[PATCH v2 047/113] commands: time: reduce strjoin runtime, drop trailing space

[Ahmad Fatoum]

time concatenates its arguments to pass it to run_command in a
suboptimal manner: The destination string is traversed from the
beginning on every iteration due to strcat and we have a left-over
separator at the end, while it's only needed in-between.

In preparation for factoring the code out as a library strjoin function,
fix these shortcomings.

Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
---
v1 -> v2:
  - swapped order with follow-up commit (Sascha)
---
 commands/time.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/commands/time.c b/commands/time.c
index 72647a3bb876..0a38db61845d 100644
--- a/commands/time.c
+++ b/commands/time.c
@@ -10,7 +10,7 @@
 static int do_time(int argc, char *argv[])
 {
 	int i, opt;
-	unsigned char *buf;
+	unsigned char *buf, *p;
 	u64 start, end, diff64;
 	bool nanoseconds = false;
 	int len = 1; /* '\0' */
@@ -34,13 +34,15 @@ static int do_time(int argc, char *argv[])
 	for (i = 0; i < argc; i++)
 		len += strlen(argv[i]) + 1;
 
-	buf = xzalloc(len);
+	p = buf = xmalloc(len);
 
-	for (i = 0; i < argc; i++) {
-		strcat(buf, argv[i]);
-		strcat(buf, " ");
+	for (i = 0; i < argc - 1; i++) {
+		p = stpcpy(p, argv[i]);
+		p = mempcpy(p, " ", strlen(" "));
 	}
 
+	stpcpy(p, argv[i]);
+
 	start = get_time_ns();
 
 	run_command(buf);
-- 
2.39.2