/src/curl/lib/splay.c

Source
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 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.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.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/
#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 splay_compare(i, j) curlx_ptimediff_us(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(const struct curltime *pkey,
                             struct Curl_tree *t)
{
  struct Curl_tree N, *l, *r, *y;

  if(!t)
    return NULL;
  N.smaller = N.larger = NULL;
  l = r = &N;

  for(;;) {
    timediff_t comp = splay_compare(pkey, &t->key);
    if(comp < 0) {
      if(!t->smaller)
        break;
      if(splay_compare(pkey, &t->smaller->key) < 0) {
        y = t->smaller;                           /* rotate smaller */
        t->smaller = y->larger;
        y->larger = t;
        t = y;
        if(!t->smaller)
          break;
      }
      r->smaller = t;                               /* link smaller */
      r = t;
      t = t->smaller;
    }
    else if(comp > 0) {
      if(!t->larger)
        break;
      if(splay_compare(pkey, &t->larger->key) > 0) {
        y = t->larger;                          /* rotate larger */
        t->larger = y->smaller;
        y->smaller = t;
        t = y;
        if(!t->larger)
          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;
}

static const struct curltime SPLAY_SUBNODE = {
  ~0, -1
};

/* 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(const struct curltime *pkey,
                                   struct Curl_tree *t,
                                   struct Curl_tree *node)
{
  DEBUGASSERT(node);

  if(t) {
    t = Curl_splay(pkey, t);
    DEBUGASSERT(t);
    if(splay_compare(pkey, &t->key) == 0) {
      /* There already exists a node in the tree with the same key. Build a
         doubly-linked circular list of nodes. We add the new 'node' struct to
         the end of this list. */

      node->key = SPLAY_SUBNODE; /* 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) {
    node->smaller = node->larger = NULL;
  }
  else if(splay_compare(pkey, &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 = *pkey;

  /* 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(const struct curltime *pkey,
                                    struct Curl_tree *t,
                                    struct Curl_tree **removed)
{
  static const 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);
  DEBUGASSERT(t);
  if(splay_compare(pkey, &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 node we point out from the tree if it is 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 is no tree left so
 * 'newroot' will be made to point to NULL.
 *
 * @unittest: 1309
 */
int Curl_splayremove(struct Curl_tree *t,
                     struct Curl_tree *removenode,
                     struct Curl_tree **newroot)
{
  struct Curl_tree *x;

  if(!t)
    return 1;

  DEBUGASSERT(removenode);

  if(splay_compare(&SPLAY_SUBNODE, &removenode->key) == 0) {
    /* It is a subnode within a 'same' linked list and thus we can unlink it
       easily. */
    DEBUGASSERT(removenode->samen != removenode);
    if(removenode->samen == removenode)
      /* A non-subnode should never be set to SPLAY_SUBNODE */
      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);
  DEBUGASSERT(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
     is not actually in the tree.

     We cannot just compare the keys here as a double remove in quick
     succession of a node with key != SPLAY_SUBNODE && same != NULL
     could return the same key but a different node. */
  DEBUGASSERT(t == removenode);
  if(t != removenode)
    return 2;

  /* Check if there is a list with identical sizes, as then we are 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)
      x = t->larger;
    else {
      x = Curl_splay(&removenode->key, t->smaller);
      DEBUGASSERT(x);
      x->larger = t->larger;
    }
  }

  *newroot = x; /* store new root pointer */

  return 0;
}

/* set and get the custom payload for this tree node */
void Curl_splayset(struct Curl_tree *node, void *payload)
{
  DEBUGASSERT(node);
  node->ptr = payload;
}

void *Curl_splayget(struct Curl_tree *node)
{
  DEBUGASSERT(node);
  return node->ptr;
}

