rbt.h

非常好的dns解析软件

/*
 * Copyright (C) 2004, 2005  Internet Systems Consortium, Inc. ("ISC")
 * Copyright (C) 1999-2002  Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

/* $Id: rbt.h,v 1.59.18.5 2005/10/13 01:26:07 marka Exp $ */

#ifndef DNS_RBT_H
#define DNS_RBT_H 1

/*! \file */

#include <isc/lang.h>
#include <isc/magic.h>
#include <isc/refcount.h>

#include <dns/types.h>

ISC_LANG_BEGINDECLS

#define DNS_RBT_USEHASH 1

/*@{*/
/*%
 * Option values for dns_rbt_findnode() and dns_rbt_findname().
 * These are used to form a bitmask.
 */
#define DNS_RBTFIND_NOOPTIONS			0x00
#define DNS_RBTFIND_EMPTYDATA			0x01
#define DNS_RBTFIND_NOEXACT			0x02
#define DNS_RBTFIND_NOPREDECESSOR		0x04
/*@}*/

#ifndef DNS_RBT_USEISCREFCOUNT
#ifdef ISC_REFCOUNT_HAVEATOMIC
#define DNS_RBT_USEISCREFCOUNT 1
#endif
#endif

/*
 * These should add up to 30.
 */
#define DNS_RBT_LOCKLENGTH			10
#define DNS_RBT_REFLENGTH			20

#define DNS_RBTNODE_MAGIC		ISC_MAGIC('R','B','N','O')
#if DNS_RBT_USEMAGIC
#define DNS_RBTNODE_VALID(n)		ISC_MAGIC_VALID(n, DNS_RBTNODE_MAGIC)
#else
#define DNS_RBTNODE_VALID(n)		ISC_TRUE
#endif

/*%
 * This is the structure that is used for each node in the red/black
 * tree of trees.  NOTE WELL:  the implementation manages this as a variable
 * length structure, with the actual wire-format name and other data
 * appended to this structure.  Allocating a contiguous block of memory for
 * multiple dns_rbtnode structures will not work.
 */
typedef struct dns_rbtnode {
#if DNS_RBT_USEMAGIC
	unsigned int magic;
#endif
	struct dns_rbtnode *parent;
	struct dns_rbtnode *left;
	struct dns_rbtnode *right;
	struct dns_rbtnode *down;
#ifdef DNS_RBT_USEHASH
	struct dns_rbtnode *hashnext;
#endif
	/*@{*/
	/*!
	 * The following bitfields add up to a total bitwidth of 32.
	 * The range of values necessary for each item is indicated,
	 * but in the case of "attributes" the field is wider to accomodate
	 * possible future expansion.  "offsetlen" could be one bit
	 * narrower by always adjusting its value by 1 to find the real
	 * offsetlen, but doing so does not gain anything (except perhaps
	 * another bit for "attributes", which doesn't yet need any more).
	 *
	 * In each case below the "range" indicated is what's _necessary_ for
	 * the bitfield to hold, not what it actually _can_ hold.
	 */
	unsigned int is_root : 1;	/*%< range is 0..1 */
	unsigned int color : 1;		/*%< range is 0..1 */
	unsigned int find_callback : 1;	/*%< range is 0..1 */
	unsigned int attributes : 4;	/*%< range is 0..2 */
	unsigned int namelen : 8;	/*%< range is 1..255 */
	unsigned int offsetlen : 8;	/*%< range is 1..128 */
	unsigned int padbytes : 9;	/*%< range is 0..380 */
	/*@}*/

