[src/trunk]: src/lib/libutil Improved handling of local times.

[apb <apb%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/85f4d1df552b
branches:  trunk
changeset: 332776:85f4d1df552b
user:      apb <apb%NetBSD.org@localhost>
date:      Wed Oct 08 17:38:28 2014 +0000

description:
Improved handling of local times.

* A magic value USE_LOCAL_TIME (defined as 99999) may be passed as the
  Timezone to Convert(), instructing it to use mktime() to work
  in the local time zone, instead of using mktime_z to work in UTC
  (and then adding the specified timezone offset).
* Some old code is removed now that there's no need to find the local
  timezone offset.
* Allow either one or both of the now and zone arguments to
  parsedate() to be NULL, treating them independently.  Previously,
  if either one was NULL, the other was ignored.
* If the zone argument is specified, then the current date is calculated
  in the specified zone, not in local time.

Also add some disabled debug code.

This should fix PR lib/47916.

diffstat:

 lib/libutil/parsedate.y |  82 ++++++++++++++++++++++--------------------------
 1 files changed, 37 insertions(+), 45 deletions(-)

diffs (135 lines):

diff -r 4b005ec572d7 -r 85f4d1df552b lib/libutil/parsedate.y
--- a/lib/libutil/parsedate.y   Wed Oct 08 17:23:03 2014 +0000
+++ b/lib/libutil/parsedate.y   Wed Oct 08 17:38:28 2014 +0000
@@ -14,7 +14,7 @@
 
 #include <sys/cdefs.h>
 #ifdef __RCSID
-__RCSID("$NetBSD: parsedate.y,v 1.19 2014/10/08 14:43:48 apb Exp $");
+__RCSID("$NetBSD: parsedate.y,v 1.20 2014/10/08 17:38:28 apb Exp $");
 #endif
 
 #include <stdio.h>
@@ -42,6 +42,7 @@
 #define HOUR(x)                ((time_t)(x) * 60)
 #define SECSPERDAY     (24L * 60L * 60L)
 
+#define USE_LOCAL_TIME 99999 /* special case for Convert() and yyTimezone */
 
 /*
 **  An entry in the lexical lookup table.
@@ -618,7 +619,8 @@
     time_t     Hours,          /* Hour of day [0-24] */
     time_t     Minutes,        /* Minute of hour [0-59] */
     time_t     Seconds,        /* Second of minute [0-60] */
-    time_t     Timezone,       /* Timezone as minutes east of UTC */
+    time_t     Timezone,       /* Timezone as minutes east of UTC,
+                                * or USE_LOCAL_TIME special case */
     MERIDIAN   Meridian,       /* Hours are am/pm/24 hour clock */
     DSTMODE    DSTmode         /* DST on/off/maybe */
 )
@@ -638,9 +640,25 @@
     default:     tm.tm_isdst = -1; break;
     }
 
-    /* We rely on mktime_z(NULL, ...) working in UTC, not in local time. */
-    result = mktime_z(NULL, &tm);
-    result += Timezone * 60;
+    if (Timezone == USE_LOCAL_TIME) {
+           result = mktime(&tm);
+    } else {
+           /* We rely on mktime_z(NULL, ...) working in UTC */
+           result = mktime_z(NULL, &tm);
+           result += Timezone * 60;
+    }
+
+#if PARSEDATE_DEBUG
+    fprintf(stderr, "%s(M=%jd D=%jd Y=%jd H=%jd M=%jd S=%jd Z=%jd"
+                   " mer=%d DST=%d)",
+       __func__,
+       (intmax_t)Month, (intmax_t)Day, (intmax_t)Year,
+       (intmax_t)Hours, (intmax_t)Minutes, (intmax_t)Seconds,
+       (intmax_t)Timezone, (int)Meridian, (int)DSTmode);
+    fprintf(stderr, " -> %jd", (intmax_t)result);
+    fprintf(stderr, " %s", ctime(&result));
+#endif
+
     return result;
 }
 
@@ -878,31 +896,10 @@
 
 #define TM_YEAR_ORIGIN 1900
 
-/* Yield A - B, measured in seconds.  */
-static time_t
-difftm (struct tm *a, struct tm *b)
-{
-  int ay = a->tm_year + (TM_YEAR_ORIGIN - 1);
-  int by = b->tm_year + (TM_YEAR_ORIGIN - 1);
-  int days = (
-             /* difference in day of year */
-             a->tm_yday - b->tm_yday
-             /* + intervening leap days */
-             +  ((ay >> 2) - (by >> 2))
-             -  (ay/100 - by/100)
-             +  ((ay/100 >> 2) - (by/100 >> 2))
-             /* + difference in years * 365 */
-             +  (long)(ay-by) * 365
-             );
-  return ((time_t)60*(60*(24*days + (a->tm_hour - b->tm_hour))
-             + (a->tm_min - b->tm_min))
-         + (a->tm_sec - b->tm_sec));
-}
-
 time_t
 parsedate(const char *p, const time_t *now, const int *zone)
 {
-    struct tm gmt, local, *gmt_ptr, *tm;
+    struct tm          local, *tm;
     time_t             nowt;
     int                        zonet;
     time_t             Start;
@@ -913,29 +910,24 @@
     saved_errno = errno;
     errno = 0;
 
-    if (now == NULL || zone == NULL) {
+    if (now == NULL) {
         now = &nowt;
+       (void)time(&nowt);
+    }
+    if (zone == NULL) {
        zone = &zonet;
-       (void)time(&nowt);
-
-       gmt_ptr = gmtime_r(now, &gmt);
+       zonet = USE_LOCAL_TIME;
        if ((tm = localtime_r(now, &local)) == NULL)
            return -1;
-
-       if (gmt_ptr != NULL)
-           zonet = difftm(&gmt, &local) / 60;
-       else
-           /* We are on a system like VMS, where the system clock is
-              in local time and the system has no concept of timezones.
-              Hopefully we can fake this out (for the case in which the
-              user specifies no timezone) by just saying the timezone
-              is zero.  */
-           zonet = 0;
-
-       if (local.tm_isdst)
-           zonet += 60;
     } else {
-       if ((tm = localtime_r(now, &local)) == NULL)
+       /*
+        * Should use the specified zone, not localtime.
+        * Fake it using gmtime and arithmetic.
+        * This is good enough because we use only the year/month/day,
+        * not other fields of struct tm.
+        */
+       time_t fake = *now + (*zone * 60);
+       if ((tm = gmtime_r(&fake, &local)) == NULL)
            return -1;
     }
     param.yyYear = tm->tm_year + 1900;