output_buffer: only realloc once, and memset just what we need

No need looping around a realloc(), just alloc what we need upfront. Additionally, don't memset the parts we'll be copying into anyway. Signed-off-by: Jens Axboe <[email protected]>
cohortfsllc · Oct 31, 2015 · f6cbf8a · f6cbf8a
1 parent 125451c
commit f6cbf8a
Showing 1 changed file with 10 additions and 3 deletions.
diff --git a/lib/output_buffer.c b/lib/output_buffer.c
@@ -4,6 +4,7 @@
 
 #include "output_buffer.h"
 #include "../log.h"
+#include "../minmax.h"
 
 #define BUF_INC	1024
 
@@ -21,12 +22,18 @@ void buf_output_free(struct buf_output *out)
 
 size_t buf_output_add(struct buf_output *out, const char *buf, size_t len)
 {
-	while (out->max_buflen - out->buflen < len) {
+	if (out->max_buflen - out->buflen < len) {
+		size_t need = len - (out->max_buflen - out->buflen);
 		size_t old_max = out->max_buflen;
 
-		out->max_buflen += BUF_INC;
+		need = max((size_t) BUF_INC, need);
+		out->max_buflen += need;
 		out->buf = realloc(out->buf, out->max_buflen);
-		memset(&out->buf[old_max], 0, BUF_INC);
+
+		old_max = max(old_max, out->buflen + len);
+		if (old_max + need > out->max_buflen)
+			need = out->max_buflen - old_max;
+		memset(&out->buf[old_max], 0, need);
 	}
 
 	memcpy(&out->buf[out->buflen], buf, len);