/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 1997 - 2017, Daniel Stenberg, , et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at https://curl.haxx.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
***************************************************************************/
#include "curl_setup.h"
#include "splay.h"
/*
* This macro compares two node keys i and j and returns:
*
* negative value: when i is smaller than j
* zero : when i is equal to j
* positive when : when i is larger than j
*/
#define compare(i,j) Curl_splaycomparekeys((i),(j))
/*
* Splay using the key i (which may or may not be in the tree.) The starting
* root is t.
*/
struct Curl_tree *Curl_splay(struct curltime i,
struct Curl_tree *t)
{
struct Curl_tree N, *l, *r, *y;
if(t == NULL)
return t;
N.smaller = N.larger = NULL;
l = r = &N;
for(;;) {
long comp = compare(i, t->key);
if(comp < 0) {
if(t->smaller == NULL)
break;
if(compare(i, t->smaller->key) < 0) {
y = t->smaller; /* rotate smaller */
t->smaller = y->larger;
y->larger = t;
t = y;
if(t->smaller == NULL)
break;
}
r->smaller = t; /* link smaller */
r = t;
t = t->smaller;
}
else if(comp > 0) {
if(t->larger == NULL)
break;
if(compare(i, t->larger->key) > 0) {
y = t->larger; /* rotate larger */
t->larger = y->smaller;
y->smaller = t;
t = y;
if(t->larger == NULL)
break;
}
l->larger = t; /* link larger */
l = t;
t = t->larger;
}
else
break;
}
l->larger = t->smaller; /* assemble */
r->smaller = t->larger;
t->smaller = N.larger;
t->larger = N.smaller;
return t;
}
/* Insert key i into the tree t. Return a pointer to the resulting tree or
* NULL if something went wrong.
*
* @unittest: 1309
*/
struct Curl_tree *Curl_splayinsert(struct curltime i,
struct Curl_tree *t,
struct Curl_tree *node)
{
static const struct curltime KEY_NOTUSED = {
(time_t)-1, (unsigned int)-1
}; /* will *NEVER* appear */
if(node == NULL)
return t;
if(t != NULL) {
t = Curl_splay(i, t);
if(compare(i, t->key) == 0) {
/* There already exists a node in the tree with the very same key. Build
a doubly-linked circular list of nodes. We add the new 'node' struct
to the end of this list. */
node->key = KEY_NOTUSED; /* we set the key in the sub node to NOTUSED
to quickly identify this node as a subnode */
node->samen = t;
node->samep = t->samep;
t->samep->samen = node;
t->samep = node;
return t; /* the root node always stays the same */
}
}
if(t == NULL) {
node->smaller = node->larger = NULL;
}
else if(compare(i, t->key) < 0) {
node->smaller = t->smaller;
node->larger = t;
t->smaller = NULL;
}
else {
node->larger = t->larger;
node->smaller = t;
t->larger = NULL;
}
node->key = i;
/* no identical nodes (yet), we are the only one in the list of nodes */
node->samen = node;
node->samep = node;
return node;
}
/* Finds and deletes the best-fit node from the tree. Return a pointer to the
resulting tree. best-fit means the smallest node if it is not larger than
the key */
struct Curl_tree *Curl_splaygetbest(struct curltime i,
struct Curl_tree *t,
struct Curl_tree **removed)
{
static struct curltime tv_zero = {0, 0};
struct Curl_tree *x;
if(!t) {
*removed = NULL; /* none removed since there was no root */
return NULL;
}
/* find smallest */
t = Curl_splay(tv_zero, t);
if(compare(i, t->key) < 0) {
/* even the smallest is too big */
*removed = NULL;
return t;
}
/* FIRST! Check if there is a list with identical keys */
x = t->samen;
if(x != t) {
/* there is, pick one from the list */
/* 'x' is the new root node */
x->key = t->key;
x->larger = t->larger;
x->smaller = t->smaller;
x->samep = t->samep;
t->samep->samen = x;
*removed = t;
return x; /* new root */
}
/* we splayed the tree to the smallest element, there is no smaller */
x = t->larger;
*removed = t;
return x;
}
/* Deletes the very node we point out from the tree if it's there. Stores a
* pointer to the new resulting tree in 'newroot'.
*
* Returns zero on success and non-zero on errors! TODO: document error codes.
* When returning error, it does not touch the 'newroot' pointer.
*
* NOTE: when the last node of the tree is removed, there's no tree left so
* 'newroot' will be made to point to NULL.
*
* @unittest: 1309
*/
int Curl_splayremovebyaddr(struct Curl_tree *t,
struct Curl_tree *removenode,
struct Curl_tree **newroot)
{
static const struct curltime KEY_NOTUSED = {
(time_t)-1, (unsigned int)-1
}; /* will *NEVER* appear */
struct Curl_tree *x;
if(!t || !removenode)
return 1;
if(compare(KEY_NOTUSED, removenode->key) == 0) {
/* Key set to NOTUSED means it is a subnode within a 'same' linked list
and thus we can unlink it easily. */
if(removenode->samen == removenode)
/* A non-subnode should never be set to KEY_NOTUSED */
return 3;
removenode->samep->samen = removenode->samen;
removenode->samen->samep = removenode->samep;
/* Ensures that double-remove gets caught. */
removenode->samen = removenode;
*newroot = t; /* return the same root */
return 0;
}
t = Curl_splay(removenode->key, t);
/* First make sure that we got the same root node as the one we want
to remove, as otherwise we might be trying to remove a node that
isn't actually in the tree.
We cannot just compare the keys here as a double remove in quick
succession of a node with key != KEY_NOTUSED && same != NULL
could return the same key but a different node. */
if(t != removenode)
return 2;
/* Check if there is a list with identical sizes, as then we're trying to
remove the root node of a list of nodes with identical keys. */
x = t->samen;
if(x != t) {
/* 'x' is the new root node, we just make it use the root node's
smaller/larger links */
x->key = t->key;
x->larger = t->larger;
x->smaller = t->smaller;
x->samep = t->samep;
t->samep->samen = x;
}
else {
/* Remove the root node */
if(t->smaller == NULL)
x = t->larger;
else {
x = Curl_splay(removenode->key, t->smaller);
x->larger = t->larger;
}
}
*newroot = x; /* store new root pointer */
return 0;
}