libbb: code shrink parse_datestr

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

1 files changed, 36 insertions, 11 deletions

diff --git a/libbb/time.c b/libbb/time.c
index cf5f2e5c8..365b1df02 100644
--- a/libbb/time.c
+++ b/libbb/time.c
@@ -11,13 +11,45 @@
 void FAST_FUNC parse_datestr(const char *date_str, struct tm *ptm)
 {
         char end = '\0';
+#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 */;
+        struct tm save;
+        const char *fmt;
+        char *endp;
+
+        save = *ptm;
+        fmt = fmt_str;
+        while (*fmt) {
+                endp = strptime(date_str, fmt, ptm);
+                if (endp && *endp == '\0')
+                        return;
+                *ptm = save;
+                while (*++fmt)
+                        continue;
+                ++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 +82,6 @@ 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 +113,7 @@ 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))