/*************************************************************************** | |

* _ _ ____ _ | |

* Project ___| | | | _ \| | | |

* / __| | | | |_) | | | |

* | (__| |_| | _ <| |___ | |

* \___|\___/|_| \_\_____| | |

* | |

* Copyright (C) 1997 - 2019, Daniel Stenberg, <daniel@haxx.se>, 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! | |

* 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; | |

} |