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 <axboe@fb.com>

diff --git a/lib/output_buffer.c b/lib/output_buffer.c
index 03cd848bfd9f05aa9dbace684766503b17d6ea55..c1fdfc95f610aca10ece35ebdc2dac437c01af66 100644 (file)
--- a/lib/output_buffer.c
+++ b/lib/output_buffer.c
@@ -4,6 +4,7 @@
 
 #include "output_buffer.h"
 #include "../log.h"
 
 #include "output_buffer.h"
 #include "../log.h"

+#include "../minmax.h"

 
 #define BUF_INC        1024
 
 
 #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)
 {
 
 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;
 
                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);
                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);
        }
 
        memcpy(&out->buf[out->buflen], buf, len);