radix.c

很好的一个嵌入式linux平台下的bootloader

/* $Id: radix.c,v 1.2 1996/01/16 14:21:56 chris Exp $ */
/*
 * Copyright (c) 1988, 1989  Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)radix.c	7.9 (Berkeley) 2/4/91
 */

/*
 * Routines to build and maintain radix trees for routing lookups.
 */
#ifndef RNF_NORMAL
#include "param.h"
#include "radix.h"
#include "malloc.h"
#define	M_DONTWAIT M_NOWAIT
#endif
struct radix_node_head *mask_rnhead;
#define rn_maskhead mask_rnhead->rnh_treetop
struct radix_mask *rn_mkfreelist;
struct radix_node_head *radix_node_head;
#undef Bcmp
#define Bcmp(a, b, l) (l == 0 ? 0 : bcmp((caddr_t)(a), (caddr_t)(b), (u_long)l))
/*
 * The data structure for the keys is a radix tree with one way
 * branching removed.  The index rn_b at an internal node n represents a bit
 * position to be tested.  The tree is arranged so that all descendants
 * of a node n have keys whose bits all agree up to position rn_b - 1.
 * (We say the index of n is rn_b.)
 *
 * There is at least one descendant which has a one bit at position rn_b,
 * and at least one with a zero there.
 *
 * A route is determined by a pair of key and mask.  We require that the
 * bit-wise logical and of the key and mask to be the key.
 * We define the index of a route to associated with the mask to be
 * the first bit number in the mask where 0 occurs (with bit number 0
 * representing the highest order bit).
 * 
 * We say a mask is normal if every bit is 0, past the index of the mask.
 * If a node n has a descendant (k, m) with index(m) == index(n) == rn_b,
 * and m is a normal mask, then the route applies to every descendant of n.
 * If the index(m) < rn_b, this implies the trailing last few bits of k
 * before bit b are all 0, (and hence consequently true of every descendant
 * of n), so the route applies to all descendants of the node as well.
 *
 * The present version of the code makes no use of normal routes,
 * but similar logic shows that a non-normal mask m such that
 * index(m) <= index(n) could potentially apply to many children of n.
 * Thus, for each non-host route, we attach its mask to a list at an internal
 * node as high in the tree as we can go. 
 */

struct radix_node *
rn_search(v, head)
	struct radix_node *head;
	register caddr_t v;
{
	register struct radix_node *x;

	for (x = head; x->rn_b >= 0;) {
		if (x->rn_bmask & v[x->rn_off])
			x = x->rn_r;
		else
			x = x->rn_l;
	}
	return x;
};

struct radix_node *
rn_search_m(v, head, m)
	struct radix_node *head;
	register caddr_t v, m;
{
	register struct radix_node *x;

	for (x = head; x->rn_b >= 0;) {
		if ((x->rn_bmask & m[x->rn_off]) &&
		    (x->rn_bmask & v[x->rn_off]))
			x = x->rn_r;
		else
			x = x->rn_l;
	}
	return x;
};


static int gotOddMasks;
static char maskedKey[MAXKEYLEN];

struct radix_node *
rn_match(v, head)
	struct radix_node *head;
	caddr_t v;
{
	register struct radix_node *t = head, *x;
	register caddr_t cp = v, cp2, cp3;
	caddr_t cplim, mstart;
	struct radix_node *saved_t;
	int off = t->rn_off, vlen = *(u_char *)cp, matched_off;

	/*
	 * Open code rn_search(v, head) to avoid overhead of extra
	 * subroutine call.
	 */
	for (; t->rn_b >= 0; ) {
		if (t->rn_bmask & cp[t->rn_off])
			t = t->rn_r;
		else
			t = t->rn_l;
	}
	/*
	 * See if we match exactly as a host destination
	 */
	cp += off; cp2 = t->rn_key + off; cplim = v + vlen;
	for (; cp < cplim; cp++, cp2++)
		if (*cp != *cp2)
			goto on1;
	/*
	 * This extra grot is in case we are explicitly asked
	 * to look up the default.  Ugh!
	 */
	if ((t->rn_flags & RNF_ROOT) && t->rn_dupedkey)
		t = t->rn_dupedkey;
	return t;
on1:
	matched_off = cp - v;
	saved_t = t;
	do {
	    if (t->rn_mask) {
		/*
		 * Even if we don't match exactly as a hosts;
		 * we may match if the leaf we wound up at is
		 * a route to a net.
		 */
		cp3 = matched_off + t->rn_mask;
		cp2 = matched_off + t->rn_key;
		for (; cp < cplim; cp++)
			if ((*cp2++ ^ *cp) & *cp3++)
				break;
		if (cp == cplim)
			return t;
		cp = matched_off + v;
	    }
	} while (t = t->rn_dupedkey);
	t = saved_t;
	/* start searching up the tree */
	do {
		register struct radix_mask *m;
		t = t->rn_p;
		if (m = t->rn_mklist) {
			/*
			 * After doing measurements here, it may
			 * turn out to be faster to open code
			 * rn_search_m here instead of always
			 * copying and masking.
			 */
			off = min(t->rn_off, matched_off);
			mstart = maskedKey + off;
			do {
				cp2 = mstart;
				cp3 = m->rm_mask + off;
				for (cp = v + off; cp < cplim;)
					*cp2++ =  *cp++ & *cp3++;
				x = rn_search(maskedKey, t);
				while (x && x->rn_mask != m->rm_mask)
					x = x->rn_dupedkey;
				if (x &&
				    (Bcmp(mstart, x->rn_key + off,
					vlen - off) == 0))
					    return x;
			} while (m = m->rm_mklist);
		}
	} while (t != head);
	return 0;
};
		