#ifdef DNS_RBT_USEHASH
	unsigned int hashval;
#endif

	/*@{*/
	/*!
	 * These values are used in the RBT DB implementation.  The appropriate
	 * node lock must be held before accessing them.
	 */
	void *data;
	unsigned int dirty:1;
	unsigned int wild:1;
	unsigned int locknum:DNS_RBT_LOCKLENGTH;
#ifndef DNS_RBT_USEISCREFCOUNT
	unsigned int references:DNS_RBT_REFLENGTH;
#else
	isc_refcount_t references; /* note that this is not in the bitfield */
#endif
	/*@}*/
} dns_rbtnode_t;

typedef isc_result_t (*dns_rbtfindcallback_t)(dns_rbtnode_t *node,
					      dns_name_t *name,
					      void *callback_arg);

/*****
 *****	Chain Info
 *****/

/*!
 * A chain is used to keep track of the sequence of nodes to reach any given
 * node from the root of the tree.  Originally nodes did not have parent
 * pointers in them (for memory usage reasons) so there was no way to find
 * the path back to the root from any given node.  Now that nodes have parent
 * pointers, chains might be going away in a future release, though the
 * movement functionality would remain.
 *
 * In any event, parent information, whether via parent pointers or chains, is
 * necessary information for iterating through the tree or for basic internal
 * tree maintenance issues (ie, the rotations that are done to rebalance the
 * tree when a node is added).  The obvious implication of this is that for a
 * chain to remain valid, the tree has to be locked down against writes for the
 * duration of the useful life of the chain, because additions or removals can
 * change the path from the root to the node the chain has targetted.
 *
 * The dns_rbtnodechain_ functions _first, _last, _prev and _next all take
 * dns_name_t parameters for the name and the origin, which can be NULL.  If
 * non-NULL, 'name' will end up pointing to the name data and offsets that are
 * stored at the node (and thus it will be read-only), so it should be a
 * regular dns_name_t that has been initialized with dns_name_init.  When
 * 'origin' is non-NULL, it will get the name of the origin stored in it, so it
 * needs to have its own buffer space and offsets, which is most easily
 * accomplished with a dns_fixedname_t.  It is _not_ necessary to reinitialize
 * either 'name' or 'origin' between calls to the chain functions.
 *
 * NOTE WELL: even though the name data at the root of the tree of trees will
 * be absolute (typically just "."), it will will be made into a relative name
 * with an origin of "." -- an empty name when the node is ".".  This is
 * because a common on operation on 'name' and 'origin' is to use
 * dns_name_concatenate() on them to generate the complete name.  An empty name
 * can be detected when dns_name_countlabels == 0, and is printed by
 * dns_name_totext()/dns_name_format() as "@", consistent with RFC1035's
 * definition of "@" as the current origin.
 *
 * dns_rbtnodechain_current is similar to the _first, _last, _prev and _next
 * functions but additionally can provide the node to which the chain points.
 */

/*%
 * The number of level blocks to allocate at a time.  Currently the maximum
 * number of levels is allocated directly in the structure, but future
 * revisions of this code might have a static initial block with dynamic
 * growth.  Allocating space for 256 levels when the tree is almost never that
 * deep is wasteful, but it's not clear that it matters, since the waste is
 * only 2MB for 1000 concurrently active chains on a system with 64-bit
 * pointers.
 */
#define DNS_RBT_LEVELBLOCK 254

typedef struct dns_rbtnodechain {
	unsigned int		magic;
	isc_mem_t *		mctx;
	/*%
	 * The terminal node of the chain.  It is not in levels[].
	 * This is ostensibly private ... but in a pinch it could be
	 * used tell that the chain points nowhere without needing to
	 * call dns_rbtnodechain_current().
	 */
	dns_rbtnode_t *		end;
	/*%
	 * The maximum number of labels in a name is 128; bitstrings mean
	 * a conceptually very large number (which I have not bothered to
	 * compute) of logical levels because splitting can potentially occur
	 * at each bit.  However, DNSSEC restricts the number of "logical"
	 * labels in a name to 255, meaning only 254 pointers are needed
	 * in the worst case.
	 */
	dns_rbtnode_t *		levels[DNS_RBT_LEVELBLOCK];
	/*%
	 * level_count indicates how deep the chain points into the
	 * tree of trees, and is the index into the levels[] array.
	 * Thus, levels[level_count - 1] is the last level node stored.
	 * A chain that points to the top level of the tree of trees has
	 * a level_count of 0, the first level has a level_count of 1, and
	 * so on.
	 */
	unsigned int		level_count;
	/*%
	 * level_matches tells how many levels matched above the node
	 * returned by dns_rbt_findnode().  A match (partial or exact) found
	 * in the first level thus results in level_matches being set to 1.
	 * This is used by the rbtdb to set the start point for a recursive
	 * search of superdomains until the RR it is looking for is found.
	 */
	unsigned int		level_matches;
} dns_rbtnodechain_t;

