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