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freebsd/usr.sbin/named/tree.c

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C
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/* tree - balanced binary tree library
*
* vix 05apr94 [removed vixie.h dependencies; cleaned up formatting, names]
* vix 22jan93 [revisited; uses RCS, ANSI, POSIX; has bug fixes]
* vix 23jun86 [added delete uar to add for replaced nodes]
* vix 20jun86 [added tree_delete per wirth a+ds (mod2 v.) p. 224]
* vix 06feb86 [added tree_mung()]
* vix 02feb86 [added tree balancing from wirth "a+ds=p" p. 220-221]
* vix 14dec85 [written]
*/
/* This program text was created by Paul Vixie using examples from the book:
* "Algorithms & Data Structures," Niklaus Wirth, Prentice-Hall, 1986, ISBN
* 0-13-022005-1. Any errors in the conversion from Modula-2 to C are Paul
* Vixie's.
*
* This code and associated documentation is hereby placed in the public
* domain, with the wish that my name and Prof. Wirth's not be removed
* from the source or documentation.
*/
#ifndef LINT
static char RCSid[] = "$Id:";
#endif
/*#define DEBUG "tree"*/
#include <stdio.h>
#ifndef _PATH_XFER
# include <stdlib.h>
#else
# include "../conf/portability.h"
#endif
#include "tree.h"
#ifdef DEBUG
static int debugDepth = 0;
static char *debugFuncs[256];
# define ENTER(proc) { \
debugFuncs[debugDepth] = proc; \
fprintf(stderr, "ENTER(%d:%s.%s)\n", \
debugDepth, DEBUG,
debugFuncs[debugDepth]); \
debugDepth++; \
}
# define RET(value) { \
debugDepth--; \
fprintf(stderr, "RET(%d:%s.%s)\n", \
debugDepth, DEBUG, \
debugFuncs[debugDepth]); \
return (value); \
}
# define RETV { \
debugDepth--; \
fprintf(stderr, "RETV(%d:%s.%s)\n", \
debugDepth, DEBUG, \
debugFuncs[debugDepth]); \
return; \
}
# define MSG(msg) fprintf(stderr, "MSG(%s)\n", msg);
#else
# define ENTER(proc) ;
# define RET(value) return (value);
# define RETV return;
# define MSG(msg) ;
#endif
#ifndef TRUE
# define TRUE 1
# define FALSE 0
#endif
static tree * sprout __P( (tree **, tree_t, int *, int (*)(), void (*)()) );
static int delete __P( (tree **, int (*)(), tree_t, void (*)(),
int *, int *) );
static void del __P( (tree **, int *, tree **, void (*)(), int *) );
static void bal_L __P( (tree **, int *) );
static void bal_R __P( (tree **, int *) );
void
tree_init(ppr_tree)
tree **ppr_tree;
{
ENTER("tree_init")
*ppr_tree = NULL;
RETV
}
tree_t
tree_srch(ppr_tree, pfi_compare, p_user)
tree **ppr_tree;
int (*pfi_compare)();
tree_t p_user;
{
register int i_comp;
ENTER("tree_srch")
if (*ppr_tree) {
i_comp = (*pfi_compare)(p_user, (**ppr_tree).data);
if (i_comp > 0)
RET(tree_srch(&(**ppr_tree).right,
pfi_compare,
p_user))
if (i_comp < 0)
RET(tree_srch(&(**ppr_tree).left,
pfi_compare,
p_user))
/* not higher, not lower... this must be the one.
*/
RET((**ppr_tree).data)
}
/* grounded. NOT found.
*/
RET(NULL)
}
tree_t
tree_add(ppr_tree, pfi_compare, p_user, pfv_uar)
tree **ppr_tree;
int (*pfi_compare)();
tree_t p_user;
void (*pfv_uar)();
{
int i_balance = FALSE;
ENTER("tree_add")
if (!sprout(ppr_tree, p_user, &i_balance, pfi_compare, pfv_uar))
RET(NULL)
RET(p_user)
}
int
tree_delete(ppr_p, pfi_compare, p_user, pfv_uar)
tree **ppr_p;
int (*pfi_compare)();
tree_t p_user;
void (*pfv_uar)();
{
int i_balance = FALSE,
i_uar_called = FALSE;
ENTER("tree_delete");
RET(delete(ppr_p, pfi_compare, p_user, pfv_uar,
&i_balance, &i_uar_called))
}
int
tree_trav(ppr_tree, pfi_uar)
tree **ppr_tree;
int (*pfi_uar)();
{
ENTER("tree_trav")
if (!*ppr_tree)
RET(TRUE)
if (!tree_trav(&(**ppr_tree).left, pfi_uar))
RET(FALSE)
if (!(*pfi_uar)((**ppr_tree).data))
RET(FALSE)
if (!tree_trav(&(**ppr_tree).right, pfi_uar))
RET(FALSE)
RET(TRUE)
}
void
tree_mung(ppr_tree, pfv_uar)
tree **ppr_tree;
void (*pfv_uar)();
{
ENTER("tree_mung")
if (*ppr_tree) {
tree_mung(&(**ppr_tree).left, pfv_uar);
tree_mung(&(**ppr_tree).right, pfv_uar);
if (pfv_uar)
(*pfv_uar)((**ppr_tree).data);
free(*ppr_tree);
*ppr_tree = NULL;
}
RETV
}
static tree *
sprout(ppr, p_data, pi_balance, pfi_compare, pfv_delete)
tree **ppr;
tree_t p_data;
int *pi_balance;
int (*pfi_compare)();
void (*pfv_delete)();
{
tree *p1, *p2, *sub;
int cmp;
ENTER("sprout")
/* are we grounded? if so, add the node "here" and set the rebalance
* flag, then exit.
