279 lines
7.4 KiB
C
279 lines
7.4 KiB
C
/***************************************************************************
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* _ _ ____ _
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* Project ___| | | | _ \| |
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* / __| | | | |_) | |
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* | (__| |_| | _ <| |___
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* \___|\___/|_| \_\_____|
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*
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* Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
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*
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* This software is licensed as described in the file COPYING, which
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* you should have received as part of this distribution. The terms
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* are also available at https://curl.se/docs/copyright.html.
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*
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* You may opt to use, copy, modify, merge, publish, distribute and/or sell
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* copies of the Software, and permit persons to whom the Software is
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* furnished to do so, under the terms of the COPYING file.
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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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* SPDX-License-Identifier: curl
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*
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***************************************************************************/
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#include "curl_setup.h"
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#include "splay.h"
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/*
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* This macro compares two node keys i and j and returns:
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*
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* negative value: when i is smaller than j
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* zero : when i is equal to j
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* positive when : when i is larger than j
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*/
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#define compare(i,j) Curl_splaycomparekeys((i),(j))
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/*
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* Splay using the key i (which may or may not be in the tree.) The starting
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* root is t.
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*/
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struct Curl_tree *Curl_splay(struct curltime i,
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struct Curl_tree *t)
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{
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struct Curl_tree N, *l, *r, *y;
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if(!t)
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return t;
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N.smaller = N.larger = NULL;
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l = r = &N;
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for(;;) {
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long comp = compare(i, t->key);
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if(comp < 0) {
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if(!t->smaller)
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break;
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if(compare(i, t->smaller->key) < 0) {
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y = t->smaller; /* rotate smaller */
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t->smaller = y->larger;
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y->larger = t;
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t = y;
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if(!t->smaller)
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break;
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}
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r->smaller = t; /* link smaller */
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r = t;
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t = t->smaller;
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}
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else if(comp > 0) {
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if(!t->larger)
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break;
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if(compare(i, t->larger->key) > 0) {
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y = t->larger; /* rotate larger */
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t->larger = y->smaller;
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y->smaller = t;
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t = y;
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if(!t->larger)
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break;
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}
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l->larger = t; /* link larger */
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l = t;
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t = t->larger;
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}
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else
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break;
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}
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l->larger = t->smaller; /* assemble */
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r->smaller = t->larger;
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t->smaller = N.larger;
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t->larger = N.smaller;
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return t;
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}
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/* Insert key i into the tree t. Return a pointer to the resulting tree or
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* NULL if something went wrong.
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*
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* @unittest: 1309
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*/
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struct Curl_tree *Curl_splayinsert(struct curltime i,
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struct Curl_tree *t,
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struct Curl_tree *node)
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{
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static const struct curltime KEY_NOTUSED = {
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~0, -1
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}; /* will *NEVER* appear */
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if(!node)
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return t;
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if(t) {
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t = Curl_splay(i, t);
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if(compare(i, t->key) == 0) {
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/* There already exists a node in the tree with the very same key. Build
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a doubly-linked circular list of nodes. We add the new 'node' struct
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to the end of this list. */
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node->key = KEY_NOTUSED; /* we set the key in the sub node to NOTUSED
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to quickly identify this node as a subnode */
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node->samen = t;
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node->samep = t->samep;
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t->samep->samen = node;
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t->samep = node;
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return t; /* the root node always stays the same */
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}
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}
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if(!t) {
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node->smaller = node->larger = NULL;
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}
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else if(compare(i, t->key) < 0) {
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node->smaller = t->smaller;
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node->larger = t;
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t->smaller = NULL;
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}
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else {
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node->larger = t->larger;
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node->smaller = t;
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t->larger = NULL;
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}
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node->key = i;
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/* no identical nodes (yet), we are the only one in the list of nodes */
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node->samen = node;
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node->samep = node;
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return node;
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}
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/* Finds and deletes the best-fit node from the tree. Return a pointer to the
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resulting tree. best-fit means the smallest node if it is not larger than
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the key */
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struct Curl_tree *Curl_splaygetbest(struct curltime i,
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struct Curl_tree *t,
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struct Curl_tree **removed)
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{
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static const struct curltime tv_zero = {0, 0};
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struct Curl_tree *x;
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if(!t) {
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*removed = NULL; /* none removed since there was no root */
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return NULL;
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}
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/* find smallest */
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t = Curl_splay(tv_zero, t);
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if(compare(i, t->key) < 0) {
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/* even the smallest is too big */
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*removed = NULL;
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return t;
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}
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/* FIRST! Check if there is a list with identical keys */
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x = t->samen;
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if(x != t) {
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/* there is, pick one from the list */
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/* 'x' is the new root node */
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x->key = t->key;
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x->larger = t->larger;
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x->smaller = t->smaller;
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x->samep = t->samep;
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t->samep->samen = x;
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*removed = t;
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return x; /* new root */
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}
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/* we splayed the tree to the smallest element, there is no smaller */
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x = t->larger;
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*removed = t;
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return x;
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}
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/* Deletes the very node we point out from the tree if it's there. Stores a
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* pointer to the new resulting tree in 'newroot'.
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*
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* Returns zero on success and non-zero on errors!
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* When returning error, it does not touch the 'newroot' pointer.
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*
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* NOTE: when the last node of the tree is removed, there's no tree left so
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* 'newroot' will be made to point to NULL.
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*
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* @unittest: 1309
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*/
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int Curl_splayremove(struct Curl_tree *t,
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struct Curl_tree *removenode,
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struct Curl_tree **newroot)
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{
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static const struct curltime KEY_NOTUSED = {
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~0, -1
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}; /* will *NEVER* appear */
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struct Curl_tree *x;
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if(!t || !removenode)
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return 1;
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if(compare(KEY_NOTUSED, removenode->key) == 0) {
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/* Key set to NOTUSED means it is a subnode within a 'same' linked list
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and thus we can unlink it easily. */
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if(removenode->samen == removenode)
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/* A non-subnode should never be set to KEY_NOTUSED */
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return 3;
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removenode->samep->samen = removenode->samen;
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removenode->samen->samep = removenode->samep;
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/* Ensures that double-remove gets caught. */
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removenode->samen = removenode;
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*newroot = t; /* return the same root */
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return 0;
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}
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t = Curl_splay(removenode->key, t);
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/* First make sure that we got the same root node as the one we want
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to remove, as otherwise we might be trying to remove a node that
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isn't actually in the tree.
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We cannot just compare the keys here as a double remove in quick
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succession of a node with key != KEY_NOTUSED && same != NULL
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could return the same key but a different node. */
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if(t != removenode)
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return 2;
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/* Check if there is a list with identical sizes, as then we're trying to
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remove the root node of a list of nodes with identical keys. */
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x = t->samen;
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if(x != t) {
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/* 'x' is the new root node, we just make it use the root node's
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smaller/larger links */
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x->key = t->key;
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x->larger = t->larger;
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x->smaller = t->smaller;
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x->samep = t->samep;
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t->samep->samen = x;
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}
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else {
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/* Remove the root node */
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if(!t->smaller)
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x = t->larger;
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else {
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x = Curl_splay(removenode->key, t->smaller);
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x->larger = t->larger;
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}
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}
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*newroot = x; /* store new root pointer */
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return 0;
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}
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