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/*
* Filters: utility functions
*
* Copyright 1998 Pavel Machek <pavel@ucw.cz>
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
#include "nest/bird.h"
#include "conf/conf.h"
#include "filter/filter.h"
/*
* find_nth - finds n-th element in linked list. Don't be confused by types, it is really a linked list.
*/
static struct f_tree *
find_nth(struct f_tree *from, int nth)
{
struct f_tree *pivot;
int lcount = 0, rcount = 0;
struct f_tree *left, *right, *next;
pivot = from;
left = right = NULL;
next = from->right;
while (from = next) {
next = from->right;
if (val_compare(pivot->from, from->from)==1) {
from->right = left;
left = from;
lcount++;
} else {
from->right = right;
right = from;
rcount++;
}
}
if (lcount == nth)
return pivot;
if (lcount < nth)
return find_nth(right, nth-lcount-1);
return find_nth(left, nth);
}
/*
* find_median - Gets list linked by @left, finds its median, trashes pointers in @right.
*/
static struct f_tree *
find_median(struct f_tree *from)
{
struct f_tree *t = from;
int cnt = 0;
if (!from)
return NULL;
do {
t->right = t->left;
cnt++;
} while (t = t->left);
return find_nth(from, cnt/2);
}
/**
* find_tree
* @t: tree to search in
* @val: value to find
*
* Search for given value in the tree. I relies on fact that sorted tree is populated
* by &f_val structures (that can be compared by val_compare()). In each node of tree,
* either single value (then t->from==t->to) or range is present.
*
* Both set matching and |switch() { }| construction is implemented using this function,
* thus both are as fast as they can be.
*/
struct f_tree *
find_tree(struct f_tree *t, struct f_val val)
{
if (!t)
return NULL;
if ((val_compare(t->from, val) != 1) &&
(val_compare(t->to, val) != -1))
return t;
if (val_compare(t->from, val) == -1)
return find_tree(t->right, val);
else
return find_tree(t->left, val);
}
/**
* build_tree
* @from: degenerated tree (linked by @tree->left) to be transformed into form suitable for find_tree()
*
* Transforms denerated tree into balanced tree.
*/
struct f_tree *
build_tree(struct f_tree *from)
{
struct f_tree *median, *t = from, *next, *left = NULL, *right = NULL;
median = find_median(from);
if (!median)
return NULL;
do {
next = t->left;
if (t == median)
continue;
if (val_compare(median->from, t->from)==1) {
t->left = left;
left = t;
} else {
t->left = right;
right = t;
}
} while(t = next);
median->left = build_tree(left);
median->right = build_tree(right);
return median;
}
struct f_tree *
f_new_tree(void)
{
struct f_tree * ret;
ret = cfg_alloc(sizeof(struct f_tree));
ret->left = ret->right = NULL;
ret->from.type = ret->to.type = T_VOID;
ret->from.val.i = ret->to.val.i = 0;
ret->data = NULL;
return ret;
}
/**
* same_tree
* @t1: first tree to be compared
* @t2: second one
*
* Compares two trees and returns 1 if they are same
*/
int
same_tree(struct f_tree *t1, struct f_tree *t2)
{
if ((!!t1) != (!!t2))
return 0;
if (!t1)
return 1;
if (val_compare(t1->from, t2->from))
return 0;
if (val_compare(t1->to, t2->to))
return 0;
if (!same_tree(t1->left, t2->left))
return 0;
if (!same_tree(t1->right, t2->right))
return 0;
if (!i_same(t1->data, t2->data))
return 0;
return 1;
}
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