*/
if (!*ppr) {
MSG("grounded. adding new node, setting h=true")
*ppr = (tree *) malloc(sizeof(tree));
if (*ppr) {
(*ppr)->left = NULL;
(*ppr)->right = NULL;
(*ppr)->bal = 0;
(*ppr)->data = p_data;
*pi_balance = TRUE;
}
RET(*ppr);
}
/* compare the data using routine passed by caller.
*/
cmp = (*pfi_compare)(p_data, (*ppr)->data);
/* if LESS, prepare to move to the left.
*/
if (cmp < 0) {
MSG("LESS. sprouting left.")
sub = sprout(&(*ppr)->left, p_data, pi_balance,
pfi_compare, pfv_delete);
if (sub && *pi_balance) { /* left branch has grown */
MSG("LESS: left branch has grown")
switch ((*ppr)->bal) {
case 1: /* right branch WAS longer; bal is ok now */
MSG("LESS: case 1.. bal restored implicitly")
(*ppr)->bal = 0;
*pi_balance = FALSE;
break;
case 0: /* balance WAS okay; now left branch longer */
MSG("LESS: case 0.. balnce bad but still ok")
(*ppr)->bal = -1;
break;
case -1: /* left branch was already too long. rebal */
MSG("LESS: case -1: rebalancing")
p1 = (*ppr)->left;
if (p1->bal == -1) { /* LL */
MSG("LESS: single LL")
(*ppr)->left = p1->right;
p1->right = *ppr;
(*ppr)->bal = 0;
*ppr = p1;
} else { /* double LR */
MSG("LESS: double LR")
p2 = p1->right;
p1->right = p2->left;
p2->left = p1;
(*ppr)->left = p2->right;
p2->right = *ppr;
if (p2->bal == -1)
(*ppr)->bal = 1;
else
(*ppr)->bal = 0;
if (p2->bal == 1)
p1->bal = -1;
else
p1->bal = 0;
*ppr = p2;
} /*else*/
(*ppr)->bal = 0;
*pi_balance = FALSE;
} /*switch*/
} /*if*/
RET(sub)
} /*if*/
/* if MORE, prepare to move to the right.
*/
if (cmp > 0) {
MSG("MORE: sprouting to the right")
sub = sprout(&(*ppr)->right, p_data, pi_balance,
pfi_compare, pfv_delete);
if (sub && *pi_balance) {
MSG("MORE: right branch has grown")
switch ((*ppr)->bal) {
case -1:
MSG("MORE: balance was off, fixed implicitly")
(*ppr)->bal = 0;
*pi_balance = FALSE;
break;
case 0:
MSG("MORE: balance was okay, now off but ok")
(*ppr)->bal = 1;
break;
case 1:
MSG("MORE: balance was off, need to rebalance")
p1 = (*ppr)->right;
if (p1->bal == 1) { /* RR */
MSG("MORE: single RR")
(*ppr)->right = p1->left;
p1->left = *ppr;
(*ppr)->bal = 0;
*ppr = p1;
} else { /* double RL */
MSG("MORE: double RL")
p2 = p1->left;
p1->left = p2->right;
p2->right = p1;
(*ppr)->right = p2->left;
p2->left = *ppr;
if (p2->bal == 1)
(*ppr)->bal = -1;
else
(*ppr)->bal = 0;
if (p2->bal == -1)
p1->bal = 1;
else
p1->bal = 0;
*ppr = p2;
} /*else*/
(*ppr)->bal = 0;
*pi_balance = FALSE;
} /*switch*/
} /*if*/
RET(sub)
} /*if*/
/* not less, not more: this is the same key! replace...
