snhash.c

来自「TCP-IP红宝书源代码」· C语言 代码 · 共 94 行

/* snhash.c - getmib, hashoid, hashinit */

#include <conf.h>
#include <kernel.h>
#include <network.h>
#include <mem.h>

#ifdef	SNMP

#include <snmp.h>
#include <mib.h>
#include <snhash.h>

struct	snhnode	*snhtab[S_HTABSIZ];

extern struct tab_info	tabtab[];

/*------------------------------------------------------------------------
 * getmib - find mib record for the given object id
 *------------------------------------------------------------------------
 */
struct mib_info *
getmib(struct oid *oip)
{
	struct snhnode	*hp;
	int		loc, i;


	loc = hashoid(oip);	/* try the regular hash table */
	for (hp = snhtab[loc]; hp; hp = hp->sh_next) 
		if (oidequ(oip, &hp->sh_mip->mi_objid)) {
			return hp->sh_mip;
		}
	for (i = 0; i < S_NUMTABS; ++i) 	/* try the table table */
		if (!memcmp(tabtab[i].ti_mip->mi_objid.id, oip->id,
			    tabtab[i].ti_mip->mi_objid.len * 2)) {
			return tabtab[i].ti_mip;
		}
	return 0;
}

/*------------------------------------------------------------------------
 * hashoid - hash the object id
 *------------------------------------------------------------------------
 */
int
hashoid(struct oid *oip)
{
	register unsigned tot;
	register int	i;

	for (tot = 0, i = oip->len - 1; i >= 0; i--) 
		tot = tot * S_HTRADIX + oip->id[i];
	return tot % S_HTABSIZ;
}

/*------------------------------------------------------------------------
 * hashinit - initialize the hash table
 *------------------------------------------------------------------------
 */
void
hashinit(void)
{
	int i;
	register struct	snhnode	**ht;
	register struct mib_info *mp;
	struct mib_info		*lastnodep;
	struct snhnode		*hp;
	int loc, tabtabct;

	/* clear the hash table */
	ht = snhtab;
	for (i = 0; i < S_HTABSIZ; i++)
		*ht++ = 0;
	lastnodep = 0;

	tabtabct = 0;
	for (i=0, mp = &mib[mib_entries - 1]; i<mib_entries; i++, mp--) {
		loc = hashoid(&mp->mi_objid);
		hp = (struct snhnode *) getmem(sizeof(struct snhnode));
		hp->sh_mip = mp;
		hp->sh_next = snhtab[loc];
		snhtab[loc] = hp;
		mp->mi_next = lastnodep;
		/* (node == table) ==> insert into array of tables */

		if (mp->mi_vartype == T_TABLE) 
			tabtab[tabtabct++].ti_mip = mp;
		if (mp->mi_varleaf || mp->mi_vartype == T_TABLE)
			lastnodep = mp;
	}
}
#endif	/* SNMP */