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List: busybox
Subject: Re: [PATCH] date,touch: allow timezone offsets in dates
From: Denys Vlasenko <vda.linux () googlemail ! com>
Date: 2021-09-16 22:23:57
Message-ID: CAK1hOcNHduieHPV6HXOxQPiQbqOddo5k4q5+r3EZTg82X5YJHQ () mail ! gmail ! com
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Applied, thank you.
On Thu, Sep 16, 2021 at 11:26 AM Ron Yorston <rmy@pobox.com> wrote:
>
> 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>
> ---
> coreutils/date.c | 7 ++++---
> coreutils/touch.c | 6 ++++--
> include/libbb.h | 2 +-
> libbb/Config.src | 11 +++++++++++
> libbb/time.c | 32 ++++++++++++++++++++++++++++----
> testsuite/date/date-timezone | 32 ++++++++++++++++++++++++++++++++
> 6 files changed, 80 insertions(+), 10 deletions(-)
> create mode 100644 testsuite/date/date-timezone
>
> 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;
> diff --git a/include/libbb.h b/include/libbb.h
> index 7d6ab4a93..1ec8d2d3b 100644
> --- a/include/libbb.h
> +++ b/include/libbb.h
> @@ -690,7 +690,7 @@ struct BUG_too_small {
> };
>
>
> -void parse_datestr(const char *date_str, struct tm *ptm) FAST_FUNC;
> +int parse_datestr(const char *date_str, struct tm *ptm) FAST_FUNC;
> time_t validate_tm_time(const char *date_str, struct tm *ptm) FAST_FUNC;
> char *strftime_HHMMSS(char *buf, unsigned len, time_t *tp) FAST_FUNC;
> char *strftime_YYYYMMDDHHMMSS(char *buf, unsigned len, time_t *tp) FAST_FUNC;
> diff --git a/libbb/Config.src b/libbb/Config.src
> index f97de8ef7..58c5fad50 100644
> --- a/libbb/Config.src
> +++ b/libbb/Config.src
> @@ -395,3 +395,14 @@ config FEATURE_HWIB
> default y
> help
> Support for printing infiniband addresses in network applets.
> +
> +config FEATURE_TIMEZONE
> + bool "Allow timezone in dates"
> + default y
> + depends on DESKTOP
> + help
> + Permit the use of timezones when parsing user-provided data
> + strings, e.g. '1996-04-09 12:45:00 -0500'.
> +
> + This requires support for the '%z' extension to strptime() which
> + may not be available in all implementations.
> diff --git a/libbb/time.c b/libbb/time.c
> index 365b1df02..e4d108c83 100644
> --- a/libbb/time.c
> +++ b/libbb/time.c
> @@ -8,7 +8,9 @@
> */
> #include "libbb.h"
>
> -void FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
> +/* Returns 0 if the time structure contains an absolute UTC time which
> + * should not be subject to DST adjustment by the caller. */
> +int FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
> {
> char end = '\0';
> #if ENABLE_DESKTOP
> @@ -27,6 +29,10 @@ void FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
> "%b %d %T %Y" "\0" /* month_name d HH:MM:SS YYYY */
> "%Y-%m-%d %R" "\0" /* yyyy-mm-dd HH:MM */
> "%Y-%m-%d %T" "\0" /* yyyy-mm-dd HH:MM:SS */
> +#if ENABLE_FEATURE_TIMEZONE
> + "%Y-%m-%d %R %z" "\0" /* yyyy-mm-dd HH:MM TZ */
> + "%Y-%m-%d %T %z" "\0" /* yyyy-mm-dd HH:MM:SS TZ */
> +#endif
> "%Y-%m-%d %H" "\0" /* yyyy-mm-dd HH */
> "%Y-%m-%d" "\0" /* yyyy-mm-dd */
> /* extra NUL */;
> @@ -38,8 +44,25 @@ void FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
> fmt = fmt_str;
> while (*fmt) {
> endp = strptime(date_str, fmt, ptm);
> - if (endp && *endp == '\0')
> - return;
> + if (endp && *endp == '\0') {
> +#if ENABLE_FEATURE_TIMEZONE
> + if (strchr(fmt, 'z')) {
> + time_t t;
> + struct tm *utm;
> +
> + /* we have timezone offset: obtain Unix time_t */
> + ptm->tm_sec -= ptm->tm_gmtoff;
> + ptm->tm_isdst = 0;
> + t = timegm(ptm);
> + /* convert Unix time_t to struct tm in user's locale */
> + if (t == (time_t)-1 || (utm = localtime(&t)) == NULL)
> + break;
> + *ptm = *utm;
> + return 0;
> + }
> +#endif
> + return 1;
> + }
> *ptm = save;
> while (*++fmt)
> continue;
> @@ -124,7 +147,7 @@ void FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
> struct tm *lt = localtime(&t);
> if (lt) {
> *ptm = *lt;
> - return;
> + return 0;
> }
> }
> end = '1';
> @@ -241,6 +264,7 @@ void FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
> if (end != '\0') {
> bb_error_msg_and_die(bb_msg_invalid_date, date_str);
> }
> + return 1;
> }
>
> time_t FAST_FUNC validate_tm_time(const char *date_str, struct tm *ptm)
> diff --git a/testsuite/date/date-timezone b/testsuite/date/date-timezone
> new file mode 100644
> index 000000000..8628aa1d7
> --- /dev/null
> +++ b/testsuite/date/date-timezone
> @@ -0,0 +1,32 @@
> +# FEATURE: CONFIG_FEATURE_TIMEZONE
> +
> +# 'Z' is UTC
> +dt=$(TZ=UTC0 busybox date -d '1999-1-2 3:4:5Z')
> +dt=$(echo "$dt" | cut -b1-19)
> +test x"$dt" = x"Sat Jan 2 03:04:05"
> +
> +# '+0600' is six hours ahead of UTC
> +dt=$(TZ=UTC0 busybox date -d '1999-1-2 3:4:5 +0600')
> +dt=$(echo "$dt" | cut -b1-19)
> +test x"$dt" = x"Fri Jan 1 21:04:05"
> +
> +# '-0600' is six hours behind UTC
> +dt=$(TZ=UTC0 busybox date -d '1999-1-2 3:4:5 -0600')
> +dt=$(echo "$dt" | cut -b1-19)
> +test x"$dt" = x"Sat Jan 2 09:04:05"
> +
> +# before dst is switched on
> +dt=$(TZ=GMT0BST,M3.5.0/1,M10.5.0/2 busybox date -d '2021-03-28 00:59:59 +0000')
> +test x"$dt" = x"Sun Mar 28 00:59:59 GMT 2021"
> +
> +# after dst is switched on
> +dt=$(TZ=GMT0BST,M3.5.0/1,M10.5.0/2 busybox date -d '2021-03-28 01:00:01 +0000')
> +test x"$dt" = x"Sun Mar 28 02:00:01 BST 2021"
> +
> +# before dst is switched off
> +dt=$(TZ=GMT0BST,M3.5.0/1,M10.5.0/2 busybox date -d '2021-10-31 00:00:01 +0000')
> +test x"$dt" = x"Sun Oct 31 01:00:01 BST 2021"
> +
> +# after dst is switched off: back to 01:00:01 but with different TZ
> +dt=$(TZ=GMT0BST,M3.5.0/1,M10.5.0/2 busybox date -d '2021-10-31 01:00:01 +0000')
> +test x"$dt" = x"Sun Oct 31 01:00:01 GMT 2021"
> --
> 2.31.1
>
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> busybox@busybox.net
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