date,touch: allow timezone offsets in dates

Allow ISO 8601 style dates to include a timezone offset.  Like
the '@' format these dates aren't relative to the user's current
timezone and shouldn't be subject to DST adjustment.

- The implementation uses the strptime() '%z' format specifier.
  This an extension which may not be available so the use of
  timezones is a configuration option.

- The 'touch' applet has been updated to respect whether DST
  adjustment is required, matching 'date'.

function                                             old     new   delta
parse_datestr                                        624     730    +106
static.fmt_str                                       106     136     +30
touch_main                                           388     392      +4
date_main                                            818     819      +1
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 141/0)             Total: 141 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 8 insertions, 5 deletions

diff --git a/coreutils/date.c b/coreutils/date.c
index 7061f1719..abcc37c33 100644
--- a/coreutils/date.c
+++ b/coreutils/date.c
@@ -266,6 +266,7 @@ int date_main(int argc UNUSED_PARAM, char **argv)
 
 	/* If date string is given, update tm_time, and maybe set date */
 	if (date_str != NULL) {
+		int check_dst = 1;
 		/* Zero out fields - take her back to midnight! */
 		tm_time.tm_sec = 0;
 		tm_time.tm_min = 0;
@@ -276,12 +277,12 @@ int date_main(int argc UNUSED_PARAM, char **argv)
 			if (strptime(date_str, fmt_str2dt, &tm_time) == NULL)
 				bb_error_msg_and_die(bb_msg_invalid_date, date_str);
 		} else {
-			parse_datestr(date_str, &tm_time);
+			check_dst = parse_datestr(date_str, &tm_time);
 		}
 
 		/* Correct any day of week and day of year etc. fields */
-		/* Be sure to recheck dst (but not if date is time_t format) */
-		if (date_str[0] != '@')
+		/* Be sure to recheck dst (but not if date is UTC) */
+		if (check_dst)
 			tm_time.tm_isdst = -1;
 		ts.tv_sec = validate_tm_time(date_str, &tm_time);
 		ts.tv_nsec = 0;
diff --git a/coreutils/touch.c b/coreutils/touch.c
index 78100ba1d..7e13a27be 100644
--- a/coreutils/touch.c
+++ b/coreutils/touch.c
@@ -140,15 +140,17 @@ int touch_main(int argc UNUSED_PARAM, char **argv)
 	if (opts & (OPT_d|OPT_t)) {
 		struct tm tm_time;
 		time_t t;
+		int check_dst;
 
 		//memset(&tm_time, 0, sizeof(tm_time));
 		/* Better than memset: makes "HH:MM" dates meaningful */
 		time(&t);
 		localtime_r(&t, &tm_time);
-		parse_datestr(date_str, &tm_time);
+		check_dst = parse_datestr(date_str, &tm_time);
 
 		/* Correct any day of week and day of year etc. fields */
-		tm_time.tm_isdst = -1;  /* Be sure to recheck dst */
+		if (check_dst)
+			tm_time.tm_isdst = -1;  /* recheck dst unless date is UTC */
 		t = validate_tm_time(date_str, &tm_time);
 
 		timebuf[1].tv_sec = timebuf[0].tv_sec = t;