[PATCH] libbb: code shrink parse_datestr

[Denys Vlasenko]

Applied, thank you.

On Tue, Sep 14, 2021 at 9:53 AM Ron Yorston <rmy at pobox.com> wrote:
>
> The default build uses strptime() in parse_datestr() to support the
> 'month_name d HH:MM:SS YYYY' format of GNU date.  If we've linked
> with strptime() there's an advantage is using it for other formats
> too.
>
> There's no change to the non-default, non-DESKTOP build.
>
> function                                             old     new   delta
> fmt_str                                                -     106    +106
> .rodata                                            99216   99145     -71
> parse_datestr                                        948     624    -324
> ------------------------------------------------------------------------------
> (add/remove: 1/0 grow/shrink: 0/2 up/down: 106/-395)         Total: -289 bytes
>
> Signed-off-by: Ron Yorston <rmy at pobox.com>
> ---
>  libbb/time.c | 49 ++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 38 insertions(+), 11 deletions(-)
>
> diff --git a/libbb/time.c b/libbb/time.c
> index cf5f2e5c8..1a00953b2 100644
> --- a/libbb/time.c
> +++ b/libbb/time.c
> @@ -8,16 +8,50 @@
>   */
>  #include "libbb.h"
>
> +#if ENABLE_DESKTOP
> +/*
> + * strptime is BIG: ~1k in uclibc, ~10k in glibc
> + * We need it for 'month_name d HH:MM:SS YYYY', supported by GNU date,
> + * but if we've linked it we might as well use it for everything.
> + */
> +static const char fmt_str[] ALIGN1 =
> +               "%R" "\0"                       /* HH:MM */
> +               "%T" "\0"                       /* HH:MM:SS */
> +               "%m.%d-%R" "\0"         /* mm.dd-HH:MM */
> +               "%m.%d-%T" "\0"         /* mm.dd-HH:MM:SS */
> +               "%Y.%m.%d-%R" "\0"      /* yyyy.mm.dd-HH:MM */
> +               "%Y.%m.%d-%T" "\0"      /* yyyy.mm.dd-HH:MM:SS */
> +               "%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 */
> +               "%Y-%m-%d %H" "\0"      /* yyyy-mm-dd HH */
> +               "%Y-%m-%d" "\0"         /* yyyy-mm-dd */
> +               /* extra NUL */;
> +#endif
> +
>  void FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
>  {
>         char end = '\0';
> +#if ENABLE_DESKTOP
> +       struct tm save;
> +       const char *fmt;
> +       char *endp;
> +
> +       save = *ptm;
> +       fmt = fmt_str;
> +       while (*fmt) {
> +               if ((endp = strptime(date_str, fmt, ptm)) != NULL && *endp == '\0')
> +                       return;
> +               *ptm = save;
> +               while (*++fmt)
> +                       ;
> +               ++fmt;
> +       }
> +#else
>         const char *last_colon = strrchr(date_str, ':');
>
>         if (last_colon != NULL) {
>                 /* Parse input and assign appropriately to ptm */
> -#if ENABLE_DESKTOP
> -               const char *endp;
> -#endif
>
>                 /* HH:MM */
>                 if (sscanf(date_str, "%u:%u%c",
> @@ -50,14 +84,6 @@ void FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
>                         ptm->tm_year -= 1900; /* Adjust years */
>                         ptm->tm_mon -= 1; /* Adjust month from 1-12 to 0-11 */
>                 } else
> -#if ENABLE_DESKTOP  /* strptime is BIG: ~1k in uclibc, ~10k in glibc */
> -               /* month_name d HH:MM:SS YYYY. Supported by GNU date */
> -               if ((endp = strptime(date_str, "%b %d %T %Y", ptm)) != NULL
> -                && *endp == '\0'
> -               ) {
> -                       return; /* don't fall through to end == ":" check */
> -               } else
> -#endif
>                 {
>                         bb_error_msg_and_die(bb_msg_invalid_date, date_str);
>                 }
> @@ -89,6 +115,7 @@ void FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
>                 ptm->tm_year -= 1900; /* Adjust years */
>                 ptm->tm_mon -= 1; /* Adjust month from 1-12 to 0-11 */
>         } else
> +#endif /* ENABLE_DESKTOP */
>         if (date_str[0] == '@') {
>                 time_t t;
>                 if (sizeof(t) <= sizeof(long))
> --
> 2.31.1
>
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