Messages in this thread | | | Date | Wed, 9 Jun 2004 22:08:34 -0700 (PDT) | From | dean gaudet <> | Subject | Re: [PATCH] ALSA: Remove subsystem-specific malloc (1/8) |
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On Wed, 9 Jun 2004, Pekka Enberg wrote:
> +void *kcalloc(size_t n, size_t size, int flags) > +{ > + if (n != 0 && size > INT_MAX / n) > + return NULL;
division isn't very efficient :) it's typically a 40+ cycle operation.
there's almost certainly more efficient ways to do this with per-target assembly... but you should probably just crib the code from glibc which avoids division for small allocations:
/* size_t is unsigned so the behavior on overflow is defined. */ bytes = n * elem_size; #define HALF_INTERNAL_SIZE_T \ (((INTERNAL_SIZE_T) 1) << (8 * sizeof (INTERNAL_SIZE_T) / 2)) if (__builtin_expect ((n | elem_size) >= HALF_INTERNAL_SIZE_T, 0)) { if (elem_size != 0 && bytes / elem_size != n) { MALLOC_FAILURE_ACTION; return 0; } }
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