (t, &gmt); + /* The timezone returned is that at the specified Universal Time, + not the local time, which is what we want. Adjust, repeat. */ + adjusted_time = time - tz; + gmt = *gmtime (&adjusted_time); /* this is safe now */ + t = localtime (&adjusted_time); + adjusted_tz = difftm (t, &gmt); + /* In case of discrepancy, adjust again for extra accuracy. */ + if (adjusted_tz != tz) + { + adjusted_time = time - adjusted_tz; + gmt = *gmtime (&adjusted_time); + t = localtime (&adjusted_time); + adjusted_tz = difftm (t, &gmt); + } + tz = adjusted_tz; + } + } + else + { + if (CONSP (zone)) + zone = Fcar (zone); + CHECK_NUMBER (zone, 6); + tz = XINT (zone); + } + + return make_time (time - tz); } DEFUN ("current-time-string", Fcurrent_time_string, Scurrent_time_string, 0, 1, 0, -- 2.20.1