libbb: introduce and use strftime_[YYYYMMDD]HHMMSS()

function                                             old     new   delta
strftime_fmt                                           -      53     +53
strftime_YYYYMMDDHHMMSS                                -      12     +12
strftime_HHMMSS                                        -      12     +12
human_time                                            44      43      -1
fmtstr_t                                               9       -      -9
step_time                                            361     345     -16
watch_main                                           261     232     -29
------------------------------------------------------------------------------
(add/remove: 3/1 grow/shrink: 0/3 up/down: 77/-55)             Total: 22 bytes
   text	   data	    bss	    dec	    hex	filename
 919203	    932	  17692	 937827	  e4f63	busybox_old
 919209	    932	  17692	 937833	  e4f69	busybox_unstripped

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

coreutils/stat.c

@@ -127,7 +127,7 @@ static const char *human_time(time_t t)
 	/*static char buf[sizeof("YYYY-MM-DD HH:MM:SS.000000000")] ALIGN1;*/
 #define buf bb_common_bufsiz1
 
-	strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S.000000000", localtime(&t));
+	strcpy(strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &t), ".000000000");
 	return buf;
 #undef buf
 }

include/libbb.h

@@ -523,7 +523,8 @@ struct BUG_too_small {
 
 void 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;
 
 int xsocket(int domain, int type, int protocol) FAST_FUNC;
 void xbind(int sockfd, struct sockaddr *my_addr, socklen_t addrlen) FAST_FUNC;

libbb/login.c

@@ -16,7 +16,6 @@
 #define LOGIN " login: "
 
 static const char fmtstr_d[] ALIGN1 = "%A, %d %B %Y";
-static const char fmtstr_t[] ALIGN1 = "%H:%M:%S";
 
 void FAST_FUNC print_login_issue(const char *issue_file, const char *tty)
 {
@@ -73,7 +72,7 @@ void FAST_FUNC print_login_issue(const char *issue_file, const char *tty)
 				strftime(buf, sizeof(buf), fmtstr_d, localtime(&t));
 				break;
 			case 't':
-				strftime(buf, sizeof(buf), fmtstr_t, localtime(&t));
+				strftime_HHMMSS(buf, sizeof(buf), &t);
 				break;
 			case 'l':
 				outbuf = tty;

libbb/time.c

@@ -187,6 +187,27 @@ time_t FAST_FUNC validate_tm_time(const char *date_str, struct tm *ptm)
 	return t;
 }
 
+static char* strftime_fmt(char *buf, unsigned len, time_t *tp, const char *fmt)
+{
+	time_t t;
+	if (!tp) {
+		tp = &t;
+		time(tp);
+	}
+	/* Returns pointer to NUL */
+	return buf + strftime(buf, len, fmt, localtime(tp));
+}
+
+char* FAST_FUNC strftime_HHMMSS(char *buf, unsigned len, time_t *tp)
+{
+	return strftime_fmt(buf, len, tp, "%H:%M:%S");
+}
+
+char* FAST_FUNC strftime_YYYYMMDDHHMMSS(char *buf, unsigned len, time_t *tp)
+{
+	return strftime_fmt(buf, len, tp, "%Y-%m-%d %H:%M:%S");
+}
+
 #if ENABLE_MONOTONIC_SYSCALL
 
 #include <sys/syscall.h>

networking/ntpd.c

@@ -887,11 +887,11 @@ step_time(double offset)
 
 	VERB2 {
 		tval = tvc.tv_sec;
-		strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", localtime(&tval));
+		strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
 		bb_error_msg("current time is %s.%06u", buf, (unsigned)tvc.tv_usec);
 	}
 	tval = tvn.tv_sec;
-	strftime(buf, sizeof(buf), "%Y-%m-%d %H:%M:%S", localtime(&tval));
+	strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
 	bb_error_msg("setting time to %s.%06u (offset %+fs)", buf, (unsigned)tvn.tv_usec, offset);
 
 	/* Correct various fields which contain time-relative values: */

networking/ntpd_simple.c

@@ -378,7 +378,7 @@ step_time_once(double offset)
 		bb_perror_msg_and_die("settimeofday");
 
 	tval = tv.tv_sec;
-	strftime(buf, sizeof(buf), "%a %b %e %H:%M:%S %Z %Y", localtime(&tval));
+	strftime_YYYYMMDDHHMMSS(buf, sizeof(buf), &tval);
 
 	bb_error_msg("setting clock to %s (offset %fs)", buf, offset);
 

procps/watch.c

@@ -69,7 +69,6 @@ int watch_main(int argc UNUSED_PARAM, char **argv)
 		printf("\033[H""\033[J");
 		if (!(opt & 0x2)) { // no -t
 			const unsigned time_len = sizeof("1234-67-90 23:56:89");
-			time_t t;
 
 			// STDERR_FILENO is procps3 compat:
 			// "watch ls 2>/dev/null" does not detect tty size
@@ -79,10 +78,13 @@ int watch_main(int argc UNUSED_PARAM, char **argv)
 				free(header);
 				header = xasprintf("Every %us: %-*s", period, (int)width, cmd);
 			}
-			time(&t);
-			if (time_len < width)
-				strftime(header + width - time_len, time_len,
-					"%Y-%m-%d %H:%M:%S", localtime(&t));
+			if (time_len < width) {
+				strftime_YYYYMMDDHHMMSS(
+					header + width - time_len,
+					time_len,
+					/*time_t*:*/ NULL
+				);
+			}
 
 			// compat: empty line between header and cmd output
 			printf("%s\n\n", header);