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https://gitlab.labs.nic.cz/labs/bird.git
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dfd48621d1
Changes the time complexity of the algorithm from O(n^2) to O(n*log(n)). This speeds up loading of huge DEC-IX config from 128 s to 15 s. It also makes the code significantly simpler.
135 lines
2.8 KiB
C
135 lines
2.8 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 "lib/alloca.h"
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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_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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static struct f_tree *
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build_tree_rec(struct f_tree **buf, int l, int h)
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{
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struct f_tree *n;
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int pos;
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if (l >= h)
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return NULL;
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pos = (l+h)/2;
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n = buf[pos];
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n->left = build_tree_rec(buf, l, pos);
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n->right = build_tree_rec(buf, pos+1, h);
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return n;
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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 *tmp, *root;
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struct f_tree **buf;
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int len, i;
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if (from == NULL)
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return NULL;
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len = 0;
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for (tmp = from; tmp != NULL; tmp = tmp->left)
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len++;
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if (len <= 1024)
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buf = alloca(len * sizeof(struct f_tree *));
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else
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buf = malloc(len * sizeof(struct f_tree *));
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/* Convert a degenerated tree into an sorted array */
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i = 0;
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for (tmp = from; tmp != NULL; tmp = tmp->left)
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buf[i++] = tmp;
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qsort(buf, len, sizeof(struct f_tree *), tree_compare);
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root = build_tree_rec(buf, 0, len);
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if (len > 1024)
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free(buf);
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return root;
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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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