325 lines
10 KiB
C
325 lines
10 KiB
C
/*
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* Elastic Binary Trees - macros for Indirect Multi-Byte data nodes.
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* Version 6.0.6
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* (C) 2002-2011 - Willy Tarreau <w@1wt.eu>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation, version 2.1
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* exclusively.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef _EBIMTREE_H
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#define _EBIMTREE_H
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#include <string.h>
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#include "ebtree.h"
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#include "ebpttree.h"
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/* These functions and macros rely on Pointer nodes and use the <key> entry as
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* a pointer to an indirect key. Most operations are performed using ebpt_*.
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*/
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/* The following functions are not inlined by default. They are declared
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* in ebimtree.c, which simply relies on their inline version.
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*/
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struct ebpt_node *ebim_lookup(struct eb_root *root, const void *x, unsigned int len);
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struct ebpt_node *ebim_insert(struct eb_root *root, struct ebpt_node *new, unsigned int len);
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/* Find the first occurrence of a key of a least <len> bytes matching <x> in the
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* tree <root>. The caller is responsible for ensuring that <len> will not exceed
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* the common parts between the tree's keys and <x>. In case of multiple matches,
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* the leftmost node is returned. This means that this function can be used to
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* lookup string keys by prefix if all keys in the tree are zero-terminated. If
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* no match is found, NULL is returned. Returns first node if <len> is zero.
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*/
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static forceinline struct ebpt_node *
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__ebim_lookup(struct eb_root *root, const void *x, unsigned int len)
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{
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struct ebpt_node *node;
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eb_troot_t *troot;
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int pos, side;
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int node_bit;
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troot = root->b[EB_LEFT];
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if (unlikely(troot == NULL))
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goto ret_null;
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if (unlikely(len == 0))
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goto walk_down;
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pos = 0;
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while (1) {
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if (eb_gettag(troot) == EB_LEAF) {
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node = container_of(eb_untag(troot, EB_LEAF),
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struct ebpt_node, node.branches);
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if (eb_memcmp(node->key + pos, x, len) != 0)
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goto ret_null;
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else
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goto ret_node;
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}
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node = container_of(eb_untag(troot, EB_NODE),
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struct ebpt_node, node.branches);
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node_bit = node->node.bit;
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if (node_bit < 0) {
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/* We have a dup tree now. Either it's for the same
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* value, and we walk down left, or it's a different
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* one and we don't have our key.
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*/
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if (eb_memcmp(node->key + pos, x, len) != 0)
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goto ret_null;
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else
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goto walk_left;
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}
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/* OK, normal data node, let's walk down. We check if all full
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* bytes are equal, and we start from the last one we did not
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* completely check. We stop as soon as we reach the last byte,
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* because we must decide to go left/right or abort.
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*/
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node_bit = ~node_bit + (pos << 3) + 8; // = (pos<<3) + (7 - node_bit)
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if (node_bit < 0) {
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/* This surprising construction gives better performance
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* because gcc does not try to reorder the loop. Tested to
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* be fine with 2.95 to 4.2.
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*/
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while (1) {
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if (*(unsigned char*)(node->key + pos++) ^ *(unsigned char*)(x++))
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goto ret_null; /* more than one full byte is different */
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if (--len == 0)
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goto walk_left; /* return first node if all bytes matched */
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node_bit += 8;
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if (node_bit >= 0)
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break;
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}
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}
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/* here we know that only the last byte differs, so node_bit < 8.
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* We have 2 possibilities :
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* - more than the last bit differs => return NULL
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* - walk down on side = (x[pos] >> node_bit) & 1
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*/
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side = *(unsigned char *)x >> node_bit;
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if (((*(unsigned char*)(node->key + pos) >> node_bit) ^ side) > 1)
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goto ret_null;
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side &= 1;
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troot = node->node.branches.b[side];
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}
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walk_left:
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troot = node->node.branches.b[EB_LEFT];
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walk_down:
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while (eb_gettag(troot) != EB_LEAF)
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troot = (eb_untag(troot, EB_NODE))->b[EB_LEFT];
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node = container_of(eb_untag(troot, EB_LEAF),
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struct ebpt_node, node.branches);
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ret_node:
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return node;
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ret_null:
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return NULL;
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}
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/* Insert ebpt_node <new> into subtree starting at node root <root>.
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* Only new->key needs be set with the key. The ebpt_node is returned.
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* If root->b[EB_RGHT]==1, the tree may only contain unique keys. The
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* len is specified in bytes.
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*/
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static forceinline struct ebpt_node *
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__ebim_insert(struct eb_root *root, struct ebpt_node *new, unsigned int len)
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{
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struct ebpt_node *old;
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unsigned int side;
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eb_troot_t *troot;
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eb_troot_t *root_right;
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int diff;
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int bit;
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int old_node_bit;
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side = EB_LEFT;
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troot = root->b[EB_LEFT];
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root_right = root->b[EB_RGHT];
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if (unlikely(troot == NULL)) {
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/* Tree is empty, insert the leaf part below the left branch */
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root->b[EB_LEFT] = eb_dotag(&new->node.branches, EB_LEAF);
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new->node.leaf_p = eb_dotag(root, EB_LEFT);
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new->node.node_p = NULL; /* node part unused */
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return new;
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}
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len <<= 3;
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/* The tree descent is fairly easy :
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* - first, check if we have reached a leaf node
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* - second, check if we have gone too far
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* - third, reiterate
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* Everywhere, we use <new> for the node node we are inserting, <root>
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* for the node we attach it to, and <old> for the node we are
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* displacing below <new>. <troot> will always point to the future node
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* (tagged with its type). <side> carries the side the node <new> is
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* attached to below its parent, which is also where previous node
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* was attached.