/*****
 ***** Public interfaces.
 *****/
isc_result_t
dns_rbt_create(isc_mem_t *mctx, void (*deleter)(void *, void *),
	       void *deleter_arg, dns_rbt_t **rbtp);
/*%<
 * Initialize a red-black tree of trees.
 *
 * Notes:
 *\li	The deleter argument, if non-null, points to a function that is
 *	responsible for cleaning up any memory associated with the data
 *	pointer of a node when the node is deleted.  It is passed the
 *	deleted node's data pointer as its first argument and deleter_arg
 *	as its second argument.
 *
 * Requires:
 * \li	mctx is a pointer to a valid memory context.
 *\li	rbtp != NULL && *rbtp == NULL
 *\li	arg == NULL iff deleter == NULL
 *
 * Ensures:
 *\li	If result is ISC_R_SUCCESS:
 *		*rbtp points to a valid red-black tree manager
 *
 *\li	If result is failure:
 *		*rbtp does not point to a valid red-black tree manager.
 *
 * Returns:
 *\li	#ISC_R_SUCCESS	Success
 *\li	#ISC_R_NOMEMORY	Resource limit: Out of Memory
 */

isc_result_t
dns_rbt_addname(dns_rbt_t *rbt, dns_name_t *name, void *data);
/*%<
 * Add 'name' to the tree of trees, associated with 'data'.
 *
 * Notes:
 *\li	'data' is never required to be non-NULL, but specifying it
 *	when the name is added is faster than searching for 'name'
 *	again and then setting the data pointer.  The lack of a data pointer
 *	for a node also has other ramifications regarding whether
 *	dns_rbt_findname considers a node to exist, or dns_rbt_deletename
 *	joins nodes.
 *
 * Requires:
 *\li	rbt is a valid rbt manager.
 *\li	dns_name_isabsolute(name) == TRUE
 *
 * Ensures:
 *\li	'name' is not altered in any way.
 *
 *\li	Any external references to nodes in the tree are unaffected by
 *	node splits that are necessary to insert the new name.
 *
 *\li	If result is #ISC_R_SUCCESS:
 *		'name' is findable in the red/black tree of trees in O(log N).
 *		The data pointer of the node for 'name' is set to 'data'.
 *
 *\li	If result is #ISC_R_EXISTS or #ISC_R_NOSPACE:
 *		The tree of trees is unaltered.
 *
 *\li	If result is #ISC_R_NOMEMORY:
 *		No guarantees.
 *
 * Returns:
 *\li	#ISC_R_SUCCESS	Success
 *\li	#ISC_R_EXISTS	The name already exists with associated data.
 *\li	#ISC_R_NOSPACE 	The name had more logical labels than are allowed.
 *\li	#ISC_R_NOMEMORY	Resource Limit: Out of Memory
 */

isc_result_t
dns_rbt_addnode(dns_rbt_t *rbt, dns_name_t *name, dns_rbtnode_t **nodep);

/*%<
 * Just like dns_rbt_addname, but returns the address of the node.
 *
 * Requires:
 *\li	rbt is a valid rbt structure.
 *\li	dns_name_isabsolute(name) == TRUE
 *\li	nodep != NULL && *nodep == NULL
 *
 * Ensures: