From 97c145919d8c702003b9cd8bac0e01083d3ab9a1 Mon Sep 17 00:00:00 2001
From: Howard Chu <hyc@openldap.org>
Date: Thu, 28 Nov 2019 21:31:06 +0000
Subject: [PATCH] ITS#9120 change reference year from 1970 to 0000

Now handles +/-8740 years centered around year 0000 (1BCE)
---
 include/lutil.h            |  5 +-
 libraries/liblutil/utils.c | 94 +++++++++++++++++++++++---------------
 2 files changed, 61 insertions(+), 38 deletions(-)

diff --git a/include/lutil.h b/include/lutil.h
index 3273496c1d..5fdc405b7d 100644
--- a/include/lutil.h
+++ b/include/lutil.h
@@ -169,8 +169,9 @@ typedef struct lutil_tm {
 } lutil_tm;
 
 typedef struct lutil_timet {
-	unsigned int tt_sec;	/* seconds since 1900 */
-	int tt_gsec;		/* seconds since 1900, high 7 bits */
+	unsigned int tt_sec;	/* seconds since 0000 */
+	int tt_gsec;		/* seconds since 0000, high 7 bits, sign-flipped */
+						/* sign flipped to sort properly as unsigned ints */
 	unsigned int tt_usec;	/* microseconds */
 } lutil_timet;
 
diff --git a/libraries/liblutil/utils.c b/libraries/liblutil/utils.c
index ab0fe4e5d2..24e2337509 100644
--- a/libraries/liblutil/utils.c
+++ b/libraries/liblutil/utils.c
@@ -151,75 +151,92 @@ size_t lutil_localtime( char *s, size_t smax, const struct tm *tm, long delta )
 	return ret + 4;
 }
 
+/* Proleptic Gregorian Calendar, 1BCE = year 0 */
+
 int lutil_tm2time( struct lutil_tm *tm, struct lutil_timet *tt )
 {
 	static int moffset[12] = {
 		0, 31, 59, 90, 120,
 		151, 181, 212, 243,
 		273, 304, 334 }; 
-	int sec;
+	int sec, year;
+	long tmp;
 
 	tt->tt_usec = tm->tm_usec;
 
-	/* special case 0000/01/01+00:00:00 is returned as zero */
-	if ( tm->tm_year == -1900 && tm->tm_mon == 0 && tm->tm_mday == 1 &&
-		tm->tm_hour == 0 && tm->tm_min == 0 && tm->tm_sec == 0 ) {
-		tt->tt_sec = 0;
-		tt->tt_gsec = 0;
-		return 0;
-	}
-
 	/* tm->tm_year is years since 1900 */
-	/* calculate days from years since 1970 (epoch) */ 
-	tt->tt_sec = tm->tm_year - 70; 
-	tt->tt_sec *= 365L; 
+	/* calculate days from 0000 */
+	year = tm->tm_year + 1900;
+	tmp = year * 365;
 
-	/* count leap days in preceding years */ 
-	tt->tt_sec += ((tm->tm_year -69) >> 2); 
+
+	/* add in leap days */
+	sec = (year - 1) / 4;
+	tmp += sec;
+	sec /= 25;
+	tmp -= sec;
+	sec /= 4;
+	tmp += sec;
+	/* Year 0000 was a leap year */
+	if (year > 0)
+		tmp++;
 
 	/* calculate days from months */ 
-	tt->tt_sec += moffset[tm->tm_mon]; 
+	tmp += moffset[tm->tm_mon];
 
-	/* add in this year's leap day, if any */ 
-	if (((tm->tm_year & 3) == 0) && (tm->tm_mon > 1)) { 
-		tt->tt_sec ++; 
-	} 
+	/* add in this year's leap day, if any */
+	if (tm->tm_mon > 1) {
+		sec = (year % 4) ? 0 : (year % 100) ? 1 : (year % 400) ? 0 : 1;
+		tmp += sec;
+	}
 
-	/* add in days in this month */ 
-	tt->tt_sec += (tm->tm_mday - 1); 
+	/* add in days in this month */
+	tmp += (tm->tm_mday - 1);
 
 	/* this function can handle a range of about 17408 years... */
 	/* 86400 seconds in a day, divided by 128 = 675 */
-	tt->tt_sec *= 675;
+	tmp *= 675;
 
 	/* move high 7 bits into tt_gsec */
-	tt->tt_gsec = tt->tt_sec >> 25;
-	tt->tt_sec -= tt->tt_gsec << 25;
+	tt->tt_gsec = tmp >> 25;
+	tmp -= tt->tt_gsec << 25;
 
-	/* get hours */ 
-	sec = tm->tm_hour; 
+	/* toggle sign bit, keep positive greater than negative */
+	tt->tt_gsec &= 0x7f;
+	tt->tt_gsec ^= 0x40;
 
-	/* convert to minutes */ 
-	sec *= 60L; 
-	sec += tm->tm_min; 
+	/* get hours */
+	sec = tm->tm_hour;
 
-	/* convert to seconds */ 
-	sec *= 60L; 
-	sec += tm->tm_sec; 
+	/* convert to minutes */
+	sec *= 60L;
+	sec += tm->tm_min;
+
+	/* convert to seconds */
+	sec *= 60L;
+	sec += tm->tm_sec;
 	
 	/* add remaining seconds */
-	tt->tt_sec <<= 7;
-	tt->tt_sec += sec;
+	tmp <<= 7;
+	tmp += sec;
+	tt->tt_sec = tmp;
 
 	/* return success */
-	return 0; 
+	return 0;
 }
 
 int lutil_parsetime( char *atm, struct lutil_tm *tm )
 {
 	while (atm && tm) {
-		char *ptr = atm;
+		char *ptr;
 		unsigned i, fracs;
+		int neg = 0;
+
+		if (*atm == '-') {
+			neg = 1;
+			atm++;
+		}
+		ptr = atm;
 
 		/* Is the stamp reasonably long? */
 		for (i=0; isdigit((unsigned char) atm[i]); i++);
@@ -234,6 +251,8 @@ int lutil_parsetime( char *atm, struct lutil_tm *tm )
 		tm->tm_year *= 10; tm->tm_year += *ptr++ - '0';
 		tm->tm_year *= 10; tm->tm_year += *ptr++ - '0';
 		tm->tm_year *= 10; tm->tm_year += *ptr++ - '0';
+		if (neg)
+			tm->tm_year = -tm->tm_year;
 		tm->tm_year -= 1900;
 		/* month 01-12 to 0-11 */
 		tm->tm_mon = *ptr++ - '0';
@@ -273,7 +292,10 @@ int lutil_parsetime( char *atm, struct lutil_tm *tm )
 				for (i = fracs; i<6; i++)
 					tm->tm_usec *= 10;
 			}
+		} else {
+			tm->tm_usec = 0;
 		}
+		tm->tm_usub = 0;
 
 		/* Must be UTC */
 		if (*ptr != 'Z') break;