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*/
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bit = 0;
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while (1) {
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if (unlikely(eb_gettag(troot) == EB_LEAF)) {
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eb_troot_t *new_left, *new_rght;
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eb_troot_t *new_leaf, *old_leaf;
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old = container_of(eb_untag(troot, EB_LEAF),
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struct ebpt_node, node.branches);
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new_left = eb_dotag(&new->node.branches, EB_LEFT);
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new_rght = eb_dotag(&new->node.branches, EB_RGHT);
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new_leaf = eb_dotag(&new->node.branches, EB_LEAF);
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old_leaf = eb_dotag(&old->node.branches, EB_LEAF);
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new->node.node_p = old->node.leaf_p;
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/* Right here, we have 3 possibilities :
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* - the tree does not contain the key, and we have
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* new->key < old->key. We insert new above old, on
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* the left ;
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*
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* - the tree does not contain the key, and we have
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* new->key > old->key. We insert new above old, on
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* the right ;
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*
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* - the tree does contain the key, which implies it
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* is alone. We add the new key next to it as a
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* first duplicate.
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*
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* The last two cases can easily be partially merged.
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*/
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bit = equal_bits(new->key, old->key, bit, len);
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/* Note: we can compare more bits than the current node's because as
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* long as they are identical, we know we descend along the correct
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* side. However we don't want to start to compare past the end.
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*/
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diff = 0;
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if (((unsigned)bit >> 3) < len)
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diff = cmp_bits(new->key, old->key, bit);
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if (diff < 0) {
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new->node.leaf_p = new_left;
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old->node.leaf_p = new_rght;
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new->node.branches.b[EB_LEFT] = new_leaf;
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new->node.branches.b[EB_RGHT] = old_leaf;
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} else {
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/* we may refuse to duplicate this key if the tree is
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* tagged as containing only unique keys.
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*/
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if (diff == 0 && eb_gettag(root_right))
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return old;
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/* new->key >= old->key, new goes the right */
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old->node.leaf_p = new_left;
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new->node.leaf_p = new_rght;
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new->node.branches.b[EB_LEFT] = old_leaf;
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new->node.branches.b[EB_RGHT] = new_leaf;
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if (diff == 0) {
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new->node.bit = -1;
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root->b[side] = eb_dotag(&new->node.branches, EB_NODE);
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return new;
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}
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}
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break;
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}
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/* OK we're walking down this link */
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old = container_of(eb_untag(troot, EB_NODE),
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struct ebpt_node, node.branches);
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old_node_bit = old->node.bit;
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/* Stop going down when we don't have common bits anymore. We
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* also stop in front of a duplicates tree because it means we
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* have to insert above. Note: we can compare more bits than
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* the current node's because as long as they are identical, we
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* know we descend along the correct side.
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*/
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if (old_node_bit < 0) {
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/* we're above a duplicate tree, we must compare till the end */
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bit = equal_bits(new->key, old->key, bit, len);
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goto dup_tree;
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}
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else if (bit < old_node_bit) {
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bit = equal_bits(new->key, old->key, bit, old_node_bit);
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}
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if (bit < old_node_bit) { /* we don't have all bits in common */
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/* The tree did not contain the key, so we insert <new> before the node
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* <old>, and set ->bit to designate the lowest bit position in <new>
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* which applies to ->branches.b[].
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*/
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eb_troot_t *new_left, *new_rght;
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eb_troot_t *new_leaf, *old_node;
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dup_tree:
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new_left = eb_dotag(&new->node.branches, EB_LEFT);
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new_rght = eb_dotag(&new->node.branches, EB_RGHT);
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new_leaf = eb_dotag(&new->node.branches, EB_LEAF);
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old_node = eb_dotag(&old->node.branches, EB_NODE);
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new->node.node_p = old->node.node_p;
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/* Note: we can compare more bits than the current node's because as
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* long as they are identical, we know we descend along the correct
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* side. However we don't want to start to compare past the end.
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*/
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diff = 0;
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if (((unsigned)bit >> 3) < len)
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diff = cmp_bits(new->key, old->key, bit);
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if (diff < 0) {
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new->node.leaf_p = new_left;
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old->node.node_p = new_rght;
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new->node.branches.b[EB_LEFT] = new_leaf;
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new->node.branches.b[EB_RGHT] = old_node;
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}
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else if (diff > 0) {
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old->node.node_p = new_left;
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new->node.leaf_p = new_rght;
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new->node.branches.b[EB_LEFT] = old_node;
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new->node.branches.b[EB_RGHT] = new_leaf;
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}
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else {
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struct eb_node *ret;
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ret = eb_insert_dup(&old->node, &new->node);
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return container_of(ret, struct ebpt_node, node);
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}
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break;
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}
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/* walk down */
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root = &old->node.branches;
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side = (((unsigned char *)new->key)[old_node_bit >> 3] >> (~old_node_bit & 7)) & 1;
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troot = root->b[side];
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}
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/* Ok, now we are inserting <new> between <root> and <old>. <old>'s
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* parent is already set to <new>, and the <root>'s branch is still in
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* <side>. Update the root's leaf till we have it. Note that we can also
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* find the side by checking the side of new->node.node_p.
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*/
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/* We need the common higher bits between new->key and old->key.
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* This number of bits is already in <bit>.
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*/
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new->node.bit = bit;
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root->b[side] = eb_dotag(&new->node.branches, EB_NODE);
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return new;
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}
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#endif /* _EBIMTREE_H */
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