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MINOR: hpack: simplify the len to bytes conversion

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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.
This commit is contained in:
Willy Tarreau 2018-12-10 13:36:56 +01:00
parent 2df026fbce
commit 1526f1942c
1 changed files with 11 additions and 6 deletions
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13
src/hpack-enc.c
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@ -43,13 +43,18 @@
*/ */
static inline int len_to_bytes(size_t len) 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; return 1;
if (len < 127 + (1 << 7)) if (slen < (1 << 14)) {
if (__builtin_expect(slen < (1 << 7), 1))
return 2; return 2;
if (len < 127 + (1 << 14)) else
return 3; return 3;
if (len < 127 + (1 << 21)) }
if (slen < (1 << 21))
return 4; return 4;
return 0; return 0;
} }