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| author | Vsevolod Stakhov <vsevolod@highsecure.ru> | 2018-07-09 17:51:41 +0100 |
|---|---|---|
| committer | Vsevolod Stakhov <vsevolod@highsecure.ru> | 2018-07-09 17:51:41 +0100 |
| commit | a444ae89b582c59aea1255f9fdf07e822f78bf26 (patch) | |
| tree | 2ec5fb4caa19ab12f062c311970d0a3fd0ebd9a8 /src/libutil/printf.c | |
| parent | c5997cb28259f093d11839845c76bf12d92f396f (diff) | |
| download | rspamd-a444ae89b582c59aea1255f9fdf07e822f78bf26.tar.gz rspamd-a444ae89b582c59aea1255f9fdf07e822f78bf26.zip | |
[Minor] Cleanup, use __builtin_clz, mention algorithm source
Diffstat (limited to 'src/libutil/printf.c')
| -rw-r--r-- | src/libutil/printf.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/src/libutil/printf.c b/src/libutil/printf.c index 5895dc89d..0ad2dce27 100644 --- a/src/libutil/printf.c +++ b/src/libutil/printf.c @@ -126,7 +126,7 @@ rspamd_decimal_digits32 (guint32 val) unsigned long r = 0; _BitScanReverse (&r, val | 1); tmp = (r + 1) * 1233 >> 12; -#elif defined(__GNUC__) && (__GNUC__ >= 30) +#elif defined(__GNUC__) && (__GNUC__ >= 3) tmp = (32 - __builtin_clz (val | 1U)) * 1233 >> 12; #else /* Software version */ @@ -189,7 +189,7 @@ rspamd_decimal_digits64 (guint64 val) _BitScanReverse64 (&r, val | 1); tmp = (r + 1) * 1233 >> 12; #endif -#elif defined(__GNUC__) && (__GNUC__ >= 30) +#elif defined(__GNUC__) && (__GNUC__ >= 3) tmp = (64 - __builtin_clzll (val | 1ULL)) * 1233 >> 12; #else /* Software version */ static const unsigned debruijn_tbl[32] = { 0, 9, 1, 10, 13, 21, 2, 29, @@ -226,6 +226,14 @@ rspamd_decimal_digits64 (guint64 val) return tmp - (val < powers_of_10[tmp]) + 1; } +/* + * Idea from https://github.com/miloyip/itoa-benchmark: + * Uses lookup table (LUT) of digit pairs for division/modulo of 100. + * + * Mentioned in: + * https://www.slideshare.net/andreialexandrescu1/three-optimization-tips-for-c-15708507 + */ + static const char int_lookup_table[200] = { '0','0','0','1','0','2','0','3','0','4', '0','5','0','6','0','7','0','8','0','9', |