*/
MSG("FOUND: Replacing data value")
*pi_balance = FALSE;
if (pfv_delete)
(*pfv_delete)((*ppr)->data);
(*ppr)->data = p_data;
RET(*ppr)
}
static int
delete(ppr_p, pfi_compare, p_user, pfv_uar, pi_balance, pi_uar_called)
tree **ppr_p;
int (*pfi_compare)();
tree_t p_user;
void (*pfv_uar)();
int *pi_balance;
int *pi_uar_called;
{
tree *pr_q;
int i_comp, i_ret;
ENTER("delete")
if (*ppr_p == NULL) {
MSG("key not in tree")
RET(FALSE)
}
i_comp = (*pfi_compare)((*ppr_p)->data, p_user);
if (i_comp > 0) {
MSG("too high - scan left")
i_ret = delete(&(*ppr_p)->left, pfi_compare, p_user, pfv_uar,
pi_balance, pi_uar_called);
if (*pi_balance)
bal_L(ppr_p, pi_balance);
} else if (i_comp < 0) {
MSG("too low - scan right")
i_ret = delete(&(*ppr_p)->right, pfi_compare, p_user, pfv_uar,
pi_balance, pi_uar_called);
if (*pi_balance)
bal_R(ppr_p, pi_balance);
} else {
MSG("equal")
pr_q = *ppr_p;
if (pr_q->right == NULL) {
MSG("right subtree null")
*ppr_p = pr_q->left;
*pi_balance = TRUE;
} else if (pr_q->left == NULL) {
MSG("right subtree non-null, left subtree null")
*ppr_p = pr_q->right;
*pi_balance = TRUE;
} else {
MSG("neither subtree null")
del(&pr_q->left, pi_balance, &pr_q,
pfv_uar, pi_uar_called);
if (*pi_balance)
bal_L(ppr_p, pi_balance);
}
if (!*pi_uar_called && pfv_uar)
(*pfv_uar)(pr_q->data);
free(pr_q); /* thanks to wuth@castrov.cuc.ab.ca */
i_ret = TRUE;
}
RET(i_ret)
}
static void
del(ppr_r, pi_balance, ppr_q, pfv_uar, pi_uar_called)
tree **ppr_r;
int *pi_balance;
tree **ppr_q;
void (*pfv_uar)();
int *pi_uar_called;
{
ENTER("del")
if ((*ppr_r)->right != NULL) {
del(&(*ppr_r)->right, pi_balance, ppr_q,
pfv_uar, pi_uar_called);
if (*pi_balance)
bal_R(ppr_r, pi_balance);
} else {
if (pfv_uar)
(*pfv_uar)((*ppr_q)->data);
*pi_uar_called = TRUE;
(*ppr_q)->data = (*ppr_r)->data;
*ppr_q = *ppr_r;
*ppr_r = (*ppr_r)->left;
*pi_balance = TRUE;
}
RETV
}
static void
bal_L(ppr_p, pi_balance)
tree **ppr_p;
int *pi_balance;
{
tree *p1, *p2;
int b1, b2;
ENTER("bal_L")
MSG("left branch has shrunk")
switch ((*ppr_p)->bal) {
case -1:
MSG("was imbalanced, fixed implicitly")
(*ppr_p)->bal = 0;
break;
case 0:
MSG("was okay, is now one off")
(*ppr_p)->bal = 1;
*pi_balance = FALSE;
break;
case 1:
MSG("was already off, this is too much")
p1 = (*ppr_p)->right;
b1 = p1->bal;
if (b1 >= 0) {
MSG("single RR")
(*ppr_p)->right = p1->left;
p1->left = *ppr_p;
if (b1 == 0) {
MSG("b1 == 0")
(*ppr_p)->bal = 1;
p1->bal = -1;
*pi_balance = FALSE;
} else {
MSG("b1 != 0")
(*ppr_p)->bal = 0;
p1->bal = 0;
}
*ppr_p = p1;
} else {
MSG("double RL")
p2 = p1->left;
b2 = p2->bal;
p1->left = p2->right;
p2->right = p1;
(*ppr_p)->right = p2->left;
p2->left = *ppr_p;
if (b2 == 1)
(*ppr_p)->bal = -1;
else
(*ppr_p)->bal = 0;
if (b2 == -1)
p1->bal = 1;
else
p1->bal = 0;
*ppr_p = p2;
p2->bal = 0;
}
}
RETV
}
static void
bal_R(ppr_p, pi_balance)
tree **ppr_p;
int *pi_balance;
{
tree *p1, *p2;
int b1, b2;
ENTER("bal_R")
MSG("right branch has shrunk")
switch ((*ppr_p)->bal) {
case 1:
MSG("was imbalanced, fixed implicitly")
(*ppr_p)->bal = 0;
break;
case 0:
MSG("was okay, is now one off")
(*ppr_p)->bal = -1;
*pi_balance = FALSE;
break;
case -1:
MSG("was already off, this is too much")
p1 = (*ppr_p)->left;
b1 = p1->bal;
if (b1 <= 0) {
MSG("single LL")
(*ppr_p)->left = p1->right;
p1->right = *ppr_p;
if (b1 == 0) {
MSG("b1 == 0")
(*ppr_p)->bal = -1;
p1->bal = 1;
*pi_balance = FALSE;
} else {
MSG("b1 != 0")
(*ppr_p)->bal = 0;
p1->bal = 0;
}
*ppr_p = p1;
} else {
MSG("double LR")
p2 = p1->right;
b2 = p2->bal;
p1->right = p2->left;
p2->left = p1;
(*ppr_p)->left = p2->right;
p2->right = *ppr_p;
if (b2 == -1)
(*ppr_p)->bal = 1;
else
(*ppr_p)->bal = 0;
if (b2 == 1)
p1->bal = -1;
else
p1->bal = 0;
*ppr_p = p2;
p2->bal = 0;
}
}
RETV
}
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