Coverage Report

Created: 2026-01-17 06:34

Line	Count	Source
1		/***************************************************************************
2		* _ _ ____ _
3		* Project ___\| \| \| \| _ \\| \|
4		* / __\| \| \| \| \|_) \| \|
5		* \| (__\| \|_\| \| _ <\| \|___
6		* \___\|\___/\|_\| \_\_____\|
7		*
8		* Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
9		*
10		* This software is licensed as described in the file COPYING, which
11		* you should have received as part of this distribution. The terms
12		* are also available at https://curl.se/docs/copyright.html.
13		*
14		* You may opt to use, copy, modify, merge, publish, distribute and/or sell
15		* copies of the Software, and permit persons to whom the Software is
16		* furnished to do so, under the terms of the COPYING file.
17		*
18		* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
19		* KIND, either express or implied.
20		*
21		* SPDX-License-Identifier: curl
22		*
23		***************************************************************************/
24		#include "curl_setup.h"
25
26		#include "splay.h"
27
28		/*
29		* This macro compares two node keys i and j and returns:
30		*
31		* negative value: when i is smaller than j
32		* zero : when i is equal to j
33		* positive when : when i is larger than j
34		*/
35	69.5M	#define splay_compare(i, j) curlx_ptimediff_us(i, j)
36
37		/*
38		* Splay using the key i (which may or may not be in the tree.) The starting
39		* root is t.
40		*/
41		struct Curl_tree Curl_splay(const struct curltime pkey,
42		struct Curl_tree *t)
43	34.5M	{
44	34.5M	struct Curl_tree N, l, r, *y;
45
46	34.5M	if(!t)
47	0	return NULL;
48	34.5M	N.smaller = N.larger = NULL;
49	34.5M	l = r = &N;
50
51	34.6M	for(;;) {
52	34.6M	timediff_t comp = splay_compare(pkey, &t->key);
53	34.6M	if(comp < 0) {
54	33.7M	if(!t->smaller)
55	33.7M	break;
56	5.88k	if(splay_compare(pkey, &t->smaller->key) < 0) {
57	5.88k	y = t->smaller; /* rotate smaller */
58	5.88k	t->smaller = y->larger;
59	5.88k	y->larger = t;
60	5.88k	t = y;
61	5.88k	if(!t->smaller)
62	1.23k	break;
63	5.88k	}
64	4.65k	r->smaller = t; /* link smaller */
65	4.65k	r = t;
66	4.65k	t = t->smaller;
67	4.65k	}
68	878k	else if(comp > 0) {
69	30.9k	if(!t->larger)
70	22.0k	break;
71	8.95k	if(splay_compare(pkey, &t->larger->key) > 0) {
72	4.22k	y = t->larger; /* rotate larger */
73	4.22k	t->larger = y->smaller;
74	4.22k	y->smaller = t;
75	4.22k	t = y;
76	4.22k	if(!t->larger)
77	2.40k	break;
78	4.22k	}
79	6.55k	l->larger = t; /* link larger */
80	6.55k	l = t;
81	6.55k	t = t->larger;
82	6.55k	}
83	847k	else
84	847k	break;
85	34.6M	}
86
87	34.5M	l->larger = t->smaller; /* assemble */
88	34.5M	r->smaller = t->larger;
89	34.5M	t->smaller = N.larger;
90	34.5M	t->larger = N.smaller;
91
92	34.5M	return t;
93	34.5M	}
94
95		static const struct curltime SPLAY_SUBNODE = {
96		~0, -1
97		};
98
99		/* Insert key i into the tree t. Return a pointer to the resulting tree or
100		* NULL if something went wrong.
101		*
102		* @unittest: 1309
103		*/
104		struct Curl_tree Curl_splayinsert(const struct curltime pkey,
105		struct Curl_tree *t,
106		struct Curl_tree *node)
107	849k	{
108	849k	DEBUGASSERT(node);
109
110	849k	if(t) {
111	376k	t = Curl_splay(pkey, t);
112	376k	DEBUGASSERT(t);
113	376k	if(splay_compare(pkey, &t->key) == 0) {
114		/* There already exists a node in the tree with the same key. Build a
115		doubly-linked circular list of nodes. We add the new 'node' struct to
116		the end of this list. */
117
118	0	node->key = SPLAY_SUBNODE; /* identify this node as a subnode */
119	0	node->samen = t;
120	0	node->samep = t->samep;
121	0	t->samep->samen = node;
122	0	t->samep = node;
123
124	0	return t; /* the root node always stays the same */
125	0	}
126	376k	}
127
128	849k	if(!t) {
129	473k	node->smaller = node->larger = NULL;
130	473k	}
131	376k	else if(splay_compare(pkey, &t->key) < 0) {
132	363k	node->smaller = t->smaller;
133	363k	node->larger = t;
134	363k	t->smaller = NULL;
135	363k	}
136	12.0k	else {
137	12.0k	node->larger = t->larger;
138	12.0k	node->smaller = t;
139	12.0k	t->larger = NULL;
140	12.0k	}
141	849k	node->key = *pkey;
142
143		/* no identical nodes (yet), we are the only one in the list of nodes */
144	849k	node->samen = node;
145	849k	node->samep = node;
146	849k	return node;
147	849k	}
148
149		/* Finds and deletes the best-fit node from the tree. Return a pointer to the
150		resulting tree. best-fit means the smallest node if it is not larger than
151		the key */
152		struct Curl_tree Curl_splaygetbest(const struct curltime pkey,
153		struct Curl_tree *t,
154		struct Curl_tree **removed)
155	33.3M	{
156	33.3M	static const struct curltime tv_zero = { 0, 0 };
157	33.3M	struct Curl_tree *x;
158
159	33.3M	if(!t) {
160	0	removed = NULL; / none removed since there was no root */
161	0	return NULL;
162	0	}
163
164		/* find smallest */
165	33.3M	t = Curl_splay(&tv_zero, t);
166	33.3M	DEBUGASSERT(t);
167	33.3M	if(splay_compare(pkey, &t->key) < 0) {
168		/* even the smallest is too big */
169	33.3M	*removed = NULL;
170	33.3M	return t;
171	33.3M	}
172
173		/* FIRST! Check if there is a list with identical keys */
174	2.28k	x = t->samen;
175	2.28k	if(x != t) {
176		/* there is, pick one from the list */
177
178		/* 'x' is the new root node */
179
180	0	x->key = t->key;
181	0	x->larger = t->larger;
182	0	x->smaller = t->smaller;
183	0	x->samep = t->samep;
184	0	t->samep->samen = x;
185
186	0	*removed = t;
187	0	return x; /* new root */
188	0	}
189
190		/* we splayed the tree to the smallest element, there is no smaller */
191	2.28k	x = t->larger;
192	2.28k	*removed = t;
193
194	2.28k	return x;
195	2.28k	}
196
197		/* Deletes the node we point out from the tree if it is there. Stores a
198		* pointer to the new resulting tree in 'newroot'.
199		*
200		* Returns zero on success and non-zero on errors!
201		* When returning error, it does not touch the 'newroot' pointer.
202		*
203		* NOTE: when the last node of the tree is removed, there is no tree left so
204		* 'newroot' will be made to point to NULL.
205		*
206		* @unittest: 1309
207		*/
208		int Curl_splayremove(struct Curl_tree *t,
209		struct Curl_tree *removenode,
210		struct Curl_tree **newroot)
211	847k	{
212	847k	struct Curl_tree *x;
213
214	847k	if(!t)
215	0	return 1;
216
217	847k	DEBUGASSERT(removenode);
218
219	847k	if(splay_compare(&SPLAY_SUBNODE, &removenode->key) == 0) {
220		/* It is a subnode within a 'same' linked list and thus we can unlink it
221		easily. */
222	0	DEBUGASSERT(removenode->samen != removenode);
223	0	if(removenode->samen == removenode)
224		/* A non-subnode should never be set to SPLAY_SUBNODE */
225	0	return 3;
226
227	0	removenode->samep->samen = removenode->samen;
228	0	removenode->samen->samep = removenode->samep;
229
230		/* Ensures that double-remove gets caught. */
231	0	removenode->samen = removenode;
232
233	0	newroot = t; / return the same root */
234	0	return 0;
235	0	}
236
237	847k	t = Curl_splay(&removenode->key, t);
238	847k	DEBUGASSERT(t);
239
240		/* First make sure that we got the same root node as the one we want
241		to remove, as otherwise we might be trying to remove a node that
242		is not actually in the tree.
243
244		We cannot just compare the keys here as a double remove in quick
245		succession of a node with key != SPLAY_SUBNODE && same != NULL
246		could return the same key but a different node. */
247	847k	DEBUGASSERT(t == removenode);
248	847k	if(t != removenode)
249	0	return 2;
250
251		/* Check if there is a list with identical sizes, as then we are trying to
252		remove the root node of a list of nodes with identical keys. */
253	847k	x = t->samen;
254	847k	if(x != t) {
255		/* 'x' is the new root node, we just make it use the root node's
256		smaller/larger links */
257
258	0	x->key = t->key;
259	0	x->larger = t->larger;
260	0	x->smaller = t->smaller;
261	0	x->samep = t->samep;
262	0	t->samep->samen = x;
263	0	}
264	847k	else {
265		/* Remove the root node */
266	847k	if(!t->smaller)
267	835k	x = t->larger;
268	12.3k	else {
269	12.3k	x = Curl_splay(&removenode->key, t->smaller);
270	12.3k	DEBUGASSERT(x);
271	12.3k	x->larger = t->larger;
272	12.3k	}
273	847k	}
274
275	847k	newroot = x; / store new root pointer */
276
277	847k	return 0;
278	847k	}
279
280		/* set and get the custom payload for this tree node */
281		void Curl_splayset(struct Curl_tree node, void payload)
282	847k	{
283	847k	DEBUGASSERT(node);
284	847k	node->ptr = payload;
285	847k	}
286
287		void Curl_splayget(struct Curl_tree node)
288	2.28k	{
289	2.28k	DEBUGASSERT(node);
290	2.28k	return node->ptr;
291	2.28k	}