From: Florian Weimer <fw@deneb.enyo.de>
Date: Sun, 12 Feb 2006 11:19:23 GMT
Subject: Re: [PATCH] Use a hashtable for objects instead of a sorted list
Message-ID: <87accwlt8k.fsf@mid.deneb.enyo.de>
In-Reply-To: <7virrli9am.fsf@assigned-by-dhcp.cox.net>

* Junio C. Hamano:

>  static int hashtable_index(const unsigned char *sha1)
>  {
> -	unsigned int i = *(unsigned int *)sha1;
> -	return (int)(i % obj_allocs);
> +	int cnt;

> +	unsigned int ix = *sha1++;
> +
> +	for (cnt = 1; cnt < sizeof(unsigned int); cnt++) {
> +		ix <<= 8;
> +		ix |= *sha1++;
> +	}

memcpy(&ix, sha1, sizeof(ix));

(GCC should do the rest.)

> +	return (int)(ix % obj_allocs);
>  }

return (int)(ix & (obj_allocs - 1));

AFAICS, obj_allocs is a power of two.