MINOR: hpack: simplify the len to bytes conversion
The len-to-bytes conversion can be slightly simplified and optimized
by hardcoding a tree lookup. Just doing this increases by 1% the
request rate on H2. It could be made almost branch-free by using
fls() but it looks overkill for most situations since most headers
are very short.
diff --git a/src/hpack-enc.c b/src/hpack-enc.c
index 836584a..7c6ef6f 100644
--- a/src/hpack-enc.c
+++ b/src/hpack-enc.c
@@ -43,13 +43,18 @@
*/
static inline int len_to_bytes(size_t len)
{
- if (len < 127)
+ ssize_t slen = len;
+
+ slen -= 127;
+ if (__builtin_expect(slen < 0, 1))
return 1;
- if (len < 127 + (1 << 7))
- return 2;
- if (len < 127 + (1 << 14))
- return 3;
- if (len < 127 + (1 << 21))
+ if (slen < (1 << 14)) {
+ if (__builtin_expect(slen < (1 << 7), 1))
+ return 2;
+ else
+ return 3;
+ }
+ if (slen < (1 << 21))
return 4;
return 0;
}