On Mon, Jan 9, 2023 at 4:29 AM Đoàn Trần Công Danh <congdanhqx@xxxxxxxxx> wrote:
>
> The newly added heuristic to parse less precision ISO-8601 conflicts
> with other heuristics to parse datetime-strings. E.g.:
>
> Thu, 7 Apr 2005 15:14:13 -0700
>
> Let's limit the new heuristic to only datetime string with a 'T'
> followed immediately by some digits, and if we failed to parse the
> upcoming string, rollback the change.
>
> Signed-off-by: Đoàn Trần Công Danh <congdanhqx@xxxxxxxxx>
> ---
>
> Here is a better thought out change, which tried to minimize the impact of
> new heuristics.
>
> While I think it's a fixup, but I still needs explaination, I think I may
> reword it's as a full patch instead.
> Range-diff:
> 1: 4036e5a944 ! 1: b703425a57 fixup! date.c: allow ISO 8601 reduced precision times
> @@ Metadata
> Author: Đoàn Trần Công Danh <congdanhqx@xxxxxxxxx>
>
> ## Commit message ##
> - fixup! date.c: allow ISO 8601 reduced precision times
> + date.c: limit less precision ISO-8601 with its marker
> +
> + The newly added heuristic to parse less precision ISO-8601 conflicts
> + with other heuristics to parse datetime-strings. E.g.:
> +
> + Thu, 7 Apr 2005 15:14:13 -0700
> +
> + Let's limit the new heuristic to only datetime string with a 'T'
> + followed immediately by some digits, and if we failed to parse the
> + upcoming string, rollback the change.
>
> Signed-off-by: Đoàn Trần Công Danh <congdanhqx@xxxxxxxxx>
>
> @@ date.c: static int match_alpha(const char *date, struct tm *tm, int *offset)
> }
>
> + /* ISO-8601 allows yyyymmDD'T'HHMMSS, with less precision */
> -+ if (*date == 'T' && isdigit(date[1])) {
> -+ tm->tm_hour = tm->tm_min = tm->tm_sec = 0;
> -+ return strlen("T");
> ++ if (*date == 'T' && isdigit(date[1]) && tm->tm_hour == -1) {
> ++ tm->tm_min = tm->tm_sec = 0;
> ++ return 1;
> + }
> +
> /* BAD CRAP */
> @@ date.c: static inline int nodate(struct tm *tm)
> - * We just do a binary 'and' to see if the sign bit
> - * is set in all the values.
> + * Have we seen an ISO-8601-alike date, i.e. 20220101T0,
> -+ * In those special case, those fields have been set to 0
> ++ * In which, hour is still unset,
> ++ * and minutes and second has been set to 0.
> */
> -static inline int notime(struct tm *tm)
> +static inline int maybeiso8601(struct tm *tm)
> @@ date.c: static inline int nodate(struct tm *tm)
> - return (tm->tm_hour &
> - tm->tm_min &
> - tm->tm_sec) < 0;
> -+ return tm->tm_hour == 0 &&
> ++ return tm->tm_hour == -1 &&
> + tm->tm_min == 0 &&
> + tm->tm_sec == 0;
> }
>
> /*
> @@ date.c: static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt
> - /* 4 digits, compact style of ISO-8601's time: HHMM */
> - /* 2 digits, compact style of ISO-8601's time: HH */
> - if (n == 8 || n == 6 ||
> +
> + /* 8 digits, compact style of ISO-8601's date: YYYYmmDD */
> + /* 6 digits, compact style of ISO-8601's time: HHMMSS */
> +- /* 4 digits, compact style of ISO-8601's time: HHMM */
> +- /* 2 digits, compact style of ISO-8601's time: HH */
> +- if (n == 8 || n == 6 ||
> - (!nodate(tm) && notime(tm) &&
> -+ (!nodate(tm) && maybeiso8601(tm) &&
> - (n == 4 || n == 2))) {
> +- (n == 4 || n == 2))) {
> ++ if (n == 8 || n == 6) {
> unsigned int num1 = num / 10000;
> unsigned int num2 = (num % 10000) / 100;
> + unsigned int num3 = num % 100;
> +@@ date.c: static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt
> + else if (n == 6 && set_time(num1, num2, num3, tm) == 0 &&
> + *end == '.' && isdigit(end[1]))
> + strtoul(end + 1, &end, 10);
> +- else if (n == 4)
> +- set_time(num2, num3, 0, tm);
> +- else if (n == 2)
> +- set_time(num3, 0, 0, tm);
> + return end - date;
> + }
> +
> ++ /* reduced precision of ISO-8601's time: HHMM or HH */
> ++ if (maybeiso8601(tm)) {
> ++ unsigned int num1 = num;
> ++ unsigned int num2 = 0;
> ++ if (n == 4) {
> ++ num1 = num / 100;
> ++ num2 = num % 100;
> ++ }
> ++ if ((n == 4 || n == 2) && !nodate(tm) &&
> ++ set_time(num1, num2, 0, tm) == 0)
> ++ return n;
> ++ /*
> ++ * We thought this is an ISO-8601 time string,
> ++ * we set minutes and seconds to 0,
> ++ * turn out it isn't, rollback the change.
