Subject: Re: [PATCH v3 2/2] date.c: allow compact version of ISO-8601 datetime

From: Junio C Hamano <[email-masked]>
Date: Wed, 22 Apr 2020 10:17:35 -0700

Đoàn Trần Công Danh  <[email-masked]> writes:

> Signed-off-by: Đoàn Trần Công Danh <[email-masked]>
> ---
>  date.c          | 22 ++++++++++++++++++++++
>  t/t0006-date.sh |  3 +++
>  2 files changed, 25 insertions(+)
>
> diff --git a/date.c b/date.c
> index 62f23b4702..882242c2db 100644
> --- a/date.c
> +++ b/date.c
> @@ -672,6 +672,28 @@ static int match_digit(const char *date, struct tm *tm, int *offset, int *tm_gmt
>  		n++;
>  	} while (isdigit(date[n]));
>  
> +	/* 8 digits, compact style of ISO-8601's date: YYYYmmDD */
> +	/* 6 digits, compact style of ISO-8601's time: HHMMSS */
> +	if (n == 8 || n == 6) {
> +		unsigned int num1 = num / 10000;
> +		unsigned int num2 = (num % 10000) / 100;
> +		unsigned int num3 = num % 100;
> +		if (n == 8 && num1 > 1900 &&
> +		    num2 > 0 && num2 <= 12 &&
> +		    num3 > 0  && num3 <= 31) {
> +			tm->tm_year = num1 - 1900;
> +			tm->tm_mon  = num2 - 1;
> +			tm->tm_mday = num3;
> +		} else if (n == 6 && num1 < 60 && num2 < 60 && num3 <= 60) {
> +			tm->tm_hour = num1;
> +			tm->tm_min  = num2;
> +			tm->tm_sec  = num3;
> +			if (*end == '.' && isdigit(end[1]))
> +				strtoul(end + 1, &end, 10);
> +		}
> +		return end - date;
> +	}
> +

Looks sensible except that on our planet, one day has only 24 hours
;-).

I think we should try to reuse existing helpers as much as possible
in date.c to avoid such stupid errors.  During my review of [1/2] I
found is_date() would be a good thing to try reusing and also
extracted is_hms() as another candidate we could reuse.

>  	/* 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 80917c81c3..75ee9a96b8 100755
> --- a/t/t0006-date.sh
> +++ b/t/t0006-date.sh
> @@ -82,6 +82,9 @@ check_parse 2008-02-14 bad
>  check_parse '2008-02-14 20:30:45' '2008-02-14 20:30:45 +0000'
>  check_parse '2008-02-14 20:30:45 -0500' '2008-02-14 20:30:45 -0500'
>  check_parse '2008.02.14 20:30:45 -0500' '2008-02-14 20:30:45 -0500'
> +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'
>  check_parse '2008-02-14 20:30:45.019-04:00' '2008-02-14 20:30:45 -0400'
>  check_parse '2008-02-14 20:30:45 -0015' '2008-02-14 20:30:45 -0015'
>  check_parse '2008-02-14 20:30:45 -5' '2008-02-14 20:30:45 +0000'