Messages in this thread | | | Subject | Re: [PATCH 1/1] lib: small update for strlen, strnlen, use less cpu instructions | From | Joe Perches <> | Date | Tue, 16 Jun 2015 15:16:45 -0700 |
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On Tue, 2015-06-16 at 13:50 -0500, Orestes Leal Rodriguez wrote: > Very small update to strlen and strnlen that now use less cpu > instructions by using a counter to avoid the memory addresses > substraction to find the length of the string. [] > @@ -418,12 +422,13 @@ EXPORT_SYMBOL(strlen); > */ > size_t strnlen(const char *s, size_t count) > { > - const char *sc; > + size_t sz = 0; > > - for (sc = s; count-- && *sc != '\0'; ++sc) > - /* nothing */; > - return sc - s; > + for (; count-- && *s++ != '\0'; sz++) > + /* empty */; > + return sz;
That's one subtraction at end-of-string vs a register increment for each non-zero byte.
smaller isn't worth slower.
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