> ++ */
> ++ tm->tm_min = tm->tm_sec = -1;
> ++ }
> ++
> + /* Four-digit year or a timezone? */
> + if (n == 4) {
> + if (num <= 1400 && *offset == -1) {
>
> ## t/t0006-date.sh ##
> @@ t/t0006-date.sh: check_parse '20080214T20:30' '2008-02-14 20:30:00 +0000'
>
> date.c | 49 +++++++++++++++++++++++++++++++++----------------
> t/t0006-date.sh | 3 ++-
> 2 files changed, 35 insertions(+), 17 deletions(-)
>
> diff --git a/date.c b/date.c
> index b011b9d6b3..6f45eeb356 100644
> --- a/date.c
> +++ b/date.c
> @@ -493,6 +493,12 @@ static int match_alpha(const char *date, struct tm *tm, int *offset)
> return 2;
> }
>
> + /* ISO-8601 allows yyyymmDD'T'HHMMSS, with less precision */
> + if (*date == 'T' && isdigit(date[1]) && tm->tm_hour == -1) {
> + tm->tm_min = tm->tm_sec = 0;
> + return 1;
> + }
> +
> /* BAD CRAP */
> return skip_alpha(date);
> }
> @@ -639,15 +645,15 @@ static inline int nodate(struct tm *tm)
> }
>
> /*
> - * Have we filled in any part of the time yet?
> - * We just do a binary 'and' to see if the sign bit
> - * is set in all the values.
> + * Have we seen an ISO-8601-alike date, i.e. 20220101T0,
> + * In which, hour is still unset,
> + * and minutes and second has been set to 0.
> */
> -static inline int notime(struct tm *tm)
> +static inline int maybeiso8601(struct tm *tm)
> {
> - return (tm->tm_hour &
> - tm->tm_min &
> - tm->tm_sec) < 0;
> + return tm->tm_hour == -1 &&
> + tm->tm_min == 0 &&
> + tm->tm_sec == 0;
> }
>
> /*
> @@ -701,11 +707,7 @@ static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt
>
> /* 8 digits, compact style of ISO-8601's date: YYYYmmDD */
> /* 6 digits, compact style of ISO-8601's time: HHMMSS */
> - /* 4 digits, compact style of ISO-8601's time: HHMM */
> - /* 2 digits, compact style of ISO-8601's time: HH */
> - if (n == 8 || n == 6 ||
> - (!nodate(tm) && notime(tm) &&
> - (n == 4 || n == 2))) {
> + if (n == 8 || n == 6) {
> unsigned int num1 = num / 10000;
> unsigned int num2 = (num % 10000) / 100;
> unsigned int num3 = num % 100;
> @@ -714,13 +716,28 @@ static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt
> else if (n == 6 && set_time(num1, num2, num3, tm) == 0 &&
> *end == '.' && isdigit(end[1]))
> strtoul(end + 1, &end, 10);
> - else if (n == 4)
> - set_time(num2, num3, 0, tm);
> - else if (n == 2)
> - set_time(num3, 0, 0, tm);
> return end - date;
> }
>
> + /* reduced precision of ISO-8601's time: HHMM or HH */
> + if (maybeiso8601(tm)) {
> + unsigned int num1 = num;
> + unsigned int num2 = 0;
> + if (n == 4) {
> + num1 = num / 100;
> + num2 = num % 100;
> + }
> + if ((n == 4 || n == 2) && !nodate(tm) &&
> + set_time(num1, num2, 0, tm) == 0)
> + return n;
> + /*
> + * We thought this is an ISO-8601 time string,
> + * we set minutes and seconds to 0,
> + * turn out it isn't, rollback the change.
> + */
> + tm->tm_min = tm->tm_sec = -1;
> + }
> +
> /* Four-digit year or a timezone? */
> if (n == 4) {
> if (num <= 1400 && *offset == -1) {
> diff --git a/t/t0006-date.sh b/t/t0006-date.sh
> index 16fb0bf4bd..130207fc04 100755
> --- a/t/t0006-date.sh
> +++ b/t/t0006-date.sh
> @@ -93,7 +93,8 @@ check_parse '20080214T20:30' '2008-02-14 20:30:00 +0000'
> check_parse '20080214T20' '2008-02-14 20:00:00 +0000'
> check_parse '20080214T203045' '2008-02-14 20:30:45 +0000'
> check_parse '20080214T2030' '2008-02-14 20:30:00 +0000'
> -check_parse '20080214T20' '2008-02-14 20:00:00 +0000'
> +check_parse '20080214T000000.20' '2008-02-14 00:00:00 +0000'
> +check_parse '20080214T00:00:00.20' '2008-02-14 00:00:00 +0000'
> check_parse '20080214T203045-04:00' '2008-02-14 20:30:45 -0400'
> check_parse '20080214T203045 -04:00' '2008-02-14 20:30:45 -0400'
> check_parse '20080214T203045.019-04:00' '2008-02-14 20:30:45 -0400'
> --
> 2.39.0.287.g690a66fa66
>
Thanks, Đoàn. LGTM, and much safer.