#ifdef RN_DEBUG
int	rn_nodenum;
struct	radix_node *rn_clist;
int	rn_saveinfo;
#endif

struct radix_node *
rn_newpair(v, b, nodes)
	caddr_t v;
	struct radix_node nodes[2];
{
	register struct radix_node *tt = nodes, *t = tt + 1;
	t->rn_b = b; t->rn_bmask = 0x80 >> (b & 7);
	t->rn_l = tt; t->rn_off = b >> 3;
	tt->rn_b = -1; tt->rn_key = v; tt->rn_p = t;
	tt->rn_flags = t->rn_flags = RNF_ACTIVE;
#ifdef RN_DEBUG
	tt->rn_info = rn_nodenum++; t->rn_info = rn_nodenum++;
	tt->rn_twin = t; tt->rn_ybro = rn_clist; rn_clist = tt;
#endif
	return t;
}

#ifdef RN_DEBUG
int rn_debug =  1;
#endif

struct radix_node *
rn_insert(v, head, dupentry, nodes)
	caddr_t v;
	struct radix_node *head;
	int *dupentry;
	struct radix_node nodes[2];
{
	int head_off = head->rn_off, vlen = (int)*((u_char *)v);
	register struct radix_node *t = rn_search(v, head);
	register caddr_t cp = v + head_off;
	register int b;
	struct radix_node *tt;
    	/*
	 *find first bit at which v and t->rn_key differ
	 */
    {
	register caddr_t cp2 = t->rn_key + head_off;
	register int cmp_res;
	caddr_t cplim = v + vlen;

	while (cp < cplim)
		if (*cp2++ != *cp++)
			goto on1;
	*dupentry = 1;
	return t;
on1:
	*dupentry = 0;
	cmp_res = (cp[-1] ^ cp2[-1]) & 0xff;
	for (b = (cp - v) << 3; cmp_res; b--)
		cmp_res >>= 1;
    }
    {
	register struct radix_node *p, *x = head;
	cp = v;
	do {
		p = x;
		if (cp[x->rn_off] & x->rn_bmask) 
			x = x->rn_r;
		else x = x->rn_l;
	} while (b > (unsigned) x->rn_b); /* x->rn_b < b && x->rn_b >= 0 */
#ifdef RN_DEBUG
	if (rn_debug)
		printf("Going In:\n"), traverse(p);
#endif
	t = rn_newpair(v, b, nodes); tt = t->rn_l;
	if ((cp[p->rn_off] & p->rn_bmask) == 0)
		p->rn_l = t;
	else
		p->rn_r = t;
	x->rn_p = t; t->rn_p = p; /* frees x, p as temp vars below */
	if ((cp[t->rn_off] & t->rn_bmask) == 0) {
		t->rn_r = x;
	} else {
		t->rn_r = tt; t->rn_l = x;
	}
#ifdef RN_DEBUG
	if (rn_debug)
		printf("Coming out:\n"), traverse(p);
#endif
    }
	return (tt);
}

struct radix_node *
rn_addmask(netmask, search, skip)
caddr_t netmask;
{
	register struct radix_node *x;
	register caddr_t cp, cplim;
	register int b, mlen, j;
	int maskduplicated;

	mlen = *(u_char *)netmask;
	if (search) {
		x = rn_search(netmask, rn_maskhead);
		mlen = *(u_char *)netmask;
		if (Bcmp(netmask, x->rn_key, mlen) == 0)
			return (x);
	}
	R_Malloc(x, struct radix_node *, MAXKEYLEN + 2 * sizeof (*x));
	if (x == 0)
		return (0);
	Bzero(x, MAXKEYLEN + 2 * sizeof (*x));
	cp = (caddr_t)(x + 2);
	Bcopy(netmask, cp, mlen);
	netmask = cp;
	x = rn_insert(netmask, rn_maskhead, &maskduplicated, x);
	/*
	 * Calculate index of mask.
	 */