utils: Greatly improve performance of osmo_hexdump routines
In the osmo-bts and libosmo-abis code the hexdump routine is used
for every incoming/outgoing packet (including voice frames) and the
usage of snprintf showed up inside profiles.
There is a semantic change when more than 4096 characters are used.
The code will now truncate at byte boundaries (and not nibbles).
Code:
static const int lengths[] = { 23, 1000, 52 };
char buf[4096];
int i;
for (i = 0; i < 30000; ++i)
char *res = osmo_hexdump(buf, lengths[i & 3]);
Results:
before: after:
real 0m3.233s real 0m0.085s
user 0m3.212s user 0m0.084s
sys 0m0.000s sys 0m0.000s
diff --git a/src/utils.c b/src/utils.c
index 5874077..cc33994 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -107,6 +107,7 @@
}
static char hexd_buff[4096];
+static const char hex_chars[] = "0123456789abcdef";
static char *_osmo_hexdump(const unsigned char *buf, int len, char *delim)
{
@@ -115,13 +116,20 @@
hexd_buff[0] = 0;
for (i = 0; i < len; i++) {
+ const char *delimp = delim;
int len_remain = sizeof(hexd_buff) - (cur - hexd_buff);
- if (len_remain <= 0)
+ if (len_remain < 3)
break;
- int rc = snprintf(cur, len_remain, "%02x%s", buf[i], delim);
- if (rc <= 0)
- break;
- cur += rc;
+
+ *cur++ = hex_chars[buf[i] >> 4];
+ *cur++ = hex_chars[buf[i] & 0xf];
+
+ while (len_remain > 1 && *delimp) {
+ *cur++ = *delimp++;
+ len_remain--;
+ }
+
+ *cur = 0;
}
hexd_buff[sizeof(hexd_buff)-1] = 0;
return hexd_buff;